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