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/**

 * @file

 * ICMP - Internet Control Message Protocol

 *

 */

/*

 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.

 * 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.

 *

 * This file is part of the lwIP TCP/IP stack.

 *

 * Author: Adam Dunkels <adam@sics.se>

 *

 */

/* Some ICMP messages should be passed to the transport protocols. This

   is not implemented. */

#include "lwip/opt.h"

#if LWIP_ICMP /* don't build if not configured for use in lwipopts.h */

#include "lwip/icmp.h"

#include "lwip/inet.h"

#include "lwip/inet_chksum.h"

#include "lwip/ip.h"

#include "lwip/def.h"

#include "lwip/stats.h"

#include "lwip/snmp.h"

#include <string.h>

/** Small optimization: set to 0 if incoming PBUF_POOL pbuf always can be

 * used to modify and send a response packet (and to 1 if this is not the case,

 * e.g. when link header is stripped of when receiving) */

#ifndef LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN

#define LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 1

#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */

/* The amount of data from the original packet to return in a dest-unreachable */

#define ICMP_DEST_UNREACH_DATASIZE 8

static void icmp_send_response(struct pbuf *p, u8_t type, u8_t code);

/**

 * Processes ICMP input packets, called from ip_input().

 *

 * Currently only processes icmp echo requests and sends

 * out the echo response.

 *

 * @param p the icmp echo request packet, p->payload pointing to the ip header

 * @param inp the netif on which this packet was received

 */

void

icmp_input(struct pbuf *p, struct netif *inp)

{

  u8_t type;

#ifdef LWIP_DEBUG

  u8_t code;

#endif /* LWIP_DEBUG */

  struct icmp_echo_hdr *iecho;

  struct ip_hdr *iphdr;

  struct ip_addr tmpaddr;

  s16_t hlen;

  ICMP_STATS_INC(icmp.recv);

  snmp_inc_icmpinmsgs();

  iphdr = p->payload;

  hlen = IPH_HL(iphdr) * 4;

  if (pbuf_header(p, -hlen) || (p->tot_len < sizeof(u16_t)*2)) {

    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len));

    goto lenerr;

  }

  type = *((u8_t *)p->payload);

#ifdef LWIP_DEBUG

  code = *(((u8_t *)p->payload)+1);

#endif /* LWIP_DEBUG */

  switch (type) {

  case ICMP_ECHO:

#if !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING

    {

      int accepted = 1;

#if !LWIP_MULTICAST_PING

      /* multicast destination address? */

      if (ip_addr_ismulticast(&iphdr->dest)) {

        accepted = 0;

      }

#endif /* LWIP_MULTICAST_PING */

#if !LWIP_BROADCAST_PING

      /* broadcast destination address? */

      if (ip_addr_isbroadcast(&iphdr->dest, inp)) {

        accepted = 0;

      }

#endif /* LWIP_BROADCAST_PING */

      /* broadcast or multicast destination address not acceptd? */

      if (!accepted) {

        LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n"));

        ICMP_STATS_INC(icmp.err);

        pbuf_free(p);

        return;

      }

    }

#endif /* !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */

    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n"));

    if (p->tot_len < sizeof(struct icmp_echo_hdr)) {

      LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n"));

      goto lenerr;

    }

    if (inet_chksum_pbuf(p) != 0) {

      LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n"));

      pbuf_free(p);

      ICMP_STATS_INC(icmp.chkerr);

      snmp_inc_icmpinerrors();

      return;

    }

#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN

    if (pbuf_header(p, (PBUF_IP_HLEN + PBUF_LINK_HLEN))) {

      /* p is not big enough to contain link headers

       * allocate a new one and copy p into it

       */

      struct pbuf *r;

      /* switch p->payload to ip header */

      if (pbuf_header(p, hlen)) {

        LWIP_ASSERT("icmp_input: moving p->payload to ip header failed\n", 0);

        goto memerr;

      }

      /* allocate new packet buffer with space for link headers */

      r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM);

      if (r == NULL) {

        LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n"));

        goto memerr;

      }

      LWIP_ASSERT("check that first pbuf can hold struct the ICMP header",

                  (r->len >= hlen + sizeof(struct icmp_echo_hdr)));

      /* copy the whole packet including ip header */

      if (pbuf_copy(r, p) != ERR_OK) {

        LWIP_ASSERT("icmp_input: copying to new pbuf failed\n", 0);

        goto memerr;

      }

      iphdr = r->payload;

      /* switch r->payload back to icmp header */

      if (pbuf_header(r, -hlen)) {

        LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);

        goto memerr;

      }

      /* free the original p */

      pbuf_free(p);

      /* we now have an identical copy of p that has room for link headers */

      p = r;

    } else {

      /* restore p->payload to point to icmp header */

      if (pbuf_header(p, -(s16_t)(PBUF_IP_HLEN + PBUF_LINK_HLEN))) {

        LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);

        goto memerr;

      }

    }

#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */

    /* At this point, all checks are OK. */

    /* We generate an answer by switching the dest and src ip addresses,

     * setting the icmp type to ECHO_RESPONSE and updating the checksum. */

    iecho = p->payload;

    tmpaddr.addr = iphdr->src.addr;

    iphdr->src.addr = iphdr->dest.addr;

    iphdr->dest.addr = tmpaddr.addr;

    ICMPH_TYPE_SET(iecho, ICMP_ER);

    /* adjust the checksum */

    if (iecho->chksum >= htons(0xffff - (ICMP_ECHO << 8))) {

      iecho->chksum += htons(ICMP_ECHO << 8) + 1;

    } else {

      iecho->chksum += htons(ICMP_ECHO << 8);

    }

    /* Set the correct TTL and recalculate the header checksum. */

    IPH_TTL_SET(iphdr, ICMP_TTL);

    IPH_CHKSUM_SET(iphdr, 0);

#if CHECKSUM_GEN_IP

    IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));

#endif /* CHECKSUM_GEN_IP */

    ICMP_STATS_INC(icmp.xmit);

    /* increase number of messages attempted to send */

    snmp_inc_icmpoutmsgs();

    /* increase number of echo replies attempted to send */

    snmp_inc_icmpoutechoreps();

    if(pbuf_header(p, hlen)) {

      LWIP_ASSERT("Can't move over header in packet", 0);

    } else {

      err_t ret;

      ret = ip_output_if(p, &(iphdr->src), IP_HDRINCL,

                   ICMP_TTL, 0, IP_PROTO_ICMP, inp);

      if (ret != ERR_OK) {

        LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %c.\n", ret));

      }

    }

    break;

  default:

    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n",

                (s16_t)type, (s16_t)code));

    ICMP_STATS_INC(icmp.proterr);

    ICMP_STATS_INC(icmp.drop);

  }

  pbuf_free(p);

  return;

lenerr:

  pbuf_free(p);

  ICMP_STATS_INC(icmp.lenerr);

  snmp_inc_icmpinerrors();

  return;

#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN

memerr:

  pbuf_free(p);

  ICMP_STATS_INC(icmp.err);

  snmp_inc_icmpinerrors();

  return;

#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */

}

/**

 * Send an icmp 'destination unreachable' packet, called from ip_input() if

 * the transport layer protocol is unknown and from udp_input() if the local

 * port is not bound.

 *

 * @param p the input packet for which the 'unreachable' should be sent,

 *          p->payload pointing to the IP header

 * @param t type of the 'unreachable' packet

 */

void

icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)

{

  icmp_send_response(p, ICMP_DUR, t);

}

#if IP_FORWARD || IP_REASSEMBLY

/**

 * Send a 'time exceeded' packet, called from ip_forward() if TTL is 0.

 *

 * @param p the input packet for which the 'time exceeded' should be sent,

 *          p->payload pointing to the IP header

 * @param t type of the 'time exceeded' packet

 */

void

icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)

{

  icmp_send_response(p, ICMP_TE, t);

}

#endif /* IP_FORWARD || IP_REASSEMBLY */

/**

 * Send an icmp packet in response to an incoming packet.

 *

 * @param p the input packet for which the 'unreachable' should be sent,

 *          p->payload pointing to the IP header

 * @param type Type of the ICMP header

 * @param code Code of the ICMP header

 */

static void

icmp_send_response(struct pbuf *p, u8_t type, u8_t code)

{

  struct pbuf *q;

  struct ip_hdr *iphdr;

  /* we can use the echo header here */

  struct icmp_echo_hdr *icmphdr;

  /* ICMP header + IP header + 8 bytes of data */

  q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,

                 PBUF_RAM);

  if (q == NULL) {

    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));

    return;

  }

  LWIP_ASSERT("check that first pbuf can hold icmp message",

             (q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));

  iphdr = p->payload;

  LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));

  ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));

  LWIP_DEBUGF(ICMP_DEBUG, (" to "));

  ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));

  LWIP_DEBUGF(ICMP_DEBUG, ("\n"));

  icmphdr = q->payload;

  icmphdr->type = type;

  icmphdr->code = code;

  icmphdr->id = 0;

  icmphdr->seqno = 0;

  /* copy fields from original packet */

  SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload,

          IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);

  /* calculate checksum */

  icmphdr->chksum = 0;

  icmphdr->chksum = inet_chksum(icmphdr, q->len);

  ICMP_STATS_INC(icmp.xmit);

  /* increase number of messages attempted to send */

  snmp_inc_icmpoutmsgs();

  /* increase number of destination unreachable messages attempted to send */

  snmp_inc_icmpouttimeexcds();

  ip_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP);

  pbuf_free(q);

}

#endif /* LWIP_ICMP */