[164] | 1 | /**
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| 2 | * @file
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| 3 | * ICMP - Internet Control Message Protocol
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| 4 | *
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| 5 | */
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| 6 |
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| 7 | /*
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| 8 | * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
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| 9 | * All rights reserved.
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| 10 | *
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| 11 | * Redistribution and use in source and binary forms, with or without modification,
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| 12 | * are permitted provided that the following conditions are met:
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| 13 | *
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| 14 | * 1. Redistributions of source code must retain the above copyright notice,
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| 15 | * this list of conditions and the following disclaimer.
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| 16 | * 2. Redistributions in binary form must reproduce the above copyright notice,
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| 17 | * this list of conditions and the following disclaimer in the documentation
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| 18 | * and/or other materials provided with the distribution.
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| 19 | * 3. The name of the author may not be used to endorse or promote products
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| 20 | * derived from this software without specific prior written permission.
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| 21 | *
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| 22 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
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| 23 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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| 24 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
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| 25 | * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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| 26 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
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| 27 | * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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| 28 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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| 29 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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| 30 | * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
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| 31 | * OF SUCH DAMAGE.
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| 32 | *
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| 33 | * This file is part of the lwIP TCP/IP stack.
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| 34 | *
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| 35 | * Author: Adam Dunkels <adam@sics.se>
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| 36 | *
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| 37 | */
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| 38 |
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| 39 | /* Some ICMP messages should be passed to the transport protocols. This
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| 40 | is not implemented. */
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| 41 |
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| 42 | #include "lwip/opt.h"
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| 43 |
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| 44 | #if LWIP_ICMP /* don't build if not configured for use in lwipopts.h */
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| 45 |
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| 46 | #include "lwip/icmp.h"
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| 47 | #include "lwip/inet_chksum.h"
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| 48 | #include "lwip/ip.h"
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| 49 | #include "lwip/def.h"
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| 50 | #include "lwip/stats.h"
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| 51 | #include "lwip/snmp.h"
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| 52 |
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| 53 | #include <string.h>
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| 54 |
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| 55 | /** Small optimization: set to 0 if incoming PBUF_POOL pbuf always can be
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| 56 | * used to modify and send a response packet (and to 1 if this is not the case,
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| 57 | * e.g. when link header is stripped of when receiving) */
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| 58 | #ifndef LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
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| 59 | #define LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 1
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| 60 | #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
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| 61 |
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| 62 | /* The amount of data from the original packet to return in a dest-unreachable */
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| 63 | #define ICMP_DEST_UNREACH_DATASIZE 8
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| 64 |
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| 65 | static void icmp_send_response(struct pbuf *p, u8_t type, u8_t code);
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| 66 |
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| 67 | /**
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| 68 | * Processes ICMP input packets, called from ip_input().
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| 69 | *
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| 70 | * Currently only processes icmp echo requests and sends
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| 71 | * out the echo response.
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| 72 | *
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| 73 | * @param p the icmp echo request packet, p->payload pointing to the ip header
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| 74 | * @param inp the netif on which this packet was received
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| 75 | */
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| 76 | void
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| 77 | icmp_input(struct pbuf *p, struct netif *inp)
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| 78 | {
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| 79 | u8_t type;
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| 80 | #ifdef LWIP_DEBUG
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| 81 | u8_t code;
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| 82 | #endif /* LWIP_DEBUG */
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| 83 | struct icmp_echo_hdr *iecho;
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| 84 | struct ip_hdr *iphdr;
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| 85 | s16_t hlen;
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| 86 |
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| 87 | ICMP_STATS_INC(icmp.recv);
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| 88 | snmp_inc_icmpinmsgs();
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| 89 |
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| 90 |
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| 91 | iphdr = (struct ip_hdr *)p->payload;
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| 92 | hlen = IPH_HL(iphdr) * 4;
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| 93 | if (pbuf_header(p, -hlen) || (p->tot_len < sizeof(u16_t)*2)) {
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| 94 | LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len));
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| 95 | goto lenerr;
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| 96 | }
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| 97 |
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| 98 | type = *((u8_t *)p->payload);
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| 99 | #ifdef LWIP_DEBUG
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| 100 | code = *(((u8_t *)p->payload)+1);
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| 101 | #endif /* LWIP_DEBUG */
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| 102 | switch (type) {
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| 103 | case ICMP_ER:
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| 104 | /* This is OK, echo reply might have been parsed by a raw PCB
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| 105 | (as obviously, an echo request has been sent, too). */
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| 106 | break;
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| 107 | case ICMP_ECHO:
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| 108 | #if !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING
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| 109 | {
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| 110 | int accepted = 1;
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| 111 | #if !LWIP_MULTICAST_PING
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| 112 | /* multicast destination address? */
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| 113 | if (ip_addr_ismulticast(¤t_iphdr_dest)) {
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| 114 | accepted = 0;
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| 115 | }
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| 116 | #endif /* LWIP_MULTICAST_PING */
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| 117 | #if !LWIP_BROADCAST_PING
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| 118 | /* broadcast destination address? */
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| 119 | if (ip_addr_isbroadcast(¤t_iphdr_dest, inp)) {
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| 120 | accepted = 0;
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| 121 | }
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| 122 | #endif /* LWIP_BROADCAST_PING */
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| 123 | /* broadcast or multicast destination address not acceptd? */
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| 124 | if (!accepted) {
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| 125 | LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n"));
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| 126 | ICMP_STATS_INC(icmp.err);
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| 127 | pbuf_free(p);
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| 128 | return;
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| 129 | }
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| 130 | }
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| 131 | #endif /* !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */
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| 132 | LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n"));
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| 133 | if (p->tot_len < sizeof(struct icmp_echo_hdr)) {
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| 134 | LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n"));
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| 135 | goto lenerr;
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| 136 | }
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| 137 | if (inet_chksum_pbuf(p) != 0) {
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| 138 | LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n"));
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| 139 | pbuf_free(p);
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| 140 | ICMP_STATS_INC(icmp.chkerr);
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| 141 | snmp_inc_icmpinerrors();
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| 142 | return;
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| 143 | }
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| 144 | #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
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| 145 | if (pbuf_header(p, (PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
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| 146 | /* p is not big enough to contain link headers
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| 147 | * allocate a new one and copy p into it
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| 148 | */
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| 149 | struct pbuf *r;
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| 150 | /* switch p->payload to ip header */
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| 151 | if (pbuf_header(p, hlen)) {
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| 152 | LWIP_ASSERT("icmp_input: moving p->payload to ip header failed\n", 0);
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| 153 | goto memerr;
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| 154 | }
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| 155 | /* allocate new packet buffer with space for link headers */
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| 156 | r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM);
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| 157 | if (r == NULL) {
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| 158 | LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n"));
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| 159 | goto memerr;
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| 160 | }
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| 161 | LWIP_ASSERT("check that first pbuf can hold struct the ICMP header",
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| 162 | (r->len >= hlen + sizeof(struct icmp_echo_hdr)));
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| 163 | /* copy the whole packet including ip header */
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| 164 | if (pbuf_copy(r, p) != ERR_OK) {
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| 165 | LWIP_ASSERT("icmp_input: copying to new pbuf failed\n", 0);
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| 166 | goto memerr;
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| 167 | }
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| 168 | iphdr = (struct ip_hdr *)r->payload;
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| 169 | /* switch r->payload back to icmp header */
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| 170 | if (pbuf_header(r, -hlen)) {
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| 171 | LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
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| 172 | goto memerr;
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| 173 | }
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| 174 | /* free the original p */
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| 175 | pbuf_free(p);
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| 176 | /* we now have an identical copy of p that has room for link headers */
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| 177 | p = r;
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| 178 | } else {
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| 179 | /* restore p->payload to point to icmp header */
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| 180 | if (pbuf_header(p, -(s16_t)(PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
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| 181 | LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
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| 182 | goto memerr;
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| 183 | }
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| 184 | }
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| 185 | #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
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| 186 | /* At this point, all checks are OK. */
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| 187 | /* We generate an answer by switching the dest and src ip addresses,
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| 188 | * setting the icmp type to ECHO_RESPONSE and updating the checksum. */
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| 189 | iecho = (struct icmp_echo_hdr *)p->payload;
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| 190 | ip_addr_copy(iphdr->src, *ip_current_dest_addr());
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| 191 | ip_addr_copy(iphdr->dest, *ip_current_src_addr());
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| 192 | ICMPH_TYPE_SET(iecho, ICMP_ER);
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| 193 | #if CHECKSUM_GEN_ICMP
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| 194 | /* adjust the checksum */
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| 195 | if (iecho->chksum >= PP_HTONS(0xffffU - (ICMP_ECHO << 8))) {
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| 196 | iecho->chksum += PP_HTONS(ICMP_ECHO << 8) + 1;
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| 197 | } else {
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| 198 | iecho->chksum += PP_HTONS(ICMP_ECHO << 8);
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| 199 | }
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| 200 | #else /* CHECKSUM_GEN_ICMP */
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| 201 | iecho->chksum = 0;
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| 202 | #endif /* CHECKSUM_GEN_ICMP */
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| 203 |
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| 204 | /* Set the correct TTL and recalculate the header checksum. */
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| 205 | IPH_TTL_SET(iphdr, ICMP_TTL);
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| 206 | IPH_CHKSUM_SET(iphdr, 0);
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| 207 | #if CHECKSUM_GEN_IP
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| 208 | IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
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| 209 | #endif /* CHECKSUM_GEN_IP */
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| 210 |
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| 211 | ICMP_STATS_INC(icmp.xmit);
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| 212 | /* increase number of messages attempted to send */
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| 213 | snmp_inc_icmpoutmsgs();
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| 214 | /* increase number of echo replies attempted to send */
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| 215 | snmp_inc_icmpoutechoreps();
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| 216 |
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| 217 | if(pbuf_header(p, hlen)) {
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| 218 | LWIP_ASSERT("Can't move over header in packet", 0);
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| 219 | } else {
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| 220 | err_t ret;
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| 221 | /* send an ICMP packet, src addr is the dest addr of the curren packet */
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| 222 | ret = ip_output_if(p, ip_current_dest_addr(), IP_HDRINCL,
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| 223 | ICMP_TTL, 0, IP_PROTO_ICMP, inp);
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| 224 | if (ret != ERR_OK) {
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| 225 | LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %c.\n", ret));
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| 226 | }
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| 227 | }
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| 228 | break;
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| 229 | default:
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| 230 | LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n",
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| 231 | (s16_t)type, (s16_t)code));
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| 232 | ICMP_STATS_INC(icmp.proterr);
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| 233 | ICMP_STATS_INC(icmp.drop);
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| 234 | }
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| 235 | pbuf_free(p);
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| 236 | return;
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| 237 | lenerr:
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| 238 | pbuf_free(p);
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| 239 | ICMP_STATS_INC(icmp.lenerr);
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| 240 | snmp_inc_icmpinerrors();
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| 241 | return;
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| 242 | #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
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| 243 | memerr:
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| 244 | pbuf_free(p);
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| 245 | ICMP_STATS_INC(icmp.err);
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| 246 | snmp_inc_icmpinerrors();
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| 247 | return;
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| 248 | #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
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| 249 | }
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| 250 |
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| 251 | /**
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| 252 | * Send an icmp 'destination unreachable' packet, called from ip_input() if
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| 253 | * the transport layer protocol is unknown and from udp_input() if the local
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| 254 | * port is not bound.
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| 255 | *
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| 256 | * @param p the input packet for which the 'unreachable' should be sent,
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| 257 | * p->payload pointing to the IP header
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| 258 | * @param t type of the 'unreachable' packet
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| 259 | */
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| 260 | void
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| 261 | icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)
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| 262 | {
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| 263 | icmp_send_response(p, ICMP_DUR, t);
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| 264 | }
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| 265 |
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| 266 | #if IP_FORWARD || IP_REASSEMBLY
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| 267 | /**
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| 268 | * Send a 'time exceeded' packet, called from ip_forward() if TTL is 0.
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| 269 | *
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| 270 | * @param p the input packet for which the 'time exceeded' should be sent,
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| 271 | * p->payload pointing to the IP header
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| 272 | * @param t type of the 'time exceeded' packet
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| 273 | */
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| 274 | void
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| 275 | icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
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| 276 | {
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| 277 | icmp_send_response(p, ICMP_TE, t);
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| 278 | }
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| 279 |
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| 280 | #endif /* IP_FORWARD || IP_REASSEMBLY */
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| 281 |
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| 282 | /**
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| 283 | * Send an icmp packet in response to an incoming packet.
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| 284 | *
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| 285 | * @param p the input packet for which the 'unreachable' should be sent,
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| 286 | * p->payload pointing to the IP header
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| 287 | * @param type Type of the ICMP header
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| 288 | * @param code Code of the ICMP header
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| 289 | */
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| 290 | static void
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| 291 | icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
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| 292 | {
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| 293 | struct pbuf *q;
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| 294 | struct ip_hdr *iphdr;
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| 295 | /* we can use the echo header here */
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| 296 | struct icmp_echo_hdr *icmphdr;
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| 297 | ip_addr_t iphdr_src;
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| 298 |
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| 299 | /* ICMP header + IP header + 8 bytes of data */
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| 300 | q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
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| 301 | PBUF_RAM);
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| 302 | if (q == NULL) {
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| 303 | LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
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| 304 | return;
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| 305 | }
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| 306 | LWIP_ASSERT("check that first pbuf can hold icmp message",
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| 307 | (q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
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| 308 |
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| 309 | iphdr = (struct ip_hdr *)p->payload;
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| 310 | LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
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| 311 | ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));
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| 312 | LWIP_DEBUGF(ICMP_DEBUG, (" to "));
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| 313 | ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
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| 314 | LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
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| 315 |
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| 316 | icmphdr = (struct icmp_echo_hdr *)q->payload;
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| 317 | icmphdr->type = type;
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| 318 | icmphdr->code = code;
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| 319 | icmphdr->id = 0;
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| 320 | icmphdr->seqno = 0;
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| 321 |
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| 322 | /* copy fields from original packet */
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| 323 | SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload,
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| 324 | IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
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| 325 |
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| 326 | /* calculate checksum */
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| 327 | icmphdr->chksum = 0;
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| 328 | icmphdr->chksum = inet_chksum(icmphdr, q->len);
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| 329 | ICMP_STATS_INC(icmp.xmit);
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| 330 | /* increase number of messages attempted to send */
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| 331 | snmp_inc_icmpoutmsgs();
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| 332 | /* increase number of destination unreachable messages attempted to send */
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| 333 | snmp_inc_icmpouttimeexcds();
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| 334 | ip_addr_copy(iphdr_src, iphdr->src);
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| 335 | ip_output(q, NULL, &iphdr_src, ICMP_TTL, 0, IP_PROTO_ICMP);
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| 336 | pbuf_free(q);
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| 337 | }
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| 338 |
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| 339 | #endif /* LWIP_ICMP */
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