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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