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. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  *      @(#)ip_icmp.c   8.2 (Berkeley) 1/4/94
  34  * ip_icmp.c,v 1.7 1995/05/30 08:09:42 rgrimes Exp
  35  */
  36
  37 #include "slirp.h"
  38 #include "ip_icmp.h"
  39
  40 struct icmpstat icmpstat;
  41
  42 /* The message sent when emulating PING */
  43 /* Be nice and tell them it's just a psuedo-ping packet */
  44 char icmp_ping_msg[] = "This is a psuedo-PING packet used by Slirp to emulate ICMP ECHO-REQUEST packets.\n";
  45
  46 /* list of actions for icmp_error() on RX of an icmp message */
  47 static int icmp_flush[19] = {
  48 /*  ECHO REPLY (0)  */   0,
  49                          1,
  50                          1,
  51 /* DEST UNREACH (3) */   1,
  52 /* SOURCE QUENCH (4)*/   1,
  53 /* REDIRECT (5) */       1,
  54                          1,
  55                          1,
  56 /* ECHO (8) */           0,
  57 /* ROUTERADVERT (9) */   1,
  58 /* ROUTERSOLICIT (10) */ 1,
  59 /* TIME EXCEEDED (11) */ 1,
  60 /* PARAMETER PROBLEM (12) */ 1,
  61 /* TIMESTAMP (13) */     0,
  62 /* TIMESTAMP REPLY (14) */ 0,
  63 /* INFO (15) */          0,
  64 /* INFO REPLY (16) */    0,
  65 /* ADDR MASK (17) */     0,
  66 /* ADDR MASK REPLY (18) */ 0
  67 };
  68
  69 /*
  70  * Process a received ICMP message.
  71  */
  72 void
  73 icmp_input(m, hlen)
  74      struct mbuf *m;
  75      int hlen;
  76 {
  77   register struct icmp *icp;
  78   register struct ip *ip=mtod(m, struct ip *);
  79   int icmplen=ip->ip_len;
  80   /* int code; */
  81
  82   DEBUG_CALL("icmp_input");
  83   DEBUG_ARG("m = %lx", (long )m);
  84   DEBUG_ARG("m_len = %d", m->m_len);
  85
  86   icmpstat.icps_received++;
  87
  88   /*
  89    * Locate icmp structure in mbuf, and check
  90    * that its not corrupted and of at least minimum length.
  91    */
  92   if (icmplen < ICMP_MINLEN) {          /* min 8 bytes payload */
  93     icmpstat.icps_tooshort++;
  94   freeit:
  95     m_freem(m);
  96     goto end_error;
  97   }
  98
  99   m->m_len -= hlen;
 100   m->m_data += hlen;
 101   icp = mtod(m, struct icmp *);
 102   if (cksum(m, icmplen)) {
 103     icmpstat.icps_checksum++;
 104     goto freeit;
 105   }
 106   m->m_len += hlen;
 107   m->m_data -= hlen;
 108
 109   /*    icmpstat.icps_inhist[icp->icmp_type]++; */
 110   /* code = icp->icmp_code; */
 111
 112   DEBUG_ARG("icmp_type = %d", icp->icmp_type);
 113   switch (icp->icmp_type) {
 114   case ICMP_ECHO:
 115     icp->icmp_type = ICMP_ECHOREPLY;
 116     ip->ip_len += hlen;              /* since ip_input subtracts this */
 117     if (ip->ip_dst.s_addr == alias_addr.s_addr) {
 118       icmp_reflect(m);
 119     } else {
 120       struct socket *so;
 121       struct sockaddr_in addr;
 122       if ((so = socreate()) == NULL) goto freeit;
 123       if(udp_attach(so) == -1) {
 124         DEBUG_MISC((dfd,"icmp_input udp_attach errno = %d-%s\n",
 125                     errno,strerror(errno)));
 126         sofree(so);
 127         m_free(m);
 128         goto end_error;
 129       }
 130       so->so_m = m;
 131       so->so_faddr = ip->ip_dst;
 132       so->so_fport = htons(7);
 133       so->so_laddr = ip->ip_src;
 134       so->so_lport = htons(9);
 135       so->so_iptos = ip->ip_tos;
 136       so->so_type = IPPROTO_ICMP;
 137       so->so_state = SS_ISFCONNECTED;
 138
 139       /* Send the packet */
 140       addr.sin_family = AF_INET;
 141       if ((so->so_faddr.s_addr & htonl(0xffffff00)) == special_addr.s_addr) {
 142         /* It's an alias */
 143         switch(ntohl(so->so_faddr.s_addr) & 0xff) {
 144         case CTL_DNS:
 145           addr.sin_addr = dns_addr;
 146           break;
 147         case CTL_ALIAS:
 148         default:
 149           addr.sin_addr = loopback_addr;
 150           break;
 151         }
 152       } else {
 153         addr.sin_addr = so->so_faddr;
 154       }
 155       addr.sin_port = so->so_fport;
 156       if(sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
 157                 (struct sockaddr *)&addr, sizeof(addr)) == -1) {
 158         DEBUG_MISC((dfd,"icmp_input udp sendto tx errno = %d-%s\n",
 159                     errno,strerror(errno)));
 160         icmp_error(m, ICMP_UNREACH,ICMP_UNREACH_NET, 0,strerror(errno));
 161         udp_detach(so);
 162       }
 163     } /* if ip->ip_dst.s_addr == alias_addr.s_addr */
 164     break;
 165   case ICMP_UNREACH:
 166     /* XXX? report error? close socket? */
 167   case ICMP_TIMXCEED:
 168   case ICMP_PARAMPROB:
 169   case ICMP_SOURCEQUENCH:
 170   case ICMP_TSTAMP:
 171   case ICMP_MASKREQ:
 172   case ICMP_REDIRECT:
 173     icmpstat.icps_notsupp++;
 174     m_freem(m);
 175     break;
 176
 177   default:
 178     icmpstat.icps_badtype++;
 179     m_freem(m);
 180   } /* swith */
 181
 182 end_error:
 183   /* m is m_free()'d xor put in a socket xor or given to ip_send */
 184   return;
 185 }
 186
 187
 188 /*
 189  *      Send an ICMP message in response to a situation
 190  *
 191  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
 192  *                      MUST NOT change this header information.
 193  *                      MUST NOT reply to a multicast/broadcast IP address.
 194  *                      MUST NOT reply to a multicast/broadcast MAC address.
 195  *                      MUST reply to only the first fragment.
 196  */
 197 /*
 198  * Send ICMP_UNREACH back to the source regarding msrc.
 199  * mbuf *msrc is used as a template, but is NOT m_free()'d.
 200  * It is reported as the bad ip packet.  The header should
 201  * be fully correct and in host byte order.
 202  * ICMP fragmentation is illegal.  All machines must accept 576 bytes in one
 203  * packet.  The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
 204  */
 205
 206 #define ICMP_MAXDATALEN (IP_MSS-28)
 207 void
 208 icmp_error(msrc, type, code, minsize, message)
 209      struct mbuf *msrc;
 210      u_char type;
 211      u_char code;
 212      int minsize;
 213      char *message;
 214 {
 215   unsigned hlen, shlen, s_ip_len;
 216   register struct ip *ip;
 217   register struct icmp *icp;
 218   register struct mbuf *m;
 219
 220   DEBUG_CALL("icmp_error");
 221   DEBUG_ARG("msrc = %lx", (long )msrc);
 222   DEBUG_ARG("msrc_len = %d", msrc->m_len);
 223
 224   if(type!=ICMP_UNREACH && type!=ICMP_TIMXCEED) goto end_error;
 225
 226   /* check msrc */
 227   if(!msrc) goto end_error;
 228   ip = mtod(msrc, struct ip *);
 229 #if DEBUG
 230   { char bufa[20], bufb[20];
 231     strcpy(bufa, inet_ntoa(ip->ip_src));
 232     strcpy(bufb, inet_ntoa(ip->ip_dst));
 233     DEBUG_MISC((dfd, " %.16s to %.16s\n", bufa, bufb));
 234   }
 235 #endif
 236   if(ip->ip_off & IP_OFFMASK) goto end_error;    /* Only reply to fragment 0 */
 237
 238   shlen=ip->ip_hl << 2;
 239   s_ip_len=ip->ip_len;
 240   if(ip->ip_p == IPPROTO_ICMP) {
 241     icp = (struct icmp *)((char *)ip + shlen);
 242     /*
 243      *  Assume any unknown ICMP type is an error. This isn't
 244      *  specified by the RFC, but think about it..
 245      */
 246     if(icp->icmp_type>18 || icmp_flush[icp->icmp_type]) goto end_error;
 247   }
 248
 249   /* make a copy */
 250   if(!(m=m_get())) goto end_error;               /* get mbuf */
 251   { int new_m_size;
 252     new_m_size=sizeof(struct ip )+ICMP_MINLEN+msrc->m_len+ICMP_MAXDATALEN;
 253     if(new_m_size>m->m_size) m_inc(m, new_m_size);
 254   }
 255   memcpy(m->m_data, msrc->m_data, msrc->m_len);
 256   m->m_len = msrc->m_len;                        /* copy msrc to m */
 257
 258   /* make the header of the reply packet */
 259   ip  = mtod(m, struct ip *);
 260   hlen= sizeof(struct ip );     /* no options in reply */
 261
 262   /* fill in icmp */
 263   m->m_data += hlen;
 264   m->m_len -= hlen;
 265
 266   icp = mtod(m, struct icmp *);
 267
 268   if(minsize) s_ip_len=shlen+ICMP_MINLEN;   /* return header+8b only */
 269   else if(s_ip_len>ICMP_MAXDATALEN)         /* maximum size */
 270     s_ip_len=ICMP_MAXDATALEN;
 271
 272   m->m_len=ICMP_MINLEN+s_ip_len;        /* 8 bytes ICMP header */
 273
 274   /* min. size = 8+sizeof(struct ip)+8 */
 275
 276   icp->icmp_type = type;
 277   icp->icmp_code = code;
 278   icp->icmp_id = 0;
 279   icp->icmp_seq = 0;
 280
 281   memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len);   /* report the ip packet */
 282   HTONS(icp->icmp_ip.ip_len);
 283   HTONS(icp->icmp_ip.ip_id);
 284   HTONS(icp->icmp_ip.ip_off);
 285
 286 #if DEBUG
 287   if(message) {           /* DEBUG : append message to ICMP packet */
 288     int message_len;
 289     char *cpnt;
 290     message_len=strlen(message);
 291     if(message_len>ICMP_MAXDATALEN) message_len=ICMP_MAXDATALEN;
 292     cpnt=(char *)m->m_data+m->m_len;
 293     memcpy(cpnt, message, message_len);
 294     m->m_len+=message_len;
 295   }
 296 #endif
 297
 298   icp->icmp_cksum = 0;
 299   icp->icmp_cksum = cksum(m, m->m_len);
 300
 301   m->m_data -= hlen;
 302   m->m_len += hlen;
 303
 304   /* fill in ip */
 305   ip->ip_hl = hlen >> 2;
 306   ip->ip_len = m->m_len;
 307
 308   ip->ip_tos=((ip->ip_tos & 0x1E) | 0xC0);  /* high priority for errors */
 309
 310   ip->ip_ttl = MAXTTL;
 311   ip->ip_p = IPPROTO_ICMP;
 312   ip->ip_dst = ip->ip_src;    /* ip adresses */
 313   ip->ip_src = alias_addr;
 314
 315   (void ) ip_output((struct socket *)NULL, m);
 316
 317   icmpstat.icps_reflect++;
 318
 319 end_error:
 320   return;
 321 }
 322 #undef ICMP_MAXDATALEN
 323
 324 /*
 325  * Reflect the ip packet back to the source
 326  */
 327 void
 328 icmp_reflect(m)
 329      struct mbuf *m;
 330 {
 331   register struct ip *ip = mtod(m, struct ip *);
 332   int hlen = ip->ip_hl << 2;
 333   int optlen = hlen - sizeof(struct ip );
 334   register struct icmp *icp;
 335
 336   /*
 337    * Send an icmp packet back to the ip level,
 338    * after supplying a checksum.
 339    */
 340   m->m_data += hlen;
 341   m->m_len -= hlen;
 342   icp = mtod(m, struct icmp *);
 343
 344   icp->icmp_cksum = 0;
 345   icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
 346
 347   m->m_data -= hlen;
 348   m->m_len += hlen;
 349
 350   /* fill in ip */
 351   if (optlen > 0) {
 352     /*
 353      * Strip out original options by copying rest of first
 354      * mbuf's data back, and adjust the IP length.
 355      */
 356     memmove((caddr_t)(ip + 1), (caddr_t)ip + hlen,
 357             (unsigned )(m->m_len - hlen));
 358     hlen -= optlen;
 359     ip->ip_hl = hlen >> 2;
 360     ip->ip_len -= optlen;
 361     m->m_len -= optlen;
 362   }
 363
 364   ip->ip_ttl = MAXTTL;
 365   { /* swap */
 366     struct in_addr icmp_dst;
 367     icmp_dst = ip->ip_dst;
 368     ip->ip_dst = ip->ip_src;
 369     ip->ip_src = icmp_dst;
 370   }
 371
 372   (void ) ip_output((struct socket *)NULL, m);
 373
 374   icmpstat.icps_reflect++;
 375 }