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snmp_api.c

/* 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.
 */

/*
 * 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>
#include <net-snmp/library/vacm.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;
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_REQUESTID);
    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_16BIT_IDS))
        return (retVal & 0x7fff);       /* mask to 15 bits */
    else
        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;
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_MESSAGEID);
    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_16BIT_IDS))
        return (retVal & 0x7fff);       /* mask to 15 bits */
    else
        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;
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_SESSIONID);
    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_16BIT_IDS))
        return (retVal & 0x7fff);       /* mask to 15 bits */
    else
        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;
    snmp_res_unlock(MT_LIBRARY_ID, MT_LIB_TRANSID);
    if (netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_16BIT_IDS))
        return (retVal & 0x7fff);       /* mask to 15 bits */
    else
        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);
    netsnmp_ds_register_config(ASN_BOOLEAN, "snmp", "noPersistentLoad",
                      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_DISABLE_PERSISTENT_LOAD);
    netsnmp_ds_register_config(ASN_BOOLEAN, "snmp", "noPersistentSave",
                      NETSNMP_DS_LIBRARY_ID, NETSNMP_DS_LIB_DISABLE_PERSISTENT_SAVE);
}

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
}



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();
    init_vacm();

    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);
}


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);
        if (cp == NULL) {
            snmp_sess_close(slp);
            return (NULL);
        }
        session->contextName = cp;
        session->contextNameLen = strlen(cp);
    } else {
        cp = strdup(SNMP_DEFAULT_CONTEXT);
        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;
}


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",
                        "snmp_sess_open(): 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 0;
    }
    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"));
        return 0;
    }
    
    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);
            slp = NULL;
        }
        if (create_user_from_session(slp->session) != SNMPERR_SUCCESS) {
            slp->session->s_snmp_errno = SNMPERR_UNKNOWN_USER_NAME;
            DEBUGMSGTL(("snmp_api",
                        "_sess_open(): failed(2) to create a new user from session\n"));
            return 0;
        }
    }

    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;
    u_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->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 */
        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;
        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 */
        if (memdup(&user->privKey, session->securityPrivLocalKey,