slirp/ip_icmp.c

   1 /*
   2  * Copyright (c) 1982, 1986, 1988, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      @(#)ip_icmp.c   8.2 (Berkeley) 1/4/94
  30  * ip_icmp.c,v 1.7 1995/05/30 08:09:42 rgrimes Exp
  31  */
  32
  33 #include "slirp.h"
  34 #include "ip_icmp.h"
  35
  36 #ifdef LOG_ENABLED
  37 struct icmpstat icmpstat;
  38 #endif
  39
  40 /* The message sent when emulating PING */
  41 /* Be nice and tell them it's just a pseudo-ping packet */
  42 static const char icmp_ping_msg[] = "This is a pseudo-PING packet used by Slirp to emulate ICMP ECHO-REQUEST packets.\n";
  43
  44 /* list of actions for icmp_error() on RX of an icmp message */
  45 static const int icmp_flush[19] = {
  46 /*  ECHO REPLY (0)  */   0,
  47                          1,
  48                          1,
  49 /* DEST UNREACH (3) */   1,
  50 /* SOURCE QUENCH (4)*/   1,
  51 /* REDIRECT (5) */       1,
  52                          1,
  53                          1,
  54 /* ECHO (8) */           0,
  55 /* ROUTERADVERT (9) */   1,
  56 /* ROUTERSOLICIT (10) */ 1,
  57 /* TIME EXCEEDED (11) */ 1,
  58 /* PARAMETER PROBLEM (12) */ 1,
  59 /* TIMESTAMP (13) */     0,
  60 /* TIMESTAMP REPLY (14) */ 0,
  61 /* INFO (15) */          0,
  62 /* INFO REPLY (16) */    0,
  63 /* ADDR MASK (17) */     0,
  64 /* ADDR MASK REPLY (18) */ 0
  65 };
  66
  67 /*
  68  * Process a received ICMP message.
  69  */
  70 void
  71 icmp_input(struct mbuf *m, int hlen)
  72 {
  73   register struct icmp *icp;
  74   register struct ip *ip=mtod(m, struct ip *);
  75   int icmplen=ip->ip_len;
  76   /* int code; */
  77
  78   DEBUG_CALL("icmp_input");
  79   DEBUG_ARG("m = %lx", (long )m);
  80   DEBUG_ARG("m_len = %d", m->m_len);
  81
  82   STAT(icmpstat.icps_received++);
  83
  84   /*
  85    * Locate icmp structure in mbuf, and check
  86    * that its not corrupted and of at least minimum length.
  87    */
  88   if (icmplen < ICMP_MINLEN) {          /* min 8 bytes payload */
  89     STAT(icmpstat.icps_tooshort++);
  90   freeit:
  91     m_freem(m);
  92     goto end_error;
  93   }
  94
  95   m->m_len -= hlen;
  96   m->m_data += hlen;
  97   icp = mtod(m, struct icmp *);
  98   if (cksum(m, icmplen)) {
  99     STAT(icmpstat.icps_checksum++);
 100     goto freeit;
 101   }
 102   m->m_len += hlen;
 103   m->m_data -= hlen;
 104
 105   /*    icmpstat.icps_inhist[icp->icmp_type]++; */
 106   /* code = icp->icmp_code; */
 107
 108   DEBUG_ARG("icmp_type = %d", icp->icmp_type);
 109   switch (icp->icmp_type) {
 110   case ICMP_ECHO:
 111     icp->icmp_type = ICMP_ECHOREPLY;
 112     ip->ip_len += hlen;              /* since ip_input subtracts this */
 113     if (ip->ip_dst.s_addr == alias_addr.s_addr) {
 114       icmp_reflect(m);
 115     } else {
 116       struct socket *so;
 117       struct sockaddr_in addr;
 118       if ((so = socreate()) == NULL) goto freeit;
 119       if(udp_attach(so) == -1) {
 120         DEBUG_MISC((dfd,"icmp_input udp_attach errno = %d-%s\n",
 121                     errno,strerror(errno)));
 122         sofree(so);
 123         m_free(m);
 124         goto end_error;
 125       }
 126       so->so_m = m;
 127       so->so_faddr = ip->ip_dst;
 128       so->so_fport = htons(7);
 129       so->so_laddr = ip->ip_src;
 130       so->so_lport = htons(9);
 131       so->so_iptos = ip->ip_tos;
 132       so->so_type = IPPROTO_ICMP;
 133       so->so_state = SS_ISFCONNECTED;
 134
 135       /* Send the packet */
 136       addr.sin_family = AF_INET;
 137       if ((so->so_faddr.s_addr & htonl(0xffffff00)) == special_addr.s_addr) {
 138         /* It's an alias */
 139         switch(ntohl(so->so_faddr.s_addr) & 0xff) {
 140         case CTL_DNS:
 141           addr.sin_addr = dns_addr;
 142           break;
 143         case CTL_ALIAS:
 144         default:
 145           addr.sin_addr = loopback_addr;
 146           break;
 147         }
 148       } else {
 149         addr.sin_addr = so->so_faddr;
 150       }
 151       addr.sin_port = so->so_fport;
 152       if(sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
 153                 (struct sockaddr *)&addr, sizeof(addr)) == -1) {
 154         DEBUG_MISC((dfd,"icmp_input udp sendto tx errno = %d-%s\n",
 155                     errno,strerror(errno)));
 156         icmp_error(m, ICMP_UNREACH,ICMP_UNREACH_NET, 0,strerror(errno));
 157         udp_detach(so);
 158       }
 159     } /* if ip->ip_dst.s_addr == alias_addr.s_addr */
 160     break;
 161   case ICMP_UNREACH:
 162     /* XXX? report error? close socket? */
 163   case ICMP_TIMXCEED:
 164   case ICMP_PARAMPROB:
 165   case ICMP_SOURCEQUENCH:
 166   case ICMP_TSTAMP:
 167   case ICMP_MASKREQ:
 168   case ICMP_REDIRECT:
 169     STAT(icmpstat.icps_notsupp++);
 170     m_freem(m);
 171     break;
 172
 173   default:
 174     STAT(icmpstat.icps_badtype++);
 175     m_freem(m);
 176   } /* swith */
 177
 178 end_error:
 179   /* m is m_free()'d xor put in a socket xor or given to ip_send */
 180   return;
 181 }
 182
 183
 184 /*
 185  *      Send an ICMP message in response to a situation
 186  *
 187  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
 188  *                      MUST NOT change this header information.
 189  *                      MUST NOT reply to a multicast/broadcast IP address.
 190  *                      MUST NOT reply to a multicast/broadcast MAC address.
 191  *                      MUST reply to only the first fragment.
 192  */
 193 /*
 194  * Send ICMP_UNREACH back to the source regarding msrc.
 195  * mbuf *msrc is used as a template, but is NOT m_free()'d.
 196  * It is reported as the bad ip packet.  The header should
 197  * be fully correct and in host byte order.
 198  * ICMP fragmentation is illegal.  All machines must accept 576 bytes in one
 199  * packet.  The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
 200  */
 201
 202 #define ICMP_MAXDATALEN (IP_MSS-28)
 203 void
 204 icmp_error(struct mbuf *msrc, u_char type, u_char code, int minsize,
 205            const char *message)
 206 {
 207   unsigned hlen, shlen, s_ip_len;
 208   register struct ip *ip;
 209   register struct icmp *icp;
 210   register struct mbuf *m;
 211
 212   DEBUG_CALL("icmp_error");
 213   DEBUG_ARG("msrc = %lx", (long )msrc);
 214   DEBUG_ARG("msrc_len = %d", msrc->m_len);
 215
 216   if(type!=ICMP_UNREACH && type!=ICMP_TIMXCEED) goto end_error;
 217
 218   /* check msrc */
 219   if(!msrc) goto end_error;
 220   ip = mtod(msrc, struct ip *);
 221 #ifdef DEBUG
 222   { char bufa[20], bufb[20];
 223     strcpy(bufa, inet_ntoa(ip->ip_src));
 224     strcpy(bufb, inet_ntoa(ip->ip_dst));
 225     DEBUG_MISC((dfd, " %.16s to %.16s\n", bufa, bufb));
 226   }
 227 #endif
 228   if(ip->ip_off & IP_OFFMASK) goto end_error;    /* Only reply to fragment 0 */
 229
 230   shlen=ip->ip_hl << 2;
 231   s_ip_len=ip->ip_len;
 232   if(ip->ip_p == IPPROTO_ICMP) {
 233     icp = (struct icmp *)((char *)ip + shlen);
 234     /*
 235      *  Assume any unknown ICMP type is an error. This isn't
 236      *  specified by the RFC, but think about it..
 237      */
 238     if(icp->icmp_type>18 || icmp_flush[icp->icmp_type]) goto end_error;
 239   }
 240
 241   /* make a copy */
 242   if(!(m=m_get())) goto end_error;               /* get mbuf */
 243   { int new_m_size;
 244     new_m_size=sizeof(struct ip )+ICMP_MINLEN+msrc->m_len+ICMP_MAXDATALEN;
 245     if(new_m_size>m->m_size) m_inc(m, new_m_size);
 246   }
 247   memcpy(m->m_data, msrc->m_data, msrc->m_len);
 248   m->m_len = msrc->m_len;                        /* copy msrc to m */
 249
 250   /* make the header of the reply packet */
 251   ip  = mtod(m, struct ip *);
 252   hlen= sizeof(struct ip );     /* no options in reply */
 253
 254   /* fill in icmp */
 255   m->m_data += hlen;
 256   m->m_len -= hlen;
 257
 258   icp = mtod(m, struct icmp *);
 259
 260   if(minsize) s_ip_len=shlen+ICMP_MINLEN;   /* return header+8b only */
 261   else if(s_ip_len>ICMP_MAXDATALEN)         /* maximum size */
 262     s_ip_len=ICMP_MAXDATALEN;
 263
 264   m->m_len=ICMP_MINLEN+s_ip_len;        /* 8 bytes ICMP header */
 265
 266   /* min. size = 8+sizeof(struct ip)+8 */
 267
 268   icp->icmp_type = type;
 269   icp->icmp_code = code;
 270   icp->icmp_id = 0;
 271   icp->icmp_seq = 0;
 272
 273   memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len);   /* report the ip packet */
 274   HTONS(icp->icmp_ip.ip_len);
 275   HTONS(icp->icmp_ip.ip_id);
 276   HTONS(icp->icmp_ip.ip_off);
 277
 278 #ifdef DEBUG
 279   if(message) {           /* DEBUG : append message to ICMP packet */
 280     int message_len;
 281     char *cpnt;
 282     message_len=strlen(message);
 283     if(message_len>ICMP_MAXDATALEN) message_len=ICMP_MAXDATALEN;
 284     cpnt=(char *)m->m_data+m->m_len;
 285     memcpy(cpnt, message, message_len);
 286     m->m_len+=message_len;
 287   }
 288 #endif
 289
 290   icp->icmp_cksum = 0;
 291   icp->icmp_cksum = cksum(m, m->m_len);
 292
 293   m->m_data -= hlen;
 294   m->m_len += hlen;
 295
 296   /* fill in ip */
 297   ip->ip_hl = hlen >> 2;
 298   ip->ip_len = m->m_len;
 299
 300   ip->ip_tos=((ip->ip_tos & 0x1E) | 0xC0);  /* high priority for errors */
 301
 302   ip->ip_ttl = MAXTTL;
 303   ip->ip_p = IPPROTO_ICMP;
 304   ip->ip_dst = ip->ip_src;    /* ip adresses */
 305   ip->ip_src = alias_addr;
 306
 307   (void ) ip_output((struct socket *)NULL, m);
 308
 309   STAT(icmpstat.icps_reflect++);
 310
 311 end_error:
 312   return;
 313 }
 314 #undef ICMP_MAXDATALEN
 315
 316 /*
 317  * Reflect the ip packet back to the source
 318  */
 319 void
 320 icmp_reflect(struct mbuf *m)
 321 {
 322   register struct ip *ip = mtod(m, struct ip *);
 323   int hlen = ip->ip_hl << 2;
 324   int optlen = hlen - sizeof(struct ip );
 325   register struct icmp *icp;
 326
 327   /*
 328    * Send an icmp packet back to the ip level,
 329    * after supplying a checksum.
 330    */
 331   m->m_data += hlen;
 332   m->m_len -= hlen;
 333   icp = mtod(m, struct icmp *);
 334
 335   icp->icmp_cksum = 0;
 336   icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
 337
 338   m->m_data -= hlen;
 339   m->m_len += hlen;
 340
 341   /* fill in ip */
 342   if (optlen > 0) {
 343     /*
 344      * Strip out original options by copying rest of first
 345      * mbuf's data back, and adjust the IP length.
 346      */
 347     memmove((caddr_t)(ip + 1), (caddr_t)ip + hlen,
 348             (unsigned )(m->m_len - hlen));
 349     hlen -= optlen;
 350     ip->ip_hl = hlen >> 2;
 351     ip->ip_len -= optlen;
 352     m->m_len -= optlen;
 353   }
 354
 355   ip->ip_ttl = MAXTTL;
 356   { /* swap */
 357     struct in_addr icmp_dst;
 358     icmp_dst = ip->ip_dst;
 359     ip->ip_dst = ip->ip_src;
 360     ip->ip_src = icmp_dst;
 361   }
 362
 363   (void ) ip_output((struct socket *)NULL, m);
 364
 365   STAT(icmpstat.icps_reflect++);
 366 }