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 /** Small optimization: set to 0 if incoming PBUF_POOL pbuf always can be
00055  * used to modify and send a response packet (and to 1 if this is not the case,
00056  * e.g. when link header is stripped of when receiving) */
00057 #ifndef LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
00058 #define LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 1
00059 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
00060 
00061 /* The amount of data from the original packet to return in a dest-unreachable */
00062 #define ICMP_DEST_UNREACH_DATASIZE 8
00063 
00064 static void icmp_send_response(struct pbuf *p, u8_t type, u8_t code);
00065 
00066 /**
00067  * Processes ICMP input packets, called from ip_input().
00068  *
00069  * Currently only processes icmp echo requests and sends
00070  * out the echo response.
00071  *
00072  * @param p the icmp echo request packet, p->payload pointing to the icmp header
00073  * @param inp the netif on which this packet was received
00074  */
00075 void
00076 icmp_input(struct pbuf *p, struct netif *inp)
00077 {
00078   u8_t type;
00079 #ifdef LWIP_DEBUG
00080   u8_t code;
00081 #endif /* LWIP_DEBUG */
00082   struct icmp_echo_hdr *iecho;
00083   const struct ip_hdr *iphdr_in;
00084   s16_t hlen;
00085   const ip4_addr_t* src;
00086 
00087   ICMP_STATS_INC(icmp.recv);
00088   MIB2_STATS_INC(mib2.icmpinmsgs);
00089 
00090   iphdr_in = ip4_current_header();
00091   hlen = IPH_HL(iphdr_in) * 4;
00092   if (hlen < IP_HLEN) {
00093     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short IP header (%"S16_F" bytes) received\n", hlen));
00094     goto lenerr;
00095   }
00096   if (p->len < sizeof(u16_t)*2) {
00097     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len));
00098     goto lenerr;
00099   }
00100 
00101   type = *((u8_t *)p->payload);
00102 #ifdef LWIP_DEBUG
00103   code = *(((u8_t *)p->payload)+1);
00104 #endif /* LWIP_DEBUG */
00105   switch (type) {
00106   case ICMP_ER:
00107     /* This is OK, echo reply might have been parsed by a raw PCB
00108        (as obviously, an echo request has been sent, too). */
00109     MIB2_STATS_INC(mib2.icmpinechoreps);
00110     break;
00111   case ICMP_ECHO:
00112     MIB2_STATS_INC(mib2.icmpinechos);
00113     src = ip4_current_dest_addr();
00114     /* multicast destination address? */
00115     if (ip4_addr_ismulticast(ip4_current_dest_addr())) {
00116 #if LWIP_MULTICAST_PING
00117       /* For multicast, use address of receiving interface as source address */
00118       src = netif_ip4_addr(inp);
00119 #else /* LWIP_MULTICAST_PING */
00120       LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast pings\n"));
00121       goto icmperr;
00122 #endif /* LWIP_MULTICAST_PING */
00123     }
00124     /* broadcast destination address? */
00125     if (ip4_addr_isbroadcast(ip4_current_dest_addr(), ip_current_netif())) {
00126 #if LWIP_BROADCAST_PING
00127       /* For broadcast, use address of receiving interface as source address */
00128       src = netif_ip4_addr(inp);
00129 #else /* LWIP_BROADCAST_PING */
00130       LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to broadcast pings\n"));
00131       goto icmperr;
00132 #endif /* LWIP_BROADCAST_PING */
00133     }
00134     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n"));
00135     if (p->tot_len < sizeof(struct icmp_echo_hdr)) {
00136       LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n"));
00137       goto lenerr;
00138     }
00139 #if CHECKSUM_CHECK_ICMP
00140     IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_CHECK_ICMP) {
00141       if (inet_chksum_pbuf(p) != 0) {
00142         LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n"));
00143         pbuf_free(p);
00144         ICMP_STATS_INC(icmp.chkerr);
00145         MIB2_STATS_INC(mib2.icmpinerrors);
00146         return;
00147       }
00148     }
00149 #endif
00150 #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
00151     if (pbuf_header(p, (hlen + PBUF_LINK_HLEN + PBUF_LINK_ENCAPSULATION_HLEN))) {
00152       /* p is not big enough to contain link headers
00153        * allocate a new one and copy p into it
00154        */
00155       struct pbuf *r;
00156       /* allocate new packet buffer with space for link headers */
00157       r = pbuf_alloc(PBUF_LINK, p->tot_len + hlen, PBUF_RAM);
00158       if (r == NULL) {
00159         LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n"));
00160         goto icmperr;
00161       }
00162       if (r->len < hlen + sizeof(struct icmp_echo_hdr)) {
00163         LWIP_DEBUGF(ICMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("first pbuf cannot hold the ICMP header"));
00164         pbuf_free(r);
00165         goto icmperr;
00166       }
00167       /* copy the ip header */
00168       MEMCPY(r->payload, iphdr_in, hlen);
00169       /* switch r->payload back to icmp header (cannot fail) */
00170       if (pbuf_header(r, -hlen)) {
00171         LWIP_ASSERT("icmp_input: moving r->payload to icmp header failed\n", 0);
00172         pbuf_free(r);
00173         goto icmperr;
00174       }
00175       /* copy the rest of the packet without ip header */
00176       if (pbuf_copy(r, p) != ERR_OK) {
00177         LWIP_DEBUGF(ICMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("icmp_input: copying to new pbuf failed"));
00178         pbuf_free(r);
00179         goto icmperr;
00180       }
00181       /* free the original p */
00182       pbuf_free(p);
00183       /* we now have an identical copy of p that has room for link headers */
00184       p = r;
00185     } else {
00186       /* restore p->payload to point to icmp header (cannot fail) */
00187       if (pbuf_header(p, -(s16_t)(hlen + PBUF_LINK_HLEN + PBUF_LINK_ENCAPSULATION_HLEN))) {
00188         LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
00189         goto icmperr;
00190       }
00191     }
00192 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
00193     /* At this point, all checks are OK. */
00194     /* We generate an answer by switching the dest and src ip addresses,
00195      * setting the icmp type to ECHO_RESPONSE and updating the checksum. */
00196     iecho = (struct icmp_echo_hdr *)p->payload;
00197     if (pbuf_header(p, hlen)) {
00198       LWIP_DEBUGF(ICMP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("Can't move over header in packet"));
00199     } else {
00200       err_t ret;
00201       struct ip_hdr *iphdr = (struct ip_hdr*)p->payload;
00202       ip4_addr_copy(iphdr->src, *src);
00203       ip4_addr_copy(iphdr->dest, *ip4_current_src_addr());
00204       ICMPH_TYPE_SET(iecho, ICMP_ER);
00205 #if CHECKSUM_GEN_ICMP
00206       IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_GEN_ICMP) {
00207         /* adjust the checksum */
00208         if (iecho->chksum > PP_HTONS(0xffffU - (ICMP_ECHO << 8))) {
00209           iecho->chksum += PP_HTONS(ICMP_ECHO << 8) + 1;
00210         } else {
00211           iecho->chksum += PP_HTONS(ICMP_ECHO << 8);
00212         }
00213       }
00214 #if LWIP_CHECKSUM_CTRL_PER_NETIF
00215       else {
00216         iecho->chksum = 0;
00217       }
00218 #endif /* LWIP_CHECKSUM_CTRL_PER_NETIF */
00219 #else /* CHECKSUM_GEN_ICMP */
00220       iecho->chksum = 0;
00221 #endif /* CHECKSUM_GEN_ICMP */
00222 
00223       /* Set the correct TTL and recalculate the header checksum. */
00224       IPH_TTL_SET(iphdr, ICMP_TTL);
00225       IPH_CHKSUM_SET(iphdr, 0);
00226 #if CHECKSUM_GEN_IP
00227       IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_GEN_IP) {
00228         IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, hlen));
00229       }
00230 #endif /* CHECKSUM_GEN_IP */
00231 
00232       ICMP_STATS_INC(icmp.xmit);
00233       /* increase number of messages attempted to send */
00234       MIB2_STATS_INC(mib2.icmpoutmsgs);
00235       /* increase number of echo replies attempted to send */
00236       MIB2_STATS_INC(mib2.icmpoutechoreps);
00237 
00238       /* send an ICMP packet */
00239       ret = ip4_output_if(p, src, IP_HDRINCL,
00240                    ICMP_TTL, 0, IP_PROTO_ICMP, inp);
00241       if (ret != ERR_OK) {
00242         LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %s\n", lwip_strerr(ret)));
00243       }
00244     }
00245     break;
00246   default:
00247     if (type == ICMP_DUR) {
00248       MIB2_STATS_INC(mib2.icmpindestunreachs);
00249     } else if (type == ICMP_TE) {
00250       MIB2_STATS_INC(mib2.icmpindestunreachs);
00251     } else if (type == ICMP_PP) {
00252       MIB2_STATS_INC(mib2.icmpinparmprobs);
00253     } else if (type == ICMP_SQ) {
00254       MIB2_STATS_INC(mib2.icmpinsrcquenchs);
00255     } else if (type == ICMP_RD) {
00256       MIB2_STATS_INC(mib2.icmpinredirects);
00257     } else if (type == ICMP_TS) {
00258       MIB2_STATS_INC(mib2.icmpintimestamps);
00259     } else if (type == ICMP_TSR) {
00260       MIB2_STATS_INC(mib2.icmpintimestampreps);
00261     } else if (type == ICMP_AM) {
00262       MIB2_STATS_INC(mib2.icmpinaddrmasks);
00263     } else if (type == ICMP_AMR) {
00264       MIB2_STATS_INC(mib2.icmpinaddrmaskreps);
00265     }
00266     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n",
00267                 (s16_t)type, (s16_t)code));
00268     ICMP_STATS_INC(icmp.proterr);
00269     ICMP_STATS_INC(icmp.drop);
00270   }
00271   pbuf_free(p);
00272   return;
00273 lenerr:
00274   pbuf_free(p);
00275   ICMP_STATS_INC(icmp.lenerr);
00276   MIB2_STATS_INC(mib2.icmpinerrors);
00277   return;
00278 #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN || !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING
00279 icmperr:
00280   pbuf_free(p);
00281   ICMP_STATS_INC(icmp.err);
00282   MIB2_STATS_INC(mib2.icmpinerrors);
00283   return;
00284 #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN || !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */
00285 }
00286 
00287 /**
00288  * Send an icmp 'destination unreachable' packet, called from ip_input() if
00289  * the transport layer protocol is unknown and from udp_input() if the local
00290  * port is not bound.
00291  *
00292  * @param p the input packet for which the 'unreachable' should be sent,
00293  *          p->payload pointing to the IP header
00294  * @param t type of the 'unreachable' packet
00295  */
00296 void
00297 icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)
00298 {
00299   MIB2_STATS_INC(mib2.icmpoutdestunreachs);
00300   icmp_send_response(p, ICMP_DUR, t);
00301 }
00302 
00303 #if IP_FORWARD || IP_REASSEMBLY
00304 /**
00305  * Send a 'time exceeded' packet, called from ip_forward() if TTL is 0.
00306  *
00307  * @param p the input packet for which the 'time exceeded' should be sent,
00308  *          p->payload pointing to the IP header
00309  * @param t type of the 'time exceeded' packet
00310  */
00311 void
00312 icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
00313 {
00314   MIB2_STATS_INC(mib2.icmpouttimeexcds);
00315   icmp_send_response(p, ICMP_TE, t);
00316 }
00317 
00318 #endif /* IP_FORWARD || IP_REASSEMBLY */
00319 
00320 /**
00321  * Send an icmp packet in response to an incoming packet.
00322  *
00323  * @param p the input packet for which the 'unreachable' should be sent,
00324  *          p->payload pointing to the IP header
00325  * @param type Type of the ICMP header
00326  * @param code Code of the ICMP header
00327  */
00328 static void
00329 icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
00330 {
00331   struct pbuf *q;
00332   struct ip_hdr *iphdr;
00333   /* we can use the echo header here */
00334   struct icmp_echo_hdr *icmphdr;
00335   ip4_addr_t iphdr_src;
00336   struct netif *netif;
00337 
00338   /* increase number of messages attempted to send */
00339   MIB2_STATS_INC(mib2.icmpoutmsgs);
00340 
00341   /* ICMP header + IP header + 8 bytes of data */
00342   q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
00343                  PBUF_RAM);
00344   if (q == NULL) {
00345     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
00346     MIB2_STATS_INC(mib2.icmpouterrors);
00347     return;
00348   }
00349   LWIP_ASSERT("check that first pbuf can hold icmp message",
00350              (q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
00351 
00352   iphdr = (struct ip_hdr *)p->payload;
00353   LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
00354   ip4_addr_debug_print_val(ICMP_DEBUG, iphdr->src);
00355   LWIP_DEBUGF(ICMP_DEBUG, (" to "));
00356   ip4_addr_debug_print_val(ICMP_DEBUG, iphdr->dest);
00357   LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
00358 
00359   icmphdr = (struct icmp_echo_hdr *)q->payload;
00360   icmphdr->type = type;
00361   icmphdr->code = code;
00362   icmphdr->id = 0;
00363   icmphdr->seqno = 0;
00364 
00365   /* copy fields from original packet */
00366   SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload,
00367           IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
00368 
00369   ip4_addr_copy(iphdr_src, iphdr->src);
00370 #ifdef LWIP_HOOK_IP4_ROUTE_SRC
00371   {
00372     ip4_addr_t iphdr_dst;
00373     ip4_addr_copy(iphdr_dst, iphdr->dest);
00374     netif = ip4_route_src(&iphdr_src, &iphdr_dst);
00375   }
00376 #else
00377   netif = ip4_route(&iphdr_src);
00378 #endif
00379   if (netif != NULL) {
00380     /* calculate checksum */
00381     icmphdr->chksum = 0;
00382 #if CHECKSUM_GEN_ICMP
00383     IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_ICMP) {
00384       icmphdr->chksum = inet_chksum(icmphdr, q->len);
00385     }
00386 #endif
00387     ICMP_STATS_INC(icmp.xmit);
00388     ip4_output_if(q, NULL, &iphdr_src, ICMP_TTL, 0, IP_PROTO_ICMP, netif);
00389   }
00390   pbuf_free(q);
00391 }
00392 
00393 #endif /* LWIP_IPV4 && LWIP_ICMP */