/* Portions of this file are subject to the following copyright(s).  See
 * the Net-SNMP's COPYING file for more details and other copyrights
 * that may apply:
 */
/******************************************************************
	Copyright 1989, 1991, 1992 by Carnegie Mellon University

                      All Rights Reserved

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the name of CMU not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.

CMU DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
CMU BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.
******************************************************************/
/*
 * Portions of this file are copyrighted by:
 * Copyright Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * Use is subject to license terms specified in the COPYING file
 * distributed with the Net-SNMP package.
 */

/** @defgroup library The Net-SNMP library
 *  @{
 */
/*
 * snmp_api.c - API for access to snmp.
 */
#include <net-snmp/net-snmp-config.h>

#include <stdio.h>
#include <ctype.h>
#if HAVE_STDLIB_H
#include <stdlib.h>
#endif
#if HAVE_STRING_H
#include <string.h>
#else
#include <strings.h>
#endif
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <sys/types.h>
#if HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif
#if TIME_WITH_SYS_TIME
# ifdef WIN32
#  include <sys/timeb.h>
# else
#  include <sys/time.h>
# endif
# include <time.h>
#else
# if HAVE_SYS_TIME_H
#  include <sys/time.h>
# else
#  include <time.h>
# endif
#endif
#if HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#if HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#if HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#if HAVE_IO_H
#include <io.h>
#endif
#if HAVE_WINSOCK_H
#include <winsock.h>
#endif
#if HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#if HAVE_SYS_UN_H
#include <sys/un.h>
#endif
#if HAVE_NETDB_H
#include <netdb.h>
#endif
#if HAVE_NET_IF_DL_H
#ifndef dynix
#include <net/if_dl.h>
#else
#include <sys/net/if_dl.h>
#endif
#endif
#include <errno.h>

#if HAVE_LOCALE_H
#include <locale.h>
#endif

#if HAVE_DMALLOC_H
#include <dmalloc.h>
#endif

#define SNMP_NEED_REQUEST_LIST
#include <net-snmp/types.h>
#include <net-snmp/output_api.h>
#include <net-snmp/config_api.h>
#include <net-snmp/utilities.h>

#include <net-snmp/library/asn1.h>
#include <net-snmp/library/snmp.h>      /* for xdump & {build,parse}_var_op */
#include <net-snmp/library/snmp_api.h>
#include <net-snmp/library/snmp_client.h>
#include <net-snmp/library/parse.h>
#include <net-snmp/library/mib.h>
#include <net-snmp/library/int64.h>
#include <net-snmp/library/snmpv3.h>
#include <net-snmp/library/callback.h>
#include <net-snmp/library/container.h>
#include <net-snmp/library/snmp_secmod.h>
#ifdef SNMP_SECMOD_USM
#include <net-snmp/library/snmpusm.h>
#endif
#ifdef SNMP_SECMOD_KSM
#include <net-snmp/library/snmpksm.h>
#endif
#include <net-snmp/library/keytools.h>
#include <net-snmp/library/lcd_time.h>
#include <net-snmp/library/snmp_alarm.h>
#include <net-snmp/library/snmp_transport.h>

static void     _init_snmp(void);

#include "../agent/mibgroup/agentx/protocol.h"
#include <net-snmp/library/transform_oids.h>
#ifndef timercmp
#define	timercmp(tvp, uvp, cmp) \
	/* CSTYLED */ \
	((tvp)->tv_sec cmp (uvp)->tv_sec || \
	((tvp)->tv_sec == (uvp)->tv_sec && \
	/* CSTYLED */ \
	(tvp)->tv_usec cmp (uvp)->tv_usec))
#endif
#ifndef timerclear
#define	timerclear(tvp)		(tvp)->tv_sec = (tvp)->tv_usec = 0
#endif

/*
 * Globals.
 */
#define MAX_PACKET_LENGTH	(0x7fffffff)
#ifndef NETSNMP_STREAM_QUEUE_LEN
#define NETSNMP_STREAM_QUEUE_LEN  5
#endif

#ifndef BSD4_3
#define BSD4_2
#endif

#ifndef FD_SET

typedef long    fd_mask;
#define NFDBITS	(sizeof(fd_mask) * NBBY)        /* bits per mask */

#define	FD_SET(n, p)	((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
#define	FD_CLR(n, p)	((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
#define	FD_ISSET(n, p)	((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
#define FD_ZERO(p)	memset((p), 0, sizeof(*(p)))
#endif

static oid      default_enterprise[] = { 1, 3, 6, 1, 4, 1, 3, 1, 1 };
/*
 * enterprises.cmu.systems.cmuSNMP 
 */

#define DEFAULT_COMMUNITY   "public"
#define DEFAULT_RETRIES	    5
#define DEFAULT_TIMEOUT	    1000000L
#define DEFAULT_REMPORT	    SNMP_PORT
#define DEFAULT_ENTERPRISE  default_enterprise
#define DEFAULT_TIME	    0

/*
 * don't set higher than 0x7fffffff, and I doubt it should be that high
 * * = 4 gig snmp messages max 
 */
#define MAXIMUM_PACKET_SIZE 0x7fffffff

/*
 * Internal information about the state of the snmp session.
 */
struct snmp_internal_session {
    netsnmp_request_list *requests;     /* Info about outstanding requests */
    netsnmp_request_list *requestsEnd;  /* ptr to end of list */
    int             (*hook_pre) (netsnmp_session *, netsnmp_transport *,
                                 void *, int);
    int             (*hook_parse) (netsnmp_session *, netsnmp_pdu *,
                                   u_char *, size_t);
    int             (*hook_post) (netsnmp_session *, netsnmp_pdu *, int);
    int             (*hook_build) (netsnmp_session *, netsnmp_pdu *,
                                   u_char *, size_t *);
    int             (*hook_realloc_build) (netsnmp_session *,
                                           netsnmp_pdu *, u_char **,
                                           size_t *, size_t *);
    int             (*check_packet) (u_char *, size_t);
    netsnmp_pdu    *(*hook_create_pdu) (netsnmp_transport *,
                                        void *, size_t);

    u_char         *packet;
    size_t          packet_len, packet_size;
};

/*
 * The list of active/open sessions.
 */
struct session_list {
    struct session_list *next;
    netsnmp_session *session;
    netsnmp_transport *transport;
    struct snmp_internal_session *internal;
};



static const char *api_errors[-SNMPERR_MAX + 1] = {
    "No error",                 /* SNMPERR_SUCCESS */
    "Generic error",            /* SNMPERR_GENERR */
    "Invalid local port",       /* SNMPERR_BAD_LOCPORT */
    "Unknown host",             /* SNMPERR_BAD_ADDRESS */
    "Unknown session",          /* SNMPERR_BAD_SESSION */
    "Too long",                 /* SNMPERR_TOO_LONG */
    "No socket",                /* SNMPERR_NO_SOCKET */
    "Cannot send V2 PDU on V1 session", /* SNMPERR_V2_IN_V1 */
    "Cannot send V1 PDU on V2 session", /* SNMPERR_V1_IN_V2 */
    "Bad value for non-repeaters",      /* SNMPERR_BAD_REPEATERS */
    "Bad value for max-repetitions",    /* SNMPERR_BAD_REPETITIONS */
    "Error building ASN.1 representation",      /* SNMPERR_BAD_ASN1_BUILD */
    "Failure in sendto",        /* SNMPERR_BAD_SENDTO */
    "Bad parse of ASN.1 type",  /* SNMPERR_BAD_PARSE */
    "Bad version specified",    /* SNMPERR_BAD_VERSION */
    "Bad source party specified",       /* SNMPERR_BAD_SRC_PARTY */
    "Bad destination party specified",  /* SNMPERR_BAD_DST_PARTY */
    "Bad context specified",    /* SNMPERR_BAD_CONTEXT */
    "Bad community specified",  /* SNMPERR_BAD_COMMUNITY */
    "Cannot send noAuth/Priv",       /* SNMPERR_NOAUTH_DESPRIV */
    "Bad ACL definition",       /* SNMPERR_BAD_ACL */
    "Bad Party definition",     /* SNMPERR_BAD_PARTY */
    "Session abort failure",    /* SNMPERR_ABORT */
    "Unknown PDU type",         /* SNMPERR_UNKNOWN_PDU */
    "Timeout",                  /* SNMPERR_TIMEOUT */
    "Failure in recvfrom",      /* SNMPERR_BAD_RECVFROM */
    "Unable to determine contextEngineID",      /* SNMPERR_BAD_ENG_ID */
    "No securityName specified",        /* SNMPERR_BAD_SEC_NAME */
    "Unable to determine securityLevel",        /* SNMPERR_BAD_SEC_LEVEL  */
    "ASN.1 parse error in message",     /* SNMPERR_ASN_PARSE_ERR */
    "Unknown security model in message",        /* SNMPERR_UNKNOWN_SEC_MODEL */
    "Invalid message (e.g. msgFlags)",  /* SNMPERR_INVALID_MSG */
    "Unknown engine ID",        /* SNMPERR_UNKNOWN_ENG_ID */
    "Unknown user name",        /* SNMPERR_UNKNOWN_USER_NAME */
    "Unsupported security level",       /* SNMPERR_UNSUPPORTED_SEC_LEVEL */
    "Authentication failure (incorrect password, community or key)",    /* SNMPERR_AUTHENTICATION_FAILURE */
    "Not in time window",       /* SNMPERR_NOT_IN_TIME_WINDOW */
    "Decryption error",         /* SNMPERR_DECRYPTION_ERR */
    "SCAPI general failure",    /* SNMPERR_SC_GENERAL_FAILURE */
    "SCAPI sub-system not configured",  /* SNMPERR_SC_NOT_CONFIGURED */
    "Key tools not available",  /* SNMPERR_KT_NOT_AVAILABLE */
    "Unknown Report message",   /* SNMPERR_UNKNOWN_REPORT */
    "USM generic error",        /* SNMPERR_USM_GENERICERROR */
    "USM unknown security name (no such user exists)",  /* SNMPERR_USM_UNKNOWNSECURITYNAME */
    "USM unsupported security level (this user has not been configured for that level of security)",    /* SNMPERR_USM_UNSUPPORTEDSECURITYLEVEL */
    "USM encryption error",     /* SNMPERR_USM_ENCRYPTIONERROR */
    "USM authentication failure (incorrect password or key)",   /* SNMPERR_USM_AUTHENTICATIONFAILURE */
    "USM parse error",          /* SNMPERR_USM_PARSEERROR */
    "USM unknown engineID",     /* SNMPERR_USM_UNKNOWNENGINEID */
    "USM not in time window",   /* SNMPERR_USM_NOTINTIMEWINDOW */
    "USM decryption error",     /* SNMPERR_USM_DECRYPTIONERROR */
    "MIB not initialized",      /* SNMPERR_NOMIB */
    "Value out of range",       /* SNMPERR_RANGE */
    "Sub-id out of range",      /* SNMPERR_MAX_SUBID */
    "Bad sub-id in object identifier",  /* SNMPERR_BAD_SUBID */
    "Object identifier too long",       /* SNMPERR_LONG_OID */
    "Bad value name",           /* SNMPERR_BAD_NAME */
    "Bad value notation",       /* SNMPERR_VALUE */
    "Unknown Object Identifier",        /* SNMPERR_UNKNOWN_OBJID */
    "No PDU in snmp_send",      /* SNMPERR_NULL_PDU */
    "Missing variables in PDU", /* SNMPERR_NO_VARS */
    "Bad variable type",        /* SNMPERR_VAR_TYPE */
    "Out of memory (malloc failure)",   /* SNMPERR_MALLOC */
    "Kerberos related error",   /* SNMPERR_KRB5 */
    "Protocol error",		/* SNMPERR_PROTOCOL */
};

static const char *secLevelName[] = {
    "BAD_SEC_LEVEL",
    "noAuthNoPriv",
    "authNoPriv",
    "authPriv"
};

/*
 * Multiple threads may changes these variables.
 * Suggest using the Single API, which does not use Sessions.
 *
 * Reqid may need to be protected. Time will tell...
 *
 */
/*
 * MTCRITICAL_RESOURCE
 */
/*
 * use token in comments to individually protect these resources 
 */
struct session_list *Sessions = NULL;   /* MT_LIB_SESSION */
static long     Reqid = 0;      /* MT_LIB_REQUESTID */
static long     Msgid = 0;      /* MT_LIB_MESSAGEID */
static long     Sessid = 0;     /* MT_LIB_SESSIONID */
static long     Transid = 0;    /* MT_LIB_TRANSID */
int             snmp_errno = 0;
/*
 * END MTCRITICAL_RESOURCE
 */

/*
 * global error detail storage
 */
static char     snmp_detail[192];
static int      snmp_detail_f = 0;

/*
 * Prototypes.
 */
int             snmp_build(u_char ** pkt, size_t * pkt_len,
                           size_t * offset, netsnmp_session * pss,
                           netsnmp_pdu *pdu);
static int      snmp_parse(void *, netsnmp_session *, netsnmp_pdu *,
                           u_char *, size_t);

static void     snmpv3_calc_msg_flags(int, int, u_char *);
static int      snmpv3_verify_msg(netsnmp_request_list *, netsnmp_pdu *);
static int      snmpv3_build_probe_pdu(netsnmp_pdu **);
static int      snmpv3_build(u_char ** pkt, size_t * pkt_len,
                             size_t * offset, netsnmp_session * session,
                             netsnmp_pdu *pdu);
static int      snmp_parse_version(u_char *, size_t);
static int      snmp_resend_request(struct session_list *slp,
                                    netsnmp_request_list *rp,
                                    int incr_retries);
static void     register_default_handlers(void);
static struct session_list *snmp_sess_copy(netsnmp_session * pss);
int             snmp_get_errno(void);
void            snmp_synch_reset(netsnmp_session * notused);
void            snmp_synch_setup(netsnmp_session * notused);

#ifndef HAVE_STRERROR
const char     *
strerror(int err)
{
    extern const char *sys_errlist[];
    extern int      sys_nerr;

    if (err < 0 || err >= sys_nerr)
        return "Unknown error";
    return sys_errlist[err];
}
#endif

const char *
snmp_pdu_type(int type)
{
    static char unknown[20];
    switch(type) {
    case SNMP_MSG_GET:
        return "GET";
    case SNMP_MSG_GETNEXT:
        return "GETNEXT";
    case SNMP_MSG_RESPONSE:
        return "RESPONSE";
    case SNMP_MSG_SET:
        return "SET";
    case SNMP_MSG_GETBULK:
        return "GETBULK";
    case SNMP_MSG_INFORM:
        return "INFORM";
    case SNMP_MSG_TRAP2:
        return "TRAP2";
    case SNMP_MSG_REPORT:
        return "REPORT";
    default:
        snprintf(unknown, sizeof(unknown), "?0x%2X?", type);
	return unknown;
    }
}

#define DEBUGPRINTPDUTYPE(token, type) \
    DEBUGDUMPSECTION(token, snmp_pdu_type(type))

long
snmp_get_next_reqid(void)
{
    long            retVal;
    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_REQUESTID);
    retVal = 1 + Reqid;         /*MTCRITICAL_RESOURCE */
    if (!retVal)
        retVal = 2;
    Reqid = retVal;
    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_16BIT_IDS))
        retVal &= 0x7fff;	/* mask to 15 bits */
    else
        retVal &= 0x7fffffff;	/* mask to 31 bits */

    if (!retVal) {
        Reqid = retVal = 2;
    }
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_REQUESTID);
    return retVal;
}

long
snmp_get_next_msgid(void)
{
    long            retVal;
    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_MESSAGEID);
    retVal = 1 + Msgid;         /*MTCRITICAL_RESOURCE */
    if (!retVal)
        retVal = 2;
    Msgid = retVal;
    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_16BIT_IDS))
        retVal &= 0x7fff;	/* mask to 15 bits */
    else
        retVal &= 0x7fffffff;	/* mask to 31 bits */

    if (!retVal) {
        Msgid = retVal = 2;
    }
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_MESSAGEID);
    return retVal;
}

long
snmp_get_next_sessid(void)
{
    long            retVal;
    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSIONID);
    retVal = 1 + Sessid;        /*MTCRITICAL_RESOURCE */
    if (!retVal)
        retVal = 2;
    Sessid = retVal;
    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_16BIT_IDS))
        retVal &= 0x7fff;	/* mask to 15 bits */
    else
        retVal &= 0x7fffffff;	/* mask to 31 bits */

    if (!retVal) {
        Sessid = retVal = 2;
    }
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSIONID);
    return retVal;
}

long
snmp_get_next_transid(void)
{
    long            retVal;
    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_TRANSID);
    retVal = 1 + Transid;       /*MTCRITICAL_RESOURCE */
    if (!retVal)
        retVal = 2;
    Transid = retVal;
    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_16BIT_IDS))
        retVal &= 0x7fff;	/* mask to 15 bits */
    else
        retVal &= 0x7fffffff;	/* mask to 31 bits */

    if (!retVal) {
        Transid = retVal = 2;
    }
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_TRANSID);
    return retVal;
}

void
snmp_perror(const char *prog_string)
{
    const char     *str;
    int             xerr;
    xerr = snmp_errno;          /*MTCRITICAL_RESOURCE */
    str = snmp_api_errstring(xerr);
    snmp_log(LOG_ERR, "%s: %s\n", prog_string, str);
}

void
snmp_set_detail(const char *detail_string)
{
    if (detail_string != NULL) {
        strncpy((char *) snmp_detail, detail_string, sizeof(snmp_detail));
        snmp_detail[sizeof(snmp_detail) - 1] = '\0';
        snmp_detail_f = 1;
    }
}

/*
 * returns pointer to static data 
 */
/*
 * results not guaranteed in multi-threaded use 
 */
const char     *
snmp_api_errstring(int snmp_errnumber)
{
    const char     *msg = "";
    static char     msg_buf[SPRINT_MAX_LEN];
    if (snmp_errnumber >= SNMPERR_MAX && snmp_errnumber <= SNMPERR_GENERR) {
        msg = api_errors[-snmp_errnumber];
    } else if (snmp_errnumber != SNMPERR_SUCCESS) {
        msg = NULL;
    }
    if (!msg)
	snprintf(msg_buf, sizeof(msg_buf), "Unknown error: %d", snmp_errnumber);
    else if (snmp_detail_f) {
        snprintf(msg_buf, sizeof(msg_buf), "%s (%s)", msg, snmp_detail);
        snmp_detail_f = 0;
    } else {
        strncpy(msg_buf, msg, sizeof(msg_buf));
    }
    msg_buf[sizeof(msg_buf)-1] = '\0';

    return (msg_buf);
}

/*
 * snmp_error - return error data
 * Inputs :  address of errno, address of snmp_errno, address of string
 * Caller must free the string returned after use.
 */
void
snmp_error(netsnmp_session * psess,
           int *p_errno, int *p_snmp_errno, char **p_str)
{
    char            buf[SPRINT_MAX_LEN];
    int             snmp_errnumber;

    if (p_errno)
        *p_errno = psess->s_errno;
    if (p_snmp_errno)
        *p_snmp_errno = psess->s_snmp_errno;
    if (p_str == NULL)
        return;

    strcpy(buf, "");
    snmp_errnumber = psess->s_snmp_errno;
    if (snmp_errnumber >= SNMPERR_MAX && snmp_errnumber <= SNMPERR_GENERR) {
	if (snmp_detail_f) {
            snprintf(buf, sizeof(buf), "%s (%s)", api_errors[-snmp_errnumber],
		    snmp_detail);
	    snmp_detail_f = 0;
	}
	else
	    strncpy(buf, api_errors[-snmp_errnumber], sizeof(buf));
    } else {
        if (snmp_errnumber)
            snprintf(buf, sizeof(buf), "Unknown Error %d", snmp_errnumber);
    }
    buf[sizeof(buf)-1] = '\0';

    /*
     * append a useful system errno interpretation. 
     */
    if (psess->s_errno) {
        const char* error = strerror(psess->s_errno);
        if(error == NULL)
            error = "Unknown Error";
        snprintf (&buf[strlen(buf)], sizeof(buf)-strlen(buf),
                 " (%s)", error);
    }
    buf[sizeof(buf)-1] = '\0';
    *p_str = strdup(buf);
}

/*
 * snmp_sess_error - same as snmp_error for single session API use.
 */
void
snmp_sess_error(void *sessp, int *p_errno, int *p_snmp_errno, char **p_str)
{
    struct session_list *slp = (struct session_list *) sessp;

    if ((slp) && (slp->session))
        snmp_error(slp->session, p_errno, p_snmp_errno, p_str);
}

/*
 * snmp_sess_perror(): print a error stored in a session pointer 
 */
void
netsnmp_sess_log_error(int priority,
                       const char *prog_string, netsnmp_session * ss)
{
    char           *err;
    snmp_error(ss, NULL, NULL, &err);
    snmp_log(priority, "%s: %s\n", prog_string, err);
    SNMP_FREE(err);
}

/*
 * snmp_sess_perror(): print a error stored in a session pointer 
 */
void
snmp_sess_perror(const char *prog_string, netsnmp_session * ss)
{
    netsnmp_sess_log_error(LOG_ERR, prog_string, ss);
}



/*
 * Primordial SNMP library initialization.
 * Initializes mutex locks.
 * Invokes minimum required initialization for displaying MIB objects.
 * Gets initial request ID for all transactions,
 * and finds which port SNMP over UDP uses.
 * SNMP over AppleTalk is not currently supported.
 *
 * Warning: no debug messages here.
 */
static void
_init_snmp(void)
{
#ifdef  HAVE_GETSERVBYNAME
    struct servent *servp;
#endif
    static char     have_done_init = 0;

    struct timeval  tv;
    long            tmpReqid, tmpMsgid;
    u_short         s_port = SNMP_PORT;

    if (have_done_init)
        return;
    have_done_init = 1;
    Reqid = 1;

    snmp_res_init();            /* initialize the mt locking structures */
#ifndef DISABLE_MIB_LOADING
    init_mib_internals();
#endif /* DISABLE_MIB_LOADING */
    netsnmp_tdomain_init();

    gettimeofday(&tv, (struct timezone *) 0);
    /*
     * Now = tv;
     */

    /*
     * get pseudo-random values for request ID and message ID 
     */
    /*
     * don't allow zero value to repeat init 
     */
#ifdef SVR4
    srand48(tv.tv_sec ^ tv.tv_usec);
    tmpReqid = lrand48();
    tmpMsgid = lrand48();
#else
    srandom(tv.tv_sec ^ tv.tv_usec);
    tmpReqid = random();
    tmpMsgid = random();
#endif

    if (tmpReqid == 0)
        tmpReqid = 1;
    if (tmpMsgid == 0)
        tmpMsgid = 1;
    Reqid = tmpReqid;
    Msgid = tmpMsgid;

#ifdef HAVE_GETSERVBYNAME
    servp = getservbyname("snmp", "udp");
    if (servp) {
        /*
         * store it in host byte order 
         */
        s_port = ntohs(servp->s_port);
    }
#endif

    netsnmp_ds_set_int(NETSNMP_DS_LIBRARY_ID, 
		       NETSNMP_DS_LIB_DEFAULT_PORT, s_port);
    netsnmp_ds_set_int(NETSNMP_DS_LIBRARY_ID, 
                       NETSNMP_DS_LIB_HEX_OUTPUT_LENGTH, 16);

#ifdef USE_REVERSE_ASNENCODING
    netsnmp_ds_set_boolean(NETSNMP_DS_LIBRARY_ID, 
			   NETSNMP_DS_LIB_REVERSE_ENCODE,
			   DEFAULT_ASNENCODING_DIRECTION);
#endif
}

/*
 * Initializes the session structure.
 * May perform one time minimal library initialization.
 * No MIB file processing is done via this call.
 */
void
snmp_sess_init(netsnmp_session * session)
{
    _init_snmp();

    /*
     * initialize session to default values 
     */

    memset(session, 0, sizeof(netsnmp_session));
    session->remote_port = SNMP_DEFAULT_REMPORT;
    session->timeout = SNMP_DEFAULT_TIMEOUT;
    session->retries = SNMP_DEFAULT_RETRIES;
    session->version = SNMP_DEFAULT_VERSION;
    session->securityModel = SNMP_DEFAULT_SECMODEL;
    session->rcvMsgMaxSize = SNMP_MAX_MSG_SIZE;
    session->flags |= SNMP_FLAGS_DONT_PROBE;
}


static void
register_default_handlers(void)
{
    netsnmp_ds_register_config(ASN_BOOLEAN, "snmp", "dumpPacket",
		      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_DUMP_PACKET);
    netsnmp_ds_register_config(ASN_BOOLEAN, "snmp", "reverseEncodeBER",
		      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_REVERSE_ENCODE);
    netsnmp_ds_register_config(ASN_INTEGER, "snmp", "defaultPort",
		      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_DEFAULT_PORT);
#if !defined(DISABLE_SNMPV1) || !defined(DISABLE_SNMPV2C)
    netsnmp_ds_register_config(ASN_OCTET_STR, "snmp", "defCommunity",
                      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_COMMUNITY);
#endif
    netsnmp_ds_register_premib(ASN_BOOLEAN, "snmp", "noTokenWarnings",
                      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_NO_TOKEN_WARNINGS);
    netsnmp_ds_register_config(ASN_BOOLEAN, "snmp", "noRangeCheck",
		      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_DONT_CHECK_RANGE);
    netsnmp_ds_register_premib(ASN_OCTET_STR, "snmp", "persistentDir",
	              NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_PERSISTENT_DIR);
    netsnmp_ds_register_config(ASN_OCTET_STR, "snmp", "tempFilePattern",
	              NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_TEMP_FILE_PATTERN);
    netsnmp_ds_register_config(ASN_BOOLEAN, "snmp", "noDisplayHint",
	              NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_NO_DISPLAY_HINT);
    netsnmp_ds_register_config(ASN_BOOLEAN, "snmp", "16bitIDs",
	              NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_16BIT_IDS);
    netsnmp_ds_register_config(ASN_OCTET_STR, "snmp", "clientaddr",
                      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_CLIENT_ADDR);
    netsnmp_ds_register_config(ASN_INTEGER, "snmp", "serverSendBuf",
		      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_SERVERSENDBUF);
    netsnmp_ds_register_config(ASN_INTEGER, "snmp", "serverRecvBuf",
		      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_SERVERRECVBUF);
    netsnmp_ds_register_config(ASN_INTEGER, "snmp", "clientSendBuf",
		      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_CLIENTSENDBUF);
    netsnmp_ds_register_config(ASN_INTEGER, "snmp", "clientRecvBuf",
		      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_CLIENTRECVBUF);
}

void
init_snmp_enums(void)
{
    se_add_pair_to_slist("asntypes", strdup("integer"), ASN_INTEGER);
    se_add_pair_to_slist("asntypes", strdup("counter"), ASN_COUNTER);
    se_add_pair_to_slist("asntypes", strdup("uinteger"), ASN_GAUGE);
    se_add_pair_to_slist("asntypes", strdup("timeticks"), ASN_TIMETICKS);
    se_add_pair_to_slist("asntypes", strdup("counter64"), ASN_COUNTER64);
    se_add_pair_to_slist("asntypes", strdup("octet_str"), ASN_OCTET_STR);
    se_add_pair_to_slist("asntypes", strdup("ipaddress"), ASN_IPADDRESS);
    se_add_pair_to_slist("asntypes", strdup("opaque"), ASN_OPAQUE);
    se_add_pair_to_slist("asntypes", strdup("nsap"), ASN_NSAP);
    se_add_pair_to_slist("asntypes", strdup("object_id"), ASN_OBJECT_ID);
    se_add_pair_to_slist("asntypes", strdup("null"), ASN_NULL);
#ifdef OPAQUE_SPECIAL_TYPES
    se_add_pair_to_slist("asntypes", strdup("opaque_counter64"),
                         ASN_OPAQUE_COUNTER64);
    se_add_pair_to_slist("asntypes", strdup("opaque_u64"), ASN_OPAQUE_U64);
    se_add_pair_to_slist("asntypes", strdup("opaque_float"),
                         ASN_OPAQUE_FLOAT);
    se_add_pair_to_slist("asntypes", strdup("opaque_double"),
                         ASN_OPAQUE_DOUBLE);
    se_add_pair_to_slist("asntypes", strdup("opaque_i64"), ASN_OPAQUE_I64);
#endif
}



/**
 * Calls the functions to do config file loading and  mib module parsing
 * in the correct order.
 *
 * @param type label for the config file "type"
 *
 * @return void
 *
 * @see init_agent
 */
void
init_snmp(const char *type)
{
    static int      done_init = 0;      /* To prevent double init's. */

    if (done_init) {
        return;
    }

    done_init = 1;

    /*
     * make the type available everywhere else 
     */
    if (type && !netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
				       NETSNMP_DS_LIB_APPTYPE)) {
        netsnmp_ds_set_string(NETSNMP_DS_LIBRARY_ID, 
			      NETSNMP_DS_LIB_APPTYPE, type);
    }

    _init_snmp();

    /*
     * set our current locale properly to initialize isprint() type functions 
     */
#ifdef HAVE_SETLOCALE
    setlocale(LC_CTYPE, "");
#endif

    snmp_debug_init();    /* should be done first, to turn on debugging ASAP */
    netsnmp_container_init_list();
    init_callbacks();
    init_snmp_logging();
    snmp_init_statistics();
    register_mib_handlers();
    register_default_handlers();
    init_snmpv3(type);
    init_snmp_alarm();
    init_snmp_enum(type);
    init_snmp_enums();

    read_premib_configs();
#ifndef DISABLE_MIB_LOADING
    init_mib();
#endif /* DISABLE_MIB_LOADING */

    read_configs();

}                               /* end init_snmp() */

void
snmp_store(const char *type)
{
    DEBUGMSGTL(("snmp_store", "storing stuff...\n"));
    snmp_save_persistent(type);
    snmp_call_callbacks(SNMP_CALLBACK_LIBRARY, SNMP_CALLBACK_STORE_DATA, NULL);
    snmp_clean_persistent(type);
}


/**
 * Shuts down the application, saving any needed persistent storage,
 * and appropriate clean up.
 * 
 * @param type Label for the config file "type" used
 *
 * @return void
 */
void
snmp_shutdown(const char *type)
{
    snmp_store(type);
    snmp_call_callbacks(SNMP_CALLBACK_LIBRARY, SNMP_CALLBACK_SHUTDOWN, NULL);
    snmp_alarm_unregister_all();
    snmp_close_sessions();
#ifndef DISABLE_MIB_LOADING
    shutdown_mib();
#endif /* DISABLE_MIB_LOADING */
    unregister_all_config_handlers();
    netsnmp_container_free_list();
    clear_sec_mod();
    clear_snmp_enum();
    netsnmp_clear_tdomain_list();
    clear_callback();
    netsnmp_ds_shutdown();
}


/*
 * Sets up the session with the snmp_session information provided by the user.
 * Then opens and binds the necessary low-level transport.  A handle to the
 * created session is returned (this is NOT the same as the pointer passed to
 * snmp_open()).  On any error, NULL is returned and snmp_errno is set to the
 * appropriate error code.
 */
netsnmp_session *
snmp_open(netsnmp_session *session)
{
    struct session_list *slp;
    slp = (struct session_list *) snmp_sess_open(session);
    if (!slp) {
        return NULL;
    }

    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);
    slp->next = Sessions;
    Sessions = slp;
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);

    return (slp->session);
}

/*
 * extended open 
 */
netsnmp_session *
snmp_open_ex(netsnmp_session *session,
             int (*fpre_parse)	(netsnmp_session *, netsnmp_transport *,
                                void *, int),
             int (*fparse)	(netsnmp_session *, netsnmp_pdu *, u_char *,
				 size_t),
	     int (*fpost_parse)	(netsnmp_session *, netsnmp_pdu *, int),

             int (*fbuild)	(netsnmp_session *, netsnmp_pdu *, u_char *,
				 size_t *),
	     int (*frbuild)	(netsnmp_session *, netsnmp_pdu *,
				 u_char **, size_t *, size_t *),
             int (*fcheck)	(u_char *, size_t)
	     )
{
    struct session_list *slp;
    slp = (struct session_list *) snmp_sess_open(session);
    if (!slp) {
        return NULL;
    }
    slp->internal->hook_pre = fpre_parse;
    slp->internal->hook_parse = fparse;
    slp->internal->hook_post = fpost_parse;
    slp->internal->hook_build = fbuild;
    slp->internal->hook_realloc_build = frbuild;
    slp->internal->check_packet = fcheck;

    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);
    slp->next = Sessions;
    Sessions = slp;
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);

    return (slp->session);
}

static struct session_list *
_sess_copy(netsnmp_session * in_session)
{
    struct session_list *slp;
    struct snmp_internal_session *isp;
    netsnmp_session *session;
    struct snmp_secmod_def *sptr;
    char           *cp;
    u_char         *ucp;
    size_t          i;

    in_session->s_snmp_errno = 0;
    in_session->s_errno = 0;

    /*
     * Copy session structure and link into list 
     */
    slp = (struct session_list *) calloc(1, sizeof(struct session_list));
    if (slp == NULL) {
        in_session->s_snmp_errno = SNMPERR_MALLOC;
        return (NULL);
    }

    slp->transport = NULL;

    isp = (struct snmp_internal_session *)calloc(1, sizeof(struct snmp_internal_session));

    if (isp == NULL) {
        snmp_sess_close(slp);
        in_session->s_snmp_errno = SNMPERR_MALLOC;
        return (NULL);
    }

    slp->internal = isp;
    slp->session = (netsnmp_session *)malloc(sizeof(netsnmp_session));
    if (slp->session == NULL) {
        snmp_sess_close(slp);
        in_session->s_snmp_errno = SNMPERR_MALLOC;
        return (NULL);
    }
    memmove(slp->session, in_session, sizeof(netsnmp_session));
    session = slp->session;

    /*
     * zero out pointers so if we have to free the session we wont free mem
     * owned by in_session 
     */
    session->peername = NULL;
    session->community = NULL;
    session->contextEngineID = NULL;
    session->contextName = NULL;
    session->securityEngineID = NULL;
    session->securityName = NULL;
    session->securityAuthProto = NULL;
    session->securityPrivProto = NULL;
    /*
     * session now points to the new structure that still contains pointers to
     * data allocated elsewhere.  Some of this data is copied to space malloc'd
     * here, and the pointer replaced with the new one.
     */

    if (in_session->peername != NULL) {
        session->peername = (char *)malloc(strlen(in_session->peername) + 1);
        if (session->peername == NULL) {
            snmp_sess_close(slp);
            in_session->s_snmp_errno = SNMPERR_MALLOC;
            return (NULL);
        }
        strcpy(session->peername, in_session->peername);
    }

    /*
     * Fill in defaults if necessary 
     */
#if !defined(DISABLE_SNMPV1) || !defined(DISABLE_SNMPV2C)
    if (in_session->community_len != SNMP_DEFAULT_COMMUNITY_LEN) {
        ucp = (u_char *) malloc(in_session->community_len);
        if (ucp != NULL)
            memmove(ucp, in_session->community, in_session->community_len);
    } else {
        if ((cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
					NETSNMP_DS_LIB_COMMUNITY)) != NULL) {
            session->community_len = strlen(cp);
            ucp = (u_char *) malloc(session->community_len);
            if (ucp)
                memmove(ucp, cp, session->community_len);
        } else {
#ifdef NO_ZEROLENGTH_COMMUNITY
            session->community_len = strlen(DEFAULT_COMMUNITY);
            ucp = (u_char *) malloc(session->community_len);
            if (ucp)
                memmove(ucp, DEFAULT_COMMUNITY, session->community_len);
#else
            ucp = (u_char *) strdup("");
#endif
        }
    }

    if (ucp == NULL) {
        snmp_sess_close(slp);
        in_session->s_snmp_errno = SNMPERR_MALLOC;
        return (NULL);
    }
    session->community = ucp;   /* replace pointer with pointer to new data */
#endif

    if (session->securityLevel <= 0) {
        session->securityLevel =
            netsnmp_ds_get_int(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_SECLEVEL);
    }

    if (session->securityLevel == 0)
        session->securityLevel = SNMP_SEC_LEVEL_NOAUTH;

    if (in_session->securityAuthProtoLen > 0) {
        session->securityAuthProto =
            snmp_duplicate_objid(in_session->securityAuthProto,
                                 in_session->securityAuthProtoLen);
        if (session->securityAuthProto == NULL) {
            snmp_sess_close(slp);
            in_session->s_snmp_errno = SNMPERR_MALLOC;
            return (NULL);
        }
    } else if (get_default_authtype(&i) != NULL) {
        session->securityAuthProto =
            snmp_duplicate_objid(get_default_authtype(NULL), i);
        session->securityAuthProtoLen = i;
    }

    if (in_session->securityPrivProtoLen > 0) {
        session->securityPrivProto =
            snmp_duplicate_objid(in_session->securityPrivProto,
                                 in_session->securityPrivProtoLen);
        if (session->securityPrivProto == NULL) {
            snmp_sess_close(slp);
            in_session->s_snmp_errno = SNMPERR_MALLOC;
            return (NULL);
        }
    } else if (get_default_privtype(&i) != NULL) {
        session->securityPrivProto =
            snmp_duplicate_objid(get_default_privtype(NULL), i);
        session->securityPrivProtoLen = i;
    }

    if (in_session->securityEngineIDLen > 0) {
        ucp = (u_char *) malloc(in_session->securityEngineIDLen);
        if (ucp == NULL) {
            snmp_sess_close(slp);
            in_session->s_snmp_errno = SNMPERR_MALLOC;
            return (NULL);
        }
        memmove(ucp, in_session->securityEngineID,
                in_session->securityEngineIDLen);
        session->securityEngineID = ucp;

    }

    if (in_session->contextEngineIDLen > 0) {
        ucp = (u_char *) malloc(in_session->contextEngineIDLen);
        if (ucp == NULL) {
            snmp_sess_close(slp);
            in_session->s_snmp_errno = SNMPERR_MALLOC;
            return (NULL);
        }
        memmove(ucp, in_session->contextEngineID,
                in_session->contextEngineIDLen);
        session->contextEngineID = ucp;
    } else if (in_session->securityEngineIDLen > 0) {
        /*
         * default contextEngineID to securityEngineIDLen if defined 
         */
        ucp = (u_char *) malloc(in_session->securityEngineIDLen);
        if (ucp == NULL) {
            snmp_sess_close(slp);
            in_session->s_snmp_errno = SNMPERR_MALLOC;
            return (NULL);
        }
        memmove(ucp, in_session->securityEngineID,
                in_session->securityEngineIDLen);
        session->contextEngineID = ucp;
        session->contextEngineIDLen = in_session->securityEngineIDLen;
    }

    if (in_session->contextName) {
        session->contextName = strdup(in_session->contextName);
        if (session->contextName == NULL) {
            snmp_sess_close(slp);
            return (NULL);
        }
    } else {
        if ((cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID,
                                        NETSNMP_DS_LIB_CONTEXT)) != NULL)
            cp = strdup(cp);
        else
            cp = strdup(SNMP_DEFAULT_CONTEXT);
        if (cp == NULL) {
            snmp_sess_close(slp);
            return (NULL);
        }
        session->contextName = cp;
        session->contextNameLen = strlen(cp);
    }

    if (in_session->securityName) {
        session->securityName = strdup(in_session->securityName);
        if (session->securityName == NULL) {
            snmp_sess_close(slp);
            return (NULL);
        }
    } else if ((cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
					   NETSNMP_DS_LIB_SECNAME)) != NULL) {
        cp = strdup(cp);
        if (cp == NULL) {
            snmp_sess_close(slp);
            return (NULL);
        }
        session->securityName = cp;
        session->securityNameLen = strlen(cp);
    }

    if ((in_session->securityAuthKeyLen <= 0) &&
        ((cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
				     NETSNMP_DS_LIB_AUTHMASTERKEY)))) {
        size_t buflen = sizeof(session->securityAuthKey);
        u_char *tmpp = session->securityAuthKey;
        session->securityAuthKeyLen = 0;
        /* it will be a hex string */
        if (!snmp_hex_to_binary(&tmpp, &buflen,
                                &session->securityAuthKeyLen, 0, cp)) {
            snmp_set_detail("error parsing authentication master key");
            snmp_sess_close(slp);
            return NULL;
        }
    } else if ((in_session->securityAuthKeyLen <= 0) &&
        ((cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
				     NETSNMP_DS_LIB_AUTHPASSPHRASE)) ||
         (cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
				     NETSNMP_DS_LIB_PASSPHRASE)))) {
        session->securityAuthKeyLen = USM_AUTH_KU_LEN;
        if (generate_Ku(session->securityAuthProto,
                        session->securityAuthProtoLen,
                        (u_char *) cp, strlen(cp),
                        session->securityAuthKey,
                        &session->securityAuthKeyLen) != SNMPERR_SUCCESS) {
            snmp_set_detail
                ("Error generating a key (Ku) from the supplied authentication pass phrase.");
            snmp_sess_close(slp);
            return NULL;
        }
    }

    
    if ((in_session->securityPrivKeyLen <= 0) &&
        ((cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
				     NETSNMP_DS_LIB_PRIVMASTERKEY)))) {
        size_t buflen = sizeof(session->securityPrivKey);
        u_char *tmpp = session->securityPrivKey;
        session->securityPrivKeyLen = 0;
        /* it will be a hex string */
        if (!snmp_hex_to_binary(&tmpp, &buflen,
                                &session->securityPrivKeyLen, 0, cp)) {
            snmp_set_detail("error parsing encryption master key");
            snmp_sess_close(slp);
            return NULL;
        }
    } else if ((in_session->securityPrivKeyLen <= 0) &&
        ((cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
				     NETSNMP_DS_LIB_PRIVPASSPHRASE)) ||
         (cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
				     NETSNMP_DS_LIB_PASSPHRASE)))) {
        session->securityPrivKeyLen = USM_PRIV_KU_LEN;
        if (generate_Ku(session->securityAuthProto,
                        session->securityAuthProtoLen,
                        (u_char *) cp, strlen(cp),
                        session->securityPrivKey,
                        &session->securityPrivKeyLen) != SNMPERR_SUCCESS) {
            snmp_set_detail
                ("Error generating a key (Ku) from the supplied privacy pass phrase.");
            snmp_sess_close(slp);
            return NULL;
        }
    }

    if (session->retries == SNMP_DEFAULT_RETRIES)
        session->retries = DEFAULT_RETRIES;
    if (session->timeout == SNMP_DEFAULT_TIMEOUT)
        session->timeout = DEFAULT_TIMEOUT;
    session->sessid = snmp_get_next_sessid();

    snmp_call_callbacks(SNMP_CALLBACK_LIBRARY, SNMP_CALLBACK_SESSION_INIT,
                        session);

    if ((sptr = find_sec_mod(session->securityModel)) != NULL &&
        sptr->session_open != NULL) {
        /*
         * security module specific inialization 
         */
        (*sptr->session_open) (session);
    }

    return (slp);
}

static struct session_list *
snmp_sess_copy(netsnmp_session * pss)
{
    struct session_list *psl;
    psl = _sess_copy(pss);
    if (!psl) {
        if (!pss->s_snmp_errno) {
            pss->s_snmp_errno = SNMPERR_GENERR;
        }
        SET_SNMP_ERROR(pss->s_snmp_errno);
    }
    return psl;
}


/**
 * probe for peer engineID
 *
 * @param slp         session list pointer.
 * @param in_session  session for errors
 *
 * @note
 *  - called by _sess_open(), snmp_sess_add_ex()
 *  - in_session is the user supplied session provided to those functions.
 *  - the first session in slp should the internal allocated copy of in_session
 *
 * @return 0 : error
 * @return 1 : ok
 *
 */
int
snmpv3_engineID_probe(struct session_list *slp,
                      netsnmp_session * in_session)
{
    netsnmp_pdu    *pdu = NULL, *response = NULL;
    netsnmp_session *session;
    unsigned int    i;
    int             status;

    if (slp == NULL || slp->session == NULL) {
        return 0;
    }

    session = slp->session;

    /*
     * If we are opening a V3 session and we don't know engineID we must probe
     * it -- this must be done after the session is created and inserted in the
     * list so that the response can handled correctly. 
     */

    if ((session->flags & SNMP_FLAGS_DONT_PROBE) == SNMP_FLAGS_DONT_PROBE)
        return 1;

    if (session->version == SNMP_VERSION_3) {
        if (session->securityEngineIDLen == 0) {
            if (snmpv3_build_probe_pdu(&pdu) != 0) {
                DEBUGMSGTL(("snmp_api", "unable to create probe PDU\n"));
                return 0;
            }
            DEBUGMSGTL(("snmp_api", "probing for engineID...\n"));
            session->flags |= SNMP_FLAGS_DONT_PROBE; /* prevent recursion */
            status = snmp_sess_synch_response(slp, pdu, &response);

            if ((response == NULL) && (status == STAT_SUCCESS)) {
                status = STAT_ERROR;
            }

            switch (status) {
            case STAT_SUCCESS:
                in_session->s_snmp_errno = SNMPERR_INVALID_MSG; /* XX?? */
                DEBUGMSGTL(("snmp_sess_open",
                            "error: expected Report as response to probe: %s (%d)\n",
                            snmp_errstring(response->errstat),
                            response->errstat));
                break;
            case STAT_ERROR:   /* this is what we expected -> Report == STAT_ERROR */
                in_session->s_snmp_errno = SNMPERR_UNKNOWN_ENG_ID;
                break;
            case STAT_TIMEOUT:
                in_session->s_snmp_errno = SNMPERR_TIMEOUT;
            default:
                DEBUGMSGTL(("snmp_sess_open",
                            "unable to connect with remote engine: %s (%d)\n",
                            snmp_api_errstring(session->s_snmp_errno),
                            session->s_snmp_errno));
                break;
            }

            if (slp->session->securityEngineIDLen == 0) {
                DEBUGMSGTL(("snmp_api",
                            "unable to determine remote engine ID\n"));
                return 0;
            }

            in_session->s_snmp_errno = SNMPERR_SUCCESS;
            if (snmp_get_do_debugging()) {
                DEBUGMSGTL(("snmp_sess_open",
                            "  probe found engineID:  "));
                for (i = 0; i < slp->session->securityEngineIDLen; i++)
                    DEBUGMSG(("snmp_sess_open", "%02x",
                              slp->session->securityEngineID[i]));
                DEBUGMSG(("snmp_sess_open", "\n"));
            }
        }

        /*
         * if boot/time supplied set it for this engineID 
         */
        if (session->engineBoots || session->engineTime) {
            set_enginetime(session->securityEngineID,
                           session->securityEngineIDLen,
                           session->engineBoots, session->engineTime,
                           TRUE);
        }

        if (create_user_from_session(slp->session) != SNMPERR_SUCCESS) {
            in_session->s_snmp_errno = SNMPERR_UNKNOWN_USER_NAME;       /* XX?? */
            DEBUGMSGTL(("snmp_api",
                        "snmpv3_engine_probe(): failed(2) to create a new user from session\n"));
            return 0;
        }
    }

    return 1;
}



/*******************************************************************-o-******
 * snmp_sess_open
 *
 * Parameters:
 *	*in_session
 *
 * Returns:
 *      Pointer to a session in the session list   -OR-		FIX -- right?
 *	NULL on failure.
 *
 * The "spin-free" version of snmp_open.
 */
static void    *
_sess_open(netsnmp_session * in_session)
{
    struct session_list *slp;
    netsnmp_session *session;
    char            *clientaddr_save = NULL;

    in_session->s_snmp_errno = 0;
    in_session->s_errno = 0;

    _init_snmp();

    if ((slp = snmp_sess_copy(in_session)) == NULL) {
        return (NULL);
    }
    session = slp->session;
    slp->transport = NULL;

    if (NULL != session->localname) {
        clientaddr_save = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID,
                                                NETSNMP_DS_LIB_CLIENT_ADDR);
        netsnmp_ds_set_string(NETSNMP_DS_LIBRARY_ID,
                              NETSNMP_DS_LIB_CLIENT_ADDR, session->localname);
    }

    if (session->flags & SNMP_FLAGS_STREAM_SOCKET) {
        slp->transport = netsnmp_tdomain_transport(session->peername,
                                                   session->local_port,
                                                   "tcp");
    } else {
        slp->transport = netsnmp_tdomain_transport(session->peername,
                                                   session->local_port,
                                                   "udp");
    }

    if (NULL != session->localname)
        netsnmp_ds_set_string(NETSNMP_DS_LIBRARY_ID,
                              NETSNMP_DS_LIB_CLIENT_ADDR, clientaddr_save);

    if (slp->transport == NULL) {
        DEBUGMSGTL(("_sess_open", "couldn't interpret peername\n"));
        in_session->s_snmp_errno = SNMPERR_BAD_ADDRESS;
        in_session->s_errno = errno;
        snmp_set_detail(session->peername);
        snmp_sess_close(slp);
        return NULL;
    }

    session->rcvMsgMaxSize = slp->transport->msgMaxSize;

    if (!snmpv3_engineID_probe(slp, in_session)) {
        snmp_sess_close(slp);
        return NULL;
    }
    if (create_user_from_session(slp->session) != SNMPERR_SUCCESS) {
        in_session->s_snmp_errno = SNMPERR_UNKNOWN_USER_NAME;       /* XX?? */
        DEBUGMSGTL(("snmp_api",
                    "_sess_open(): failed(2) to create a new user from session\n"));
        snmp_sess_close(slp);
        return NULL;
    }
    
    session->flags &= ~SNMP_FLAGS_DONT_PROBE;


    return (void *) slp;
}                               /* end snmp_sess_open() */



/*
 * EXPERIMENTAL API EXTENSIONS ------------------------------------------ 
 * 
 * snmp_sess_add_ex, snmp_sess_add, snmp_add 
 * 
 * Analogous to snmp_open family of functions, but taking a netsnmp_transport
 * pointer as an extra argument.  Unlike snmp_open et al. it doesn't attempt
 * to interpret the in_session->peername as a transport endpoint specifier,
 * but instead uses the supplied transport.  JBPN
 * 
 */

netsnmp_session *
snmp_add(netsnmp_session * in_session,
         netsnmp_transport *transport,
         int (*fpre_parse) (netsnmp_session *, netsnmp_transport *, void *,
                            int), int (*fpost_parse) (netsnmp_session *,
                                                      netsnmp_pdu *, int))
{
    struct session_list *slp;
    slp = (struct session_list *) snmp_sess_add_ex(in_session, transport,
                                                   fpre_parse, NULL,
                                                   fpost_parse, NULL, NULL,
                                                   NULL, NULL);
    if (slp == NULL) {
        return NULL;
    }

    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);
    slp->next = Sessions;
    Sessions = slp;
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);

    return (slp->session);
}

netsnmp_session *
snmp_add_full(netsnmp_session * in_session,
              netsnmp_transport *transport,
              int (*fpre_parse) (netsnmp_session *, netsnmp_transport *,
                                 void *, int),
              int (*fparse) (netsnmp_session *, netsnmp_pdu *, u_char *,
                             size_t),
              int (*fpost_parse) (netsnmp_session *, netsnmp_pdu *, int),
              int (*fbuild) (netsnmp_session *, netsnmp_pdu *, u_char *,
                             size_t *), int (*frbuild) (netsnmp_session *,
                                                        netsnmp_pdu *,
                                                        u_char **,
                                                        size_t *,
                                                        size_t *),
              int (*fcheck) (u_char *, size_t),
              netsnmp_pdu *(*fcreate_pdu) (netsnmp_transport *, void *,
                                           size_t))
{
    struct session_list *slp;
    slp = (struct session_list *) snmp_sess_add_ex(in_session, transport,
                                                   fpre_parse, fparse,
                                                   fpost_parse, fbuild,
                                                   frbuild, fcheck,
                                                   fcreate_pdu);
    if (slp == NULL) {
        return NULL;
    }

    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);
    slp->next = Sessions;
    Sessions = slp;
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);

    return (slp->session);
}



void           *
snmp_sess_add_ex(netsnmp_session * in_session,
                 netsnmp_transport *transport,
                 int (*fpre_parse) (netsnmp_session *, netsnmp_transport *,
                                    void *, int),
                 int (*fparse) (netsnmp_session *, netsnmp_pdu *, u_char *,
                                size_t),
                 int (*fpost_parse) (netsnmp_session *, netsnmp_pdu *,
                                     int),
                 int (*fbuild) (netsnmp_session *, netsnmp_pdu *, u_char *,
                                size_t *),
                 int (*frbuild) (netsnmp_session *, netsnmp_pdu *,
                                 u_char **, size_t *, size_t *),
                 int (*fcheck) (u_char *, size_t),
                 netsnmp_pdu *(*fcreate_pdu) (netsnmp_transport *, void *,
                                              size_t))
{
    struct session_list *slp;

    _init_snmp();

    if (in_session == NULL || transport == NULL) {
        return NULL;
    }

    DEBUGMSGTL(("snmp_sess_add", "fd %d\n", transport->sock));

    if ((slp = snmp_sess_copy(in_session)) == NULL) {
        return (NULL);
    }

    slp->transport = transport;
    slp->internal->hook_pre = fpre_parse;
    slp->internal->hook_parse = fparse;
    slp->internal->hook_post = fpost_parse;
    slp->internal->hook_build = fbuild;
    slp->internal->hook_realloc_build = frbuild;
    slp->internal->check_packet = fcheck;
    slp->internal->hook_create_pdu = fcreate_pdu;

    slp->session->rcvMsgMaxSize = transport->msgMaxSize;

    if (slp->session->version == SNMP_VERSION_3) {
        DEBUGMSGTL(("snmp_sess_add",
                    "adding v3 session -- engineID probe now\n"));
        if (!snmpv3_engineID_probe(slp, in_session)) {
            DEBUGMSGTL(("snmp_sess_add", "engine ID probe failed\n"));
            snmp_sess_close(slp);
            return NULL;
        }
        if (create_user_from_session(slp->session) != SNMPERR_SUCCESS) {
            in_session->s_snmp_errno = SNMPERR_UNKNOWN_USER_NAME;
            DEBUGMSGTL(("snmp_api",
                        "snmp_sess_add(): failed(2) to create a new user from session\n"));
            snmp_sess_close(slp);
            return NULL;
        }
    }

    slp->session->flags &= ~SNMP_FLAGS_DONT_PROBE;

    return (void *) slp;
}                               /*  end snmp_sess_add_ex()  */



void           *
snmp_sess_add(netsnmp_session * in_session,
              netsnmp_transport *transport,
              int (*fpre_parse) (netsnmp_session *, netsnmp_transport *,
                                 void *, int),
              int (*fpost_parse) (netsnmp_session *, netsnmp_pdu *, int))
{
    return snmp_sess_add_ex(in_session, transport, fpre_parse, NULL,
                            fpost_parse, NULL, NULL, NULL, NULL);
}



void           *
snmp_sess_open(netsnmp_session * pss)
{
    void           *pvoid;
    pvoid = _sess_open(pss);
    if (!pvoid) {
        SET_SNMP_ERROR(pss->s_snmp_errno);
    }
    return pvoid;
}



/*
 * create_user_from_session(netsnmp_session *session):
 * 
 * creates a user in the usm table from the information in a session.
 * If the user already exists, it is updated with the current
 * information from the session
 * 
 * Parameters:
 * session -- IN: pointer to the session to use when creating the user.
 * 
 * Returns:
 * SNMPERR_SUCCESS
 * SNMPERR_GENERR 
 */
int
create_user_from_session(netsnmp_session * session)
{
    struct usmUser *user;
    int             user_just_created = 0;
    char *cp;

    /*
     * - don't create-another/copy-into user for this session by default
     * - bail now (no error) if we don't have an engineID
     */
    if (SNMP_FLAGS_USER_CREATED == (session->flags & SNMP_FLAGS_USER_CREATED) ||
        session->securityModel != SNMP_SEC_MODEL_USM ||
        session->version != SNMP_VERSION_3 ||
        session->securityNameLen == 0 ||
        session->securityEngineIDLen == 0)
        return SNMPERR_SUCCESS;

    session->flags |= SNMP_FLAGS_USER_CREATED;

    /*
     * now that we have the engineID, create an entry in the USM list
     * for this user using the information in the session 
     */
    user = usm_get_user_from_list(session->securityEngineID,
                                  session->securityEngineIDLen,
                                  session->securityName,
                                  usm_get_userList(), 0);
    if (user == NULL) {
        DEBUGMSGTL(("snmp_api", "Building user %s...\n",
                    session->securityName));
        /*
         * user doesn't exist so we create and add it 
         */
        user = (struct usmUser *) calloc(1, sizeof(struct usmUser));
        if (user == NULL)
            return SNMPERR_GENERR;

        /*
         * copy in the securityName 
         */
        if (session->securityName) {
            user->name = strdup(session->securityName);
            user->secName = strdup(session->securityName);
            if (user->name == NULL || user->secName == NULL) {
                usm_free_user(user);
                return SNMPERR_GENERR;
            }
        }

        /*
         * copy in the engineID 
         */
        if (memdup(&user->engineID, session->securityEngineID,
                   session->securityEngineIDLen) != SNMPERR_SUCCESS) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
        user->engineIDLen = session->securityEngineIDLen;

        user_just_created = 1;
    }
    /*
     * copy the auth protocol 
     */
    if (session->securityAuthProto != NULL) {
        SNMP_FREE(user->authProtocol);
        user->authProtocol =
            snmp_duplicate_objid(session->securityAuthProto,
                                 session->securityAuthProtoLen);
        if (user->authProtocol == NULL) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
        user->authProtocolLen = session->securityAuthProtoLen;
    }

    /*
     * copy the priv protocol 
     */
    if (session->securityPrivProto != NULL) {
        SNMP_FREE(user->privProtocol);
        user->privProtocol =
            snmp_duplicate_objid(session->securityPrivProto,
                                 session->securityPrivProtoLen);
        if (user->privProtocol == NULL) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
        user->privProtocolLen = session->securityPrivProtoLen;
    }

    /*
     * copy in the authentication Key.  If not localized, localize it 
     */
    if (session->securityAuthLocalKey != NULL
        && session->securityAuthLocalKeyLen != 0) {
        /* already localized key passed in.  use it */
        SNMP_FREE(user->authKey);
        if (memdup(&user->authKey, session->securityAuthLocalKey,
                   session->securityAuthLocalKeyLen) != SNMPERR_SUCCESS) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
        user->authKeyLen = session->securityAuthLocalKeyLen;
    } else if (session->securityAuthKey != NULL
        && session->securityAuthKeyLen != 0) {
        SNMP_FREE(user->authKey);
        user->authKey = (u_char *) calloc(1, USM_LENGTH_KU_HASHBLOCK);
        if (user->authKey == NULL) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
        user->authKeyLen = USM_LENGTH_KU_HASHBLOCK;
        if (generate_kul(user->authProtocol, user->authProtocolLen,
                         session->securityEngineID,
                         session->securityEngineIDLen,
                         session->securityAuthKey,
                         session->securityAuthKeyLen, user->authKey,
                         &user->authKeyLen) != SNMPERR_SUCCESS) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
    } else if ((cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
                                           NETSNMP_DS_LIB_AUTHLOCALIZEDKEY))) {
        size_t buflen = USM_AUTH_KU_LEN;
        SNMP_FREE(user->authKey);
        user->authKey = malloc(buflen); /* max length needed */
        user->authKeyLen = 0;
        /* it will be a hex string */
        if (!snmp_hex_to_binary(&user->authKey, &buflen, &user->authKeyLen,
                                0, cp)) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
    }

    /*
     * copy in the privacy Key.  If not localized, localize it 
     */
    if (session->securityPrivLocalKey != NULL
        && session->securityPrivLocalKeyLen != 0) {
        /* already localized key passed in.  use it */
        SNMP_FREE(user->privKey);
        if (memdup(&user->privKey, session->securityPrivLocalKey,
                   session->securityPrivLocalKeyLen) != SNMPERR_SUCCESS) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
        user->privKeyLen = session->securityPrivLocalKeyLen;
    } else if (session->securityPrivKey != NULL
        && session->securityPrivKeyLen != 0) {
        SNMP_FREE(user->privKey);
        user->privKey = (u_char *) calloc(1, USM_LENGTH_KU_HASHBLOCK);
        if (user->privKey == NULL) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
        user->privKeyLen = USM_LENGTH_KU_HASHBLOCK;
        if (generate_kul(user->authProtocol, user->authProtocolLen,
                         session->securityEngineID,
                         session->securityEngineIDLen,
                         session->securityPrivKey,
                         session->securityPrivKeyLen, user->privKey,
                         &user->privKeyLen) != SNMPERR_SUCCESS) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
    } else if ((cp = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID, 
                                           NETSNMP_DS_LIB_PRIVLOCALIZEDKEY))) {
        size_t buflen = USM_PRIV_KU_LEN;
        SNMP_FREE(user->privKey);
        user->privKey = malloc(buflen); /* max length needed */
        user->privKeyLen = 0;
        /* it will be a hex string */
        if (!snmp_hex_to_binary(&user->privKey, &buflen, &user->privKeyLen,
                                0, cp)) {
            usm_free_user(user);
            return SNMPERR_GENERR;
        }
    }

    if (user_just_created) {
        /*
         * add the user into the database 
         */
        user->userStatus = RS_ACTIVE;
        user->userStorageType = ST_READONLY;
        usm_add_user(user);
    }

    return SNMPERR_SUCCESS;


}                               /* end create_user_from_session() */

/*
 *  Do a "deep free()" of a netsnmp_session.
 *
 *  CAUTION:  SHOULD ONLY BE USED FROM snmp_sess_close() OR SIMILAR.
 *                                                      (hence it is static)
 */

static void
snmp_free_session(netsnmp_session * s)
{
    if (s) {
        SNMP_FREE(s->peername);
        SNMP_FREE(s->community);
        SNMP_FREE(s->contextEngineID);
        SNMP_FREE(s->contextName);
        SNMP_FREE(s->securityEngineID);
        SNMP_FREE(s->securityName);
        SNMP_FREE(s->securityAuthProto);
        SNMP_FREE(s->securityPrivProto);

        /*
         * clear session from any callbacks
         */
        netsnmp_callback_clear_client_arg(s, 0, 0);

        free((char *) s);
    }
}

/*
 * Close the input session.  Frees all data allocated for the session,
 * dequeues any pending requests, and closes any sockets allocated for
 * the session.  Returns 0 on error, 1 otherwise.
 */
int
snmp_sess_close(void *sessp)
{
    struct session_list *slp = (struct session_list *) sessp;
    netsnmp_transport *transport;
    struct snmp_internal_session *isp;
    netsnmp_session *sesp = NULL;
    struct snmp_secmod_def *sptr;

    if (slp == NULL) {
        return 0;
    }

    if (slp->session != NULL &&
        (sptr = find_sec_mod(slp->session->securityModel)) != NULL &&
        sptr->session_close != NULL) {
        (*sptr->session_close) (slp->session);
    }

    isp = slp->internal;
    slp->internal = 0;

    if (isp) {
        netsnmp_request_list *rp, *orp;

        SNMP_FREE(isp->packet);

        /*
         * Free each element in the input request list.  
         */
        rp = isp->requests;
        while (rp) {
            orp = rp;
            rp = rp->next_request;
            snmp_free_pdu(orp->pdu);
            free((char *) orp);
        }

        free((char *) isp);
    }

    transport = slp->transport;
    slp->transport = 0;

    if (transport) {
        transport->f_close(transport);
        netsnmp_transport_free(transport);
    }

    sesp = slp->session;
    slp->session = 0;

    /*
     * The following is necessary to avoid memory leakage when closing AgentX 
     * sessions that may have multiple subsessions.  These hang off the main
     * session at ->subsession, and chain through ->next.  
     */

    if (sesp != NULL && sesp->subsession != NULL) {
        netsnmp_session *subsession = sesp->subsession, *tmpsub;

        while (subsession != NULL) {
            DEBUGMSGTL(("snmp_sess_close",
                        "closing session %p, subsession %p\n", sesp,
                        subsession));
            tmpsub = subsession->next;
            snmp_free_session(subsession);
            subsession = tmpsub;
        }
    }

    snmp_free_session(sesp);
    free((char *) slp);
    return 1;
}

int
snmp_close(netsnmp_session * session)
{
    struct session_list *slp = NULL, *oslp = NULL;

    {                           /*MTCRITICAL_RESOURCE */
        snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);
        if (Sessions && Sessions->session == session) { /* If first entry */
            slp = Sessions;
            Sessions = slp->next;
        } else {
            for (slp = Sessions; slp; slp = slp->next) {
                if (slp->session == session) {
                    if (oslp)   /* if we found entry that points here */
                        oslp->next = slp->next; /* link around this entry */
                    break;
                }
                oslp = slp;
            }
        }
        snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);
    }                           /*END MTCRITICAL_RESOURCE */
    if (slp == NULL) {
        return 0;
    }
    return snmp_sess_close((void *) slp);
}

int
snmp_close_sessions(void)
{
    struct session_list *slp;

    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);
    while (Sessions) {
        slp = Sessions;
        Sessions = Sessions->next;
        snmp_sess_close((void *) slp);
    }
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);
    return 1;
}

static int
snmpv3_build_probe_pdu(netsnmp_pdu **pdu)
{
    struct usmUser *user;

    /*
     * create the pdu 
     */
    if (!pdu)
        return -1;
    *pdu = snmp_pdu_create(SNMP_MSG_GET);
    if (!(*pdu))
        return -1;
    (*pdu)->version = SNMP_VERSION_3;
    (*pdu)->securityName = strdup("");
    (*pdu)->securityNameLen = strlen((*pdu)->securityName);
    (*pdu)->securityLevel = SNMP_SEC_LEVEL_NOAUTH;
    (*pdu)->securityModel = SNMP_SEC_MODEL_USM;

    /*
     * create the empty user 
     */
    user = usm_get_user(NULL, 0, (*pdu)->securityName);
    if (user == NULL) {
        user = (struct usmUser *) calloc(1, sizeof(struct usmUser));
        if (user == NULL) {
            snmp_free_pdu(*pdu);
            *pdu = (netsnmp_pdu *) NULL;
            return -1;
        }
        user->name = strdup((*pdu)->securityName);
        user->secName = strdup((*pdu)->securityName);
        user->authProtocolLen = sizeof(usmNoAuthProtocol) / sizeof(oid);
        user->authProtocol =
            snmp_duplicate_objid(usmNoAuthProtocol, user->authProtocolLen);
        user->privProtocolLen = sizeof(usmNoPrivProtocol) / sizeof(oid);
        user->privProtocol =
            snmp_duplicate_objid(usmNoPrivProtocol, user->privProtocolLen);
        usm_add_user(user);
    }
    return 0;
}

static void
snmpv3_calc_msg_flags(int sec_level, int msg_command, u_char * flags)
{
    *flags = 0;
    if (sec_level == SNMP_SEC_LEVEL_AUTHNOPRIV)
        *flags = SNMP_MSG_FLAG_AUTH_BIT;
    else if (sec_level == SNMP_SEC_LEVEL_AUTHPRIV)
        *flags = SNMP_MSG_FLAG_AUTH_BIT | SNMP_MSG_FLAG_PRIV_BIT;

    if (SNMP_CMD_CONFIRMED(msg_command))
        *flags |= SNMP_MSG_FLAG_RPRT_BIT;

    return;
}

static int
snmpv3_verify_msg(netsnmp_request_list *rp, netsnmp_pdu *pdu)
{
    netsnmp_pdu    *rpdu;

    if (!rp || !rp->pdu || !pdu)
        return 0;
    /*
     * Reports don't have to match anything according to the spec 
     */
    if (pdu->command == SNMP_MSG_REPORT)
        return 1;
    rpdu = rp->pdu;
    if (rp->request_id != pdu->reqid || rpdu->reqid != pdu->reqid)
        return 0;
    if (rpdu->version != pdu->version)
        return 0;
    if (rpdu->securityModel != pdu->securityModel)
        return 0;
    if (rpdu->securityLevel != pdu->securityLevel)
        return 0;

    if (rpdu->contextEngineIDLen != pdu->contextEngineIDLen ||
        memcmp(rpdu->contextEngineID, pdu->contextEngineID,
               pdu->contextEngineIDLen))
        return 0;
    if (rpdu->contextNameLen != pdu->contextNameLen ||
        memcmp(rpdu->contextName, pdu->contextName, pdu->contextNameLen))
        return 0;
    if (rpdu->securityEngineIDLen != pdu->securityEngineIDLen ||
        memcmp(rpdu->securityEngineID, pdu->securityEngineID,
               pdu->securityEngineIDLen))
        return 0;
    if (rpdu->securityNameLen != pdu->securityNameLen ||
        memcmp(rpdu->securityName, pdu->securityName,
               pdu->securityNameLen))
        return 0;
    return 1;
}


/*
 * SNMPv3
 * * Takes a session and a pdu and serializes the ASN PDU into the area
 * * pointed to by packet.  out_length is the size of the data area available.
 * * Returns the length of the completed packet in out_length.  If any errors
 * * occur, -1 is returned.  If all goes well, 0 is returned.
 */
static int
snmpv3_build(u_char ** pkt, size_t * pkt_len, size_t * offset,
             netsnmp_session * session, netsnmp_pdu *pdu)
{
    int             ret;

    session->s_snmp_errno = 0;
    session->s_errno = 0;

    /*
     * do validation for PDU types 
     */
    switch (pdu->command) {
    case SNMP_MSG_RESPONSE:
    case SNMP_MSG_TRAP2:
    case SNMP_MSG_REPORT:
        netsnmp_assert(0 == (pdu->flags & UCD_MSG_FLAG_EXPECT_RESPONSE));
        /*
         * Fallthrough 
         */
    case SNMP_MSG_GET:
    case SNMP_MSG_GETNEXT:
    case SNMP_MSG_SET:
    case SNMP_MSG_INFORM:
        if (pdu->errstat == SNMP_DEFAULT_ERRSTAT)
            pdu->errstat = 0;
        if (pdu->errindex == SNMP_DEFAULT_ERRINDEX)
            pdu->errindex = 0;
        break;

    case SNMP_MSG_GETBULK:
        if (pdu->max_repetitions < 0) {
            session->s_snmp_errno = SNMPERR_BAD_REPETITIONS;
            return -1;
        }
        if (pdu->non_repeaters < 0) {
            session->s_snmp_errno = SNMPERR_BAD_REPEATERS;
            return -1;
        }
        break;

    case SNMP_MSG_TRAP:
        session->s_snmp_errno = SNMPERR_V1_IN_V2;
        return -1;

    default:
        session->s_snmp_errno = SNMPERR_UNKNOWN_PDU;
        return -1;
    }

    /* Do we need to set the session security engineid? */
    if (pdu->securityEngineIDLen == 0) {
        if (session->securityEngineIDLen) {
            snmpv3_clone_engineID(&pdu->securityEngineID,
                                  &pdu->securityEngineIDLen,
                                  session->securityEngineID,
                                  session->securityEngineIDLen);
        }
    }
    
    /* Do we need to set the session context engineid? */
    if (pdu->contextEngineIDLen == 0) {
        if (session->contextEngineIDLen) {
            snmpv3_clone_engineID(&pdu->contextEngineID,
                                  &pdu->contextEngineIDLen,
                                  session->contextEngineID,
                                  session->contextEngineIDLen);
        } else if (pdu->securityEngineIDLen) {
            snmpv3_clone_engineID(&pdu->contextEngineID,
                                  &pdu->contextEngineIDLen,
                                  pdu->securityEngineID,
                                  pdu->securityEngineIDLen);
        }
    }

    if (pdu->contextName == NULL) {
        if (!session->contextName) {
            session->s_snmp_errno = SNMPERR_BAD_CONTEXT;
            return -1;
        }
        pdu->contextName = strdup(session->contextName);
        if (pdu->contextName == NULL) {
            session->s_snmp_errno = SNMPERR_GENERR;
            return -1;
        }
        pdu->contextNameLen = session->contextNameLen;
    }
    if (pdu->securityModel == SNMP_DEFAULT_SECMODEL) {
        pdu->securityModel = session->securityModel;
        if (pdu->securityModel == SNMP_DEFAULT_SECMODEL) {
            pdu->securityModel = SNMP_SEC_MODEL_USM;
        }
    }
    if (pdu->securityNameLen == 0 && pdu->securityName == 0) {
        if (session->securityNameLen == 0) {
            session->s_snmp_errno = SNMPERR_BAD_SEC_NAME;
            return -1;
        }
        pdu->securityName = strdup(session->securityName);
        if (pdu->securityName == NULL) {
            session->s_snmp_errno = SNMPERR_GENERR;
            return -1;
        }
        pdu->securityNameLen = session->securityNameLen;
    }
    if (pdu->securityLevel == 0) {
        if (session->securityLevel == 0) {
            session->s_snmp_errno = SNMPERR_BAD_SEC_LEVEL;
            return -1;
        }
        pdu->securityLevel = session->securityLevel;
    }
    DEBUGMSGTL(("snmp_build",
                "Building SNMPv3 message (secName:\"%s\", secLevel:%s)...\n",
                ((session->securityName) ? (char *) session->securityName :
                 ((pdu->securityName) ? (char *) pdu->securityName :
                  "ERROR: undefined")), secLevelName[pdu->securityLevel]));

    DEBUGDUMPSECTION("send", "SNMPv3 Message");
#ifdef USE_REVERSE_ASNENCODING
    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_REVERSE_ENCODE)) {
        ret = snmpv3_packet_realloc_rbuild(pkt, pkt_len, offset,
                                           session, pdu, NULL, 0);
    } else {
#endif
        ret = snmpv3_packet_build(session, pdu, *pkt, pkt_len, NULL, 0);
#ifdef USE_REVERSE_ASNENCODING
    }
#endif
    DEBUGINDENTLESS();
    if (-1 != ret) {
        session->s_snmp_errno = ret;
    }

    return ret;

}                               /* end snmpv3_build() */




static u_char  *
snmpv3_header_build(netsnmp_session * session, netsnmp_pdu *pdu,
                    u_char * packet, size_t * out_length,
                    size_t length, u_char ** msg_hdr_e)
{
    u_char         *global_hdr, *global_hdr_e;
    u_char         *cp;
    u_char          msg_flags;
    long            max_size;
    long            sec_model;
    u_char         *pb, *pb0e;

    /*
     * Save current location and build SEQUENCE tag and length placeholder
     * * for SNMP message sequence (actual length inserted later)
     */
    cp = asn_build_sequence(packet, out_length,
                            (u_char) (ASN_SEQUENCE | ASN_CONSTRUCTOR),
                            length);
    if (cp == NULL)
        return NULL;
    if (msg_hdr_e != NULL)
        *msg_hdr_e = cp;
    pb0e = cp;


    /*
     * store the version field - msgVersion
     */
    DEBUGDUMPHEADER("send", "SNMP Version Number");
    cp = asn_build_int(cp, out_length,
                       (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                 ASN_INTEGER), (long *) &pdu->version,
                       sizeof(pdu->version));
    DEBUGINDENTLESS();
    if (cp == NULL)
        return NULL;

    global_hdr = cp;
    /*
     * msgGlobalData HeaderData 
     */
    DEBUGDUMPSECTION("send", "msgGlobalData");
    cp = asn_build_sequence(cp, out_length,
                            (u_char) (ASN_SEQUENCE | ASN_CONSTRUCTOR), 0);
    if (cp == NULL)
        return NULL;
    global_hdr_e = cp;


    /*
     * msgID 
     */
    DEBUGDUMPHEADER("send", "msgID");
    cp = asn_build_int(cp, out_length,
                       (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                 ASN_INTEGER), &pdu->msgid,
                       sizeof(pdu->msgid));
    DEBUGINDENTLESS();
    if (cp == NULL)
        return NULL;

    /*
     * msgMaxSize 
     */
    max_size = session->rcvMsgMaxSize;
    DEBUGDUMPHEADER("send", "msgMaxSize");
    cp = asn_build_int(cp, out_length,
                       (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                 ASN_INTEGER), &max_size,
                       sizeof(max_size));
    DEBUGINDENTLESS();
    if (cp == NULL)
        return NULL;

    /*
     * msgFlags 
     */
    snmpv3_calc_msg_flags(pdu->securityLevel, pdu->command, &msg_flags);
    DEBUGDUMPHEADER("send", "msgFlags");
    cp = asn_build_string(cp, out_length,
                          (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                    ASN_OCTET_STR), &msg_flags,
                          sizeof(msg_flags));
    DEBUGINDENTLESS();
    if (cp == NULL)
        return NULL;

    /*
     * msgSecurityModel 
     */
    sec_model = pdu->securityModel;
    DEBUGDUMPHEADER("send", "msgSecurityModel");
    cp = asn_build_int(cp, out_length,
                       (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                 ASN_INTEGER), &sec_model,
                       sizeof(sec_model));
    DEBUGINDENTADD(-4);         /* return from global data indent */
    if (cp == NULL)
        return NULL;


    /*
     * insert actual length of globalData
     */
    pb = asn_build_sequence(global_hdr, out_length,
                            (u_char) (ASN_SEQUENCE | ASN_CONSTRUCTOR),
                            cp - global_hdr_e);
    if (pb == NULL)
        return NULL;


    /*
     * insert the actual length of the entire packet
     */
    pb = asn_build_sequence(packet, out_length,
                            (u_char) (ASN_SEQUENCE | ASN_CONSTRUCTOR),
                            length + (cp - pb0e));
    if (pb == NULL)
        return NULL;

    return cp;

}                               /* end snmpv3_header_build() */

#ifdef USE_REVERSE_ASNENCODING

int
snmpv3_header_realloc_rbuild(u_char ** pkt, size_t * pkt_len,
                             size_t * offset, netsnmp_session * session,
                             netsnmp_pdu *pdu)
{
    size_t          start_offset = *offset;
    u_char          msg_flags;
    long            max_size, sec_model;
    int             rc = 0;

    /*
     * msgSecurityModel.  
     */
    sec_model = pdu->securityModel;
    DEBUGDUMPHEADER("send", "msgSecurityModel");
    rc = asn_realloc_rbuild_int(pkt, pkt_len, offset, 1,
                                (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                          ASN_INTEGER), &sec_model,
                                sizeof(sec_model));
    DEBUGINDENTLESS();
    if (rc == 0) {
        return 0;
    }

    /*
     * msgFlags.  
     */
    snmpv3_calc_msg_flags(pdu->securityLevel, pdu->command, &msg_flags);
    DEBUGDUMPHEADER("send", "msgFlags");
    rc = asn_realloc_rbuild_string(pkt, pkt_len, offset, 1,
                                   (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE
                                             | ASN_OCTET_STR), &msg_flags,
                                   sizeof(msg_flags));
    DEBUGINDENTLESS();
    if (rc == 0) {
        return 0;
    }

    /*
     * msgMaxSize.  
     */
    max_size = session->rcvMsgMaxSize;
    DEBUGDUMPHEADER("send", "msgMaxSize");
    rc = asn_realloc_rbuild_int(pkt, pkt_len, offset, 1,
                                (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                          ASN_INTEGER), &max_size,
                                sizeof(max_size));
    DEBUGINDENTLESS();
    if (rc == 0) {
        return 0;
    }

    /*
     * msgID.  
     */
    DEBUGDUMPHEADER("send", "msgID");
    rc = asn_realloc_rbuild_int(pkt, pkt_len, offset, 1,
                                (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                          ASN_INTEGER), &pdu->msgid,
                                sizeof(pdu->msgid));
    DEBUGINDENTLESS();
    if (rc == 0) {
        return 0;
    }

    /*
     * Global data sequence.  
     */
    rc = asn_realloc_rbuild_sequence(pkt, pkt_len, offset, 1,
                                     (u_char) (ASN_SEQUENCE |
                                               ASN_CONSTRUCTOR),
                                     *offset - start_offset);
    if (rc == 0) {
        return 0;
    }

    /*
     * Store the version field - msgVersion.  
     */
    DEBUGDUMPHEADER("send", "SNMP Version Number");
    rc = asn_realloc_rbuild_int(pkt, pkt_len, offset, 1,
                                (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                          ASN_INTEGER),
                                (long *) &pdu->version,
                                sizeof(pdu->version));
    DEBUGINDENTLESS();
    return rc;
}                               /* end snmpv3_header_realloc_rbuild() */
#endif                          /* USE_REVERSE_ASNENCODING */

static u_char  *
snmpv3_scopedPDU_header_build(netsnmp_pdu *pdu,
                              u_char * packet, size_t * out_length,
                              u_char ** spdu_e)
{
    size_t          init_length;
    u_char         *scopedPdu, *pb;


    init_length = *out_length;

    pb = scopedPdu = packet;
    pb = asn_build_sequence(pb, out_length,
                            (u_char) (ASN_SEQUENCE | ASN_CONSTRUCTOR), 0);
    if (pb == NULL)
        return NULL;
    if (spdu_e)
        *spdu_e = pb;

    DEBUGDUMPHEADER("send", "contextEngineID");
    pb = asn_build_string(pb, out_length,
                          (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_OCTET_STR),
                          pdu->contextEngineID, pdu->contextEngineIDLen);
    DEBUGINDENTLESS();
    if (pb == NULL)
        return NULL;

    DEBUGDUMPHEADER("send", "contextName");
    pb = asn_build_string(pb, out_length,
                          (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_OCTET_STR),
                          (u_char *) pdu->contextName,
                          pdu->contextNameLen);
    DEBUGINDENTLESS();
    if (pb == NULL)
        return NULL;

    return pb;

}                               /* end snmpv3_scopedPDU_header_build() */


#ifdef USE_REVERSE_ASNENCODING
int
snmpv3_scopedPDU_header_realloc_rbuild(u_char ** pkt, size_t * pkt_len,
                                       size_t * offset, netsnmp_pdu *pdu,
                                       size_t body_len)
{
    size_t          start_offset = *offset;
    int             rc = 0;

    /*
     * contextName.  
     */
    DEBUGDUMPHEADER("send", "contextName");
    rc = asn_realloc_rbuild_string(pkt, pkt_len, offset, 1,
                                   (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE
                                             | ASN_OCTET_STR),
                                   (u_char *) pdu->contextName,
                                   pdu->contextNameLen);
    DEBUGINDENTLESS();
    if (rc == 0) {
        return 0;
    }

    /*
     * contextEngineID.  
     */
    DEBUGDUMPHEADER("send", "contextEngineID");
    rc = asn_realloc_rbuild_string(pkt, pkt_len, offset, 1,
                                   (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE
                                             | ASN_OCTET_STR),
                                   pdu->contextEngineID,
                                   pdu->contextEngineIDLen);
    DEBUGINDENTLESS();
    if (rc == 0) {
        return 0;
    }

    rc = asn_realloc_rbuild_sequence(pkt, pkt_len, offset, 1,
                                     (u_char) (ASN_SEQUENCE |
                                               ASN_CONSTRUCTOR),
                                     *offset - start_offset + body_len);

    return rc;
}                               /* end snmpv3_scopedPDU_header_realloc_rbuild() */
#endif                          /* USE_REVERSE_ASNENCODING */

#ifdef USE_REVERSE_ASNENCODING
/*
 * returns 0 if success, -1 if fail, not 0 if SM build failure 
 */
int
snmpv3_packet_realloc_rbuild(u_char ** pkt, size_t * pkt_len,
                             size_t * offset, netsnmp_session * session,
                             netsnmp_pdu *pdu, u_char * pdu_data,
                             size_t pdu_data_len)
{
    u_char         *scoped_pdu, *hdrbuf = NULL, *hdr = NULL;
    size_t          hdrbuf_len = SNMP_MAX_MSG_V3_HDRS, hdr_offset =
        0, spdu_offset = 0;
    size_t          body_end_offset = *offset, body_len = 0;
    struct snmp_secmod_def *sptr = NULL;
    int             rc = 0;

    /*
     * Build a scopedPDU structure into the packet buffer.  
     */
    DEBUGPRINTPDUTYPE("send", pdu->command);
    if (pdu_data) {
        while ((*pkt_len - *offset) < pdu_data_len) {
            if (!asn_realloc(pkt, pkt_len)) {
                return -1;
            }
        }

        *offset += pdu_data_len;
        memcpy(*pkt + *pkt_len - *offset, pdu_data, pdu_data_len);
    } else {
        rc = snmp_pdu_realloc_rbuild(pkt, pkt_len, offset, pdu);
        if (rc == 0) {
            return -1;
        }
    }
    body_len = *offset - body_end_offset;

    DEBUGDUMPSECTION("send", "ScopedPdu");
    rc = snmpv3_scopedPDU_header_realloc_rbuild(pkt, pkt_len, offset,
                                                pdu, body_len);
    if (rc == 0) {
        return -1;
    }
    spdu_offset = *offset;
    DEBUGINDENTADD(-4);         /*  Return from Scoped PDU.  */

    if ((hdrbuf = (u_char *) malloc(hdrbuf_len)) == NULL) {
        return -1;
    }

    rc = snmpv3_header_realloc_rbuild(&hdrbuf, &hdrbuf_len, &hdr_offset,
                                      session, pdu);
    if (rc == 0) {
        SNMP_FREE(hdrbuf);
        return -1;
    }
    hdr = hdrbuf + hdrbuf_len - hdr_offset;
    scoped_pdu = *pkt + *pkt_len - spdu_offset;

    /*
     * Call the security module to possibly encrypt and authenticate the
     * message---the entire message to transmitted on the wire is returned.  
     */

    sptr = find_sec_mod(pdu->securityModel);
    DEBUGDUMPSECTION("send", "SM msgSecurityParameters");
    if (sptr && sptr->encode_reverse) {
        struct snmp_secmod_outgoing_params parms;

        parms.msgProcModel = pdu->msgParseModel;
        parms.globalData = hdr;
        parms.globalDataLen = hdr_offset;
        parms.maxMsgSize = SNMP_MAX_MSG_SIZE;
        parms.secModel = pdu->securityModel;
        parms.secEngineID = pdu->securityEngineID;
        parms.secEngineIDLen = pdu->securityEngineIDLen;
        parms.secName = pdu->securityName;
        parms.secNameLen = pdu->securityNameLen;
        parms.secLevel = pdu->securityLevel;
        parms.scopedPdu = scoped_pdu;
        parms.scopedPduLen = spdu_offset;
        parms.secStateRef = pdu->securityStateRef;
        parms.wholeMsg = pkt;
        parms.wholeMsgLen = pkt_len;
        parms.wholeMsgOffset = offset;
        parms.session = session;
        parms.pdu = pdu;

        rc = (*sptr->encode_reverse) (&parms);
    } else {
        if (!sptr) {
            snmp_log(LOG_ERR,
                     "no such security service available: %d\n",
                     pdu->securityModel);
        } else if (!sptr->encode_reverse) {
            snmp_log(LOG_ERR,
                     "security service %d doesn't support reverse encoding.\n",
                     pdu->securityModel);
        }
        rc = -1;
    }

    DEBUGINDENTLESS();
    SNMP_FREE(hdrbuf);
    return rc;
}                               /* end snmpv3_packet_realloc_rbuild() */
#endif                          /* USE_REVERSE_ASNENCODING */

/*
 * returns 0 if success, -1 if fail, not 0 if SM build failure 
 */
int
snmpv3_packet_build(netsnmp_session * session, netsnmp_pdu *pdu,
                    u_char * packet, size_t * out_length,
                    u_char * pdu_data, size_t pdu_data_len)
{
    u_char         *global_data, *sec_params, *spdu_hdr_e;
    size_t          global_data_len, sec_params_len;
    u_char          spdu_buf[SNMP_MAX_MSG_SIZE];
    size_t          spdu_buf_len, spdu_len;
    u_char         *cp;
    int             result;
    struct snmp_secmod_def *sptr;

    global_data = packet;

    /*
     * build the headers for the packet, returned addr = start of secParams
     */
    sec_params = snmpv3_header_build(session, pdu, global_data,
                                     out_length, 0, NULL);
    if (sec_params == NULL)
        return -1;
    global_data_len = sec_params - global_data;
    sec_params_len = *out_length;       /* length left in packet buf for sec_params */


    /*
     * build a scopedPDU structure into spdu_buf
     */
    spdu_buf_len = SNMP_MAX_MSG_SIZE;
    DEBUGDUMPSECTION("send", "ScopedPdu");
    cp = snmpv3_scopedPDU_header_build(pdu, spdu_buf, &spdu_buf_len,
                                       &spdu_hdr_e);
    if (cp == NULL)
        return -1;

    /*
     * build the PDU structure onto the end of spdu_buf 
     */
    DEBUGPRINTPDUTYPE("send", ((pdu_data) ? *pdu_data : 0x00));
    if (pdu_data) {
        memcpy(cp, pdu_data, pdu_data_len);
        cp += pdu_data_len;
    } else {
        cp = snmp_pdu_build(pdu, cp, &spdu_buf_len);
        if (cp == NULL)
            return -1;
    }
    DEBUGINDENTADD(-4);         /* return from Scoped PDU */

    /*
     * re-encode the actual ASN.1 length of the scopedPdu
     */
    spdu_len = cp - spdu_hdr_e; /* length of scopedPdu minus ASN.1 headers */
    spdu_buf_len = SNMP_MAX_MSG_SIZE;
    if (asn_build_sequence(spdu_buf, &spdu_buf_len,
                           (u_char) (ASN_SEQUENCE | ASN_CONSTRUCTOR),
                           spdu_len) == NULL)
        return -1;
    spdu_len = cp - spdu_buf;   /* the length of the entire scopedPdu */


    /*
     * call the security module to possibly encrypt and authenticate the
     * message - the entire message to transmitted on the wire is returned
     */
    cp = NULL;
    *out_length = SNMP_MAX_MSG_SIZE;
    DEBUGDUMPSECTION("send", "SM msgSecurityParameters");
    sptr = find_sec_mod(pdu->securityModel);
    if (sptr && sptr->encode_forward) {
        struct snmp_secmod_outgoing_params parms;
        parms.msgProcModel = pdu->msgParseModel;
        parms.globalData = global_data;
        parms.globalDataLen = global_data_len;
        parms.maxMsgSize = SNMP_MAX_MSG_SIZE;
        parms.secModel = pdu->securityModel;
        parms.secEngineID = pdu->securityEngineID;
        parms.secEngineIDLen = pdu->securityEngineIDLen;
        parms.secName = pdu->securityName;
        parms.secNameLen = pdu->securityNameLen;
        parms.secLevel = pdu->securityLevel;
        parms.scopedPdu = spdu_buf;
        parms.scopedPduLen = spdu_len;
        parms.secStateRef = pdu->securityStateRef;
        parms.secParams = sec_params;
        parms.secParamsLen = &sec_params_len;
        parms.wholeMsg = &cp;
        parms.wholeMsgLen = out_length;
        parms.session = session;
        parms.pdu = pdu;
        result = (*sptr->encode_forward) (&parms);
    } else {
        if (!sptr) {
            snmp_log(LOG_ERR, "no such security service available: %d\n",
                     pdu->securityModel);
        } else if (!sptr->encode_forward) {
            snmp_log(LOG_ERR,
                     "security service %d doesn't support forward out encoding.\n",
                     pdu->securityModel);
        }
        result = -1;
    }
    DEBUGINDENTLESS();
    return result;

}                               /* end snmpv3_packet_build() */


/*
 * Takes a session and a pdu and serializes the ASN PDU into the area
 * pointed to by *pkt.  *pkt_len is the size of the data area available.
 * Returns the length of the completed packet in *offset.  If any errors
 * occur, -1 is returned.  If all goes well, 0 is returned.
 */

static int
_snmp_build(u_char ** pkt, size_t * pkt_len, size_t * offset,
            netsnmp_session * session, netsnmp_pdu *pdu)
{
#if !defined(DISABLE_SNMPV1) || !defined(DISABLE_SNMPV2C)
    u_char         *h0e = 0;
    size_t          start_offset = *offset;
    long            version;
    int             rc = 0;
#endif /* support for community based SNMP */
    
    u_char         *h0, *h1;
    u_char         *cp;
    size_t          length;

    session->s_snmp_errno = 0;
    session->s_errno = 0;

    if (pdu->version == SNMP_VERSION_3) {
        return snmpv3_build(pkt, pkt_len, offset, session, pdu);
    }

    switch (pdu->command) {
    case SNMP_MSG_RESPONSE:
        netsnmp_assert(0 == (pdu->flags & UCD_MSG_FLAG_EXPECT_RESPONSE));
        /*
         * Fallthrough 
         */
    case SNMP_MSG_GET:
    case SNMP_MSG_GETNEXT:
    case SNMP_MSG_SET:
        /*
         * all versions support these PDU types 
         */
        /*
         * initialize defaulted PDU fields 
         */

        if (pdu->errstat == SNMP_DEFAULT_ERRSTAT)
            pdu->errstat = 0;
        if (pdu->errindex == SNMP_DEFAULT_ERRINDEX)
            pdu->errindex = 0;
        break;

    case SNMP_MSG_TRAP2:
        netsnmp_assert(0 == (pdu->flags & UCD_MSG_FLAG_EXPECT_RESPONSE));
        /*
         * Fallthrough 
         */
    case SNMP_MSG_INFORM:
#ifndef DISABLE_SNMPV1
        /*
         * not supported in SNMPv1 and SNMPsec 
         */
        if (pdu->version == SNMP_VERSION_1) {
            session->s_snmp_errno = SNMPERR_V2_IN_V1;
            return -1;
        }
#endif
        if (pdu->errstat == SNMP_DEFAULT_ERRSTAT)
            pdu->errstat = 0;
        if (pdu->errindex == SNMP_DEFAULT_ERRINDEX)
            pdu->errindex = 0;
        break;

    case SNMP_MSG_GETBULK:
        /*
         * not supported in SNMPv1 and SNMPsec 
         */
#ifndef DISABLE_SNMPV1
        if (pdu->version == SNMP_VERSION_1) {
            session->s_snmp_errno = SNMPERR_V2_IN_V1;
            return -1;
        }
#endif
        if (pdu->max_repetitions < 0) {
            session->s_snmp_errno = SNMPERR_BAD_REPETITIONS;
            return -1;
        }
        if (pdu->non_repeaters < 0) {
            session->s_snmp_errno = SNMPERR_BAD_REPEATERS;
            return -1;
        }
        break;

    case SNMP_MSG_TRAP:
        /*
         * *only* supported in SNMPv1 and SNMPsec 
         */
#ifndef DISABLE_SNMPV1
        if (pdu->version != SNMP_VERSION_1) {
            session->s_snmp_errno = SNMPERR_V1_IN_V2;
            return -1;
        }
#endif
        /*
         * initialize defaulted Trap PDU fields 
         */
        pdu->reqid = 1;         /* give a bogus non-error reqid for traps */
        if (pdu->enterprise_length == SNMP_DEFAULT_ENTERPRISE_LENGTH) {
            pdu->enterprise = (oid *) malloc(sizeof(DEFAULT_ENTERPRISE));
            if (pdu->enterprise == NULL) {
                session->s_snmp_errno = SNMPERR_MALLOC;
                return -1;
            }
            memmove(pdu->enterprise, DEFAULT_ENTERPRISE,
                    sizeof(DEFAULT_ENTERPRISE));
            pdu->enterprise_length =
                sizeof(DEFAULT_ENTERPRISE) / sizeof(oid);
        }
        if (pdu->time == SNMP_DEFAULT_TIME)
            pdu->time = DEFAULT_TIME;
        /*
         * don't expect a response 
         */
        pdu->flags &= (~UCD_MSG_FLAG_EXPECT_RESPONSE);
        break;

    case SNMP_MSG_REPORT:      /* SNMPv3 only */
    default:
        session->s_snmp_errno = SNMPERR_UNKNOWN_PDU;
        return -1;
    }

    /*
     * save length 
     */
    length = *pkt_len;

    /*
     * setup administrative fields based on version 
     */
    /*
     * build the message wrapper and all the administrative fields
     * upto the PDU sequence
     * (note that actual length of message will be inserted later) 
     */
    h0 = *pkt;
    switch (pdu->version) {
#ifndef DISABLE_SNMPV1
    case SNMP_VERSION_1:
#endif
#ifndef DISABLE_SNMPV2C
    case SNMP_VERSION_2c:
#endif
#if !defined(DISABLE_SNMPV1) || !defined(DISABLE_SNMPV2C)
#ifdef NO_ZEROLENGTH_COMMUNITY
        if (pdu->community_len == 0) {
            if (session->community_len == 0) {
                session->s_snmp_errno = SNMPERR_BAD_COMMUNITY;
                return -1;
            }
            pdu->community = (u_char *) malloc(session->community_len);
            if (pdu->community == NULL) {
                session->s_snmp_errno = SNMPERR_MALLOC;
                return -1;
            }
            memmove(pdu->community,
                    session->community, session->community_len);
            pdu->community_len = session->community_len;
        }
#else                           /* !NO_ZEROLENGTH_COMMUNITY */
        if (pdu->community_len == 0 && pdu->command != SNMP_MSG_RESPONSE) {
            /*
             * copy session community exactly to pdu community 
             */
            if (0 == session->community_len) {
                SNMP_FREE(pdu->community);
                pdu->community = NULL;
            } else if (pdu->community_len == session->community_len) {
                memmove(pdu->community,
                        session->community, session->community_len);
            } else {
                SNMP_FREE(pdu->community);
                pdu->community = (u_char *) malloc(session->community_len);
                if (pdu->community == NULL) {
                    session->s_snmp_errno = SNMPERR_MALLOC;
                    return -1;
                }
                memmove(pdu->community,
                        session->community, session->community_len);
            }
            pdu->community_len = session->community_len;
        }
#endif                          /* !NO_ZEROLENGTH_COMMUNITY */

        DEBUGMSGTL(("snmp_send", "Building SNMPv%d message...\n",
                    (1 + pdu->version)));
#ifdef USE_REVERSE_ASNENCODING
        if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_REVERSE_ENCODE)) {
            DEBUGPRINTPDUTYPE("send", pdu->command);
            rc = snmp_pdu_realloc_rbuild(pkt, pkt_len, offset, pdu);
            if (rc == 0) {
                return -1;
            }

            DEBUGDUMPHEADER("send", "Community String");
            rc = asn_realloc_rbuild_string(pkt, pkt_len, offset, 1,
                                           (u_char) (ASN_UNIVERSAL |
                                                     ASN_PRIMITIVE |
                                                     ASN_OCTET_STR),
                                           pdu->community,
                                           pdu->community_len);
            DEBUGINDENTLESS();
            if (rc == 0) {
                return -1;
            }


            /*
             * Store the version field.  
             */
            DEBUGDUMPHEADER("send", "SNMP Version Number");

            version = pdu->version;
            rc = asn_realloc_rbuild_int(pkt, pkt_len, offset, 1,
                                        (u_char) (ASN_UNIVERSAL |
                                                  ASN_PRIMITIVE |
                                                  ASN_INTEGER),
                                        (long *) &version,
                                        sizeof(version));
            DEBUGINDENTLESS();
            if (rc == 0) {
                return -1;
            }

            /*
             * Build the final sequence.  
             */
            if (pdu->version == SNMP_VERSION_1) {
                DEBUGDUMPSECTION("send", "SNMPv1 Message");
            } else {
                DEBUGDUMPSECTION("send", "SNMPv2c Message");
            }
            rc = asn_realloc_rbuild_sequence(pkt, pkt_len, offset, 1,
                                             (u_char) (ASN_SEQUENCE |
                                                       ASN_CONSTRUCTOR),
                                             *offset - start_offset);
            DEBUGINDENTLESS();

            if (rc == 0) {
                return -1;
            }
            return 0;
        } else {

#endif                          /* USE_REVERSE_ASNENCODING */
            /*
             * Save current location and build SEQUENCE tag and length
             * placeholder for SNMP message sequence
             * (actual length will be inserted later) 
             */
            cp = asn_build_sequence(*pkt, pkt_len,
                                    (u_char) (ASN_SEQUENCE |
                                              ASN_CONSTRUCTOR), 0);
            if (cp == NULL) {
                return -1;
            }
            h0e = cp;

            if (pdu->version == SNMP_VERSION_1) {
                DEBUGDUMPSECTION("send", "SNMPv1 Message");
            } else {
                DEBUGDUMPSECTION("send", "SNMPv2c Message");
            }

            /*
             * store the version field 
             */
            DEBUGDUMPHEADER("send", "SNMP Version Number");

            version = pdu->version;
            cp = asn_build_int(cp, pkt_len,
                               (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                         ASN_INTEGER), (long *) &version,
                               sizeof(version));
            DEBUGINDENTLESS();
            if (cp == NULL)
                return -1;

            /*
             * store the community string 
             */
            DEBUGDUMPHEADER("send", "Community String");
            cp = asn_build_string(cp, pkt_len,
                                  (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                            ASN_OCTET_STR), pdu->community,
                                  pdu->community_len);
            DEBUGINDENTLESS();
            if (cp == NULL)
                return -1;
            break;

#ifdef USE_REVERSE_ASNENCODING
        }
#endif                          /* USE_REVERSE_ASNENCODING */
        break;
#endif /* support for community based SNMP */
    case SNMP_VERSION_2p:
    case SNMP_VERSION_sec:
    case SNMP_VERSION_2u:
    case SNMP_VERSION_2star:
    default:
        session->s_snmp_errno = SNMPERR_BAD_VERSION;
        return -1;
    }

    h1 = cp;
    DEBUGPRINTPDUTYPE("send", pdu->command);
    cp = snmp_pdu_build(pdu, cp, pkt_len);
    DEBUGINDENTADD(-4);         /* return from entire v1/v2c message */
    if (cp == NULL)
        return -1;

    /*
     * insert the actual length of the message sequence 
     */
    switch (pdu->version) {
#ifndef DISABLE_SNMPV1
    case SNMP_VERSION_1:
#endif
#ifndef DISABLE_SNMPV2C
    case SNMP_VERSION_2c:
#endif
#if !defined(DISABLE_SNMPV1) || !defined(DISABLE_SNMPV2C)
        asn_build_sequence(*pkt, &length,
                           (u_char) (ASN_SEQUENCE | ASN_CONSTRUCTOR),
                           cp - h0e);
        break;
#endif /* support for community based SNMP */

    case SNMP_VERSION_2p:
    case SNMP_VERSION_sec:
    case SNMP_VERSION_2u:
    case SNMP_VERSION_2star:
    default:
        session->s_snmp_errno = SNMPERR_BAD_VERSION;
        return -1;
    }
    *pkt_len = cp - *pkt;
    return 0;
}

int
snmp_build(u_char ** pkt, size_t * pkt_len, size_t * offset,
           netsnmp_session * pss, netsnmp_pdu *pdu)
{
    int             rc;
    rc = _snmp_build(pkt, pkt_len, offset, pss, pdu);
    if (rc) {
        if (!pss->s_snmp_errno) {
            snmp_log( LOG_ERR, "snmp_build: unknown failure");
            pss->s_snmp_errno = SNMPERR_BAD_ASN1_BUILD;
        }
        SET_SNMP_ERROR(pss->s_snmp_errno);
        rc = -1;
    }
    return rc;
}

/*
 * on error, returns NULL (likely an encoding problem). 
 */
u_char         *
snmp_pdu_build(netsnmp_pdu *pdu, u_char * cp, size_t * out_length)
{
    u_char         *h1, *h1e, *h2, *h2e;
    netsnmp_variable_list *vp;
    size_t          length;

    length = *out_length;
    /*
     * Save current location and build PDU tag and length placeholder
     * (actual length will be inserted later) 
     */
    h1 = cp;
    cp = asn_build_sequence(cp, out_length, (u_char) pdu->command, 0);
    if (cp == NULL)
        return NULL;
    h1e = cp;

    /*
     * store fields in the PDU preceeding the variable-bindings sequence 
     */
    if (pdu->command != SNMP_MSG_TRAP) {
        /*
         * PDU is not an SNMPv1 trap 
         */

        DEBUGDUMPHEADER("send", "request_id");
        /*
         * request id 
         */
        cp = asn_build_int(cp, out_length,
                           (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                     ASN_INTEGER), &pdu->reqid,
                           sizeof(pdu->reqid));
        DEBUGINDENTLESS();
        if (cp == NULL)
            return NULL;

        /*
         * error status (getbulk non-repeaters) 
         */
        DEBUGDUMPHEADER("send", "error status");
        cp = asn_build_int(cp, out_length,
                           (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                     ASN_INTEGER), &pdu->errstat,
                           sizeof(pdu->errstat));
        DEBUGINDENTLESS();
        if (cp == NULL)
            return NULL;

        /*
         * error index (getbulk max-repetitions) 
         */
        DEBUGDUMPHEADER("send", "error index");
        cp = asn_build_int(cp, out_length,
                           (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                     ASN_INTEGER), &pdu->errindex,
                           sizeof(pdu->errindex));
        DEBUGINDENTLESS();
        if (cp == NULL)
            return NULL;
    } else {
        /*
         * an SNMPv1 trap PDU 
         */

        /*
         * enterprise 
         */
        DEBUGDUMPHEADER("send", "enterprise OBJID");
        cp = asn_build_objid(cp, out_length,
                             (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                       ASN_OBJECT_ID),
                             (oid *) pdu->enterprise,
                             pdu->enterprise_length);
        DEBUGINDENTLESS();
        if (cp == NULL)
            return NULL;

        /*
         * agent-addr 
         */
        DEBUGDUMPHEADER("send", "agent Address");
        cp = asn_build_string(cp, out_length,
                              (u_char) (ASN_IPADDRESS | ASN_PRIMITIVE),
                              (u_char *) pdu->agent_addr, 4);
        DEBUGINDENTLESS();
        if (cp == NULL)
            return NULL;

        /*
         * generic trap 
         */
        DEBUGDUMPHEADER("send", "generic trap number");
        cp = asn_build_int(cp, out_length,
                           (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                     ASN_INTEGER),
                           (long *) &pdu->trap_type,
                           sizeof(pdu->trap_type));
        DEBUGINDENTLESS();
        if (cp == NULL)
            return NULL;

        /*
         * specific trap 
         */
        DEBUGDUMPHEADER("send", "specific trap number");
        cp = asn_build_int(cp, out_length,
                           (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE |
                                     ASN_INTEGER),
                           (long *) &pdu->specific_type,
                           sizeof(pdu->specific_type));
        DEBUGINDENTLESS();
        if (cp == NULL)
            return NULL;

        /*
         * timestamp  
         */
        DEBUGDUMPHEADER("send", "timestamp");
        cp = asn_build_unsigned_int(cp, out_length,
                                    (u_char) (ASN_TIMETICKS |
                                              ASN_PRIMITIVE), &pdu->time,
                                    sizeof(pdu->time));
        DEBUGINDENTLESS();
        if (cp == NULL)
            return NULL;
    }

    /*
     * Save current location and build SEQUENCE tag and length placeholder
     * for variable-bindings sequence
     * (actual length will be inserted later) 
     */
    h2 = cp;
    cp = asn_build_sequence(cp, out_length,
                            (u_char) (ASN_SEQUENCE | ASN_CONSTRUCTOR), 0);
    if (cp == NULL)
        return NULL;
    h2e = cp;

    /*
     * Store variable-bindings 
     */
    DEBUGDUMPSECTION("send", "VarBindList");
    for (vp = pdu->variables; vp; vp = vp->next_variable) {
        DEBUGDUMPSECTION("send", "VarBind");
        cp = snmp_build_var_op(cp, vp->name, &vp->name_length, vp->type,
                               vp->val_len, (u_char *) vp->val.string,
                               out_length);
        DEBUGINDENTLESS();
        if (cp == NULL)
            return NULL;
    }
    DEBUGINDENTLESS();

    /*
     * insert actual length of variable-bindings sequence 
     */
    asn_build_sequence(h2, &length,
                       (u_char) (ASN_SEQUENCE | ASN_CONSTRUCTOR),
                       cp - h2e);

    /*
     * insert actual length of PDU sequence 
     */
    asn_build_sequence(h1, &length, (u_char) pdu->command, cp - h1e);

    return cp;
}

#ifdef USE_REVERSE_ASNENCODING
/*
 * On error, returns 0 (likely an encoding problem).  
 */
int
snmp_pdu_realloc_rbuild(u_char ** pkt, size_t * pkt_len, size_t * offset,
                        netsnmp_pdu *pdu)
{
#ifndef VPCACHE_SIZE
#define VPCACHE_SIZE 50
#endif
    netsnmp_variable_list *vpcache[VPCACHE_SIZE];
    netsnmp_variable_list *vp, *tmpvp;
    size_t          start_offset = *offset;
    int             i, wrapped = 0, notdone, final, rc = 0;

    DEBUGMSGTL(("snmp_pdu_realloc_rbuild", "starting\n"));
    for (vp = pdu->variables, i = VPCACHE_SIZE - 1; vp;
         vp = vp->next_variable, i--) {
        if (i < 0) {
            wrapped = notdone = 1;
            i = VPCACHE_SIZE - 1;
            DEBUGMSGTL(("snmp_pdu_realloc_rbuild", "wrapped\n"));
        }
        vpcache[i] = vp;
    }
    final = i + 1;

    do {
        for (i = final; i < VPCACHE_SIZE; i++) {
            vp = vpcache[i];
            DEBUGDUMPSECTION("send", "VarBind");
            rc = snmp_realloc_rbuild_var_op(pkt, pkt_len, offset, 1,
                                            vp->name, &vp->name_length,
                                            vp->type,
                                            (u_char *) vp->val.string,
                                            vp->val_len);
            DEBUGINDENTLESS();
            if (rc == 0) {
                return 0;
            }
        }

        DEBUGINDENTLESS();
        if (wrapped) {
            notdone = 1;
            for (i = 0; i < final; i++) {
                vp = vpcache[i];
                DEBUGDUMPSECTION("send", "VarBind");
                rc = snmp_realloc_rbuild_var_op(pkt, pkt_len, offset, 1,
                                                vp->name, &vp->name_length,
                                                vp->type,
                                                (u_char *) vp->val.string,
                                                vp->val_len);
                DEBUGINDENTLESS();
                if (rc == 0) {
                    return 0;
                }
            }

            if (final == 0) {
                tmpvp = vpcache[VPCACHE_SIZE - 1];
            } else {
                tmpvp = vpcache[final - 1];
            }
            wrapped = 0;

            for (vp = pdu->variables, i = VPCACHE_SIZE - 1;
                 vp && vp != tmpvp; vp = vp->next_variable, i--) {
                if (i < 0) {
                    wrapped = 1;
                    i = VPCACHE_SIZE - 1;
                    DEBUGMSGTL(("snmp_pdu_realloc_rbuild", "wrapped\n"));
                }
                vpcache[i] = vp;
            }
            final = i + 1;
        } else {
            notdone = 0;
        }
    } while (notdone);

    /*
     * Save current location and build SEQUENCE tag and length placeholder for
     * variable-bindings sequence (actual length will be inserted later).  
     */

    rc = asn_realloc_rbuild_sequence(pkt, pkt_len, offset, 1,
                                     (u_char) (ASN_SEQUENCE |
                                               ASN_CONSTRUCTOR),
                                     *offset - start_offset);

    /*
     * Store fields in the PDU preceeding the variable-bindings sequence.  
     */
    if (pdu->command != SNMP_MSG_TRAP) {
        /*
         * Error index (getbulk max-repetitions).  
         */
        DEBUGDUMPHEADER("send", "error index");
        rc = asn_realloc_rbuild_int(pkt, pkt_len, offset, 1,
                                    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE
                                              | ASN_INTEGER),
                                    &pdu->errindex, sizeof(pdu->errindex));
        DEBUGINDENTLESS();
        if (rc == 0) {
            return 0;
        }

        /*
         * Error status (getbulk non-repeaters).  
         */
        DEBUGDUMPHEADER("send", "error status");
        rc = asn_realloc_rbuild_int(pkt, pkt_len, offset, 1,
                                    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE
                                              | ASN_INTEGER),
                                    &pdu->errstat, sizeof(pdu->errstat));
        DEBUGINDENTLESS();
        if (rc == 0) {
            return 0;
        }

        /*
         * Request ID.  
         */
        DEBUGDUMPHEADER("send", "request_id");
        rc = asn_realloc_rbuild_int(pkt, pkt_len, offset, 1,
                                    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE
                                              | ASN_INTEGER), &pdu->reqid,
                                    sizeof(pdu->reqid));
        DEBUGINDENTLESS();
        if (rc == 0) {
            return 0;
        }
    } else {
        /*
         * An SNMPv1 trap PDU.  
         */

        /*
         * Timestamp.  
         */
        DEBUGDUMPHEADER("send", "timestamp");
        rc = asn_realloc_rbuild_unsigned_int(pkt, pkt_len, offset, 1,
                                             (u_char) (ASN_TIMETICKS |
                                                       ASN_PRIMITIVE),
                                             &pdu->time,
                                             sizeof(pdu->time));
        DEBUGINDENTLESS();
        if (rc == 0) {
            return 0;
        }

        /*
         * Specific trap.  
         */
        DEBUGDUMPHEADER("send", "specific trap number");
        rc = asn_realloc_rbuild_int(pkt, pkt_len, offset, 1,
                                    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE
                                              | ASN_INTEGER),
                                    (long *) &pdu->specific_type,
                                    sizeof(pdu->specific_type));
        DEBUGINDENTLESS();
        if (rc == 0) {
            return 0;
        }

        /*
         * Generic trap.  
         */
        DEBUGDUMPHEADER("send", "generic trap number");
        rc = asn_realloc_rbuild_int(pkt, pkt_len, offset, 1,
                                    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE
                                              | ASN_INTEGER),
                                    (long *) &pdu->trap_type,
                                    sizeof(pdu->trap_type));
        DEBUGINDENTLESS();
        if (rc == 0) {
            return 0;
        }

        /*
         * Agent-addr.  
         */
        DEBUGDUMPHEADER("send", "agent Address");
        rc = asn_realloc_rbuild_string(pkt, pkt_len, offset, 1,
                                       (u_char) (ASN_IPADDRESS |
                                                 ASN_PRIMITIVE),
                                       (u_char *) pdu->agent_addr, 4);
        DEBUGINDENTLESS();
        if (rc == 0) {
            return 0;
        }

        /*
         * Enterprise.  
         */
        DEBUGDUMPHEADER("send", "enterprise OBJID");
        rc = asn_realloc_rbuild_objid(pkt, pkt_len, offset, 1,
                                      (u_char) (ASN_UNIVERSAL |
                                                ASN_PRIMITIVE |
                                                ASN_OBJECT_ID),
                                      (oid *) pdu->enterprise,
                                      pdu->enterprise_length);
        DEBUGINDENTLESS();
        if (rc == 0) {
            return 0;
        }
    }

    /*
     * Build the PDU sequence.  
     */
    rc = asn_realloc_rbuild_sequence(pkt, pkt_len, offset, 1,
                                     (u_char) pdu->command,
                                     *offset - start_offset);
    return rc;
}
#endif                          /* USE_REVERSE_ASNENCODING */

/*
 * Parses the packet received to determine version, either directly
 * from packets version field or inferred from ASN.1 construct.
 */
static int
snmp_parse_version(u_char * data, size_t length)
{
    u_char          type;
    long            version = SNMPERR_BAD_VERSION;

    data = asn_parse_sequence(data, &length, &type,
                              (ASN_SEQUENCE | ASN_CONSTRUCTOR), "version");
    if (data) {
        data =
            asn_parse_int(data, &length, &type, &version, sizeof(version));
        if (!data || type != ASN_INTEGER) {
            return SNMPERR_BAD_VERSION;
        }
    }
    return version;
}


int
snmpv3_parse(netsnmp_pdu *pdu,
             u_char * data,
             size_t * length,
             u_char ** after_header, netsnmp_session * sess)
{
    u_char          type, msg_flags;
    long            ver, msg_max_size, msg_sec_model;
    size_t          max_size_response;
    u_char          tmp_buf[SNMP_MAX_MSG_SIZE];
    size_t          tmp_buf_len;
    u_char          pdu_buf[SNMP_MAX_MSG_SIZE];
    u_char         *mallocbuf = NULL;
    size_t          pdu_buf_len = SNMP_MAX_MSG_SIZE;
    u_char         *sec_params;
    u_char         *msg_data;
    u_char         *cp;
    size_t          asn_len, msg_len;
    int             ret, ret_val;
    struct snmp_secmod_def *sptr;


    msg_data = data;
    msg_len = *length;


    /*
     * message is an ASN.1 SEQUENCE  
     */
    DEBUGDUMPSECTION("recv", "SNMPv3 Message");
    data = asn_parse_sequence(data, length, &type,
                              (ASN_SEQUENCE | ASN_CONSTRUCTOR), "message");
    if (data == NULL) {
        /*
         * error msg detail is set 
         */
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        DEBUGINDENTLESS();
        return SNMPERR_ASN_PARSE_ERR;
    }

    /*
     * parse msgVersion  
     */
    DEBUGDUMPHEADER("recv", "SNMP Version Number");
    data = asn_parse_int(data, length, &type, &ver, sizeof(ver));
    DEBUGINDENTLESS();
    if (data == NULL) {
        ERROR_MSG("bad parse of version");
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        DEBUGINDENTLESS();
        return SNMPERR_ASN_PARSE_ERR;
    }
    pdu->version = ver;

    /*
     * parse msgGlobalData sequence  
     */
    cp = data;
    asn_len = *length;
    DEBUGDUMPSECTION("recv", "msgGlobalData");
    data = asn_parse_sequence(data, &asn_len, &type,
                              (ASN_SEQUENCE | ASN_CONSTRUCTOR),
                              "msgGlobalData");
    if (data == NULL) {
        /*
         * error msg detail is set 
         */
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        DEBUGINDENTADD(-4);
        return SNMPERR_ASN_PARSE_ERR;
    }
    *length -= data - cp;       /* subtract off the length of the header */

    /*
     * msgID 
     */
    DEBUGDUMPHEADER("recv", "msgID");
    data =
        asn_parse_int(data, length, &type, &pdu->msgid,
                      sizeof(pdu->msgid));
    DEBUGINDENTLESS();
    if (data == NULL || type != ASN_INTEGER) {
        ERROR_MSG("error parsing msgID");
        DEBUGINDENTADD(-4);
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        return SNMPERR_ASN_PARSE_ERR;
    }

    /*
     * Check the msgID we received is a legal value.  If not, then increment
     * snmpInASNParseErrs and return the appropriate error (see RFC 2572,
     * para. 7.2, section 2 -- note that a bad msgID means that the received
     * message is NOT a serialiization of an SNMPv3Message, since the msgID
     * field is out of bounds).  
     */

    if (pdu->msgid < 0 || pdu->msgid > 0x7fffffff) {
        snmp_log(LOG_ERR, "Received bad msgID (%ld %s %s).\n", pdu->msgid,
                 (pdu->msgid < 0) ? "<" : ">",
                 (pdu->msgid < 0) ? "0" : "2^31 - 1");
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        DEBUGINDENTADD(-4);
        return SNMPERR_ASN_PARSE_ERR;
    }

    /*
     * msgMaxSize 
     */
    DEBUGDUMPHEADER("recv", "msgMaxSize");
    data = asn_parse_int(data, length, &type, &msg_max_size,
                         sizeof(msg_max_size));
    DEBUGINDENTLESS();
    if (data == NULL || type != ASN_INTEGER) {
        ERROR_MSG("error parsing msgMaxSize");
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        DEBUGINDENTADD(-4);
        return SNMPERR_ASN_PARSE_ERR;
    }

    /*
     * Check the msgMaxSize we received is a legal value.  If not, then
     * increment snmpInASNParseErrs and return the appropriate error (see RFC
     * 2572, para. 7.2, section 2 -- note that a bad msgMaxSize means that the
     * received message is NOT a serialiization of an SNMPv3Message, since the
     * msgMaxSize field is out of bounds).
     * 
     * Note we store the msgMaxSize on a per-session basis which also seems
     * reasonable; it could vary from PDU to PDU but that would be strange
     * (also since we deal with a PDU at a time, it wouldn't make any
     * difference to our responses, if any).  
     */

    if (msg_max_size < 484) {
        snmp_log(LOG_ERR, "Received bad msgMaxSize (%lu < 484).\n",
                 msg_max_size);
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        DEBUGINDENTADD(-4);
        return SNMPERR_ASN_PARSE_ERR;
    } else if (msg_max_size > 0x7fffffff) {
        snmp_log(LOG_ERR, "Received bad msgMaxSize (%lu > 2^31 - 1).\n",
                 msg_max_size);
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        DEBUGINDENTADD(-4);
        return SNMPERR_ASN_PARSE_ERR;
    } else {
        DEBUGMSGTL(("snmpv3_parse", "msgMaxSize %lu received\n",
                    msg_max_size));
        sess->sndMsgMaxSize = msg_max_size;
    }

    /*
     * msgFlags 
     */
    tmp_buf_len = SNMP_MAX_MSG_SIZE;
    DEBUGDUMPHEADER("recv", "msgFlags");
    data = asn_parse_string(data, length, &type, tmp_buf, &tmp_buf_len);
    DEBUGINDENTLESS();
    if (data == NULL || type != ASN_OCTET_STR || tmp_buf_len != 1) {
        ERROR_MSG("error parsing msgFlags");
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        DEBUGINDENTADD(-4);
        return SNMPERR_ASN_PARSE_ERR;
    }
    msg_flags = *tmp_buf;
    if (msg_flags & SNMP_MSG_FLAG_RPRT_BIT)
        pdu->flags |= SNMP_MSG_FLAG_RPRT_BIT;
    else
        pdu->flags &= (~SNMP_MSG_FLAG_RPRT_BIT);

    /*
     * msgSecurityModel 
     */
    DEBUGDUMPHEADER("recv", "msgSecurityModel");
    data = asn_parse_int(data, length, &type, &msg_sec_model,
                         sizeof(msg_sec_model));
    DEBUGINDENTADD(-4);         /* return from global data indent */
    if (data == NULL || type != ASN_INTEGER ||
        msg_sec_model < 1 || msg_sec_model > 0x7fffffff) {
        ERROR_MSG("error parsing msgSecurityModel");
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        DEBUGINDENTLESS();
        return SNMPERR_ASN_PARSE_ERR;
    }
    sptr = find_sec_mod(msg_sec_model);
    if (!sptr) {
        snmp_log(LOG_WARNING, "unknown security model: %ld\n",
                 msg_sec_model);
        snmp_increment_statistic(STAT_SNMPUNKNOWNSECURITYMODELS);
        DEBUGINDENTLESS();
        return SNMPERR_UNKNOWN_SEC_MODEL;
    }
    pdu->securityModel = msg_sec_model;

    if (msg_flags & SNMP_MSG_FLAG_PRIV_BIT &&
        !(msg_flags & SNMP_MSG_FLAG_AUTH_BIT)) {
        ERROR_MSG("invalid message, illegal msgFlags");
        snmp_increment_statistic(STAT_SNMPINVALIDMSGS);
        DEBUGINDENTLESS();
        return SNMPERR_INVALID_MSG;
    }
    pdu->securityLevel = ((msg_flags & SNMP_MSG_FLAG_AUTH_BIT)
                          ? ((msg_flags & SNMP_MSG_FLAG_PRIV_BIT)
                             ? SNMP_SEC_LEVEL_AUTHPRIV
                             : SNMP_SEC_LEVEL_AUTHNOPRIV)
                          : SNMP_SEC_LEVEL_NOAUTH);
    /*
     * end of msgGlobalData 
     */

    /*
     * securtityParameters OCTET STRING begins after msgGlobalData 
     */
    sec_params = data;
    pdu->contextEngineID = (u_char *) calloc(1, SNMP_MAX_ENG_SIZE);
    pdu->contextEngineIDLen = SNMP_MAX_ENG_SIZE;

    /*
     * Note: there is no length limit on the msgAuthoritativeEngineID field,
     * although we would EXPECT it to be limited to 32 (the SnmpEngineID TC
     * limit).  We'll use double that here to be on the safe side.  
     */

    pdu->securityEngineID = (u_char *) calloc(1, SNMP_MAX_ENG_SIZE * 2);
    pdu->securityEngineIDLen = SNMP_MAX_ENG_SIZE * 2;
    pdu->securityName = (char *) calloc(1, SNMP_MAX_SEC_NAME_SIZE);
    pdu->securityNameLen = SNMP_MAX_SEC_NAME_SIZE;

    if ((pdu->securityName == NULL) ||
        (pdu->securityEngineID == NULL) ||
        (pdu->contextEngineID == NULL)) {
        return SNMPERR_MALLOC;
    }

    if (pdu_buf_len < msg_len
        && pdu->securityLevel == SNMP_SEC_LEVEL_AUTHPRIV) {
        /*
         * space needed is larger than we have in the default buffer 
         */
        mallocbuf = (u_char *) calloc(1, msg_len);
        pdu_buf_len = msg_len;
        cp = mallocbuf;
    } else {
        memset(pdu_buf, 0, pdu_buf_len);
        cp = pdu_buf;
    }

    DEBUGDUMPSECTION("recv", "SM msgSecurityParameters");
    if (sptr->decode) {
        struct snmp_secmod_incoming_params parms;
        parms.msgProcModel = pdu->msgParseModel;
        parms.maxMsgSize = msg_max_size;
        parms.secParams = sec_params;
        parms.secModel = msg_sec_model;
        parms.secLevel = pdu->securityLevel;
        parms.wholeMsg = msg_data;
        parms.wholeMsgLen = msg_len;
        parms.secEngineID = pdu->securityEngineID;
        parms.secEngineIDLen = &pdu->securityEngineIDLen;
        parms.secName = pdu->securityName;
        parms.secNameLen = &pdu->securityNameLen;
        parms.scopedPdu = &cp;
        parms.scopedPduLen = &pdu_buf_len;
        parms.maxSizeResponse = &max_size_response;
        parms.secStateRef = &pdu->securityStateRef;
        parms.sess = sess;
        parms.pdu = pdu;
        parms.msg_flags = msg_flags;
        ret_val = (*sptr->decode) (&parms);
    } else {
        SNMP_FREE(mallocbuf);
        DEBUGINDENTLESS();
        snmp_log(LOG_WARNING, "security service %ld can't decode packets\n",
                 msg_sec_model);
        return (-1);
    }

    if (ret_val != SNMPERR_SUCCESS) {
        DEBUGDUMPSECTION("recv", "ScopedPDU");
        /*
         * Parse as much as possible -- though I don't see the point? [jbpn].  
         */
        if (cp) {
            cp = snmpv3_scopedPDU_parse(pdu, cp, &pdu_buf_len);
        }
        if (cp) {
            DEBUGPRINTPDUTYPE("recv", *cp);
            snmp_pdu_parse(pdu, cp, &pdu_buf_len);
            DEBUGINDENTADD(-8);
        } else {
            DEBUGINDENTADD(-4);
        }

        if (mallocbuf) {
            SNMP_FREE(mallocbuf);
        }
        return ret_val;
    }

    /*
     * parse plaintext ScopedPDU sequence 
     */
    *length = pdu_buf_len;
    DEBUGDUMPSECTION("recv", "ScopedPDU");
    data = snmpv3_scopedPDU_parse(pdu, cp, length);
    if (data == NULL) {
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        DEBUGINDENTADD(-4);
        if (mallocbuf) {
            SNMP_FREE(mallocbuf);
        }
        return SNMPERR_ASN_PARSE_ERR;
    }

    /*
     * parse the PDU.  
     */
    if (after_header != NULL) {
        *after_header = data;
        tmp_buf_len = *length;
    }

    DEBUGPRINTPDUTYPE("recv", *data);
    ret = snmp_pdu_parse(pdu, data, length);
    DEBUGINDENTADD(-8);

    if (after_header != NULL) {
        *length = tmp_buf_len;
    }

    if (ret != SNMPERR_SUCCESS) {
        ERROR_MSG("error parsing PDU");
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        if (mallocbuf) {
            SNMP_FREE(mallocbuf);
        }
        return SNMPERR_ASN_PARSE_ERR;
    }

    if (mallocbuf) {
        SNMP_FREE(mallocbuf);
    }
    return SNMPERR_SUCCESS;
}                               /* end snmpv3_parse() */

#define ERROR_STAT_LENGTH 11

int
snmpv3_make_report(netsnmp_pdu *pdu, int error)
{

    long            ltmp;
    static oid      unknownSecurityLevel[] =
        { 1, 3, 6, 1, 6, 3, 15, 1, 1, 1, 0 };
    static oid      notInTimeWindow[] =
        { 1, 3, 6, 1, 6, 3, 15, 1, 1, 2, 0 };
    static oid      unknownUserName[] =
        { 1, 3, 6, 1, 6, 3, 15, 1, 1, 3, 0 };
    static oid      unknownEngineID[] =
        { 1, 3, 6, 1, 6, 3, 15, 1, 1, 4, 0 };
    static oid      wrongDigest[] = { 1, 3, 6, 1, 6, 3, 15, 1, 1, 5, 0 };
    static oid      decryptionError[] =
        { 1, 3, 6, 1, 6, 3, 15, 1, 1, 6, 0 };
    oid            *err_var;
    int             err_var_len;
    int             stat_ind;
    struct snmp_secmod_def *sptr;

    switch (error) {
    case SNMPERR_USM_UNKNOWNENGINEID:
        stat_ind = STAT_USMSTATSUNKNOWNENGINEIDS;
        err_var = unknownEngineID;
        err_var_len = ERROR_STAT_LENGTH;
        break;
    case SNMPERR_USM_UNKNOWNSECURITYNAME:
        stat_ind = STAT_USMSTATSUNKNOWNUSERNAMES;
        err_var = unknownUserName;
        err_var_len = ERROR_STAT_LENGTH;
        break;
    case SNMPERR_USM_UNSUPPORTEDSECURITYLEVEL:
        stat_ind = STAT_USMSTATSUNSUPPORTEDSECLEVELS;
        err_var = unknownSecurityLevel;
        err_var_len = ERROR_STAT_LENGTH;
        break;
    case SNMPERR_USM_AUTHENTICATIONFAILURE:
        stat_ind = STAT_USMSTATSWRONGDIGESTS;
        err_var = wrongDigest;
        err_var_len = ERROR_STAT_LENGTH;
        break;
    case SNMPERR_USM_NOTINTIMEWINDOW:
        stat_ind = STAT_USMSTATSNOTINTIMEWINDOWS;
        err_var = notInTimeWindow;
        err_var_len = ERROR_STAT_LENGTH;
        break;
    case SNMPERR_USM_DECRYPTIONERROR:
        stat_ind = STAT_USMSTATSDECRYPTIONERRORS;
        err_var = decryptionError;
        err_var_len = ERROR_STAT_LENGTH;
        break;
    default:
        return SNMPERR_GENERR;
    }

    snmp_free_varbind(pdu->variables);  /* free the current varbind */

    pdu->variables = NULL;
    SNMP_FREE(pdu->securityEngineID);
    pdu->securityEngineID =
        snmpv3_generate_engineID(&pdu->securityEngineIDLen);
    SNMP_FREE(pdu->contextEngineID);
    pdu->contextEngineID =
        snmpv3_generate_engineID(&pdu->contextEngineIDLen);
    pdu->command = SNMP_MSG_REPORT;
    pdu->errstat = 0;
    pdu->errindex = 0;
    SNMP_FREE(pdu->contextName);
    pdu->contextName = strdup("");
    pdu->contextNameLen = strlen(pdu->contextName);

    /*
     * reports shouldn't cache previous data. 
     */
    /*
     * FIX - yes they should but USM needs to follow new EoP to determine
     * which cached values to use 
     */
    if (pdu->securityStateRef) {
        sptr = find_sec_mod(pdu->securityModel);
        if (sptr) {
            if (sptr->pdu_free_state_ref) {
                (*sptr->pdu_free_state_ref) (pdu->securityStateRef);
            } else {
                snmp_log(LOG_ERR,
                         "Security Model %d can't free state references\n",
                         pdu->securityModel);
            }
        } else {
            snmp_log(LOG_ERR,
                     "Can't find security model to free ptr: %d\n",
                     pdu->securityModel);
        }
        pdu->securityStateRef = NULL;
    }

    if (error == SNMPERR_USM_NOTINTIMEWINDOW) {
        pdu->securityLevel = SNMP_SEC_LEVEL_AUTHNOPRIV;
    } else {
        pdu->securityLevel = SNMP_SEC_LEVEL_NOAUTH;
    }

    /*
     * find the appropriate error counter  
     */
    ltmp = snmp_get_statistic(stat_ind);

    /*
     * return the appropriate error counter  
     */
    snmp_pdu_add_variable(pdu, err_var, err_var_len,
                          ASN_COUNTER, (u_char *) & ltmp, sizeof(ltmp));

    return SNMPERR_SUCCESS;
}                               /* end snmpv3_make_report() */


int
snmpv3_get_report_type(netsnmp_pdu *pdu)
{
    static oid      snmpMPDStats[] = { 1, 3, 6, 1, 6, 3, 11, 2, 1 };
    static oid      usmStats[] = { 1, 3, 6, 1, 6, 3, 15, 1, 1 };
    netsnmp_variable_list *vp;
    int             rpt_type = SNMPERR_UNKNOWN_REPORT;

    if (pdu == NULL || pdu->variables == NULL)
        return rpt_type;
    vp = pdu->variables;
    if (vp->name_length == REPORT_STATS_LEN + 2) {
        if (memcmp(snmpMPDStats, vp->name, REPORT_STATS_LEN * sizeof(oid))
            == 0) {
            switch (vp->name[REPORT_STATS_LEN]) {
            case REPORT_snmpUnknownSecurityModels_NUM:
                rpt_type = SNMPERR_UNKNOWN_SEC_MODEL;
                break;
            case REPORT_snmpInvalidMsgs_NUM:
                rpt_type = SNMPERR_INVALID_MSG;
                break;
            }
        } else
            if (memcmp(usmStats, vp->name, REPORT_STATS_LEN * sizeof(oid))
                == 0) {
            switch (vp->name[REPORT_STATS_LEN]) {
            case REPORT_usmStatsUnsupportedSecLevels_NUM:
                rpt_type = SNMPERR_UNSUPPORTED_SEC_LEVEL;
                break;
            case REPORT_usmStatsNotInTimeWindows_NUM:
                rpt_type = SNMPERR_NOT_IN_TIME_WINDOW;
                break;
            case REPORT_usmStatsUnknownUserNames_NUM:
                rpt_type = SNMPERR_UNKNOWN_USER_NAME;
                break;
            case REPORT_usmStatsUnknownEngineIDs_NUM:
                rpt_type = SNMPERR_UNKNOWN_ENG_ID;
                break;
            case REPORT_usmStatsWrongDigests_NUM:
                rpt_type = SNMPERR_AUTHENTICATION_FAILURE;
                break;
            case REPORT_usmStatsDecryptionErrors_NUM:
                rpt_type = SNMPERR_DECRYPTION_ERR;
                break;
            }
        }
    }
    DEBUGMSGTL(("report", "Report type: %d\n", rpt_type));
    return rpt_type;
}

/*
 * Parses the packet received on the input session, and places the data into
 * the input pdu.  length is the length of the input packet.
 * If any errors are encountered, -1 or USM error is returned.
 * Otherwise, a 0 is returned.
 */
static int
_snmp_parse(void *sessp,
            netsnmp_session * session,
            netsnmp_pdu *pdu, u_char * data, size_t length)
{
#if !defined(DISABLE_SNMPV1) || !defined(DISABLE_SNMPV2C)
    u_char          community[COMMUNITY_MAX_LEN];
    size_t          community_length = COMMUNITY_MAX_LEN;
#endif
    int             result = -1;

    session->s_snmp_errno = 0;
    session->s_errno = 0;

    /*
     * Ensure all incoming PDUs have a unique means of identification 
     * (This is not restricted to AgentX handling,
     * though that is where the need becomes visible)   
     */
    pdu->transid = snmp_get_next_transid();

    if (session->version != SNMP_DEFAULT_VERSION) {
        pdu->version = session->version;
    } else {
        pdu->version = snmp_parse_version(data, length);
    }

    switch (pdu->version) {
#ifndef DISABLE_SNMPV1
    case SNMP_VERSION_1:
#endif
#ifndef DISABLE_SNMPV2C
    case SNMP_VERSION_2c:
#endif
#if !defined(DISABLE_SNMPV1) || !defined(DISABLE_SNMPV2C)
        DEBUGMSGTL(("snmp_api", "Parsing SNMPv%d message...\n",
                    (1 + pdu->version)));

        /*
         * authenticates message and returns length if valid 
         */
        if (pdu->version == SNMP_VERSION_1) {
            DEBUGDUMPSECTION("recv", "SNMPv1 message\n");
        } else {
            DEBUGDUMPSECTION("recv", "SNMPv2c message\n");
        }
        data = snmp_comstr_parse(data, &length,
                                 community, &community_length,
                                 &pdu->version);
        if (data == NULL)
            return -1;

        if (pdu->version != session->version &&
            session->version != SNMP_DEFAULT_VERSION) {
            session->s_snmp_errno = SNMPERR_BAD_VERSION;
            return -1;
        }

        /*
         * maybe get the community string. 
         */
        pdu->securityLevel = SNMP_SEC_LEVEL_NOAUTH;
        pdu->securityModel = (pdu->version == SNMP_VERSION_1) ?
            SNMP_SEC_MODEL_SNMPv1 : SNMP_SEC_MODEL_SNMPv2c;
        SNMP_FREE(pdu->community);
        pdu->community_len = 0;
        pdu->community = (u_char *) 0;
        if (community_length) {
            pdu->community_len = community_length;
            pdu->community = (u_char *) malloc(community_length);
            if (pdu->community == NULL) {
                session->s_snmp_errno = SNMPERR_MALLOC;
                return -1;
            }
            memmove(pdu->community, community, community_length);
        }
        if (session->authenticator) {
            data = session->authenticator(data, &length,
                                          community, community_length);
            if (data == NULL) {
                session->s_snmp_errno = SNMPERR_AUTHENTICATION_FAILURE;
                return -1;
            }
        }

        DEBUGDUMPSECTION("recv", "PDU");
        result = snmp_pdu_parse(pdu, data, &length);
        if (result < 0) {
            /*
             * This indicates a parse error.  
             */
            snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        }
        DEBUGINDENTADD(-6);
        break;
#endif /* support for community based SNMP */

    case SNMP_VERSION_3:
        result = snmpv3_parse(pdu, data, &length, NULL, session);
        DEBUGMSGTL(("snmp_parse",
                    "Parsed SNMPv3 message (secName:%s, secLevel:%s): %s\n",
                    pdu->securityName, secLevelName[pdu->securityLevel],
                    snmp_api_errstring(result)));

        if (result) {
            struct snmp_secmod_def *secmod =
                find_sec_mod(pdu->securityModel);
            if (!sessp) {
                session->s_snmp_errno = result;
            } else {
                /*
                 * Call the security model to special handle any errors
                 */

                if (secmod && secmod->handle_report) {
                    struct session_list *slp = (struct session_list *) sessp;
                    (*secmod->handle_report)(sessp, slp->transport, session,
                                             result, pdu);
                }
            }
            if (pdu->securityStateRef != NULL) {
                if (secmod && secmod->pdu_free_state_ref) {
                    secmod->pdu_free_state_ref(pdu->securityStateRef);
                    pdu->securityStateRef = NULL;
                }
            }
        }
        break;
    case SNMPERR_BAD_VERSION:
        ERROR_MSG("error parsing snmp message version");
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        session->s_snmp_errno = SNMPERR_BAD_VERSION;
        break;
    case SNMP_VERSION_sec:
    case SNMP_VERSION_2u:
    case SNMP_VERSION_2star:
    case SNMP_VERSION_2p:
    default:
        ERROR_MSG("unsupported snmp message version");
        snmp_increment_statistic(STAT_SNMPINBADVERSIONS);

        /*
         * need better way to determine OS independent
         * INT32_MAX value, for now hardcode
         */
        if (pdu->version < 0 || pdu->version > 2147483647) {
            snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        }
        session->s_snmp_errno = SNMPERR_BAD_VERSION;
        break;
    }

    return result;
}

static int
snmp_parse(void *sessp,
           netsnmp_session * pss,
           netsnmp_pdu *pdu, u_char * data, size_t length)
{
    int             rc;

    rc = _snmp_parse(sessp, pss, pdu, data, length);
    if (rc) {
        if (!pss->s_snmp_errno) {
            pss->s_snmp_errno = SNMPERR_BAD_PARSE;
        }
        SET_SNMP_ERROR(pss->s_snmp_errno);
    }

    return rc;
}

int
snmp_pdu_parse(netsnmp_pdu *pdu, u_char * data, size_t * length)
{
    u_char          type;
    u_char          msg_type;
    u_char         *var_val;
    int             badtype = 0;
    size_t          len;
    size_t          four;
    netsnmp_variable_list *vp = NULL;
    oid             objid[MAX_OID_LEN];

    /*
     * Get the PDU type 
     */
    data = asn_parse_header(data, length, &msg_type);
    if (data == NULL)
        return -1;
    DEBUGMSGTL(("dumpv_recv","    Command %s\n", snmp_pdu_type(msg_type)));
    pdu->command = msg_type;
    pdu->flags &= (~UCD_MSG_FLAG_RESPONSE_PDU);

    /*
     * get the fields in the PDU preceeding the variable-bindings sequence 
     */
    switch (pdu->command) {
    case SNMP_MSG_TRAP:
        /*
         * enterprise 
         */
        pdu->enterprise_length = MAX_OID_LEN;
        data = asn_parse_objid(data, length, &type, objid,
                               &pdu->enterprise_length);
        if (data == NULL)
            return -1;
        pdu->enterprise =
            (oid *) malloc(pdu->enterprise_length * sizeof(oid));
        if (pdu->enterprise == NULL) {
            return -1;
        }
        memmove(pdu->enterprise, objid,
                pdu->enterprise_length * sizeof(oid));

        /*
         * agent-addr 
         */
        four = 4;
        data = asn_parse_string(data, length, &type,
                                (u_char *) pdu->agent_addr, &four);
        if (data == NULL)
            return -1;

        /*
         * generic trap 
         */
        data = asn_parse_int(data, length, &type, (long *) &pdu->trap_type,
                             sizeof(pdu->trap_type));
        if (data == NULL)
            return -1;
        /*
         * specific trap 
         */
        data =
            asn_parse_int(data, length, &type,
                          (long *) &pdu->specific_type,
                          sizeof(pdu->specific_type));
        if (data == NULL)
            return -1;

        /*
         * timestamp  
         */
        data = asn_parse_unsigned_int(data, length, &type, &pdu->time,
                                      sizeof(pdu->time));
        if (data == NULL)
            return -1;

        break;

    case SNMP_MSG_RESPONSE:
    case SNMP_MSG_REPORT:
        pdu->flags |= UCD_MSG_FLAG_RESPONSE_PDU;
        /*
         * fallthrough 
         */

    case SNMP_MSG_GET:
    case SNMP_MSG_GETNEXT:
    case SNMP_MSG_GETBULK:
    case SNMP_MSG_TRAP2:
    case SNMP_MSG_INFORM:
    case SNMP_MSG_SET:
        /*
         * PDU is not an SNMPv1 TRAP 
         */

        /*
         * request id 
         */
        DEBUGDUMPHEADER("recv", "request_id");
        data = asn_parse_int(data, length, &type, &pdu->reqid,
                             sizeof(pdu->reqid));
        DEBUGINDENTLESS();
        if (data == NULL) {
            return -1;
        }

        /*
         * error status (getbulk non-repeaters) 
         */
        DEBUGDUMPHEADER("recv", "error status");
        data = asn_parse_int(data, length, &type, &pdu->errstat,
                             sizeof(pdu->errstat));
        DEBUGINDENTLESS();
        if (data == NULL) {
            return -1;
        }

        /*
         * error index (getbulk max-repetitions) 
         */
        DEBUGDUMPHEADER("recv", "error index");
        data = asn_parse_int(data, length, &type, &pdu->errindex,
                             sizeof(pdu->errindex));
        DEBUGINDENTLESS();
        if (data == NULL) {
            return -1;
        }
	break;

    default:
        snmp_log(LOG_ERR, "Bad PDU type received: 0x%.2x\n", pdu->command);
        snmp_increment_statistic(STAT_SNMPINASNPARSEERRS);
        return -1;
    }

    /*
     * get header for variable-bindings sequence 
     */
    DEBUGDUMPSECTION("recv", "VarBindList");
    data = asn_parse_sequence(data, length, &type,
                              (ASN_SEQUENCE | ASN_CONSTRUCTOR),
                              "varbinds");
    if (data == NULL)
        return -1;

    /*
     * get each varBind sequence 
     */
    while ((int) *length > 0) {
        netsnmp_variable_list *vptemp;
        vptemp = (netsnmp_variable_list *) malloc(sizeof(*vptemp));
        if (0 == vptemp) {
            return -1;
        }
        if (0 == vp) {
            pdu->variables = vptemp;
        } else {
            vp->next_variable = vptemp;
        }
        vp = vptemp;

        vp->next_variable = NULL;
        vp->val.string = NULL;
        vp->name_length = MAX_OID_LEN;
        vp->name = 0;
        vp->index = 0;
        vp->data = 0;
        vp->dataFreeHook = 0;
        DEBUGDUMPSECTION("recv", "VarBind");
        data = snmp_parse_var_op(data, objid, &vp->name_length, &vp->type,
                                 &vp->val_len, &var_val, length);
        if (data == NULL)
            return -1;
        if (snmp_set_var_objid(vp, objid, vp->name_length))
            return -1;

        len = MAX_PACKET_LENGTH;
        DEBUGDUMPHEADER("recv", "Value");
        switch ((short) vp->type) {
        case ASN_INTEGER:
            vp->val.integer = (long *) vp->buf;
            vp->val_len = sizeof(long);
            asn_parse_int(var_val, &len, &vp->type,
                          (long *) vp->val.integer,
                          sizeof(*vp->val.integer));
            break;
        case ASN_COUNTER:
        case ASN_GAUGE:
        case ASN_TIMETICKS:
        case ASN_UINTEGER:
            vp->val.integer = (long *) vp->buf;
            vp->val_len = sizeof(u_long);
            asn_parse_unsigned_int(var_val, &len, &vp->type,
                                   (u_long *) vp->val.integer,
                                   vp->val_len);
            break;
#ifdef OPAQUE_SPECIAL_TYPES
        case ASN_OPAQUE_COUNTER64:
        case ASN_OPAQUE_U64:
#endif                          /* OPAQUE_SPECIAL_TYPES */
        case ASN_COUNTER64:
            vp->val.counter64 = (struct counter64 *) vp->buf;
            vp->val_len = sizeof(struct counter64);
            asn_parse_unsigned_int64(var_val, &len, &vp->type,
                                     (struct counter64 *) vp->val.
                                     counter64, vp->val_len);
            break;
#ifdef OPAQUE_SPECIAL_TYPES
        case ASN_OPAQUE_FLOAT:
            vp->val.floatVal = (float *) vp->buf;
            vp->val_len = sizeof(float);
            asn_parse_float(var_val, &len, &vp->type,
                            vp->val.floatVal, vp->val_len);
            break;
        case ASN_OPAQUE_DOUBLE:
            vp->val.doubleVal = (double *) vp->buf;
            vp->val_len = sizeof(double);
            asn_parse_double(var_val, &len, &vp->type,
                             vp->val.doubleVal, vp->val_len);
            break;
        case ASN_OPAQUE_I64:
            vp->val.counter64 = (struct counter64 *) vp->buf;
            vp->val_len = sizeof(struct counter64);
            asn_parse_signed_int64(var_val, &len, &vp->type,
                                   (struct counter64 *) vp->val.counter64,
                                   sizeof(*vp->val.counter64));

            break;
#endif                          /* OPAQUE_SPECIAL_TYPES */
        case ASN_OCTET_STR:
        case ASN_IPADDRESS:
        case ASN_OPAQUE:
        case ASN_NSAP:
            if (vp->val_len < sizeof(vp->buf)) {
                vp->val.string = (u_char *) vp->buf;
            } else {
                vp->val.string = (u_char *) malloc(vp->val_len);
            }
            if (vp->val.string == NULL) {
                return -1;
            }
            asn_parse_string(var_val, &len, &vp->type, vp->val.string,
                             &vp->val_len);
            break;
        case ASN_OBJECT_ID:
            vp->val_len = MAX_OID_LEN;
            asn_parse_objid(var_val, &len, &vp->type, objid, &vp->val_len);
            vp->val_len *= sizeof(oid);
            vp->val.objid = (oid *) malloc(vp->val_len);
            if (vp->val.objid == NULL) {
                return -1;
            }
            memmove(vp->val.objid, objid, vp->val_len);
            break;
        case SNMP_NOSUCHOBJECT:
        case SNMP_NOSUCHINSTANCE:
        case SNMP_ENDOFMIBVIEW:
        case ASN_NULL:
            break;
        case ASN_BIT_STR:
            vp->val.bitstring = (u_char *) malloc(vp->val_len);
            if (vp->val.bitstring == NULL) {
                return -1;
            }
            asn_parse_bitstring(var_val, &len, &vp->type,
                                vp->val.bitstring, &vp->val_len);
            break;
        default:
            snmp_log(LOG_ERR, "bad type returned (%x)\n", vp->type);
            badtype = -1;
            break;
        }
        DEBUGINDENTADD(-4);
    }
    return badtype;
}

/*
 * snmp v3 utility function to parse into the scopedPdu. stores contextName
 * and contextEngineID in pdu struct. Also stores pdu->command (handy for 
 * Report generation).
 * 
 * returns pointer to begining of PDU or NULL on error.
 */
u_char         *
snmpv3_scopedPDU_parse(netsnmp_pdu *pdu, u_char * cp, size_t * length)
{
    u_char          tmp_buf[SNMP_MAX_MSG_SIZE];
    size_t          tmp_buf_len;
    u_char          type;
    size_t          asn_len;
    u_char         *data;

    pdu->command = 0;           /* initialize so we know if it got parsed */
    asn_len = *length;
    data = asn_parse_sequence(cp, &asn_len, &type,
                              (ASN_SEQUENCE | ASN_CONSTRUCTOR),
                              "plaintext scopedPDU");
    if (data == NULL) {
        return NULL;
    }
    *length -= data - cp;

    /*
     * contextEngineID from scopedPdu  
     */
    DEBUGDUMPHEADER("recv", "contextEngineID");
    data = asn_parse_string(data, length, &type, pdu->contextEngineID,
                            &pdu->contextEngineIDLen);
    DEBUGINDENTLESS();
    if (data == NULL) {
        ERROR_MSG("error parsing contextEngineID from scopedPdu");
        return NULL;
    }

    /*
     * check that it agrees with engineID returned from USM above
     * * only a warning because this could be legal if we are a proxy
     */
    if (pdu->securityEngineIDLen != pdu->contextEngineIDLen ||
        memcmp(pdu->securityEngineID, pdu->contextEngineID,
               pdu->securityEngineIDLen) != 0) {
        DEBUGMSGTL(("scopedPDU_parse",
                    "inconsistent engineID information in message\n"));
    }

    /*
     * parse contextName from scopedPdu
     */
    tmp_buf_len = SNMP_MAX_CONTEXT_SIZE;
    DEBUGDUMPHEADER("recv", "contextName");
    data = asn_parse_string(data, length, &type, tmp_buf, &tmp_buf_len);
    DEBUGINDENTLESS();
    if (data == NULL) {
        ERROR_MSG("error parsing contextName from scopedPdu");
        return NULL;
    }

    if (tmp_buf_len) {
        pdu->contextName = (char *) malloc(tmp_buf_len);
        memmove(pdu->contextName, tmp_buf, tmp_buf_len);
        pdu->contextNameLen = tmp_buf_len;
    } else {
        pdu->contextName = strdup("");
        pdu->contextNameLen = 0;
    }
    if (pdu->contextName == NULL) {
        ERROR_MSG("error copying contextName from scopedPdu");
        return NULL;
    }

    /*
     * Get the PDU type 
     */
    asn_len = *length;
    cp = asn_parse_header(data, &asn_len, &type);
    if (cp == NULL)
        return NULL;

    pdu->command = type;

    return data;
}

/*
 * These functions send PDUs using an active session:
 * snmp_send             - traditional API, no callback
 * snmp_async_send       - traditional API, with callback
 * snmp_sess_send        - single session API, no callback
 * snmp_sess_async_send  - single session API, with callback
 *
 * Call snmp_build to create a serialized packet (the pdu).
 * If necessary, set some of the pdu data from the
 * session defaults.
 * If there is an expected response for this PDU,
 * queue a corresponding request on the list
 * of outstanding requests for this session,
 * and store the callback vectors in the request.
 *
 * Send the pdu to the target identified by this session.
 * Return on success:
 *   The request id of the pdu is returned, and the pdu is freed.
 * Return on failure:
 *   Zero (0) is returned.
 *   The caller must call snmp_free_pdu if 0 is returned.
 */
int
snmp_send(netsnmp_session * session, netsnmp_pdu *pdu)
{
    return snmp_async_send(session, pdu, NULL, NULL);
}

int
snmp_sess_send(void *sessp, netsnmp_pdu *pdu)
{
    return snmp_sess_async_send(sessp, pdu, NULL, NULL);
}

int
snmp_async_send(netsnmp_session * session,
                netsnmp_pdu *pdu, snmp_callback callback, void *cb_data)
{
    void           *sessp = snmp_sess_pointer(session);
    return snmp_sess_async_send(sessp, pdu, callback, cb_data);
}

static int
_sess_async_send(void *sessp,
                 netsnmp_pdu *pdu, snmp_callback callback, void *cb_data)
{
    struct session_list *slp = (struct session_list *) sessp;
    netsnmp_session *session;
    struct snmp_internal_session *isp;
    netsnmp_transport *transport = NULL;
    u_char         *pktbuf = NULL, *packet = NULL;
    size_t          pktbuf_len = 0, offset = 0, length = 0;
    int             result;
    long            reqid;

    if (slp == NULL) {
        return 0;
    } else {
        session = slp->session;
        isp = slp->internal;
        transport = slp->transport;
        if (!session || !isp || !transport) {
            DEBUGMSGTL(("sess_async_send", "send fail: closing...\n"));
            return 0;
        }
    }

    if (pdu == NULL) {
        session->s_snmp_errno = SNMPERR_NULL_PDU;
        return 0;
    }

    session->s_snmp_errno = 0;
    session->s_errno = 0;

    /*
     * Check/setup the version.  
     */
    if (pdu->version == SNMP_DEFAULT_VERSION) {
        if (session->version == SNMP_DEFAULT_VERSION) {
            session->s_snmp_errno = SNMPERR_BAD_VERSION;
            return 0;
        }
        pdu->version = session->version;
    } else if (session->version == SNMP_DEFAULT_VERSION) {
        /*
         * It's OK  
         */
    } else if (pdu->version != session->version) {
        /*
         * ENHANCE: we should support multi-lingual sessions  
         */
        session->s_snmp_errno = SNMPERR_BAD_VERSION;
        return 0;
    }

    /*
     * do we expect a response?
     */
    switch (pdu->command) {

        case SNMP_MSG_RESPONSE:
        case SNMP_MSG_TRAP:
        case SNMP_MSG_TRAP2:
        case SNMP_MSG_REPORT:
        case AGENTX_MSG_CLEANUPSET:
        case AGENTX_MSG_RESPONSE:
            pdu->flags &= ~UCD_MSG_FLAG_EXPECT_RESPONSE;
            break;
            
        default:
            pdu->flags |= UCD_MSG_FLAG_EXPECT_RESPONSE;
            break;
    }

    /*
     * check to see if we need a v3 engineID probe
     */
    if ((pdu->version == SNMP_VERSION_3) &&
        (pdu->flags & UCD_MSG_FLAG_EXPECT_RESPONSE) &&
        (session->securityEngineIDLen == 0) &&
        (0 == (session->flags & SNMP_FLAGS_DONT_PROBE))) {
        int rc;
        DEBUGMSGTL(("snmpv3_build", "delayed probe for engineID\n"));
        rc = snmpv3_engineID_probe(slp, session);
        if (rc == 0)
            return 0; /* s_snmp_errno already set */
    }

    /*
     * check to see if we need to create a v3 user from the session info
     */
    if (create_user_from_session(session) != SNMPERR_SUCCESS) {
        session->s_snmp_errno = SNMPERR_UNKNOWN_USER_NAME;  /* XX?? */
        DEBUGMSGTL(("snmp_api",
                    "snmp_send(): failed(2) to create a new user from session\n"));
        return 0;
    }

    if ((pktbuf = malloc(2048)) == NULL) {
        DEBUGMSGTL(("sess_async_send",
                    "couldn't malloc initial packet buffer\n"));
        session->s_snmp_errno = SNMPERR_MALLOC;
        return 0;
    } else {
        pktbuf_len = 2048;
    }

#if TEMPORARILY_DISABLED
    /*
     *  NULL variable are allowed in certain PDU types.
     *  In particular, SNMPv3 engineID probes are of this form.
     *  There is an internal PDU flag to indicate that this
     *    is acceptable, but until the construction of engineID
     *    probes can be amended to set this flag, we'll simply
     *    skip this test altogether.
     */
    if (pdu->variables == NULL) {
        switch (pdu->command) {
        case SNMP_MSG_GET:
        case SNMP_MSG_SET:
        case SNMP_MSG_GETNEXT:
        case SNMP_MSG_GETBULK:
        case SNMP_MSG_RESPONSE:
        case SNMP_MSG_TRAP2:
        case SNMP_MSG_REPORT:
        case SNMP_MSG_INFORM:
            session->s_snmp_errno = snmp_errno = SNMPERR_NO_VARS;
            return 0;
        case SNMP_MSG_TRAP:
            break;
        }
    }
#endif


    /*
     * Build the message to send.  
     */
    if (isp->hook_realloc_build) {
        result = isp->hook_realloc_build(session, pdu,
                                         &pktbuf, &pktbuf_len, &offset);
        packet = pktbuf;
        length = offset;
    } else if (isp->hook_build) {
        packet = pktbuf;
        length = pktbuf_len;
        result = isp->hook_build(session, pdu, pktbuf, &length);
    } else {
#ifdef USE_REVERSE_ASNENCODING
        if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_REVERSE_ENCODE)) {
            result =
                snmp_build(&pktbuf, &pktbuf_len, &offset, session, pdu);
            packet = pktbuf + pktbuf_len - offset;
            length = offset;
        } else {
#endif
            packet = pktbuf;
            length = pktbuf_len;
            result = snmp_build(&pktbuf, &length, &offset, session, pdu);
#ifdef USE_REVERSE_ASNENCODING
        }
#endif
    }

    if (result < 0) {
        DEBUGMSGTL(("sess_async_send", "encoding failure\n"));
        SNMP_FREE(pktbuf);
        return 0;
    }

    /*
     * Make sure we don't send something that is bigger than the msgMaxSize
     * specified in the received PDU.  
     */

    if (session->sndMsgMaxSize != 0 && length > session->sndMsgMaxSize) {
        DEBUGMSGTL(("sess_async_send",
                    "length of packet (%lu) exceeds session maximum (%lu)\n",
                    length, session->sndMsgMaxSize));
        session->s_snmp_errno = SNMPERR_TOO_LONG;
        SNMP_FREE(pktbuf);
        return 0;
    }

    /*
     * Check that the underlying transport is capable of sending a packet as
     * large as length.  
     */

    if (transport->msgMaxSize != 0 && length > transport->msgMaxSize) {
        DEBUGMSGTL(("sess_async_send",
                    "length of packet (%lu) exceeds transport maximum (%lu)\n",
                    length, transport->msgMaxSize));
        session->s_snmp_errno = SNMPERR_TOO_LONG;
        SNMP_FREE(pktbuf);
        return 0;
    }

    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_DUMP_PACKET)) {
        if (transport->f_fmtaddr != NULL) {
            char           *dest_txt =
                transport->f_fmtaddr(transport, pdu->transport_data,
                                     pdu->transport_data_length);
            if (dest_txt != NULL) {
                snmp_log(LOG_DEBUG, "\nSending %u bytes to %s\n", length,
                         dest_txt);
                SNMP_FREE(dest_txt);
            } else {
                snmp_log(LOG_DEBUG, "\nSending %u bytes to <UNKNOWN>\n",
                         length);
            }
        }
        xdump(packet, length, "");
    }

    /*
     * Send the message.  
     */

    result = transport->f_send(transport, packet, length,
                               &(pdu->transport_data),
                               &(pdu->transport_data_length));

    SNMP_FREE(pktbuf);

    if (result < 0) {
        session->s_snmp_errno = SNMPERR_BAD_SENDTO;
        session->s_errno = errno;
        return 0;
    }

    reqid = pdu->reqid;

    /*
     * Add to pending requests list if we expect a response.  
     */
    if (pdu->flags & UCD_MSG_FLAG_EXPECT_RESPONSE) {
        netsnmp_request_list *rp;
        struct timeval  tv;

        rp = (netsnmp_request_list *) calloc(1,
                                             sizeof(netsnmp_request_list));
        if (rp == NULL) {
            session->s_snmp_errno = SNMPERR_GENERR;
            return 0;
        }

        gettimeofday(&tv, (struct timezone *) 0);
        rp->pdu = pdu;
        rp->request_id = pdu->reqid;
        rp->message_id = pdu->msgid;
        rp->callback = callback;
        rp->cb_data = cb_data;
        rp->retries = 0;
        if (pdu->flags & UCD_MSG_FLAG_PDU_TIMEOUT) {
            rp->timeout = pdu->time * 1000000L;
        } else {
            rp->timeout = session->timeout;
        }
        rp->time = tv;
        tv.tv_usec += rp->timeout;
        tv.tv_sec += tv.tv_usec / 1000000L;
        tv.tv_usec %= 1000000L;
        rp->expire = tv;

        /*
         * XX lock should be per session ! 
         */
        snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);
        if (isp->requestsEnd) {
            rp->next_request = isp->requestsEnd->next_request;
            isp->requestsEnd->next_request = rp;
            isp->requestsEnd = rp;
        } else {
            rp->next_request = isp->requests;
            isp->requests = rp;
            isp->requestsEnd = rp;
        }
        snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);
    } else {
        /*
         * No response expected...  
         */
        if (reqid) {
            /*
             * Free v1 or v2 TRAP PDU iff no error  
             */
            snmp_free_pdu(pdu);
        }
    }

    return reqid;
}

int
snmp_sess_async_send(void *sessp,
                     netsnmp_pdu *pdu,
                     snmp_callback callback, void *cb_data)
{
    int             rc;

    if (sessp == NULL) {
        snmp_errno = SNMPERR_BAD_SESSION;       /*MTCRITICAL_RESOURCE */
        return (0);
    }
    /*
     * send pdu
     */
    rc = _sess_async_send(sessp, pdu, callback, cb_data);
    if (rc == 0) {
        struct session_list *psl;
        netsnmp_session *pss;
        psl = (struct session_list *) sessp;
        pss = psl->session;
        SET_SNMP_ERROR(pss->s_snmp_errno);
    }
    return rc;
}


/*
 * Frees the variable and any malloc'd data associated with it.
 */
void
snmp_free_var(netsnmp_variable_list * var)
{
    if (!var)
        return;

    if (var->name != var->name_loc)
        SNMP_FREE(var->name);
    if (var->val.string != var->buf)
        SNMP_FREE(var->val.string);
    if (var->data) {
        if (var->dataFreeHook) {
            var->dataFreeHook(var->data);
            var->data = NULL;
        } else {
            SNMP_FREE(var->data);
        }
    }

    free((char *) var);
}

void
snmp_free_varbind(netsnmp_variable_list * var)
{
    netsnmp_variable_list *ptr;
    while (var) {
        ptr = var->next_variable;
        snmp_free_var(var);
        var = ptr;
    }
}

/*
 * Frees the pdu and any malloc'd data associated with it.
 */
void
snmp_free_pdu(netsnmp_pdu *pdu)
{
    struct snmp_secmod_def *sptr;

    if (!pdu)
        return;

    /*
     * If the command field is empty, that probably indicates
     *   that this PDU structure has already been freed.
     *   Log a warning and return (rather than freeing things again)
     *
     * Note that this does not pick up dual-frees where the
     *   memory is set to random junk, which is probably more serious.
     *
     * rks: while this is a good idea, there are two problems.
     *         1) agentx sets command to 0 in some cases
     *         2) according to Wes, a bad decode of a v3 message could
     *            result in a 0 at this offset.
     *      so I'm commenting it out until a better solution is found.
     *      note that I'm leaving the memset, below....
     *
    if (pdu->command == 0) {
        snmp_log(LOG_WARNING, "snmp_free_pdu probably called twice\n");
        return;
    }
     */
    if ((sptr = find_sec_mod(pdu->securityModel)) != NULL &&
        sptr->pdu_free != NULL) {
        (*sptr->pdu_free) (pdu);
    }
    snmp_free_varbind(pdu->variables);
    SNMP_FREE(pdu->enterprise);
    SNMP_FREE(pdu->community);
    SNMP_FREE(pdu->contextEngineID);
    SNMP_FREE(pdu->securityEngineID);
    SNMP_FREE(pdu->contextName);
    SNMP_FREE(pdu->securityName);
    SNMP_FREE(pdu->transport_data);
    memset(pdu, 0, sizeof(netsnmp_pdu));
    free((char *) pdu);
}

netsnmp_pdu    *
snmp_create_sess_pdu(netsnmp_transport *transport, void *opaque,
                     size_t olength)
{
    netsnmp_pdu *pdu = (netsnmp_pdu *)calloc(1, sizeof(netsnmp_pdu));
    if (pdu == NULL) {
        DEBUGMSGTL(("sess_process_packet", "can't malloc space for PDU\n"));
        return NULL;
    }

    /*
     * Save the transport-level data specific to this reception (e.g. UDP
     * source address).  
     */

    pdu->transport_data = opaque;
    pdu->transport_data_length = olength;
    pdu->tDomain = transport->domain;
    pdu->tDomainLen = transport->domain_length;
    return pdu;
}


/*
 * This function processes a complete (according to asn_check_packet or the
 * AgentX equivalent) packet, parsing it into a PDU and calling the relevant
 * callbacks.  On entry, packetptr points at the packet in the session's
 * buffer and length is the length of the packet.  
 */

static int
_sess_process_packet(void *sessp, netsnmp_session * sp,
                     struct snmp_internal_session *isp,
                     netsnmp_transport *transport,
                     void *opaque, int olength,
                     u_char * packetptr, int length)
{
  struct session_list *slp = (struct session_list *) sessp;
  netsnmp_pdu    *pdu;
  netsnmp_request_list *rp, *orp = NULL;
  struct snmp_secmod_def *sptr;
  int             ret = 0, handled = 0;

  DEBUGMSGTL(("sess_process_packet",
	      "session %p fd %d pkt %p length %d\n", sessp,
	      transport->sock, packetptr, length));

  if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, 
			     NETSNMP_DS_LIB_DUMP_PACKET)) {
    if (transport->f_fmtaddr != NULL) {
      char *addrtxt = transport->f_fmtaddr(transport, opaque, olength);
      if (addrtxt != NULL) {
	snmp_log(LOG_DEBUG, "\nReceived %d bytes from %s\n",
		 length, addrtxt);
	SNMP_FREE(addrtxt);
      } else {
	snmp_log(LOG_DEBUG, "\nReceived %d bytes from <UNKNOWN>\n",
		 length);
      }
    }
    xdump(packetptr, length, "");
  }

  /*
   * Do transport-level filtering (e.g. IP-address based allow/deny).  
   */

  if (isp->hook_pre) {
    if (isp->hook_pre(sp, transport, opaque, olength) == 0) {
      DEBUGMSGTL(("sess_process_packet", "pre-parse fail\n"));
      if (opaque != NULL) {
	SNMP_FREE(opaque);
      }
      return -1;
    }
  }

  if (isp->hook_create_pdu) {
    pdu = isp->hook_create_pdu(transport, opaque, olength);
  } else {
    pdu = snmp_create_sess_pdu(transport, opaque, olength);
  }
  if (pdu == NULL) {
    snmp_log(LOG_ERR, "pdu failed to be created\n");
    if (opaque != NULL) {
      SNMP_FREE(opaque);
    }
    return -1;
  }

  if (isp->hook_parse) {
    ret = isp->hook_parse(sp, pdu, packetptr, length);
  } else {
    ret = snmp_parse(sessp, sp, pdu, packetptr, length);
  }

  if (ret != SNMP_ERR_NOERROR) {
    DEBUGMSGTL(("sess_process_packet", "parse fail\n"));
  }

  if (isp->hook_post) {
    if (isp->hook_post(sp, pdu, ret) == 0) {
      DEBUGMSGTL(("sess_process_packet", "post-parse fail\n"));
      ret = SNMPERR_ASN_PARSE_ERR;
    }
  }

  if (ret != SNMP_ERR_NOERROR) {
    /*
     * Call the security model to free any securityStateRef supplied w/ msg.  
     */
    if (pdu->securityStateRef != NULL) {
      sptr = find_sec_mod(pdu->securityModel);
      if (sptr != NULL) {
	if (sptr->pdu_free_state_ref != NULL) {
	  (*sptr->pdu_free_state_ref) (pdu->securityStateRef);
	} else {
	  snmp_log(LOG_ERR,
		   "Security Model %d can't free state references\n",
		   pdu->securityModel);
	}
      } else {
	snmp_log(LOG_ERR,
		 "Can't find security model to free ptr: %d\n",
		 pdu->securityModel);
      }
      pdu->securityStateRef = NULL;
    }
    snmp_free_pdu(pdu);
    return -1;
  }

  if (pdu->flags & UCD_MSG_FLAG_RESPONSE_PDU) {
    /*
     * Call USM to free any securityStateRef supplied with the message.  
     */
    if (pdu->securityStateRef) {
      sptr = find_sec_mod(pdu->securityModel);
      if (sptr) {
	if (sptr->pdu_free_state_ref) {
	  (*sptr->pdu_free_state_ref) (pdu->securityStateRef);
	} else {
	  snmp_log(LOG_ERR,
		   "Security Model %d can't free state references\n",
		   pdu->securityModel);
	}
      } else {
	snmp_log(LOG_ERR,
		 "Can't find security model to free ptr: %d\n",
		 pdu->securityModel);
      }
      pdu->securityStateRef = NULL;
    }

    for (rp = isp->requests; rp; orp = rp, rp = rp->next_request) {
      snmp_callback   callback;
      void           *magic;

      if (pdu->version == SNMP_VERSION_3) {
	/*
	 * msgId must match for v3 messages.  
	 */
	if (rp->message_id != pdu->msgid) {
	  continue;
	}

	/*
	 * Check that message fields match original, if not, no further
	 * processing.  
	 */
	if (!snmpv3_verify_msg(rp, pdu)) {
	  break;
	}
      } else {
	if (rp->request_id != pdu->reqid) {
	  continue;
	}
      }

      if (rp->callback) {
	callback = rp->callback;
	magic = rp->cb_data;
      } else {
	callback = sp->callback;
	magic = sp->callback_magic;
      }
      handled = 1;

      /*
       * MTR snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);  ?* XX lock
       * should be per session ! 
       */

      if (callback == NULL
	  || callback(NETSNMP_CALLBACK_OP_RECEIVED_MESSAGE, sp,
		      pdu->reqid, pdu, magic) == 1) {
	if (pdu->command == SNMP_MSG_REPORT) {
	  if (sp->s_snmp_errno == SNMPERR_NOT_IN_TIME_WINDOW ||
	      snmpv3_get_report_type(pdu) ==
	      SNMPERR_NOT_IN_TIME_WINDOW) {
	    /*
	     * trigger immediate retry on recoverable Reports 
	     * * (notInTimeWindow), incr_retries == TRUE to prevent
	     * * inifinite resend                      
	     */
	    if (rp->retries <= sp->retries) {
	      snmp_resend_request(slp, rp, TRUE);
	      break;
	    }
	  } else {
	    if (SNMPV3_IGNORE_UNAUTH_REPORTS) {
	      break;
	    }
	  }

	  /*
	   * Handle engineID discovery.  
	   */
	  if (!sp->securityEngineIDLen && pdu->securityEngineIDLen) {
	    sp->securityEngineID =
	      (u_char *) malloc(pdu->securityEngineIDLen);
	    if (sp->securityEngineID == NULL) {
	      /*
	       * TODO FIX: recover after message callback *?
	       * return -1;
	       */
	    }
	    memcpy(sp->securityEngineID, pdu->securityEngineID,
		   pdu->securityEngineIDLen);
	    sp->securityEngineIDLen = pdu->securityEngineIDLen;
	    if (!sp->contextEngineIDLen) {
	      sp->contextEngineID =
		(u_char *) malloc(pdu->
				  securityEngineIDLen);
	      if (sp->contextEngineID == NULL) {
		/*
		 * TODO FIX: recover after message callback *?
		 * return -1;
		 */
	      }
	      memcpy(sp->contextEngineID,
		     pdu->securityEngineID,
		     pdu->securityEngineIDLen);
	      sp->contextEngineIDLen =
		pdu->securityEngineIDLen;
	    }
	  }
	}

	/*
	 * Successful, so delete request.  
	 */
	if (isp->requests == rp) {
	  isp->requests = rp->next_request;
	  if (isp->requestsEnd == rp) {
	    isp->requestsEnd = NULL;
	  }
	} else {
	  orp->next_request = rp->next_request;
	  if (isp->requestsEnd == rp) {
	    isp->requestsEnd = orp;
	  }
	}
	snmp_free_pdu(rp->pdu);
	free((char *) rp);
	/*
	 * There shouldn't be any more requests with the same reqid.  
	 */
	break;
      }
      /*
       * MTR snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);  ?* XX lock should be per session ! 
       */
    }
  } else {
    if (sp->callback) {
      /*
       * MTR snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION); 
       */
      handled = 1;
      sp->callback(NETSNMP_CALLBACK_OP_RECEIVED_MESSAGE,
		   sp, pdu->reqid, pdu, sp->callback_magic);
      /*
       * MTR snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION); 
       */
    }
  }

  /*
   * Call USM to free any securityStateRef supplied with the message.  
   */
  if (pdu != NULL && pdu->securityStateRef &&
      pdu->command == SNMP_MSG_TRAP2) {
    sptr = find_sec_mod(pdu->securityModel);
    if (sptr) {
      if (sptr->pdu_free_state_ref) {
	(*sptr->pdu_free_state_ref) (pdu->securityStateRef);
      } else {
	snmp_log(LOG_ERR,
		 "Security Model %d can't free state references\n",
		 pdu->securityModel);
      }
    } else {
      snmp_log(LOG_ERR,
	       "Can't find security model to free ptr: %d\n",
	       pdu->securityModel);
    }
    pdu->securityStateRef = NULL;
  }

  if (!handled) {
    snmp_increment_statistic(STAT_SNMPUNKNOWNPDUHANDLERS);
    DEBUGMSGTL(("sess_process_packet", "unhandled PDU\n"));
  }

  snmp_free_pdu(pdu);
  return 0;
}

/*
 * Checks to see if any of the fd's set in the fdset belong to
 * snmp.  Each socket with it's fd set has a packet read from it
 * and snmp_parse is called on the packet received.  The resulting pdu
 * is passed to the callback routine for that session.  If the callback
 * routine returns successfully, the pdu and it's request are deleted.
 */
void
snmp_read(fd_set * fdset)
{
    struct session_list *slp;
    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);
    for (slp = Sessions; slp; slp = slp->next) {
        snmp_sess_read((void *) slp, fdset);
    }
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);
}

/*
 * Same as snmp_read, but works just one session. 
 * returns 0 if success, -1 if fail 
 * MTR: can't lock here and at snmp_read 
 * Beware recursive send maybe inside snmp_read callback function. 
 */
int
_sess_read(void *sessp, fd_set * fdset)
{
    struct session_list *slp = (struct session_list *) sessp;
    netsnmp_session *sp = slp ? slp->session : NULL;
    struct snmp_internal_session *isp = slp ? slp->internal : NULL;
    netsnmp_transport *transport = slp ? slp->transport : NULL;
    size_t          pdulen = 0, rxbuf_len = 65536;
    u_char         *rxbuf = NULL;
    int             length = 0, olength = 0, rc = 0;
    void           *opaque = NULL;

    if (!sp || !isp || !transport) {
        DEBUGMSGTL(("sess_read", "read fail: closing...\n"));
        return 0;
    }

    /* to avoid subagent crash */ 
    if (transport->sock < 0) { 
        snmp_log (LOG_INFO, "transport->sock got negative fd value %d\n", transport->sock);
        return 0; 
    }

    if (!fdset || !(FD_ISSET(transport->sock, fdset))) {
        DEBUGMSGTL(("sess_read", "not reading %d (fdset %p set %d)\n",
                    transport->sock, fdset,
                    fdset ? FD_ISSET(transport->sock, fdset) : -9));
        return 0;
    }

    sp->s_snmp_errno = 0;
    sp->s_errno = 0;

    if (transport->flags & NETSNMP_TRANSPORT_FLAG_LISTEN) {
        int             data_sock = transport->f_accept(transport);

        if (data_sock >= 0) {
            /*
             * We've successfully accepted a new stream-based connection.
             * It's not too clear what should happen here if we are using the
             * single-session API at this point.  Basically a "session
             * accepted" callback is probably needed to hand the new session
             * over to the application.
             * 
             * However, for now, as in the original snmp_api, we will ASSUME
             * that we're using the traditional API, and simply add the new
             * session to the list.  Note we don't have to get the Session
             * list lock here, because under that assumption we already hold
             * it (this is also why we don't just use snmp_add).
             * 
             * The moral of the story is: don't use listening stream-based
             * transports in a multi-threaded environment because something
             * will go HORRIBLY wrong (and also that SNMP/TCP is not trivial).
             * 
             * Another open issue: what should happen to sockets that have
             * been accept()ed from a listening socket when that original
             * socket is closed?  If they are left open, then attempting to
             * re-open the listening socket will fail, which is semantically
             * confusing.  Perhaps there should be some kind of chaining in
             * the transport structure so that they can all be closed.
             * Discuss.  ;-)
             */

	    netsnmp_transport *new_transport=netsnmp_transport_copy(transport);
            if (new_transport != NULL) {
                struct session_list *nslp = NULL;

                new_transport->sock = data_sock;
                new_transport->flags &= ~NETSNMP_TRANSPORT_FLAG_LISTEN;

                nslp = (struct session_list *)snmp_sess_add_ex(sp,
			  new_transport, isp->hook_pre, isp->hook_parse,
			  isp->hook_post, isp->hook_build,
			  isp->hook_realloc_build, isp->check_packet,
			  isp->hook_create_pdu);

                if (nslp != NULL) {
                    nslp->next = Sessions;
                    Sessions = nslp;
                } else {
                    new_transport->f_close(new_transport);
                    netsnmp_transport_free(new_transport);
                }
                return 0;
            } else {
                sp->s_snmp_errno = SNMPERR_MALLOC;
                sp->s_errno = errno;
                snmp_set_detail(strerror(errno));
                return -1;
            }
        } else {
            sp->s_snmp_errno = SNMPERR_BAD_RECVFROM;
            sp->s_errno = errno;
            snmp_set_detail(strerror(errno));
            return -1;
        }
    }

    /*
     * Work out where to receive the data to.  
     */

    if (transport->flags & NETSNMP_TRANSPORT_FLAG_STREAM) {
        if (isp->packet == NULL) {
            /*
             * We have no saved packet.  Allocate one.  
             */
            if ((isp->packet = (u_char *) malloc(rxbuf_len)) == NULL) {
                DEBUGMSGTL(("sess_read", "can't malloc %d bytes for rxbuf\n",
                            rxbuf_len));
                return 0;
            } else {
                rxbuf = isp->packet;
                isp->packet_size = rxbuf_len;
                isp->packet_len = 0;
            }
        } else {
            /*
             * We have saved a partial packet from last time.  Extend that, if
             * necessary, and receive new data after the old data.  
             */
            u_char         *newbuf;

            if (isp->packet_size < isp->packet_len + rxbuf_len) {
                newbuf =
                    (u_char *) realloc(isp->packet,
                                       isp->packet_len + rxbuf_len);
                if (newbuf == NULL) {
                    DEBUGMSGTL(("sess_read",
                                "can't malloc %d more for rxbuf (%d tot)\n",
                                rxbuf_len, isp->packet_len + rxbuf_len));
                    return 0;
                } else {
                    isp->packet = newbuf;
                    isp->packet_size = isp->packet_len + rxbuf_len;
                    rxbuf = isp->packet + isp->packet_len;
                }
            } else {
                rxbuf = isp->packet + isp->packet_len;
                rxbuf_len = isp->packet_size - isp->packet_len;
            }
        }
    } else {
        if ((rxbuf = (u_char *) malloc(rxbuf_len)) == NULL) {
            DEBUGMSGTL(("sess_read", "can't malloc %d bytes for rxbuf\n",
                        rxbuf_len));
            return 0;
        }
    }

    length = transport->f_recv(transport, rxbuf, rxbuf_len, &opaque, &olength);

    if (length == -1 && !(transport->flags & NETSNMP_TRANSPORT_FLAG_STREAM)) {
        sp->s_snmp_errno = SNMPERR_BAD_RECVFROM;
        sp->s_errno = errno;
        snmp_set_detail(strerror(errno));
        SNMP_FREE(rxbuf);
        if (opaque != NULL) {
            SNMP_FREE(opaque);
        }
        return -1;
    }

    /*
     * Remote end closed connection.  
     */

    if (length <= 0 && transport->flags & NETSNMP_TRANSPORT_FLAG_STREAM) {
        /*
         * Alert the application if possible.  
         */
        if (sp->callback != NULL) {
            DEBUGMSGTL(("sess_read", "perform callback with op=DISCONNECT\n"));
            (void) sp->callback(NETSNMP_CALLBACK_OP_DISCONNECT, sp, 0,
                                NULL, sp->callback_magic);
        }
        /*
         * Close socket and mark session for deletion.  
         */
        DEBUGMSGTL(("sess_read", "fd %d closed\n", transport->sock));
        transport->f_close(transport);
        SNMP_FREE(isp->packet);
        if (opaque != NULL) {
            SNMP_FREE(opaque);
        }
        return -1;
    }

    if (transport->flags & NETSNMP_TRANSPORT_FLAG_STREAM) {
        u_char *pptr = isp->packet;
	void *ocopy = NULL;

        isp->packet_len += length;

        while (isp->packet_len > 0) {

            /*
             * Get the total data length we're expecting (and need to wait
             * for).
             */
            if (isp->check_packet) {
                pdulen = isp->check_packet(pptr, isp->packet_len);
            } else {
                pdulen = asn_check_packet(pptr, isp->packet_len);
            }

            DEBUGMSGTL(("sess_read", "  loop packet_len %d, PDU length %d\n",
                        isp->packet_len, pdulen));
             
            if ((pdulen > MAX_PACKET_LENGTH) || (pdulen < 0)) {
                /*
                 * Illegal length, drop the connection.  
                 */
                snmp_log(LOG_ERR, 
			 "Received broken packet. Closing session.\n");
		if (sp->callback != NULL) {
		  DEBUGMSGTL(("sess_read",
			      "perform callback with op=DISCONNECT\n"));
		  (void)sp->callback(NETSNMP_CALLBACK_OP_DISCONNECT,
				     sp, 0, NULL, sp->callback_magic);
		}
		DEBUGMSGTL(("sess_read", "fd %d closed\n", transport->sock));
                transport->f_close(transport);
                if (opaque != NULL) {
                    SNMP_FREE(opaque);
                }
                /** XXX-rks: why no SNMP_FREE(isp->packet); ?? */
                return -1;
            }

            if (pdulen > isp->packet_len || pdulen == 0) {
                /*
                 * We don't have a complete packet yet.  If we've already
                 * processed a packet, break out so we'll shift this packet
                 * to the start of the buffer. If we're already at the
                 * start, simply return and wait for more data to arrive.
                 */
                DEBUGMSGTL(("sess_read",
                            "pkt not complete (need %d got %d so far)\n",
                            pdulen, isp->packet_len));

                if (pptr != isp->packet)
                    break; /* opaque freed for us outside of loop. */

                if (opaque != NULL) {
                    SNMP_FREE(opaque);
                }
                return 0;
            }

            /*  We have *at least* one complete packet in the buffer now.  If
		we have possibly more than one packet, we must copy the opaque
		pointer because we may need to reuse it for a later packet.  */

	    if (pdulen < isp->packet_len) {
		if (olength > 0 && opaque != NULL) {
		    ocopy = malloc(olength);
		    if (ocopy != NULL) {
			memcpy(ocopy, opaque, olength);
		    }
		}
	    } else if (pdulen == isp->packet_len) {
		/*  Common case -- exactly one packet.  No need to copy the
		    opaque pointer.  */
		ocopy = opaque;
		opaque = NULL;
	    }

            if ((rc = _sess_process_packet(sessp, sp, isp, transport,
                                           ocopy, ocopy?olength:0, pptr,
                                           pdulen))) {
                /*
                 * Something went wrong while processing this packet -- set the
                 * errno.  
                 */
                if (sp->s_snmp_errno != 0) {
                    SET_SNMP_ERROR(sp->s_snmp_errno);
                }
            }

	    /*  ocopy has been free()d by _sess_process_packet by this point,
		so set it to NULL.  */

	    ocopy = NULL;

	    /*  Step past the packet we've just dealt with.  */

            pptr += pdulen;
            isp->packet_len -= pdulen;
        }

	/*  If we had more than one packet, then we were working with copies
	    of the opaque pointer, so we still need to free() the opaque
	    pointer itself.  */

	if (opaque != NULL) {
	    SNMP_FREE(opaque);
	}

        if (isp->packet_len >= MAXIMUM_PACKET_SIZE) {
            /*
             * Obviously this should never happen!  
             */
            snmp_log(LOG_ERR,
                     "too large packet_len = %d, dropping connection %d\n",
                     isp->packet_len, transport->sock);
            transport->f_close(transport);
            /** XXX-rks: why no SNMP_FREE(isp->packet); ?? */
            return -1;
        } else if (isp->packet_len == 0) {
            /*
             * This is good: it means the packet buffer contained an integral
             * number of PDUs, so we don't have to save any data for next
             * time.  We can free() the buffer now to keep the memory
             * footprint down.
             */
            SNMP_FREE(isp->packet);
            isp->packet = NULL;
            isp->packet_size = 0;
            isp->packet_len = 0;
            return rc;
        }

        /*
         * If we get here, then there is a partial packet of length
         * isp->packet_len bytes starting at pptr left over.  Move that to the
         * start of the buffer, and then realloc() the buffer down to size to
         * reduce the memory footprint.  
         */

        memmove(isp->packet, pptr, isp->packet_len);
        DEBUGMSGTL(("sess_read", "end: memmove(%p, %p, %d); realloc(%p, %d)\n",
                    isp->packet, pptr, isp->packet_len, isp->packet,
                    isp->packet_len));

        if ((rxbuf = realloc(isp->packet, isp->packet_len)) == NULL) {
            /*
             * I don't see why this should ever fail, but it's not a big deal.
             */
            DEBUGMSGTL(("sess_read", "realloc() failed\n"));
        } else {
            DEBUGMSGTL(("sess_read", "realloc() okay, old buffer %p, new %p\n",
                        isp->packet, rxbuf));
            isp->packet = rxbuf;
            isp->packet_size = isp->packet_len;
        }
        return rc;
    } else {
        rc = _sess_process_packet(sessp, sp, isp, transport, opaque,
                                  olength, rxbuf, length);
        SNMP_FREE(rxbuf);
        return rc;
    }
}



/*
 * returns 0 if success, -1 if fail 
 */
int
snmp_sess_read(void *sessp, fd_set * fdset)
{
    struct session_list *psl;
    netsnmp_session *pss;
    int             rc;

    rc = _sess_read(sessp, fdset);
    psl = (struct session_list *) sessp;
    pss = psl->session;
    if (rc && pss->s_snmp_errno) {
        SET_SNMP_ERROR(pss->s_snmp_errno);
    }
    return rc;
}


/*
 * Returns info about what snmp requires from a select statement.
 * numfds is the number of fds in the list that are significant.
 * All file descriptors opened for SNMP are OR'd into the fdset.
 * If activity occurs on any of these file descriptors, snmp_read
 * should be called with that file descriptor set
 *
 * The timeout is the latest time that SNMP can wait for a timeout.  The
 * select should be done with the minimum time between timeout and any other
 * timeouts necessary.  This should be checked upon each invocation of select.
 * If a timeout is received, snmp_timeout should be called to check if the
 * timeout was for SNMP.  (snmp_timeout is idempotent)
 *
 * The value of block indicates how the timeout value is interpreted.
 * If block is true on input, the timeout value will be treated as undefined,
 * but it must be available for setting in snmp_select_info.  On return,
 * block is set to true if the value returned for timeout is undefined;
 * when block is set to false, timeout may be used as a parmeter to 'select'.
 *
 * snmp_select_info returns the number of open sockets.  (i.e. The number of
 * sessions open)
 */

int
snmp_select_info(int *numfds,
                 fd_set * fdset, struct timeval *timeout, int *block)
    /*
     * input:  set to 1 if input timeout value is undefined  
     * set to 0 if input timeout value is defined    
     * output: set to 1 if output timeout value is undefined 
     * set to 0 if output rimeout vlaue id defined   
     */
{
    return snmp_sess_select_info((void *) 0, numfds, fdset, timeout,
                                 block);
}

/*
 * Same as snmp_select_info, but works just one session. 
 */
int
snmp_sess_select_info(void *sessp,
                      int *numfds,
                      fd_set * fdset, struct timeval *timeout, int *block)
{
    struct session_list *slptest = (struct session_list *) sessp;
    struct session_list *slp, *next = NULL;
    netsnmp_request_list *rp;
    struct timeval  now, earliest, delta;
    int             active = 0, requests = 0;
    int             next_alarm = 0;

    timerclear(&earliest);

    /*
     * For each request outstanding, add its socket to the fdset,
     * and if it is the earliest timeout to expire, mark it as lowest.
     * If a single session is specified, do just for that session.
     */

    if (sessp) {
        slp = slptest;
    } else {
        slp = Sessions;
    }

    DEBUGMSGTL(("sess_select", "for %s session%s: ",
                sessp ? "single" : "all", sessp ? "" : "s"));

    for (; slp; slp = next) {
        next = slp->next;

        if (slp->transport == NULL) {
            /*
             * Close in progress -- skip this one.  
             */
            DEBUGMSG(("sess_select", "skip "));
            continue;
        }

        if (slp->transport->sock == -1) {
            /*
             * This session was marked for deletion.  
             */
            DEBUGMSG(("sess_select", "delete\n"));
            if (sessp == NULL) {
                snmp_close(slp->session);
            } else {
                snmp_sess_close(slp);
            }
            DEBUGMSGTL(("sess_select", "for %s session%s: ",
                        sessp ? "single" : "all", sessp ? "" : "s"));
            continue;
        }

        DEBUGMSG(("sess_select", "%d ", slp->transport->sock));
        if ((slp->transport->sock + 1) > *numfds) {
            *numfds = (slp->transport->sock + 1);
        }

        FD_SET(slp->transport->sock, fdset);
        if (slp->internal != NULL && slp->internal->requests) {
            /*
             * Found another session with outstanding requests.  
             */
            requests++;
            for (rp = slp->internal->requests; rp; rp = rp->next_request) {
                if ((!timerisset(&earliest)
                     || (timercmp(&rp->expire, &earliest, <)))) {
                    earliest = rp->expire;
                    DEBUGMSG(("verbose:sess_select","(to in %d.%d sec) ",
                               earliest.tv_sec, earliest.tv_usec));
                }
            }
        }

        active++;
        if (sessp) {
            /*
             * Single session processing.  
             */
            break;
        }
    }
    DEBUGMSG(("sess_select", "\n"));

    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_ALARM_DONT_USE_SIG)) {
        next_alarm = get_next_alarm_delay_time(&delta);
        DEBUGMSGT(("sess_select","next alarm %d.%d sec\n",
                   delta.tv_sec, delta.tv_usec));
    }
    if (next_alarm == 0 && requests == 0) {
        /*
         * If none are active, skip arithmetic.  
         */
        DEBUGMSGT(("sess_select","blocking:no session requests or alarms.\n"));
        *block = 1; /* can block - timeout value is undefined if no requests */
        return active;
    }

    /*
     * * Now find out how much time until the earliest timeout.  This
     * * transforms earliest from an absolute time into a delta time, the
     * * time left until the select should timeout.
     */
    gettimeofday(&now, (struct timezone *) 0);
    /*
     * Now = now;
     */

    if (next_alarm) {
        delta.tv_sec += now.tv_sec;
        delta.tv_usec += now.tv_usec;
        while (delta.tv_usec >= 1000000) {
            delta.tv_usec -= 1000000;
            delta.tv_sec += 1;
        }
        if (!timerisset(&earliest) ||
            ((earliest.tv_sec > delta.tv_sec) ||
             ((earliest.tv_sec == delta.tv_sec) &&
              (earliest.tv_usec > delta.tv_usec)))) {
            earliest.tv_sec = delta.tv_sec;
            earliest.tv_usec = delta.tv_usec;
        }
    }

    if (earliest.tv_sec < now.tv_sec) {
        DEBUGMSGT(("verbose:sess_select","timer overdue\n"));
        earliest.tv_sec = 0;
        earliest.tv_usec = 0;
    } else if (earliest.tv_sec == now.tv_sec) {
        earliest.tv_sec = 0;
        earliest.tv_usec = (earliest.tv_usec - now.tv_usec);
        if (earliest.tv_usec < 0) {
            earliest.tv_usec = 100;
        }
        DEBUGMSGT(("verbose:sess_select","timer due *real* soon. %d usec\n",
                   earliest.tv_usec));
    } else {
        earliest.tv_sec = (earliest.tv_sec - now.tv_sec);
        earliest.tv_usec = (earliest.tv_usec - now.tv_usec);
        if (earliest.tv_usec < 0) {
            earliest.tv_sec--;
            earliest.tv_usec = (1000000L + earliest.tv_usec);
        }
        DEBUGMSGT(("verbose:sess_select","timer due in %d.%d sec\n",
                   earliest.tv_sec, earliest.tv_usec));
    }

    /*
     * if it was blocking before or our delta time is less, reset timeout 
     */
    if ((*block || (timercmp(&earliest, timeout, <)))) {
        DEBUGMSGT(("verbose:sess_select",
                   "setting timer to %d.%d sec, clear block (was %d)\n",
                   earliest.tv_sec, earliest.tv_usec, *block));
        *timeout = earliest;
        *block = 0;
    }
    return active;
}

/*
 * snmp_timeout should be called whenever the timeout from snmp_select_info
 * expires, but it is idempotent, so snmp_timeout can be polled (probably a
 * cpu expensive proposition).  snmp_timeout checks to see if any of the
 * sessions have an outstanding request that has timed out.  If it finds one
 * (or more), and that pdu has more retries available, a new packet is formed
 * from the pdu and is resent.  If there are no more retries available, the
 *  callback for the session is used to alert the user of the timeout.
 */
void
snmp_timeout(void)
{
    struct session_list *slp;
    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);
    for (slp = Sessions; slp; slp = slp->next) {
        snmp_sess_timeout((void *) slp);
    }
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);
}

static int
snmp_resend_request(struct session_list *slp, netsnmp_request_list *rp,
                    int incr_retries)
{
    struct snmp_internal_session *isp;
    netsnmp_session *sp;
    netsnmp_transport *transport;
    u_char         *pktbuf = NULL, *packet = NULL;
    size_t          pktbuf_len = 0, offset = 0, length = 0;
    struct timeval  tv, now;
    int             result = 0;

    sp = slp->session;
    isp = slp->internal;
    transport = slp->transport;
    if (!sp || !isp || !transport) {
        DEBUGMSGTL(("sess_read", "resend fail: closing...\n"));
        return 0;
    }

    if ((pktbuf = malloc(2048)) == NULL) {
        DEBUGMSGTL(("sess_resend",
                    "couldn't malloc initial packet buffer\n"));
        return 0;
    } else {
        pktbuf_len = 2048;
    }

    if (incr_retries) {
        rp->retries++;
    }

    /*
     * Always increment msgId for resent messages.  
     */
    rp->pdu->msgid = rp->message_id = snmp_get_next_msgid();

    if (isp->hook_realloc_build) {
        result = isp->hook_realloc_build(sp, rp->pdu,
                                         &pktbuf, &pktbuf_len, &offset);

        packet = pktbuf;
        length = offset;
    } else if (isp->hook_build) {
        packet = pktbuf;
        length = pktbuf_len;
        result = isp->hook_build(sp, rp->pdu, pktbuf, &length);
    } else {
#ifdef USE_REVERSE_ASNENCODING
        if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_REVERSE_ENCODE)) {
            result =
                snmp_build(&pktbuf, &pktbuf_len, &offset, sp, rp->pdu);
            packet = pktbuf + pktbuf_len - offset;
            length = offset;
        } else {
#endif
            packet = pktbuf;
            length = pktbuf_len;
            result = snmp_build(&pktbuf, &length, &offset, sp, rp->pdu);
#ifdef USE_REVERSE_ASNENCODING
        }
#endif
    }

    if (result < 0) {
        /*
         * This should never happen.  
         */
        DEBUGMSGTL(("sess_resend", "encoding failure\n"));
        if (pktbuf != NULL) {
            SNMP_FREE(pktbuf);
        }
        return -1;
    }

    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_DUMP_PACKET)) {
        if (transport->f_fmtaddr != NULL) {
            char           *str = NULL;
            str = transport->f_fmtaddr(transport, rp->pdu->transport_data,
                                       rp->pdu->transport_data_length);
            if (str != NULL) {
                snmp_log(LOG_DEBUG, "\nResending %d bytes to %s\n", length,
                         str);
                SNMP_FREE(str);
            } else {
                snmp_log(LOG_DEBUG, "\nResending %d bytes to <UNKNOWN>\n",
                         length);
            }
        }
        xdump(packet, length, "");
    }

    result = transport->f_send(transport, packet, length,
                               &(rp->pdu->transport_data),
                               &(rp->pdu->transport_data_length));

    /*
     * We are finished with the local packet buffer, if we allocated one (due
     * to there being no saved packet).  
     */

    if (pktbuf != NULL) {
        SNMP_FREE(pktbuf);
        pktbuf = packet = NULL;
    }

    if (result < 0) {
        sp->s_snmp_errno = SNMPERR_BAD_SENDTO;
        sp->s_errno = errno;
        snmp_set_detail(strerror(errno));
        return -1;
    } else {
        gettimeofday(&now, (struct timezone *) 0);
        tv = now;
        rp->time = tv;
        tv.tv_usec += rp->timeout;
        tv.tv_sec += tv.tv_usec / 1000000L;
        tv.tv_usec %= 1000000L;
        rp->expire = tv;
    }
    return 0;
}



void
snmp_sess_timeout(void *sessp)
{
    struct session_list *slp = (struct session_list *) sessp;
    netsnmp_session *sp;
    struct snmp_internal_session *isp;
    netsnmp_request_list *rp, *orp = NULL, *freeme = NULL;
    struct timeval  now;
    snmp_callback   callback;
    void           *magic;
    struct snmp_secmod_def *sptr;

    sp = slp->session;
    isp = slp->internal;
    if (!sp || !isp) {
        DEBUGMSGTL(("sess_read", "timeout fail: closing...\n"));
        return;
    }

    gettimeofday(&now, (struct timezone *) 0);

    /*
     * For each request outstanding, check to see if it has expired.
     */
    for (rp = isp->requests; rp; rp = rp->next_request) {
        if (freeme != NULL) {
            /*
             * frees rp's after the for loop goes on to the next_request 
             */
            free((char *) freeme);
            freeme = NULL;
        }

        if ((timercmp(&rp->expire, &now, <))) {
            if ((sptr = find_sec_mod(rp->pdu->securityModel)) != NULL &&
                sptr->pdu_timeout != NULL) {
                /*
                 * call security model if it needs to know about this 
                 */
                (*sptr->pdu_timeout) (rp->pdu);
            }

            /*
             * this timer has expired 
             */
            if (rp->retries >= sp->retries) {
                if (rp->callback) {
                    callback = rp->callback;
                    magic = rp->cb_data;
                } else {
                    callback = sp->callback;
                    magic = sp->callback_magic;
                }

                /*
                 * No more chances, delete this entry 
                 */
                if (callback) {
                    callback(NETSNMP_CALLBACK_OP_TIMED_OUT, sp,
                             rp->pdu->reqid, rp->pdu, magic);
                }
                if (isp->requests == rp) {
                    isp->requests = rp->next_request;
                    if (isp->requestsEnd == rp) {
                        isp->requestsEnd = NULL;
                    }
                } else {
                    orp->next_request = rp->next_request;
                    if (isp->requestsEnd == rp) {
                        isp->requestsEnd = orp;
                    }
                }
                snmp_free_pdu(rp->pdu); /* FIX  rp is already free'd! */
                freeme = rp;
                continue;       /* don't update orp below */
            } else {
                if (snmp_resend_request(slp, rp, TRUE)) {
                    break;
                }
            }
        }
        orp = rp;
    }

    if (freeme != NULL) {
        free((char *) freeme);
        freeme = NULL;
    }
}

/*
 * lexicographical compare two object identifiers.
 * * Returns -1 if name1 < name2,
 * *          0 if name1 = name2,
 * *          1 if name1 > name2
 * *
 * * Caution: this method is called often by
 * *          command responder applications (ie, agent).
 */
int
snmp_oid_ncompare(const oid * in_name1,
                  size_t len1,
                  const oid * in_name2, size_t len2, size_t max_len)
{
    register int    len;
    register const oid *name1 = in_name1;
    register const oid *name2 = in_name2;
    size_t          min_len;

    /*
     * len = minimum of len1 and len2 
     */
    if (len1 < len2)
        min_len = len1;
    else
        min_len = len2;

    if (min_len > max_len)
        min_len = max_len;

    len = min_len;

    /*
     * find first non-matching OID 
     */
    while (len-- > 0) {
        /*
         * these must be done in seperate comparisons, since
         * subtracting them and using that result has problems with
         * subids > 2^31. 
         */
        if (*(name1) != *(name2)) {
            if (*(name1) < *(name2))
                return -1;
            return 1;
        }
        name1++;
        name2++;
    }

    if (min_len != max_len) {
        /*
         * both OIDs equal up to length of shorter OID 
         */
        if (len1 < len2)
            return -1;
        if (len2 < len1)
            return 1;
    }

    return 0;
}

/** lexicographical compare two object identifiers.
 * 
 * Caution: this method is called often by
 *          command responder applications (ie, agent).
 *
 * @return -1 if name1 < name2, 0 if name1 = name2, 1 if name1 > name2
 */
int
snmp_oid_compare(const oid * in_name1,
                 size_t len1, const oid * in_name2, size_t len2)
{
    register int    len;
    register const oid *name1 = in_name1;
    register const oid *name2 = in_name2;

    /*
     * len = minimum of len1 and len2 
     */
    if (len1 < len2)
        len = len1;
    else
        len = len2;
    /*
     * find first non-matching OID 
     */
    while (len-- > 0) {
        /*
         * these must be done in seperate comparisons, since
         * subtracting them and using that result has problems with
         * subids > 2^31. 
         */
        if (*(name1) != *(name2)) {
            if (*(name1) < *(name2))
                return -1;
            return 1;
        }
        name1++;
        name2++;
    }
    /*
     * both OIDs equal up to length of shorter OID 
     */
    if (len1 < len2)
        return -1;
    if (len2 < len1)
        return 1;
    return 0;
}

/** Compares 2 OIDs to determine if they are equal up until the shortest length.
 * @param in_name1 A pointer to the first oid.
 * @param len1     length of the first OID (in segments, not bytes)
 * @param in_name2 A pointer to the second oid.
 * @param len2     length of the second OID (in segments, not bytes)
 * @return 0 if they are equal, 1 if in_name1 is > in_name2, or -1 if <.
 */ 
int
snmp_oidtree_compare(const oid * in_name1,
                     size_t len1, const oid * in_name2, size_t len2)
{
    int             len = ((len1 < len2) ? len1 : len2);

    return (snmp_oid_compare(in_name1, len, in_name2, len));
}

/** Compares 2 OIDs to determine if they are exactly equal.
 *  This should be faster than doing a snmp_oid_compare for different
 *  length OIDs, since the length is checked first and if != returns
 *  immediately.  Might be very slighly faster if lengths are ==.
 * @param in_name1 A pointer to the first oid.
 * @param len1     length of the first OID (in segments, not bytes)
 * @param in_name2 A pointer to the second oid.
 * @param len2     length of the second OID (in segments, not bytes)
 * @return 0 if they are equal, 1 if they are not.
 */ 
int
netsnmp_oid_equals(const oid * in_name1,
                   size_t len1, const oid * in_name2, size_t len2)
{
    register const oid *name1 = in_name1;
    register const oid *name2 = in_name2;
    register int    len = len1;

    /*
     * len = minimum of len1 and len2 
     */
    if (len1 != len2)
        return 1;
    /*
     * find first non-matching OID 
     */
    while (len-- > 0) {
        /*
         * these must be done in seperate comparisons, since
         * subtracting them and using that result has problems with
         * subids > 2^31. 
         */
        if (*(name1++) != *(name2++))
            return 1;
    }
    return 0;
}

/** Identical to netsnmp_oid_equals, except only the length up to len1 is compared.
 * Functionally, this determines if in_name2 is equal or a subtree of in_name1
 * @param in_name1 A pointer to the first oid.
 * @param len1     length of the first OID (in segments, not bytes)
 * @param in_name2 A pointer to the second oid.
 * @param len2     length of the second OID (in segments, not bytes)
 * @return 0 if one is a common prefix of the other.
 */ 
int
netsnmp_oid_is_subtree(const oid * in_name1,
                       size_t len1, const oid * in_name2, size_t len2)
{
    if (len1 > len2)
        return 1;

    if (memcmp(in_name1, in_name2, len1 * sizeof(oid)))
        return 1;

    return 0;
}

/** Given two OIDs, determine the common prefix to them both.
 * @param in_name1 A pointer to the first oid.
 * @param len1     Length of the first oid.
 * @param in_name2 A pointer to the second oid.
 * @param len2     Length of the second oid.
 * @return length of largest common index of commonality.  1 = first, 0 if none *         or -1 on error.
 */
int
netsnmp_oid_find_prefix(const oid * in_name1, size_t len1,
                        const oid * in_name2, size_t len2)
{
    int i;
    size_t min_size;

    if (!in_name1 || !in_name2 || !len1 || !len2)
        return -1;

    if (in_name1[0] != in_name2[0])
        return 0;   /* No match */
    min_size = SNMP_MIN(len1, len2);
    for(i = 0; i < (int)min_size; i++) {
        if (in_name1[i] != in_name2[i])
            return i + 1;    /* Why +1 ?? */
    }
    return min_size;    /* or +1? - the spec isn't totally clear */
}

static int _check_range(struct tree *tp, long ltmp, int *resptr,
	                const char *errmsg)
{
    char *cp   = NULL;
    char *temp = NULL;
    int   temp_len = 0;
    int check = !netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID,
	                                NETSNMP_DS_LIB_DONT_CHECK_RANGE);
  
    if (check && tp && tp->ranges) {
	struct range_list *rp = tp->ranges;
	while (rp) {
	    if (rp->low <= ltmp && ltmp <= rp->high) break;
                                  /* Allow four digits per range value */
            temp_len += ((rp->low != rp->high) ? 14 : 8 );
	    rp = rp->next;
	}
	if (!rp) {
	    *resptr = SNMPERR_RANGE;
            temp = (char *)malloc( temp_len+strlen(errmsg)+7);
            if ( temp ) {
                /* Append the Display Hint range information to the error message */
                sprintf( temp, "%s :: {", errmsg );
                cp = temp+(strlen(temp));
                for ( rp = tp->ranges; rp; rp=rp->next ) {
                    if ( rp->low != rp->high ) 
                        sprintf( cp, "(%d..%d), ", rp->low, rp->high );
                    else
                        sprintf( cp, "(%d), ", rp->low );
                    cp += strlen(cp);
                }
                *(cp-2) = '}';   /* Replace the final comma with a '}' */
                *(cp-1) = 0;
	        snmp_set_detail(temp);
	        free(temp);
            }
	    return 0;
	}
    }
    free(temp);
    return 1;
}
        

/*
 * Add a variable with the requested name to the end of the list of
 * variables for this pdu.
 */
netsnmp_variable_list *
snmp_pdu_add_variable(netsnmp_pdu *pdu,
                      const oid * name,
                      size_t name_length,
                      u_char type, const u_char * value, size_t len)
{
    return snmp_varlist_add_variable(&pdu->variables, name, name_length,
                                     type, value, len);
}

/*
 * Add a variable with the requested name to the end of the list of
 * variables for this pdu.
 */
netsnmp_variable_list *
snmp_varlist_add_variable(netsnmp_variable_list ** varlist,
                          const oid * name,
                          size_t name_length,
                          u_char type, const u_char * value, size_t len)
{
    netsnmp_variable_list *vars, *vtmp;
    int rc;

    if (varlist == NULL)
        return NULL;

    vars = SNMP_MALLOC_TYPEDEF(netsnmp_variable_list);
    if (vars == NULL)
        return NULL;

    vars->type = type;

    rc = snmp_set_var_value( vars, value, len );
    if (( 0 != rc ) ||
        (name != NULL && snmp_set_var_objid(vars, name, name_length))) {
        snmp_free_var(vars);
        return (0);
    }

    /*
     * put only qualified variable onto varlist 
     */
    if (*varlist == NULL) {
        *varlist = vars;
    } else {
        for (vtmp = *varlist; vtmp->next_variable;
             vtmp = vtmp->next_variable);

        vtmp->next_variable = vars;
    }

    return vars;
}



/*
 * Add a variable with the requested name to the end of the list of
 * variables for this pdu.
 * Returns:
 * may set these error types :
 * SNMPERR_RANGE - type, value, or length not found or out of range
 * SNMPERR_VALUE - value is not correct
 * SNMPERR_VAR_TYPE - type is not correct
 * SNMPERR_BAD_NAME - name is not found
 *
 * returns 0 if success, error if failure.
 */
int
snmp_add_var(netsnmp_pdu *pdu,
             const oid * name, size_t name_length, char type, const char *value)
{
    char           *st;
    const char     *cp;
    char           *ecp, *vp;
    int             result = SNMPERR_SUCCESS;
#ifndef DISABLE_MIB_LOADING
    int             check = !netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID,
					     NETSNMP_DS_LIB_DONT_CHECK_RANGE);
    int             do_hint = !netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID,
					     NETSNMP_DS_LIB_NO_DISPLAY_HINT);
    u_char         *hintptr;
    struct tree    *tp;
#endif /* DISABLE_MIB_LOADING */
    u_char         *buf = NULL;
    const u_char   *buf_ptr = NULL;
    size_t          buf_len = 0, value_len = 0, tint;
    in_addr_t       atmp;
    long            ltmp;
    int             itmp;
    struct enum_list *ep;
#ifdef OPAQUE_SPECIAL_TYPES
    double          dtmp;
    float           ftmp;
#endif                          /* OPAQUE_SPECIAL_TYPES */
    struct counter64 c64tmp;

#ifndef DISABLE_MIB_LOADING
    tp = get_tree(name, name_length, get_tree_head());
    if (!tp || !tp->type || tp->type > TYPE_SIMPLE_LAST) {
        check = 0;
    }
    if (!(tp && tp->hint))
	do_hint = 0;

    if (tp && type == '=') {
        /*
         * generic assignment - let the tree node decide value format 
         */
        switch (tp->type) {
        case TYPE_INTEGER:
        case TYPE_INTEGER32:
            type = 'i';
            break;
        case TYPE_GAUGE:
        case TYPE_UNSIGNED32:
            type = 'u';
            break;
        case TYPE_UINTEGER:
            type = '3';
            break;
        case TYPE_COUNTER:
            type = 'c';
            break;
        case TYPE_COUNTER64:
            type = 'C';
            break;
        case TYPE_TIMETICKS:
            type = 't';
            break;
        case TYPE_OCTETSTR:
            type = 's';
            break;
        case TYPE_BITSTRING:
            type = 'b';
            break;
        case TYPE_IPADDR:
            type = 'a';
            break;
        case TYPE_OBJID:
            type = 'o';
            break;
        }
    }
#endif /* DISABLE_MIB_LOADING */

    switch (type) {
    case 'i':
#ifndef DISABLE_MIB_LOADING
        if (check && tp->type != TYPE_INTEGER
            && tp->type != TYPE_INTEGER32) {
            value = "INTEGER";
            result = SNMPERR_VALUE;
            goto type_error;
        }
#endif /* DISABLE_MIB_LOADING */
        if (!*value)
            goto fail;
        ltmp = strtol(value, &ecp, 10);
        if (*ecp) {
#ifndef DISABLE_MIB_LOADING
            ep = tp ? tp->enums : NULL;
            while (ep) {
                if (strcmp(value, ep->label) == 0) {
                    ltmp = ep->value;
                    break;
                }
                ep = ep->next;
            }
            if (!ep) {
#endif /* DISABLE_MIB_LOADING */
                result = SNMPERR_RANGE;   /* ?? or SNMPERR_VALUE; */
                snmp_set_detail(value);
                break;
#ifndef DISABLE_MIB_LOADING
            }
#endif /* DISABLE_MIB_LOADING */
        }

#ifndef DISABLE_MIB_LOADING
        if (!_check_range(tp, ltmp, &result, value))
            break;
#endif /* DISABLE_MIB_LOADING */
        snmp_pdu_add_variable(pdu, name, name_length, ASN_INTEGER,
                              (u_char *) & ltmp, sizeof(ltmp));
        break;

    case 'u':
#ifndef DISABLE_MIB_LOADING
        if (check && tp->type != TYPE_GAUGE && tp->type != TYPE_UNSIGNED32) {
            value = "Unsigned32";
            result = SNMPERR_VALUE;
            goto type_error;
        }
#endif /* DISABLE_MIB_LOADING */
        ltmp = strtoul(value, &ecp, 10);
        if (*value && !*ecp)
            snmp_pdu_add_variable(pdu, name, name_length, ASN_UNSIGNED,
                                  (u_char *) & ltmp, sizeof(ltmp));
        else
            goto fail;
        break;

    case '3':
#ifndef DISABLE_MIB_LOADING
        if (check && tp->type != TYPE_UINTEGER) {
            value = "UInteger32";
            result = SNMPERR_VALUE;
            goto type_error;
        }
#endif /* DISABLE_MIB_LOADING */
        ltmp = strtoul(value, &ecp, 10);
        if (*value && !*ecp)
            snmp_pdu_add_variable(pdu, name, name_length, ASN_UINTEGER,
                                  (u_char *) & ltmp, sizeof(ltmp));
        else
            goto fail;
        break;

    case 'c':
#ifndef DISABLE_MIB_LOADING
        if (check && tp->type != TYPE_COUNTER) {
            value = "Counter32";
            result = SNMPERR_VALUE;
            goto type_error;
        }
#endif /* DISABLE_MIB_LOADING */
        ltmp = strtoul(value, &ecp, 10);
        if (*value && !*ecp)
            snmp_pdu_add_variable(pdu, name, name_length, ASN_COUNTER,
                                  (u_char *) & ltmp, sizeof(ltmp));
        else
            goto fail;
        break;

    case 'C':
#ifndef DISABLE_MIB_LOADING
        if (check && tp->type != TYPE_COUNTER64) {
            value = "Counter64";
            result = SNMPERR_VALUE;
            goto type_error;
        }
#endif /* DISABLE_MIB_LOADING */
        if (read64(&c64tmp, value))
            snmp_pdu_add_variable(pdu, name, name_length, ASN_COUNTER64,
                                  (u_char *) & c64tmp, sizeof(c64tmp));
        else
            goto fail;
        break;

    case 't':
#ifndef DISABLE_MIB_LOADING
        if (check && tp->type != TYPE_TIMETICKS) {
            value = "Timeticks";
            result = SNMPERR_VALUE;
            goto type_error;
        }
#endif /* DISABLE_MIB_LOADING */
        ltmp = strtoul(value, &ecp, 10);
        if (*value && !*ecp)
            snmp_pdu_add_variable(pdu, name, name_length, ASN_TIMETICKS,
                                  (u_char *) & ltmp, sizeof(long));
        else
            goto fail;
        break;

    case 'a':
#ifndef DISABLE_MIB_LOADING
        if (check && tp->type != TYPE_IPADDR) {
            value = "IpAddress";
            result = SNMPERR_VALUE;
            goto type_error;
        }
#endif /* DISABLE_MIB_LOADING */
        atmp = inet_addr(value);
        if (atmp != (in_addr_t) -1 || !strcmp(value, "255.255.255.255"))
            snmp_pdu_add_variable(pdu, name, name_length, ASN_IPADDRESS,
                                  (u_char *) & atmp, sizeof(atmp));
        else
            goto fail;
        break;

    case 'o':
#ifndef DISABLE_MIB_LOADING
        if (check && tp->type != TYPE_OBJID) {
            value = "OBJECT IDENTIFIER";
            result = SNMPERR_VALUE;
            goto type_error;
        }
#endif /* DISABLE_MIB_LOADING */
        if ((buf = malloc(sizeof(oid) * MAX_OID_LEN)) == NULL) {
            result = SNMPERR_MALLOC;
        } else {
            tint = MAX_OID_LEN;
            if (snmp_parse_oid(value, (oid *) buf, &tint)) {
                snmp_pdu_add_variable(pdu, name, name_length,
                                      ASN_OBJECT_ID, buf,
                                      sizeof(oid) * tint);
            } else {
                result = snmp_errno;    /*MTCRITICAL_RESOURCE */
            }
        }
        break;

    case 's':
    case 'x':
    case 'd':
#ifndef DISABLE_MIB_LOADING
        if (check && tp->type != TYPE_OCTETSTR && tp->type != TYPE_BITSTRING) {
            value = "OCTET STRING";
            result = SNMPERR_VALUE;
            goto type_error;
        }
	if ('s' == type && do_hint && !parse_octet_hint(tp->hint, value, &hintptr, &itmp)) {
            if (_check_range(tp, itmp, &result, "Value does not match DISPLAY-HINT")) {
                snmp_pdu_add_variable(pdu, name, name_length,
                                      ASN_OCTET_STR, hintptr, itmp);
            }
            SNMP_FREE(hintptr);
            hintptr = buf;
            break;
        }
#endif /* DISABLE_MIB_LOADING */
        if (type == 'd') {
            if (!snmp_decimal_to_binary
                (&buf, &buf_len, &value_len, 1, value)) {
                result = SNMPERR_VALUE;
                snmp_set_detail(value);
                break;
            }
            buf_ptr = buf;
        } else if (type == 'x') {
            if (!snmp_hex_to_binary(&buf, &buf_len, &value_len, 1, value)) {
                result = SNMPERR_VALUE;
                snmp_set_detail(value);
                break;
            }
            /* initialize itmp value so that range check below works */
            itmp = value_len;
            buf_ptr = buf;
        } else if (type == 's') {
            buf_ptr = (const u_char *)value;
            value_len = strlen(value);
        }
#ifndef DISABLE_MIB_LOADING
        if (!_check_range(tp, value_len, &result, "Bad string length"))
            break;
#endif /* DISABLE_MIB_LOADING */
        snmp_pdu_add_variable(pdu, name, name_length, ASN_OCTET_STR,
                              buf_ptr, value_len);
        break;

    case 'n':
        snmp_pdu_add_variable(pdu, name, name_length, ASN_NULL, 0, 0);
        break;

    case 'b':
#ifndef DISABLE_MIB_LOADING
        if (check && (tp->type != TYPE_BITSTRING || !tp->enums)) {
            value = "BITS";
            result = SNMPERR_VALUE;
            goto type_error;
        }
#endif /* DISABLE_MIB_LOADING */
        tint = 0;
        if ((buf = (u_char *) malloc(256)) == NULL) {
            result = SNMPERR_MALLOC;
            break;
        } else {
            buf_len = 256;
            memset(buf, 0, buf_len);
        }

#ifndef DISABLE_MIB_LOADING
        for (ep = tp ? tp->enums : NULL; ep; ep = ep->next) {
            if (ep->value / 8 >= (int) tint) {
                tint = ep->value / 8 + 1;
            }
        }
#endif /* DISABLE_MIB_LOADING */

	vp = strdup(value);
	for (cp = strtok_r(vp, " ,\t", &st); cp; cp = strtok_r(NULL, " ,\t", &st)) {
            int             ix, bit;

            ltmp = strtoul(cp, &ecp, 0);
            if (*ecp != 0) {
#ifndef DISABLE_MIB_LOADING
                for (ep = tp ? tp->enums : NULL; ep != NULL; ep = ep->next) {
                    if (strncmp(ep->label, cp, strlen(ep->label)) == 0) {
                        break;
                    }
                }
                if (ep != NULL) {
                    ltmp = ep->value;
                } else {
#endif /* DISABLE_MIB_LOADING */
                    result = SNMPERR_RANGE;   /* ?? or SNMPERR_VALUE; */
                    snmp_set_detail(cp);
                    SNMP_FREE(buf);
		    SNMP_FREE(vp);
                    goto out;
#ifndef DISABLE_MIB_LOADING
                }
#endif /* DISABLE_MIB_LOADING */
            }

            ix = ltmp / 8;
            if (ix >= (int) tint) {
                tint = ix + 1;
            }
            if (ix >= (int)buf_len && !snmp_realloc(&buf, &buf_len)) {
                result = SNMPERR_MALLOC;
                break;
            }
            bit = 0x80 >> ltmp % 8;
            buf[ix] |= bit;
	    
        }
	SNMP_FREE(vp);
        snmp_pdu_add_variable(pdu, name, name_length, ASN_OCTET_STR,
                              buf, tint);
        break;

#ifdef OPAQUE_SPECIAL_TYPES
    case 'U':
        if (read64(&c64tmp, value))
            snmp_pdu_add_variable(pdu, name, name_length, ASN_OPAQUE_U64,
                                  (u_char *) & c64tmp, sizeof(c64tmp));
        else
            goto fail;
        break;

    case 'I':
        if (read64(&c64tmp, value))
            snmp_pdu_add_variable(pdu, name, name_length, ASN_OPAQUE_I64,
                                  (u_char *) & c64tmp, sizeof(c64tmp));
        else
            goto fail;
        break;

    case 'F':
        if (sscanf(value, "%f", &ftmp) == 1)
            snmp_pdu_add_variable(pdu, name, name_length, ASN_OPAQUE_FLOAT,
                                  (u_char *) & ftmp, sizeof(ftmp));
        else
            goto fail;
        break;

    case 'D':
        if (sscanf(value, "%lf", &dtmp) == 1)
            snmp_pdu_add_variable(pdu, name, name_length,
                                  ASN_OPAQUE_DOUBLE, (u_char *) & dtmp,
                                  sizeof(dtmp));
        else
            goto fail;
        break;
#endif                          /* OPAQUE_SPECIAL_TYPES */

    default:
        result = SNMPERR_VAR_TYPE;
	buf = calloc(1, 4);
	if (buf != NULL) {
	    sprintf((char *)buf, "\"%c\"", type);
	    snmp_set_detail((char *)buf);
	}
        break;
    }

    SNMP_FREE(buf);
    SET_SNMP_ERROR(result);
    return result;

#ifndef DISABLE_MIB_LOADING
  type_error:
    {
        char            error_msg[256];
        char            undef_msg[32];
        const char     *var_type;
        switch (tp->type) {
        case TYPE_OBJID:
            var_type = "OBJECT IDENTIFIER";
            break;
        case TYPE_OCTETSTR:
            var_type = "OCTET STRING";
            break;
        case TYPE_INTEGER:
            var_type = "INTEGER";
            break;
        case TYPE_NETADDR:
            var_type = "NetworkAddress";
            break;
        case TYPE_IPADDR:
            var_type = "IpAddress";
            break;
        case TYPE_COUNTER:
            var_type = "Counter32";
            break;
        case TYPE_GAUGE:
            var_type = "Gauge32";
            break;
        case TYPE_TIMETICKS:
            var_type = "Timeticks";
            break;
        case TYPE_OPAQUE:
            var_type = "Opaque";
            break;
        case TYPE_NULL:
            var_type = "Null";
            break;
        case TYPE_COUNTER64:
            var_type = "Counter64";
            break;
        case TYPE_BITSTRING:
            var_type = "BITS";
            break;
        case TYPE_NSAPADDRESS:
            var_type = "NsapAddress";
            break;
        case TYPE_UINTEGER:
            var_type = "UInteger";
            break;
        case TYPE_UNSIGNED32:
            var_type = "Unsigned32";
            break;
        case TYPE_INTEGER32:
            var_type = "Integer32";
            break;
        default:
            sprintf(undef_msg, "TYPE_%d", tp->type);
            var_type = undef_msg;
        }
        snprintf(error_msg, sizeof(error_msg),
               "Type of attribute is %s, not %s", var_type, value);
        error_msg[ sizeof(error_msg)-1 ] = 0;
        result = SNMPERR_VAR_TYPE;
        snmp_set_detail(error_msg);
        goto out;
    }
#endif /* DISABLE_MIB_LOADING */
  fail:
    result = SNMPERR_VALUE;
    snmp_set_detail(value);
  out:
    SET_SNMP_ERROR(result);
    return result;
}

/*
 * returns NULL or internal pointer to session
 * use this pointer for the other snmp_sess* routines,
 * which guarantee action will occur ONLY for this given session.
 */
void           *
snmp_sess_pointer(netsnmp_session * session)
{
    struct session_list *slp;

    snmp_res_lock(MT_LIBRARY_ID, MT_LIB_SESSION);
    for (slp = Sessions; slp; slp = slp->next) {
        if (slp->session == session) {
            break;
        }
    }
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSION);

    if (slp == NULL) {
        snmp_errno = SNMPERR_BAD_SESSION;       /*MTCRITICAL_RESOURCE */
        return (NULL);
    }
    return ((void *) slp);
}

/*
 * Input : an opaque pointer, returned by snmp_sess_open.
 * returns NULL or pointer to session.
 */
netsnmp_session *
snmp_sess_session(void *sessp)
{
    struct session_list *slp = (struct session_list *) sessp;
    if (slp == NULL)
        return (NULL);
    return (slp->session);
}



/*
 * snmp_sess_transport: takes an opaque pointer (as returned by
 * snmp_sess_open or snmp_sess_pointer) and returns the corresponding
 * netsnmp_transport pointer (or NULL if the opaque pointer does not correspond
 * to an active internal session).  
 */

netsnmp_transport *
snmp_sess_transport(void *sessp)
{
    struct session_list *slp = (struct session_list *) sessp;
    if (slp == NULL) {
        return NULL;
    } else {
        return slp->transport;
    }
}



/*
 * snmp_sess_transport_set: set the transport pointer for the opaque
 * session pointer sp.  
 */

void
snmp_sess_transport_set(void *sp, netsnmp_transport *t)
{
    struct session_list *slp = (struct session_list *) sp;
    if (slp != NULL) {
        slp->transport = t;
    }
}


/*
 * snmp_duplicate_objid: duplicates (mallocs) an objid based on the
 * input objid 
 */
oid            *
snmp_duplicate_objid(const oid * objToCopy, size_t objToCopyLen)
{
    oid            *returnOid = NULL;
    if (objToCopy != NULL && objToCopyLen != 0) {
        returnOid = (oid *) malloc(objToCopyLen * sizeof(oid));
        if (returnOid) {
            memmove(returnOid, objToCopy, objToCopyLen * sizeof(oid));
        }
    }
    return returnOid;
}

/*
 * generic statistics counter functions 
 */
static u_int    statistics[MAX_STATS];

u_int
snmp_increment_statistic(int which)
{
    if (which >= 0 && which < MAX_STATS) {
        statistics[which]++;
        return statistics[which];
    }
    return 0;
}

u_int
snmp_increment_statistic_by(int which, int count)
{
    if (which >= 0 && which < MAX_STATS) {
        statistics[which] += count;
        return statistics[which];
    }
    return 0;
}

u_int
snmp_get_statistic(int which)
{
    if (which >= 0 && which < MAX_STATS)
        return statistics[which];
    return 0;
}

void
snmp_init_statistics(void)
{
    memset(statistics, 0, sizeof(statistics));
}
/**  @} */

