lwip_icmp.c

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_IPV4 && 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 
00052 #include <string.h>
00053 
00054 #ifdef LWIP_HOOK_FILENAME
00055 #include LWIP_HOOK_FILENAME
00056 #endif
00057 
00058 /** Small optimization: set to 0 if incoming PBUF_POOL pbuf always can be
00059  * used to modify and send a response packet (and to 1 if this is not the case,
00060  * e.g. when link header is stripped off when receiving) */
00061 #ifndef LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
00062 #define LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 1
00063 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
00064 
00065 /* The amount of data from the original packet to return in a dest-unreachable */
00066 #define ICMP_DEST_UNREACH_DATASIZE 8
00067 
00068 static void icmp_send_response(struct pbuf *p, u8_t type, u8_t code);
00069 
00070 /**
00071  * Processes ICMP input packets, called from ip_input().
00072  *
00073  * Currently only processes icmp echo requests and sends
00074  * out the echo response.
00075  *
00076  * @param p the icmp echo request packet, p->payload pointing to the icmp header
00077  * @param inp the netif on which this packet was received
00078  */
00079 void
00080 icmp_input(struct pbuf *p, struct netif *inp)
00081 {
00082   u8_t type;
00083 #ifdef LWIP_DEBUG
00084   u8_t code;
00085 #endif /* LWIP_DEBUG */
00086   struct icmp_echo_hdr *iecho;
00087   const struct ip_hdr *iphdr_in;
00088   u16_t hlen;
00089   const ip4_addr_t *src;
00090 
00091   ICMP_STATS_INC(icmp.recv);
00092   MIB2_STATS_INC(mib2.icmpinmsgs);
00093 
00094   iphdr_in = ip4_current_header();
00095   hlen = IPH_HL_BYTES(iphdr_in);
00096   if (hlen < IP_HLEN) {
00097     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short IP header (%"S16_F" bytes) received\n", hlen));
00098     goto lenerr;
00099   }
00100   if (p->len < sizeof(u16_t) * 2) {
00101     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len));
00102     goto lenerr;
00103   }
00104 
00105   type = *((u8_t *)p->payload);
00106 #ifdef LWIP_DEBUG
00107   code = *(((u8_t *)p->payload) + 1);
00108   /* if debug is enabled but debug statement below is somehow disabled: */
00109   LWIP_UNUSED_ARG(code);
00110 #endif /* LWIP_DEBUG */
00111   switch (type) {
00112     case ICMP_ER:
00113       /* This is OK, echo reply might have been parsed by a raw PCB
00114          (as obviously, an echo request has been sent, too). */
00115       MIB2_STATS_INC(mib2.icmpinechoreps);
00116       break;
00117     case ICMP_ECHO:
00118       MIB2_STATS_INC(mib2.icmpinechos);
00119       src = ip4_current_dest_addr();
00120       /* multicast destination address? */
00121       if (ip4_addr_ismulticast(ip4_current_dest_addr())) {
00122 #if LWIP_MULTICAST_PING
00123         /* For multicast, use address of receiving interface as source address */
00124         src = netif_ip4_addr(inp);
00125 #else /* LWIP_MULTICAST_PING */
00126         LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast pings\n"));
00127         goto icmperr;
00128 #endif /* LWIP_MULTICAST_PING */
00129       }
00130       /* broadcast destination address? */
00131       if (ip4_addr_isbroadcast(ip4_current_dest_addr(), ip_current_netif())) {
00132 #if LWIP_BROADCAST_PING
00133         /* For broadcast, use address of receiving interface as source address */
00134         src = netif_ip4_addr(inp);
00135 #else /* LWIP_BROADCAST_PING */
00136         LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to broadcast pings\n"));
00137         goto icmperr;
00138 #endif /* LWIP_BROADCAST_PING */
00139       }
00140       LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n"));
00141       if (p->tot_len < sizeof(struct icmp_echo_hdr)) {
00142         LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n"));
00143         goto lenerr;
00144       }
00145 #if CHECKSUM_CHECK_ICMP
00146       IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_CHECK_ICMP) {
00147         if (inet_chksum_pbuf(p) != 0) {
00148           LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n"));
00149           pbuf_free(p);
00150           ICMP_STATS_INC(icmp.chkerr);
00151           MIB2_STATS_INC(mib2.icmpinerrors);
00152           return;
00153         }
00154       }
00155 #endif
00156 #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
00157       if (pbuf_add_header(p, hlen + PBUF_LINK_HLEN + PBUF_LINK_ENCAPSULATION_HLEN)) {
00158         /* p is not big enough to contain link headers
00159          * allocate a new one and copy p into it
00160          */
00161         struct pbuf *r;
00162         u16_t alloc_len = (u16_t)(p->tot_len + hlen);
00163         if (alloc_len < p->tot_len) {
00164           LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed (tot_len overflow)\n"));
00165           goto icmperr;
00166         }
00167         /* allocate new packet buffer with space for link headers */
00168         r = pbuf_alloc(PBUF_LINK, alloc_len, PBUF_RAM);
00169         if (r == NULL) {
00170           LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n"));
00171           goto icmperr;
00172         }
00173         if (r->len < hlen + sizeof(struct icmp_echo_hdr)) {
00174           LWIP_DEBUGF(ICMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("first pbuf cannot hold the ICMP header"));
00175           pbuf_free(r);
00176           goto icmperr;
00177         }
00178         /* copy the ip header */
00179         MEMCPY(r->payload, iphdr_in, hlen);
00180         /* switch r->payload back to icmp header (cannot fail) */
00181         if (pbuf_remove_header(r, hlen)) {
00182           LWIP_ASSERT("icmp_input: moving r->payload to icmp header failed\n", 0);
00183           pbuf_free(r);
00184           goto icmperr;
00185         }
00186         /* copy the rest of the packet without ip header */
00187         if (pbuf_copy(r, p) != ERR_OK) {
00188           LWIP_DEBUGF(ICMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("icmp_input: copying to new pbuf failed"));
00189           pbuf_free(r);
00190           goto icmperr;
00191         }
00192         /* free the original p */
00193         pbuf_free(p);
00194         /* we now have an identical copy of p that has room for link headers */
00195         p = r;
00196       } else {
00197         /* restore p->payload to point to icmp header (cannot fail) */
00198         if (pbuf_remove_header(p, hlen + PBUF_LINK_HLEN + PBUF_LINK_ENCAPSULATION_HLEN)) {
00199           LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
00200           goto icmperr;
00201         }
00202       }
00203 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
00204       /* At this point, all checks are OK. */
00205       /* We generate an answer by switching the dest and src ip addresses,
00206        * setting the icmp type to ECHO_RESPONSE and updating the checksum. */
00207       iecho = (struct icmp_echo_hdr *)p->payload;
00208       if (pbuf_add_header(p, hlen)) {
00209         LWIP_DEBUGF(ICMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("Can't move over header in packet"));
00210       } else {
00211         err_t ret;
00212         struct ip_hdr *iphdr = (struct ip_hdr *)p->payload;
00213         ip4_addr_copy(iphdr->src, *src);
00214         ip4_addr_copy(iphdr->dest, *ip4_current_src_addr());
00215         ICMPH_TYPE_SET(iecho, ICMP_ER);
00216 #if CHECKSUM_GEN_ICMP
00217         IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_GEN_ICMP) {
00218           /* adjust the checksum */
00219           if (iecho->chksum > PP_HTONS(0xffffU - (ICMP_ECHO << 8))) {
00220             iecho->chksum = (u16_t)(iecho->chksum + PP_HTONS((u16_t)(ICMP_ECHO << 8)) + 1);
00221           } else {
00222             iecho->chksum = (u16_t)(iecho->chksum + PP_HTONS(ICMP_ECHO << 8));
00223           }
00224         }
00225 #if LWIP_CHECKSUM_CTRL_PER_NETIF
00226         else {
00227           iecho->chksum = 0;
00228         }
00229 #endif /* LWIP_CHECKSUM_CTRL_PER_NETIF */
00230 #else /* CHECKSUM_GEN_ICMP */
00231         iecho->chksum = 0;
00232 #endif /* CHECKSUM_GEN_ICMP */
00233 
00234         /* Set the correct TTL and recalculate the header checksum. */
00235         IPH_TTL_SET(iphdr, ICMP_TTL);
00236         IPH_CHKSUM_SET(iphdr, 0);
00237 #if CHECKSUM_GEN_IP
00238         IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_GEN_IP) {
00239           IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, hlen));
00240         }
00241 #endif /* CHECKSUM_GEN_IP */
00242 
00243         ICMP_STATS_INC(icmp.xmit);
00244         /* increase number of messages attempted to send */
00245         MIB2_STATS_INC(mib2.icmpoutmsgs);
00246         /* increase number of echo replies attempted to send */
00247         MIB2_STATS_INC(mib2.icmpoutechoreps);
00248 
00249         /* send an ICMP packet */
00250         ret = ip4_output_if(p, src, LWIP_IP_HDRINCL,
00251                             ICMP_TTL, 0, IP_PROTO_ICMP, inp);
00252         if (ret != ERR_OK) {
00253           LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %s\n", lwip_strerr(ret)));
00254         }
00255       }
00256       break;
00257     default:
00258       if (type == ICMP_DUR) {
00259         MIB2_STATS_INC(mib2.icmpindestunreachs);
00260       } else if (type == ICMP_TE) {
00261         MIB2_STATS_INC(mib2.icmpintimeexcds);
00262       } else if (type == ICMP_PP) {
00263         MIB2_STATS_INC(mib2.icmpinparmprobs);
00264       } else if (type == ICMP_SQ) {
00265         MIB2_STATS_INC(mib2.icmpinsrcquenchs);
00266       } else if (type == ICMP_RD) {
00267         MIB2_STATS_INC(mib2.icmpinredirects);
00268       } else if (type == ICMP_TS) {
00269         MIB2_STATS_INC(mib2.icmpintimestamps);
00270       } else if (type == ICMP_TSR) {
00271         MIB2_STATS_INC(mib2.icmpintimestampreps);
00272       } else if (type == ICMP_AM) {
00273         MIB2_STATS_INC(mib2.icmpinaddrmasks);
00274       } else if (type == ICMP_AMR) {
00275         MIB2_STATS_INC(mib2.icmpinaddrmaskreps);
00276       }
00277       LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n",
00278                                (s16_t)type, (s16_t)code));
00279       ICMP_STATS_INC(icmp.proterr);
00280       ICMP_STATS_INC(icmp.drop);
00281   }
00282   pbuf_free(p);
00283   return;
00284 lenerr:
00285   pbuf_free(p);
00286   ICMP_STATS_INC(icmp.lenerr);
00287   MIB2_STATS_INC(mib2.icmpinerrors);
00288   return;
00289 #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN || !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING
00290 icmperr:
00291   pbuf_free(p);
00292   ICMP_STATS_INC(icmp.err);
00293   MIB2_STATS_INC(mib2.icmpinerrors);
00294   return;
00295 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN || !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */
00296 }
00297 
00298 /**
00299  * Send an icmp 'destination unreachable' packet, called from ip_input() if
00300  * the transport layer protocol is unknown and from udp_input() if the local
00301  * port is not bound.
00302  *
00303  * @param p the input packet for which the 'unreachable' should be sent,
00304  *          p->payload pointing to the IP header
00305  * @param t type of the 'unreachable' packet
00306  */
00307 void
00308 icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)
00309 {
00310   MIB2_STATS_INC(mib2.icmpoutdestunreachs);
00311   icmp_send_response(p, ICMP_DUR, t);
00312 }
00313 
00314 #if IP_FORWARD || IP_REASSEMBLY
00315 /**
00316  * Send a 'time exceeded' packet, called from ip_forward() if TTL is 0.
00317  *
00318  * @param p the input packet for which the 'time exceeded' should be sent,
00319  *          p->payload pointing to the IP header
00320  * @param t type of the 'time exceeded' packet
00321  */
00322 void
00323 icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
00324 {
00325   MIB2_STATS_INC(mib2.icmpouttimeexcds);
00326   icmp_send_response(p, ICMP_TE, t);
00327 }
00328 
00329 #endif /* IP_FORWARD || IP_REASSEMBLY */
00330 
00331 /**
00332  * Send an icmp packet in response to an incoming packet.
00333  *
00334  * @param p the input packet for which the 'unreachable' should be sent,
00335  *          p->payload pointing to the IP header
00336  * @param type Type of the ICMP header
00337  * @param code Code of the ICMP header
00338  */
00339 static void
00340 icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
00341 {
00342   struct pbuf *q;
00343   struct ip_hdr *iphdr;
00344   /* we can use the echo header here */
00345   struct icmp_echo_hdr *icmphdr;
00346   ip4_addr_t iphdr_src;
00347   struct netif *netif;
00348 
00349   /* increase number of messages attempted to send */
00350   MIB2_STATS_INC(mib2.icmpoutmsgs);
00351 
00352   /* ICMP header + IP header + 8 bytes of data */
00353   q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
00354                  PBUF_RAM);
00355   if (q == NULL) {
00356     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
00357     MIB2_STATS_INC(mib2.icmpouterrors);
00358     return;
00359   }
00360   LWIP_ASSERT("check that first pbuf can hold icmp message",
00361               (q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
00362 
00363   iphdr = (struct ip_hdr *)p->payload;
00364   LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
00365   ip4_addr_debug_print_val(ICMP_DEBUG, iphdr->src);
00366   LWIP_DEBUGF(ICMP_DEBUG, (" to "));
00367   ip4_addr_debug_print_val(ICMP_DEBUG, iphdr->dest);
00368   LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
00369 
00370   icmphdr = (struct icmp_echo_hdr *)q->payload;
00371   icmphdr->type = type;
00372   icmphdr->code = code;
00373   icmphdr->id = 0;
00374   icmphdr->seqno = 0;
00375 
00376   /* copy fields from original packet */
00377   SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload,
00378           IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
00379 
00380   ip4_addr_copy(iphdr_src, iphdr->src);
00381 #ifdef LWIP_HOOK_IP4_ROUTE_SRC
00382   {
00383     ip4_addr_t iphdr_dst;
00384     ip4_addr_copy(iphdr_dst, iphdr->dest);
00385     netif = ip4_route_src(&iphdr_dst, &iphdr_src);
00386   }
00387 #else
00388   netif = ip4_route(&iphdr_src);
00389 #endif
00390   if (netif != NULL) {
00391     /* calculate checksum */
00392     icmphdr->chksum = 0;
00393 #if CHECKSUM_GEN_ICMP
00394     IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_ICMP) {
00395       icmphdr->chksum = inet_chksum(icmphdr, q->len);
00396     }
00397 #endif
00398     ICMP_STATS_INC(icmp.xmit);
00399     ip4_output_if(q, NULL, &iphdr_src, ICMP_TTL, 0, IP_PROTO_ICMP, netif);
00400   }
00401   pbuf_free(q);
00402 }
00403 
00404 #endif /* LWIP_IPV4 && LWIP_ICMP */