lwip-1.4.1 (partial)
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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 s16_t hlen; 00086 00087 ICMP_STATS_INC(icmp.recv); 00088 snmp_inc_icmpinmsgs(); 00089 00090 00091 iphdr = (struct ip_hdr *)p->payload; 00092 hlen = IPH_HL(iphdr) * 4; 00093 if (pbuf_header(p, -hlen) || (p->tot_len < sizeof(u16_t)*2)) { 00094 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len)); 00095 goto lenerr; 00096 } 00097 00098 type = *((u8_t *)p->payload); 00099 #ifdef LWIP_DEBUG 00100 code = *(((u8_t *)p->payload)+1); 00101 #endif /* LWIP_DEBUG */ 00102 switch (type) { 00103 case ICMP_ER: 00104 /* This is OK, echo reply might have been parsed by a raw PCB 00105 (as obviously, an echo request has been sent, too). */ 00106 break; 00107 case ICMP_ECHO: 00108 #if !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING 00109 { 00110 int accepted = 1; 00111 #if !LWIP_MULTICAST_PING 00112 /* multicast destination address? */ 00113 if (ip_addr_ismulticast(¤t_iphdr_dest)) { 00114 accepted = 0; 00115 } 00116 #endif /* LWIP_MULTICAST_PING */ 00117 #if !LWIP_BROADCAST_PING 00118 /* broadcast destination address? */ 00119 if (ip_addr_isbroadcast(¤t_iphdr_dest, inp)) { 00120 accepted = 0; 00121 } 00122 #endif /* LWIP_BROADCAST_PING */ 00123 /* broadcast or multicast destination address not acceptd? */ 00124 if (!accepted) { 00125 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n")); 00126 ICMP_STATS_INC(icmp.err); 00127 pbuf_free(p); 00128 return; 00129 } 00130 } 00131 #endif /* !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */ 00132 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n")); 00133 if (p->tot_len < sizeof(struct icmp_echo_hdr)) { 00134 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n")); 00135 goto lenerr; 00136 } 00137 if (inet_chksum_pbuf(p) != 0) { 00138 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n")); 00139 pbuf_free(p); 00140 ICMP_STATS_INC(icmp.chkerr); 00141 snmp_inc_icmpinerrors(); 00142 return; 00143 } 00144 #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 00145 if (pbuf_header(p, (PBUF_IP_HLEN + PBUF_LINK_HLEN))) { 00146 /* p is not big enough to contain link headers 00147 * allocate a new one and copy p into it 00148 */ 00149 struct pbuf *r; 00150 /* switch p->payload to ip header */ 00151 if (pbuf_header(p, hlen)) { 00152 LWIP_ASSERT("icmp_input: moving p->payload to ip header failed\n", 0); 00153 goto memerr; 00154 } 00155 /* allocate new packet buffer with space for link headers */ 00156 r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM); 00157 if (r == NULL) { 00158 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n")); 00159 goto memerr; 00160 } 00161 LWIP_ASSERT("check that first pbuf can hold struct the ICMP header", 00162 (r->len >= hlen + sizeof(struct icmp_echo_hdr))); 00163 /* copy the whole packet including ip header */ 00164 if (pbuf_copy(r, p) != ERR_OK) { 00165 LWIP_ASSERT("icmp_input: copying to new pbuf failed\n", 0); 00166 goto memerr; 00167 } 00168 iphdr = (struct ip_hdr *)r->payload; 00169 /* switch r->payload back to icmp header */ 00170 if (pbuf_header(r, -hlen)) { 00171 LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0); 00172 goto memerr; 00173 } 00174 /* free the original p */ 00175 pbuf_free(p); 00176 /* we now have an identical copy of p that has room for link headers */ 00177 p = r; 00178 } else { 00179 /* restore p->payload to point to icmp header */ 00180 if (pbuf_header(p, -(s16_t)(PBUF_IP_HLEN + PBUF_LINK_HLEN))) { 00181 LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0); 00182 goto memerr; 00183 } 00184 } 00185 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */ 00186 /* At this point, all checks are OK. */ 00187 /* We generate an answer by switching the dest and src ip addresses, 00188 * setting the icmp type to ECHO_RESPONSE and updating the checksum. */ 00189 iecho = (struct icmp_echo_hdr *)p->payload; 00190 ip_addr_copy(iphdr->src, *ip_current_dest_addr()); 00191 ip_addr_copy(iphdr->dest, *ip_current_src_addr()); 00192 ICMPH_TYPE_SET(iecho, ICMP_ER); 00193 #if CHECKSUM_GEN_ICMP 00194 /* adjust the checksum */ 00195 if (iecho->chksum >= PP_HTONS(0xffffU - (ICMP_ECHO << 8))) { 00196 iecho->chksum += PP_HTONS(ICMP_ECHO << 8) + 1; 00197 } else { 00198 iecho->chksum += PP_HTONS(ICMP_ECHO << 8); 00199 } 00200 #else /* CHECKSUM_GEN_ICMP */ 00201 iecho->chksum = 0; 00202 #endif /* CHECKSUM_GEN_ICMP */ 00203 00204 /* Set the correct TTL and recalculate the header checksum. */ 00205 IPH_TTL_SET(iphdr, ICMP_TTL); 00206 IPH_CHKSUM_SET(iphdr, 0); 00207 #if CHECKSUM_GEN_IP 00208 IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN)); 00209 #endif /* CHECKSUM_GEN_IP */ 00210 00211 ICMP_STATS_INC(icmp.xmit); 00212 /* increase number of messages attempted to send */ 00213 snmp_inc_icmpoutmsgs(); 00214 /* increase number of echo replies attempted to send */ 00215 snmp_inc_icmpoutechoreps(); 00216 00217 if(pbuf_header(p, hlen)) { 00218 LWIP_ASSERT("Can't move over header in packet", 0); 00219 } else { 00220 err_t ret; 00221 /* send an ICMP packet, src addr is the dest addr of the curren packet */ 00222 ret = ip_output_if(p, ip_current_dest_addr(), IP_HDRINCL, 00223 ICMP_TTL, 0, IP_PROTO_ICMP, inp); 00224 if (ret != ERR_OK) { 00225 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %c.\n", ret)); 00226 } 00227 } 00228 break; 00229 default: 00230 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n", 00231 (s16_t)type, (s16_t)code)); 00232 ICMP_STATS_INC(icmp.proterr); 00233 ICMP_STATS_INC(icmp.drop); 00234 } 00235 pbuf_free(p); 00236 return; 00237 lenerr: 00238 pbuf_free(p); 00239 ICMP_STATS_INC(icmp.lenerr); 00240 snmp_inc_icmpinerrors(); 00241 return; 00242 #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 00243 memerr: 00244 pbuf_free(p); 00245 ICMP_STATS_INC(icmp.err); 00246 snmp_inc_icmpinerrors(); 00247 return; 00248 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */ 00249 } 00250 00251 /** 00252 * Send an icmp 'destination unreachable' packet, called from ip_input() if 00253 * the transport layer protocol is unknown and from udp_input() if the local 00254 * port is not bound. 00255 * 00256 * @param p the input packet for which the 'unreachable' should be sent, 00257 * p->payload pointing to the IP header 00258 * @param t type of the 'unreachable' packet 00259 */ 00260 void 00261 icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t) 00262 { 00263 icmp_send_response(p, ICMP_DUR, t); 00264 } 00265 00266 #if IP_FORWARD || IP_REASSEMBLY 00267 /** 00268 * Send a 'time exceeded' packet, called from ip_forward() if TTL is 0. 00269 * 00270 * @param p the input packet for which the 'time exceeded' should be sent, 00271 * p->payload pointing to the IP header 00272 * @param t type of the 'time exceeded' packet 00273 */ 00274 void 00275 icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t) 00276 { 00277 icmp_send_response(p, ICMP_TE, t); 00278 } 00279 00280 #endif /* IP_FORWARD || IP_REASSEMBLY */ 00281 00282 /** 00283 * Send an icmp packet in response to an incoming packet. 00284 * 00285 * @param p the input packet for which the 'unreachable' should be sent, 00286 * p->payload pointing to the IP header 00287 * @param type Type of the ICMP header 00288 * @param code Code of the ICMP header 00289 */ 00290 static void 00291 icmp_send_response(struct pbuf *p, u8_t type, u8_t code) 00292 { 00293 struct pbuf *q; 00294 struct ip_hdr *iphdr; 00295 /* we can use the echo header here */ 00296 struct icmp_echo_hdr *icmphdr; 00297 ip_addr_t iphdr_src; 00298 00299 /* ICMP header + IP header + 8 bytes of data */ 00300 q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE, 00301 PBUF_RAM); 00302 if (q == NULL) { 00303 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n")); 00304 return; 00305 } 00306 LWIP_ASSERT("check that first pbuf can hold icmp message", 00307 (q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE))); 00308 00309 iphdr = (struct ip_hdr *)p->payload; 00310 LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from ")); 00311 ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src)); 00312 LWIP_DEBUGF(ICMP_DEBUG, (" to ")); 00313 ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest)); 00314 LWIP_DEBUGF(ICMP_DEBUG, ("\n")); 00315 00316 icmphdr = (struct icmp_echo_hdr *)q->payload; 00317 icmphdr->type = type; 00318 icmphdr->code = code; 00319 icmphdr->id = 0; 00320 icmphdr->seqno = 0; 00321 00322 /* copy fields from original packet */ 00323 SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload, 00324 IP_HLEN + ICMP_DEST_UNREACH_DATASIZE); 00325 00326 /* calculate checksum */ 00327 icmphdr->chksum = 0; 00328 icmphdr->chksum = inet_chksum(icmphdr, q->len); 00329 ICMP_STATS_INC(icmp.xmit); 00330 /* increase number of messages attempted to send */ 00331 snmp_inc_icmpoutmsgs(); 00332 /* increase number of destination unreachable messages attempted to send */ 00333 snmp_inc_icmpouttimeexcds(); 00334 ip_addr_copy(iphdr_src, iphdr->src); 00335 ip_output(q, NULL, &iphdr_src, ICMP_TTL, 0, IP_PROTO_ICMP); 00336 pbuf_free(q); 00337 } 00338 00339 #endif /* LWIP_ICMP */
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