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