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 of 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(iphdr_in) * 4;
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 #endif /* LWIP_DEBUG */
00109   switch (type) {
00110   case ICMP_ER:
00111     /* This is OK, echo reply might have been parsed by a raw PCB
00112        (as obviously, an echo request has been sent, too). */
00113     MIB2_STATS_INC(mib2.icmpinechoreps);
00114     break;
00115   case ICMP_ECHO:
00116     MIB2_STATS_INC(mib2.icmpinechos);
00117     src = ip4_current_dest_addr();
00118     /* multicast destination address? */
00119     if (ip4_addr_ismulticast(ip4_current_dest_addr())) {
00120 #if LWIP_MULTICAST_PING
00121       /* For multicast, use address of receiving interface as source address */
00122       src = netif_ip4_addr(inp);
00123 #else /* LWIP_MULTICAST_PING */
00124       LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast pings\n"));
00125       goto icmperr;
00126 #endif /* LWIP_MULTICAST_PING */
00127     }
00128     /* broadcast destination address? */
00129     if (ip4_addr_isbroadcast(ip4_current_dest_addr(), ip_current_netif())) {
00130 #if LWIP_BROADCAST_PING
00131       /* For broadcast, use address of receiving interface as source address */
00132       src = netif_ip4_addr(inp);
00133 #else /* LWIP_BROADCAST_PING */
00134       LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to broadcast pings\n"));
00135       goto icmperr;
00136 #endif /* LWIP_BROADCAST_PING */
00137     }
00138     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n"));
00139     if (p->tot_len < sizeof(struct icmp_echo_hdr)) {
00140       LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n"));
00141       goto lenerr;
00142     }
00143 #if CHECKSUM_CHECK_ICMP
00144     IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_CHECK_ICMP) {
00145       if (inet_chksum_pbuf(p) != 0) {
00146         LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n"));
00147         pbuf_free(p);
00148         ICMP_STATS_INC(icmp.chkerr);
00149         MIB2_STATS_INC(mib2.icmpinerrors);
00150         return;
00151       }
00152     }
00153 #endif
00154 #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
00155     if (pbuf_header(p, (s16_t)(hlen + PBUF_LINK_HLEN + PBUF_LINK_ENCAPSULATION_HLEN))) {
00156       /* p is not big enough to contain link headers
00157        * allocate a new one and copy p into it
00158        */
00159       struct pbuf *r;
00160       /* allocate new packet buffer with space for link headers */
00161       r = pbuf_alloc(PBUF_LINK, p->tot_len + hlen, PBUF_RAM);
00162       if (r == NULL) {
00163         LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n"));
00164         goto icmperr;
00165       }
00166       if (r->len < hlen + sizeof(struct icmp_echo_hdr)) {
00167         LWIP_DEBUGF(ICMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("first pbuf cannot hold the ICMP header"));
00168         pbuf_free(r);
00169         goto icmperr;
00170       }
00171       /* copy the ip header */
00172       MEMCPY(r->payload, iphdr_in, hlen);
00173       /* switch r->payload back to icmp header (cannot fail) */
00174       if (pbuf_header(r, (s16_t)-hlen)) {
00175         LWIP_ASSERT("icmp_input: moving r->payload to icmp header failed\n", 0);
00176         pbuf_free(r);
00177         goto icmperr;
00178       }
00179       /* copy the rest of the packet without ip header */
00180       if (pbuf_copy(r, p) != ERR_OK) {
00181         LWIP_DEBUGF(ICMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("icmp_input: copying to new pbuf failed"));
00182         pbuf_free(r);
00183         goto icmperr;
00184       }
00185       /* free the original p */
00186       pbuf_free(p);
00187       /* we now have an identical copy of p that has room for link headers */
00188       p = r;
00189     } else {
00190       /* restore p->payload to point to icmp header (cannot fail) */
00191       if (pbuf_header(p, -(s16_t)(hlen + PBUF_LINK_HLEN + PBUF_LINK_ENCAPSULATION_HLEN))) {
00192         LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
00193         goto icmperr;
00194       }
00195     }
00196 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
00197     /* At this point, all checks are OK. */
00198     /* We generate an answer by switching the dest and src ip addresses,
00199      * setting the icmp type to ECHO_RESPONSE and updating the checksum. */
00200     iecho = (struct icmp_echo_hdr *)p->payload;
00201     if (pbuf_header(p, (s16_t)hlen)) {
00202       LWIP_DEBUGF(ICMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("Can't move over header in packet"));
00203     } else {
00204       err_t ret;
00205       struct ip_hdr *iphdr = (struct ip_hdr*)p->payload;
00206       ip4_addr_copy(iphdr->src, *src);
00207       ip4_addr_copy(iphdr->dest, *ip4_current_src_addr());
00208       ICMPH_TYPE_SET(iecho, ICMP_ER);
00209 #if CHECKSUM_GEN_ICMP
00210       IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_GEN_ICMP) {
00211         /* adjust the checksum */
00212         if (iecho->chksum > PP_HTONS(0xffffU - (ICMP_ECHO << 8))) {
00213           iecho->chksum += PP_HTONS(ICMP_ECHO << 8) + 1;
00214         } else {
00215           iecho->chksum += PP_HTONS(ICMP_ECHO << 8);
00216         }
00217       }
00218 #if LWIP_CHECKSUM_CTRL_PER_NETIF
00219       else {
00220         iecho->chksum = 0;
00221       }
00222 #endif /* LWIP_CHECKSUM_CTRL_PER_NETIF */
00223 #else /* CHECKSUM_GEN_ICMP */
00224       iecho->chksum = 0;
00225 #endif /* CHECKSUM_GEN_ICMP */
00226 
00227       /* Set the correct TTL and recalculate the header checksum. */
00228       IPH_TTL_SET(iphdr, ICMP_TTL);
00229       IPH_CHKSUM_SET(iphdr, 0);
00230 #if CHECKSUM_GEN_IP
00231       IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_GEN_IP) {
00232         IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, hlen));
00233       }
00234 #endif /* CHECKSUM_GEN_IP */
00235 
00236       ICMP_STATS_INC(icmp.xmit);
00237       /* increase number of messages attempted to send */
00238       MIB2_STATS_INC(mib2.icmpoutmsgs);
00239       /* increase number of echo replies attempted to send */
00240       MIB2_STATS_INC(mib2.icmpoutechoreps);
00241 
00242       /* send an ICMP packet */
00243       ret = ip4_output_if(p, src, LWIP_IP_HDRINCL,
00244                    ICMP_TTL, 0, IP_PROTO_ICMP, inp);
00245       if (ret != ERR_OK) {
00246         LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %s\n", lwip_strerr(ret)));
00247       }
00248     }
00249     break;
00250   default:
00251     if (type == ICMP_DUR) {
00252       MIB2_STATS_INC(mib2.icmpindestunreachs);
00253     } else if (type == ICMP_TE) {
00254       MIB2_STATS_INC(mib2.icmpintimeexcds);
00255     } else if (type == ICMP_PP) {
00256       MIB2_STATS_INC(mib2.icmpinparmprobs);
00257     } else if (type == ICMP_SQ) {
00258       MIB2_STATS_INC(mib2.icmpinsrcquenchs);
00259     } else if (type == ICMP_RD) {
00260       MIB2_STATS_INC(mib2.icmpinredirects);
00261     } else if (type == ICMP_TS) {
00262       MIB2_STATS_INC(mib2.icmpintimestamps);
00263     } else if (type == ICMP_TSR) {
00264       MIB2_STATS_INC(mib2.icmpintimestampreps);
00265     } else if (type == ICMP_AM) {
00266       MIB2_STATS_INC(mib2.icmpinaddrmasks);
00267     } else if (type == ICMP_AMR) {
00268       MIB2_STATS_INC(mib2.icmpinaddrmaskreps);
00269     }
00270     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n",
00271                 (s16_t)type, (s16_t)code));
00272     ICMP_STATS_INC(icmp.proterr);
00273     ICMP_STATS_INC(icmp.drop);
00274   }
00275   pbuf_free(p);
00276   return;
00277 lenerr:
00278   pbuf_free(p);
00279   ICMP_STATS_INC(icmp.lenerr);
00280   MIB2_STATS_INC(mib2.icmpinerrors);
00281   return;
00282 #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN || !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING
00283 icmperr:
00284   pbuf_free(p);
00285   ICMP_STATS_INC(icmp.err);
00286   MIB2_STATS_INC(mib2.icmpinerrors);
00287   return;
00288 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN || !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */
00289 }
00290 
00291 /**
00292  * Send an icmp 'destination unreachable' packet, called from ip_input() if
00293  * the transport layer protocol is unknown and from udp_input() if the local
00294  * port is not bound.
00295  *
00296  * @param p the input packet for which the 'unreachable' should be sent,
00297  *          p->payload pointing to the IP header
00298  * @param t type of the 'unreachable' packet
00299  */
00300 void
00301 icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)
00302 {
00303   MIB2_STATS_INC(mib2.icmpoutdestunreachs);
00304   icmp_send_response(p, ICMP_DUR, t);
00305 }
00306 
00307 #if IP_FORWARD || IP_REASSEMBLY
00308 /**
00309  * Send a 'time exceeded' packet, called from ip_forward() if TTL is 0.
00310  *
00311  * @param p the input packet for which the 'time exceeded' should be sent,
00312  *          p->payload pointing to the IP header
00313  * @param t type of the 'time exceeded' packet
00314  */
00315 void
00316 icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
00317 {
00318   MIB2_STATS_INC(mib2.icmpouttimeexcds);
00319   icmp_send_response(p, ICMP_TE, t);
00320 }
00321 
00322 #endif /* IP_FORWARD || IP_REASSEMBLY */
00323 
00324 /**
00325  * Send an icmp packet in response to an incoming packet.
00326  *
00327  * @param p the input packet for which the 'unreachable' should be sent,
00328  *          p->payload pointing to the IP header
00329  * @param type Type of the ICMP header
00330  * @param code Code of the ICMP header
00331  */
00332 static void
00333 icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
00334 {
00335   struct pbuf *q;
00336   struct ip_hdr *iphdr;
00337   /* we can use the echo header here */
00338   struct icmp_echo_hdr *icmphdr;
00339   ip4_addr_t iphdr_src;
00340   struct netif *netif;
00341 
00342   /* increase number of messages attempted to send */
00343   MIB2_STATS_INC(mib2.icmpoutmsgs);
00344 
00345   /* ICMP header + IP header + 8 bytes of data */
00346   q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
00347                  PBUF_RAM);
00348   if (q == NULL) {
00349     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
00350     MIB2_STATS_INC(mib2.icmpouterrors);
00351     return;
00352   }
00353   LWIP_ASSERT("check that first pbuf can hold icmp message",
00354              (q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
00355 
00356   iphdr = (struct ip_hdr *)p->payload;
00357   LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
00358   ip4_addr_debug_print_val(ICMP_DEBUG, iphdr->src);
00359   LWIP_DEBUGF(ICMP_DEBUG, (" to "));
00360   ip4_addr_debug_print_val(ICMP_DEBUG, iphdr->dest);
00361   LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
00362 
00363   icmphdr = (struct icmp_echo_hdr *)q->payload;
00364   icmphdr->type = type;
00365   icmphdr->code = code;
00366   icmphdr->id = 0;
00367   icmphdr->seqno = 0;
00368 
00369   /* copy fields from original packet */
00370   SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload,
00371           IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
00372 
00373   ip4_addr_copy(iphdr_src, iphdr->src);
00374 #ifdef LWIP_HOOK_IP4_ROUTE_SRC
00375   {
00376     ip4_addr_t iphdr_dst;
00377     ip4_addr_copy(iphdr_dst, iphdr->dest);
00378     netif = ip4_route_src(&iphdr_src, &iphdr_dst);
00379   }
00380 #else
00381   netif = ip4_route(&iphdr_src);
00382 #endif
00383   if (netif != NULL) {
00384     /* calculate checksum */
00385     icmphdr->chksum = 0;
00386 #if CHECKSUM_GEN_ICMP
00387     IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_ICMP) {
00388       icmphdr->chksum = inet_chksum(icmphdr, q->len);
00389     }
00390 #endif
00391     ICMP_STATS_INC(icmp.xmit);
00392     ip4_output_if(q, NULL, &iphdr_src, ICMP_TTL, 0, IP_PROTO_ICMP, netif);
00393   }
00394   pbuf_free(q);
00395 }
00396 
00397 #endif /* LWIP_IPV4 && LWIP_ICMP */