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/**

 * @file

 * SNMP output message processing (RFC1157).

 *

 * Output responses and traps are build in two passes:

 *

 * Pass 0: iterate over the output message backwards to determine encoding lengths

 * Pass 1: the actual forward encoding of internal form into ASN1

 *

 * The single-pass encoding method described by Comer & Stevens

 * requires extra buffer space and copying for reversal of the packet.

 * The buffer requirement can be prohibitively large for big payloads

 * (>= 484) therefore we use the two encoding passes.

 */

/*

 * Copyright (c) 2006 Axon Digital Design B.V., The Netherlands.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without modification,

 * are permitted provided that the following conditions are met:

 *

 * 1. Redistributions of source code must retain the above copyright notice,

 *    this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright notice,

 *    this list of conditions and the following disclaimer in the documentation

 *    and/or other materials provided with the distribution.

 * 3. The name of the author may not be used to endorse or promote products

 *    derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED

 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT

 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT

 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING

 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY

 * OF SUCH DAMAGE.

 *

 * Author: Christiaan Simons <christiaan.simons@axon.tv>

 */

#include "lwip/opt.h"

#if LWIP_SNMP

#include "arch/cc.h"

#include "lwip/udp.h"

#include "lwip/netif.h"

#include "lwip/snmp.h"

#include "lwip/snmp_asn1.h"

#include "lwip/snmp_msg.h"

struct snmp_trap_dst

{

  /* destination IP address in network order */

  struct ip_addr dip;

  /* set to 0 when disabled, >0 when enabled */

  u8_t enable;

};

#if (SNMP_TRAP_DESTINATIONS == 0)

#error "need at least one trap destination"

#endif

struct snmp_trap_dst trap_dst[SNMP_TRAP_DESTINATIONS];

/** TRAP message structure */

struct snmp_msg_trap trap_msg;

static u16_t snmp_resp_header_sum(struct snmp_msg_pstat *m_stat, u16_t vb_len);

static u16_t snmp_trap_header_sum(struct snmp_msg_trap *m_trap, u16_t vb_len);

static u16_t snmp_varbind_list_sum(struct snmp_varbind_root *root);

static u16_t snmp_resp_header_enc(struct snmp_msg_pstat *m_stat, struct pbuf *p);

static u16_t snmp_trap_header_enc(struct snmp_msg_trap *m_trap, struct pbuf *p);

static u16_t snmp_varbind_list_enc(struct snmp_varbind_root *root, struct pbuf *p, u16_t ofs);

/**

 * Sets enable switch for this trap destination.

 * @param dst_idx index in 0 .. SNMP_TRAP_DESTINATIONS-1

 * @param enable switch if 0 destination is disabled >0 enabled.

 */

void

snmp_trap_dst_enable(u8_t dst_idx, u8_t enable)

{

  if (dst_idx < SNMP_TRAP_DESTINATIONS)

  {

    trap_dst[dst_idx].enable = enable;

  }

}

/**

 * Sets IPv4 address for this trap destination.

 * @param dst_idx index in 0 .. SNMP_TRAP_DESTINATIONS-1

 * @param dst IPv4 address in host order.

 */

void

snmp_trap_dst_ip_set(u8_t dst_idx, struct ip_addr *dst)

{

  if (dst_idx < SNMP_TRAP_DESTINATIONS)

  {

    trap_dst[dst_idx].dip.addr = htonl(dst->addr);

  }

}

/**

 * Sends a 'getresponse' message to the request originator.

 *

 * @param m_stat points to the current message request state source

 * @return ERR_OK when success, ERR_MEM if we're out of memory

 *

 * @note the caller is responsible for filling in outvb in the m_stat

 * and provide error-status and index (except for tooBig errors) ...

 */

err_t

snmp_send_response(struct snmp_msg_pstat *m_stat)

{

  struct snmp_varbind_root emptyvb = {NULL, NULL, 0, 0, 0};

  struct pbuf *p;

  u16_t tot_len;

  err_t err;

  /* pass 0, calculate length fields */

  tot_len = snmp_varbind_list_sum(&m_stat->outvb);

  tot_len = snmp_resp_header_sum(m_stat, tot_len);

  /* try allocating pbuf(s) for complete response */

  p = pbuf_alloc(PBUF_TRANSPORT, tot_len, PBUF_POOL);

  if (p == NULL)

  {

    LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_snd_response() tooBig\n"));

    /* can't construct reply, return error-status tooBig */

    m_stat->error_status = SNMP_ES_TOOBIG;

    m_stat->error_index = 0;

    /* pass 0, recalculate lengths, for empty varbind-list */

    tot_len = snmp_varbind_list_sum(&emptyvb);

    tot_len = snmp_resp_header_sum(m_stat, tot_len);

    /* retry allocation once for header and empty varbind-list */

    p = pbuf_alloc(PBUF_TRANSPORT, tot_len, PBUF_POOL);

  }

  if (p != NULL)

  {

    /* first pbuf alloc try or retry alloc success */

    u16_t ofs;

    LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_snd_response() p != NULL\n"));

    /* pass 1, size error, encode packet ino the pbuf(s) */

    ofs = snmp_resp_header_enc(m_stat, p);

    if (m_stat->error_status == SNMP_ES_TOOBIG)

    {

      snmp_varbind_list_enc(&emptyvb, p, ofs);

    }

    else

    {

      snmp_varbind_list_enc(&m_stat->outvb, p, ofs);

    }

    switch (m_stat->error_status)

    {

      case SNMP_ES_TOOBIG:

        snmp_inc_snmpouttoobigs();

        break;

      case SNMP_ES_NOSUCHNAME:

        snmp_inc_snmpoutnosuchnames();

        break;

      case SNMP_ES_BADVALUE:

        snmp_inc_snmpoutbadvalues();

        break;

      case SNMP_ES_GENERROR:

        snmp_inc_snmpoutgenerrs();

        break;

    }

    snmp_inc_snmpoutgetresponses();

    snmp_inc_snmpoutpkts();

    /** @todo do we need separate rx and tx pcbs for threaded case? */

    /** connect to the originating source */

    udp_connect(m_stat->pcb, &m_stat->sip, m_stat->sp);

    err = udp_send(m_stat->pcb, p);

    if (err == ERR_MEM)

    {

      /** @todo release some memory, retry and return tooBig? tooMuchHassle? */

      err = ERR_MEM;

    }

    else

    {

      err = ERR_OK;

    }

    /** disassociate remote address and port with this pcb */

    udp_disconnect(m_stat->pcb);

    pbuf_free(p);

    LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_snd_response() done\n"));

    return err;

  }

  else

  {

    /* first pbuf alloc try or retry alloc failed

       very low on memory, couldn't return tooBig */

    return ERR_MEM;

  }

}

/**

 * Sends an generic or enterprise specific trap message.

 *

 * @param generic_trap is the trap code

 * @param eoid points to enterprise object identifier

 * @param specific_trap used for enterprise traps when generic_trap == 6

 * @return ERR_OK when success, ERR_MEM if we're out of memory

 *

 * @note the caller is responsible for filling in outvb in the trap_msg

 * @note the use of the enterpise identifier field

 * is per RFC1215.

 * Use .iso.org.dod.internet.mgmt.mib-2.snmp for generic traps

 * and .iso.org.dod.internet.private.enterprises.yourenterprise

 * (sysObjectID) for specific traps.

 */

err_t

snmp_send_trap(s8_t generic_trap, struct snmp_obj_id *eoid, s32_t specific_trap)

{

  struct snmp_trap_dst *td;

  struct netif *dst_if;

  struct ip_addr dst_ip;

  struct pbuf *p;

  u16_t i,tot_len;

  for (i=0, td = &trap_dst[0]; i<SNMP_TRAP_DESTINATIONS; i++, td++)

  {

    if ((td->enable != 0) && (td->dip.addr != 0))

    {

      /* network order trap destination */

      trap_msg.dip.addr = td->dip.addr;

      /* lookup current source address for this dst */

      dst_if = ip_route(&td->dip);

      dst_ip.addr = ntohl(dst_if->ip_addr.addr);

      trap_msg.sip_raw[0] = dst_ip.addr >> 24;

      trap_msg.sip_raw[1] = dst_ip.addr >> 16;

      trap_msg.sip_raw[2] = dst_ip.addr >> 8;

      trap_msg.sip_raw[3] = dst_ip.addr;

      trap_msg.gen_trap = generic_trap;

      trap_msg.spc_trap = specific_trap;

      if (generic_trap == SNMP_GENTRAP_ENTERPRISESPC)

      {

        /* enterprise-Specific trap */

        trap_msg.enterprise = eoid;

      }

      else

      {

        /* generic (MIB-II) trap */

        snmp_get_snmpgrpid_ptr(&trap_msg.enterprise);

      }

      snmp_get_sysuptime(&trap_msg.ts);

      /* pass 0, calculate length fields */

      tot_len = snmp_varbind_list_sum(&trap_msg.outvb);

      tot_len = snmp_trap_header_sum(&trap_msg, tot_len);

      /* allocate pbuf(s) */

      p = pbuf_alloc(PBUF_TRANSPORT, tot_len, PBUF_POOL);

      if (p != NULL)

      {

        u16_t ofs;

        /* pass 1, encode packet ino the pbuf(s) */

        ofs = snmp_trap_header_enc(&trap_msg, p);

        snmp_varbind_list_enc(&trap_msg.outvb, p, ofs);

        snmp_inc_snmpouttraps();

        snmp_inc_snmpoutpkts();

        /** connect to the TRAP destination */

        udp_connect(trap_msg.pcb, &trap_msg.dip, SNMP_TRAP_PORT);

        udp_send(trap_msg.pcb, p);

        /** disassociate remote address and port with this pcb */

        udp_disconnect(trap_msg.pcb);

        pbuf_free(p);

      }

      else

      {

        return ERR_MEM;

      }

    }

  }

  return ERR_OK;

}

void

snmp_coldstart_trap(void)

{

  trap_msg.outvb.head = NULL;

  trap_msg.outvb.tail = NULL;

  trap_msg.outvb.count = 0;

  snmp_send_trap(SNMP_GENTRAP_COLDSTART, NULL, 0);

}

void

snmp_authfail_trap(void)

{

  u8_t enable;

  snmp_get_snmpenableauthentraps(&enable);

  if (enable == 1)

  {

    trap_msg.outvb.head = NULL;

    trap_msg.outvb.tail = NULL;

    trap_msg.outvb.count = 0;

    snmp_send_trap(SNMP_GENTRAP_AUTHFAIL, NULL, 0);

  }

}

/**

 * Sums response header field lengths from tail to head and

 * returns resp_header_lengths for second encoding pass.

 *

 * @param vb_len varbind-list length

 * @param rhl points to returned header lengths

 * @return the required lenght for encoding the response header

 */

static u16_t

snmp_resp_header_sum(struct snmp_msg_pstat *m_stat, u16_t vb_len)

{

  u16_t tot_len;

  struct snmp_resp_header_lengths *rhl;

  rhl = &m_stat->rhl;

  tot_len = vb_len;

  snmp_asn1_enc_s32t_cnt(m_stat->error_index, &rhl->erridxlen);

  snmp_asn1_enc_length_cnt(rhl->erridxlen, &rhl->erridxlenlen);

  tot_len += 1 + rhl->erridxlenlen + rhl->erridxlen;

  snmp_asn1_enc_s32t_cnt(m_stat->error_status, &rhl->errstatlen);

  snmp_asn1_enc_length_cnt(rhl->errstatlen, &rhl->errstatlenlen);

  tot_len += 1 + rhl->errstatlenlen + rhl->errstatlen;

  snmp_asn1_enc_s32t_cnt(m_stat->rid, &rhl->ridlen);

  snmp_asn1_enc_length_cnt(rhl->ridlen, &rhl->ridlenlen);

  tot_len += 1 + rhl->ridlenlen + rhl->ridlen;

  rhl->pdulen = tot_len;

  snmp_asn1_enc_length_cnt(rhl->pdulen, &rhl->pdulenlen);

  tot_len += 1 + rhl->pdulenlen;

  rhl->comlen = m_stat->com_strlen;

  snmp_asn1_enc_length_cnt(rhl->comlen, &rhl->comlenlen);

  tot_len += 1 + rhl->comlenlen + rhl->comlen;

  snmp_asn1_enc_s32t_cnt(snmp_version, &rhl->verlen);

  snmp_asn1_enc_length_cnt(rhl->verlen, &rhl->verlenlen);

  tot_len += 1 + rhl->verlen + rhl->verlenlen;

  rhl->seqlen = tot_len;

  snmp_asn1_enc_length_cnt(rhl->seqlen, &rhl->seqlenlen);

  tot_len += 1 + rhl->seqlenlen;

  return tot_len;

}

/**

 * Sums trap header field lengths from tail to head and

 * returns trap_header_lengths for second encoding pass.

 *

 * @param vb_len varbind-list length

 * @param thl points to returned header lengths

 * @return the required lenght for encoding the trap header

 */

static u16_t

snmp_trap_header_sum(struct snmp_msg_trap *m_trap, u16_t vb_len)

{

  u16_t tot_len;

  struct snmp_trap_header_lengths *thl;

  thl = &m_trap->thl;

  tot_len = vb_len;

  snmp_asn1_enc_u32t_cnt(m_trap->ts, &thl->tslen);

  snmp_asn1_enc_length_cnt(thl->tslen, &thl->tslenlen);

  tot_len += 1 + thl->tslen + thl->tslenlen;

  snmp_asn1_enc_s32t_cnt(m_trap->spc_trap, &thl->strplen);

  snmp_asn1_enc_length_cnt(thl->strplen, &thl->strplenlen);

  tot_len += 1 + thl->strplen + thl->strplenlen;

  snmp_asn1_enc_s32t_cnt(m_trap->gen_trap, &thl->gtrplen);

  snmp_asn1_enc_length_cnt(thl->gtrplen, &thl->gtrplenlen);

  tot_len += 1 + thl->gtrplen + thl->gtrplenlen;

  thl->aaddrlen = 4;

  snmp_asn1_enc_length_cnt(thl->aaddrlen, &thl->aaddrlenlen);

  tot_len += 1 + thl->aaddrlen + thl->aaddrlenlen;

  snmp_asn1_enc_oid_cnt(m_trap->enterprise->len, &m_trap->enterprise->id[0], &thl->eidlen);

  snmp_asn1_enc_length_cnt(thl->eidlen, &thl->eidlenlen);

  tot_len += 1 + thl->eidlen + thl->eidlenlen;

  thl->pdulen = tot_len;

  snmp_asn1_enc_length_cnt(thl->pdulen, &thl->pdulenlen);

  tot_len += 1 + thl->pdulenlen;

  thl->comlen = sizeof(snmp_publiccommunity) - 1;

  snmp_asn1_enc_length_cnt(thl->comlen, &thl->comlenlen);

  tot_len += 1 + thl->comlenlen + thl->comlen;

  snmp_asn1_enc_s32t_cnt(snmp_version, &thl->verlen);

  snmp_asn1_enc_length_cnt(thl->verlen, &thl->verlenlen);

  tot_len += 1 + thl->verlen + thl->verlenlen;

  thl->seqlen = tot_len;

  snmp_asn1_enc_length_cnt(thl->seqlen, &thl->seqlenlen);

  tot_len += 1 + thl->seqlenlen;

  return tot_len;

}

/**

 * Sums varbind lengths from tail to head and

 * annotates lengths in varbind for second encoding pass.

 *

 * @param root points to the root of the variable binding list

 * @return the required lenght for encoding the variable bindings

 */

static u16_t

snmp_varbind_list_sum(struct snmp_varbind_root *root)

{

  struct snmp_varbind *vb;

  u32_t *uint_ptr;

  s32_t *sint_ptr;

  u16_t tot_len;

  tot_len = 0;

  vb = root->tail;

  while ( vb != NULL )

  {

    /* encoded value lenght depends on type */

    switch (vb->value_type)

    {

      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG):

        sint_ptr = vb->value;

        snmp_asn1_enc_s32t_cnt(*sint_ptr, &vb->vlen);

        break;

      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_COUNTER):

      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_GAUGE):

      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_TIMETICKS):

        uint_ptr = vb->value;

        snmp_asn1_enc_u32t_cnt(*uint_ptr, &vb->vlen);

        break;

      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OC_STR):

      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_NUL):

      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_IPADDR):

      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_OPAQUE):

        vb->vlen = vb->value_len;

        break;

      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OBJ_ID):

        sint_ptr = vb->value;

        snmp_asn1_enc_oid_cnt(vb->value_len / sizeof(s32_t), sint_ptr, &vb->vlen);

        break;

      default:

        /* unsupported type */

        vb->vlen = 0;

        break;

    };

    /* encoding length of value length field */

    snmp_asn1_enc_length_cnt(vb->vlen, &vb->vlenlen);

    snmp_asn1_enc_oid_cnt(vb->ident_len, vb->ident, &vb->olen);

    snmp_asn1_enc_length_cnt(vb->olen, &vb->olenlen);

    vb->seqlen = 1 + vb->vlenlen + vb->vlen;

    vb->seqlen += 1 + vb->olenlen + vb->olen;

    snmp_asn1_enc_length_cnt(vb->seqlen, &vb->seqlenlen);

    /* varbind seq */

    tot_len += 1 + vb->seqlenlen + vb->seqlen;

    vb = vb->prev;

  }

  /* varbind-list seq */

  root->seqlen = tot_len;

  snmp_asn1_enc_length_cnt(root->seqlen, &root->seqlenlen);

  tot_len += 1 + root->seqlenlen;

  return tot_len;

}

/**

 * Encodes response header from head to tail.

 */

static u16_t

snmp_resp_header_enc(struct snmp_msg_pstat *m_stat, struct pbuf *p)

{

  u16_t ofs;

  ofs = 0;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_stat->rhl.seqlen);

  ofs += m_stat->rhl.seqlenlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_stat->rhl.verlen);

  ofs += m_stat->rhl.verlenlen;

  snmp_asn1_enc_s32t(p, ofs, m_stat->rhl.verlen, snmp_version);

  ofs += m_stat->rhl.verlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OC_STR));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_stat->rhl.comlen);

  ofs += m_stat->rhl.comlenlen;

  snmp_asn1_enc_raw(p, ofs, m_stat->rhl.comlen, m_stat->community);

  ofs += m_stat->rhl.comlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_RESP));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_stat->rhl.pdulen);

  ofs += m_stat->rhl.pdulenlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_stat->rhl.ridlen);

  ofs += m_stat->rhl.ridlenlen;

  snmp_asn1_enc_s32t(p, ofs, m_stat->rhl.ridlen, m_stat->rid);

  ofs += m_stat->rhl.ridlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_stat->rhl.errstatlen);

  ofs += m_stat->rhl.errstatlenlen;

  snmp_asn1_enc_s32t(p, ofs, m_stat->rhl.errstatlen, m_stat->error_status);

  ofs += m_stat->rhl.errstatlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_stat->rhl.erridxlen);

  ofs += m_stat->rhl.erridxlenlen;

  snmp_asn1_enc_s32t(p, ofs, m_stat->rhl.erridxlen, m_stat->error_index);

  ofs += m_stat->rhl.erridxlen;

  return ofs;

}

/**

 * Encodes trap header from head to tail.

 */

static u16_t

snmp_trap_header_enc(struct snmp_msg_trap *m_trap, struct pbuf *p)

{

  u16_t ofs;

  ofs = 0;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_trap->thl.seqlen);

  ofs += m_trap->thl.seqlenlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_trap->thl.verlen);

  ofs += m_trap->thl.verlenlen;

  snmp_asn1_enc_s32t(p, ofs, m_trap->thl.verlen, snmp_version);

  ofs += m_trap->thl.verlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OC_STR));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_trap->thl.comlen);

  ofs += m_trap->thl.comlenlen;

  snmp_asn1_enc_raw(p, ofs, m_trap->thl.comlen, (u8_t *)&snmp_publiccommunity[0]);

  ofs += m_trap->thl.comlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_TRAP));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_trap->thl.pdulen);

  ofs += m_trap->thl.pdulenlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OBJ_ID));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_trap->thl.eidlen);

  ofs += m_trap->thl.eidlenlen;

  snmp_asn1_enc_oid(p, ofs, m_trap->enterprise->len, &m_trap->enterprise->id[0]);

  ofs += m_trap->thl.eidlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_IPADDR));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_trap->thl.aaddrlen);

  ofs += m_trap->thl.aaddrlenlen;

  snmp_asn1_enc_raw(p, ofs, m_trap->thl.aaddrlen, &m_trap->sip_raw[0]);

  ofs += m_trap->thl.aaddrlen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_trap->thl.gtrplen);

  ofs += m_trap->thl.gtrplenlen;

  snmp_asn1_enc_u32t(p, ofs, m_trap->thl.gtrplen, m_trap->gen_trap);

  ofs += m_trap->thl.gtrplen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_trap->thl.strplen);

  ofs += m_trap->thl.strplenlen;

  snmp_asn1_enc_u32t(p, ofs, m_trap->thl.strplen, m_trap->spc_trap);

  ofs += m_trap->thl.strplen;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_TIMETICKS));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, m_trap->thl.tslen);

  ofs += m_trap->thl.tslenlen;

  snmp_asn1_enc_u32t(p, ofs, m_trap->thl.tslen, m_trap->ts);

  ofs += m_trap->thl.tslen;

  return ofs;

}

/**

 * Encodes varbind list from head to tail.

 */

static u16_t

snmp_varbind_list_enc(struct snmp_varbind_root *root, struct pbuf *p, u16_t ofs)

{

  struct snmp_varbind *vb;

  s32_t *sint_ptr;

  u32_t *uint_ptr;

  u8_t *raw_ptr;

  snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ));

  ofs += 1;

  snmp_asn1_enc_length(p, ofs, root->seqlen);

  ofs += root->seqlenlen;

  vb = root->head;

  while ( vb != NULL )

  {

    snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ));

    ofs += 1;

    snmp_asn1_enc_length(p, ofs, vb->seqlen);

    ofs += vb->seqlenlen;

    snmp_asn1_enc_type(p, ofs, (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OBJ_ID));

    ofs += 1;

    snmp_asn1_enc_length(p, ofs, vb->olen);

    ofs += vb->olenlen;

    snmp_asn1_enc_oid(p, ofs, vb->ident_len, &vb->ident[0]);

    ofs += vb->olen;

    snmp_asn1_enc_type(p, ofs, vb->value_type);

    ofs += 1;

    snmp_asn1_enc_length(p, ofs, vb->vlen);

    ofs += vb->vlenlen;

    switch (vb->value_type)

    {

      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG):

        sint_ptr = vb->value;

        snmp_asn1_enc_s32t(p, ofs, vb->vlen, *sint_ptr);

        break;

      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_COUNTER):

      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_GAUGE):

      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_TIMETICKS):