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icmp.c
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00001 /** 00002 * @file 00003 * ICMP - Internet Control Message Protocol 00004 * 00005 */ 00006 00007 /* 00008 * Copyright (c) 2001-2004 Swedish Institute of Computer Science. 00009 * All rights reserved. 00010 * 00011 * Redistribution and use in source and binary forms, with or without modification, 00012 * are permitted provided that the following conditions are met: 00013 * 00014 * 1. Redistributions of source code must retain the above copyright notice, 00015 * this list of conditions and the following disclaimer. 00016 * 2. Redistributions in binary form must reproduce the above copyright notice, 00017 * this list of conditions and the following disclaimer in the documentation 00018 * and/or other materials provided with the distribution. 00019 * 3. The name of the author may not be used to endorse or promote products 00020 * derived from this software without specific prior written permission. 00021 * 00022 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED 00023 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 00024 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT 00025 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 00026 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT 00027 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 00028 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 00029 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 00030 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 00031 * OF SUCH DAMAGE. 00032 * 00033 * This file is part of the lwIP TCP/IP stack. 00034 * 00035 * Author: Adam Dunkels <adam@sics.se> 00036 * 00037 */ 00038 00039 /* Some ICMP messages should be passed to the transport protocols. This 00040 is not implemented. */ 00041 00042 #include "lwip/opt.h" 00043 00044 #if LWIP_ICMP /* don't build if not configured for use in lwipopts.h */ 00045 00046 #include "lwip/icmp.h" 00047 #include "lwip/inet_chksum.h" 00048 #include "lwip/ip.h" 00049 #include "lwip/def.h" 00050 #include "lwip/stats.h" 00051 #include "lwip/snmp.h" 00052 00053 #include <string.h> 00054 00055 /** Small optimization: set to 0 if incoming PBUF_POOL pbuf always can be 00056 * used to modify and send a response packet (and to 1 if this is not the case, 00057 * e.g. when link header is stripped of when receiving) */ 00058 #ifndef LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 00059 #define LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 1 00060 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */ 00061 00062 /* The amount of data from the original packet to return in a dest-unreachable */ 00063 #define ICMP_DEST_UNREACH_DATASIZE 8 00064 00065 static void icmp_send_response(struct pbuf *p, u8_t type, u8_t code); 00066 00067 /** 00068 * Processes ICMP input packets, called from ip_input(). 00069 * 00070 * Currently only processes icmp echo requests and sends 00071 * out the echo response. 00072 * 00073 * @param p the icmp echo request packet, p->payload pointing to the ip header 00074 * @param inp the netif on which this packet was received 00075 */ 00076 void 00077 icmp_input(struct pbuf *p, struct netif *inp) 00078 { 00079 u8_t type; 00080 #ifdef LWIP_DEBUG 00081 u8_t code; 00082 #endif /* LWIP_DEBUG */ 00083 struct icmp_echo_hdr *iecho; 00084 struct ip_hdr *iphdr; 00085 ip_addr_t tmpaddr; 00086 s16_t hlen; 00087 00088 ICMP_STATS_INC(icmp.recv); 00089 snmp_inc_icmpinmsgs(); 00090 00091 00092 iphdr = (struct ip_hdr *)p->payload; 00093 hlen = IPH_HL(iphdr) * 4; 00094 if (pbuf_header(p, -hlen) || (p->tot_len < sizeof(u16_t)*2)) { 00095 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len)); 00096 goto lenerr; 00097 } 00098 00099 type = *((u8_t *)p->payload); 00100 #ifdef LWIP_DEBUG 00101 code = *(((u8_t *)p->payload)+1); 00102 #endif /* LWIP_DEBUG */ 00103 switch (type) { 00104 case ICMP_ER: 00105 /* This is OK, echo reply might have been parsed by a raw PCB 00106 (as obviously, an echo request has been sent, too). */ 00107 break; 00108 case ICMP_ECHO: 00109 #if !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING 00110 { 00111 int accepted = 1; 00112 #if !LWIP_MULTICAST_PING 00113 /* multicast destination address? */ 00114 if (ip_addr_ismulticast(&iphdr->dest)) { 00115 accepted = 0; 00116 } 00117 #endif /* LWIP_MULTICAST_PING */ 00118 #if !LWIP_BROADCAST_PING 00119 /* broadcast destination address? */ 00120 if (ip_addr_isbroadcast(&iphdr->dest, inp)) { 00121 accepted = 0; 00122 } 00123 #endif /* LWIP_BROADCAST_PING */ 00124 /* broadcast or multicast destination address not acceptd? */ 00125 if (!accepted) { 00126 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n")); 00127 ICMP_STATS_INC(icmp.err); 00128 pbuf_free(p); 00129 return; 00130 } 00131 } 00132 #endif /* !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */ 00133 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n")); 00134 if (p->tot_len < sizeof(struct icmp_echo_hdr)) { 00135 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n")); 00136 goto lenerr; 00137 } 00138 if (inet_chksum_pbuf(p) != 0) { 00139 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n")); 00140 pbuf_free(p); 00141 ICMP_STATS_INC(icmp.chkerr); 00142 snmp_inc_icmpinerrors(); 00143 return; 00144 } 00145 #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 00146 if (pbuf_header(p, (PBUF_IP_HLEN + PBUF_LINK_HLEN))) { 00147 /* p is not big enough to contain link headers 00148 * allocate a new one and copy p into it 00149 */ 00150 struct pbuf *r; 00151 /* switch p->payload to ip header */ 00152 if (pbuf_header(p, hlen)) { 00153 LWIP_ASSERT("icmp_input: moving p->payload to ip header failed\n", 0); 00154 goto memerr; 00155 } 00156 /* allocate new packet buffer with space for link headers */ 00157 r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM); 00158 if (r == NULL) { 00159 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n")); 00160 goto memerr; 00161 } 00162 LWIP_ASSERT("check that first pbuf can hold struct the ICMP header", 00163 (r->len >= hlen + sizeof(struct icmp_echo_hdr))); 00164 /* copy the whole packet including ip header */ 00165 if (pbuf_copy(r, p) != ERR_OK) { 00166 LWIP_ASSERT("icmp_input: copying to new pbuf failed\n", 0); 00167 goto memerr; 00168 } 00169 iphdr = (struct ip_hdr *)r->payload; 00170 /* switch r->payload back to icmp header */ 00171 if (pbuf_header(r, -hlen)) { 00172 LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0); 00173 goto memerr; 00174 } 00175 /* free the original p */ 00176 pbuf_free(p); 00177 /* we now have an identical copy of p that has room for link headers */ 00178 p = r; 00179 } else { 00180 /* restore p->payload to point to icmp header */ 00181 if (pbuf_header(p, -(s16_t)(PBUF_IP_HLEN + PBUF_LINK_HLEN))) { 00182 LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0); 00183 goto memerr; 00184 } 00185 } 00186 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */ 00187 /* At this point, all checks are OK. */ 00188 /* We generate an answer by switching the dest and src ip addresses, 00189 * setting the icmp type to ECHO_RESPONSE and updating the checksum. */ 00190 iecho = (struct icmp_echo_hdr *)p->payload; 00191 ip_addr_copy(tmpaddr, iphdr->src); 00192 ip_addr_copy(iphdr->src, iphdr->dest); 00193 ip_addr_copy(iphdr->dest, tmpaddr); 00194 ICMPH_TYPE_SET(iecho, ICMP_ER); 00195 /* adjust the checksum */ 00196 if (iecho->chksum >= htons(0xffff - (ICMP_ECHO << 8))) { 00197 iecho->chksum += htons(ICMP_ECHO << 8) + 1; 00198 } else { 00199 iecho->chksum += htons(ICMP_ECHO << 8); 00200 } 00201 00202 /* Set the correct TTL and recalculate the header checksum. */ 00203 IPH_TTL_SET(iphdr, ICMP_TTL); 00204 IPH_CHKSUM_SET(iphdr, 0); 00205 #if CHECKSUM_GEN_IP 00206 IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN)); 00207 #endif /* CHECKSUM_GEN_IP */ 00208 00209 ICMP_STATS_INC(icmp.xmit); 00210 /* increase number of messages attempted to send */ 00211 snmp_inc_icmpoutmsgs(); 00212 /* increase number of echo replies attempted to send */ 00213 snmp_inc_icmpoutechoreps(); 00214 00215 if(pbuf_header(p, hlen)) { 00216 LWIP_ASSERT("Can't move over header in packet", 0); 00217 } else { 00218 err_t ret; 00219 ret = ip_output_if(p, &(iphdr->src), IP_HDRINCL, 00220 ICMP_TTL, 0, IP_PROTO_ICMP, inp); 00221 if (ret != ERR_OK) { 00222 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %c.\n", ret)); 00223 } 00224 } 00225 break; 00226 default: 00227 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n", 00228 (s16_t)type, (s16_t)code)); 00229 ICMP_STATS_INC(icmp.proterr); 00230 ICMP_STATS_INC(icmp.drop); 00231 } 00232 pbuf_free(p); 00233 return; 00234 lenerr: 00235 pbuf_free(p); 00236 ICMP_STATS_INC(icmp.lenerr); 00237 snmp_inc_icmpinerrors(); 00238 return; 00239 #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 00240 memerr: 00241 pbuf_free(p); 00242 ICMP_STATS_INC(icmp.err); 00243 snmp_inc_icmpinerrors(); 00244 return; 00245 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */ 00246 } 00247 00248 /** 00249 * Send an icmp 'destination unreachable' packet, called from ip_input() if 00250 * the transport layer protocol is unknown and from udp_input() if the local 00251 * port is not bound. 00252 * 00253 * @param p the input packet for which the 'unreachable' should be sent, 00254 * p->payload pointing to the IP header 00255 * @param t type of the 'unreachable' packet 00256 */ 00257 void 00258 icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t) 00259 { 00260 icmp_send_response(p, ICMP_DUR, t); 00261 } 00262 00263 #if IP_FORWARD || IP_REASSEMBLY 00264 /** 00265 * Send a 'time exceeded' packet, called from ip_forward() if TTL is 0. 00266 * 00267 * @param p the input packet for which the 'time exceeded' should be sent, 00268 * p->payload pointing to the IP header 00269 * @param t type of the 'time exceeded' packet 00270 */ 00271 void 00272 icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t) 00273 { 00274 icmp_send_response(p, ICMP_TE, t); 00275 } 00276 00277 #endif /* IP_FORWARD || IP_REASSEMBLY */ 00278 00279 /** 00280 * Send an icmp packet in response to an incoming packet. 00281 * 00282 * @param p the input packet for which the 'unreachable' should be sent, 00283 * p->payload pointing to the IP header 00284 * @param type Type of the ICMP header 00285 * @param code Code of the ICMP header 00286 */ 00287 static void 00288 icmp_send_response(struct pbuf *p, u8_t type, u8_t code) 00289 { 00290 struct pbuf *q; 00291 struct ip_hdr *iphdr; 00292 /* we can use the echo header here */ 00293 struct icmp_echo_hdr *icmphdr; 00294 00295 /* ICMP header + IP header + 8 bytes of data */ 00296 q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE, 00297 PBUF_RAM); 00298 if (q == NULL) { 00299 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n")); 00300 return; 00301 } 00302 LWIP_ASSERT("check that first pbuf can hold icmp message", 00303 (q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE))); 00304 00305 iphdr = (struct ip_hdr *)p->payload; 00306 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from ")); 00307 ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src)); 00308 LWIP_DEBUGF(ICMP_DEBUG, (" to ")); 00309 ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest)); 00310 LWIP_DEBUGF(ICMP_DEBUG, ("\n")); 00311 00312 icmphdr = (struct icmp_echo_hdr *)q->payload; 00313 icmphdr->type = type; 00314 icmphdr->code = code; 00315 icmphdr->id = 0; 00316 icmphdr->seqno = 0; 00317 00318 /* copy fields from original packet */ 00319 SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload, 00320 IP_HLEN + ICMP_DEST_UNREACH_DATASIZE); 00321 00322 /* calculate checksum */ 00323 icmphdr->chksum = 0; 00324 icmphdr->chksum = inet_chksum(icmphdr, q->len); 00325 ICMP_STATS_INC(icmp.xmit); 00326 /* increase number of messages attempted to send */ 00327 snmp_inc_icmpoutmsgs(); 00328 /* increase number of destination unreachable messages attempted to send */ 00329 snmp_inc_icmpouttimeexcds(); 00330 ip_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP); 00331 pbuf_free(q); 00332 } 00333 00334 #endif /* LWIP_ICMP */
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