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 #ifndef WITH_ICMP_ERROR_MSG
  37 #define WITH_ICMP_ERROR_MSG 0
  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_send_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 void icmp_init(Slirp *slirp)
  68 {
  69     slirp->icmp.so_next = slirp->icmp.so_prev = &slirp->icmp;
  70     slirp->icmp_last_so = &slirp->icmp;
  71 }
  72
  73 void icmp_cleanup(Slirp *slirp)
  74 {
  75     while (slirp->icmp.so_next != &slirp->icmp) {
  76         icmp_detach(slirp->icmp.so_next);
  77     }
  78 }
  79
  80 static int icmp_send(struct socket *so, struct mbuf *m, int hlen)
  81 {
  82     struct ip *ip = mtod(m, struct ip *);
  83     struct sockaddr_in addr;
  84
  85     so->s = slirp_socket(AF_INET, SOCK_DGRAM, IPPROTO_ICMP);
  86     if (so->s == -1) {
  87         return -1;
  88     }
  89
  90     so->so_m = m;
  91     so->so_faddr = ip->ip_dst;
  92     so->so_laddr = ip->ip_src;
  93     so->so_iptos = ip->ip_tos;
  94     so->so_type = IPPROTO_ICMP;
  95     so->so_state = SS_ISFCONNECTED;
  96     so->so_expire = curtime + SO_EXPIRE;
  97
  98     addr.sin_family = AF_INET;
  99     addr.sin_addr = so->so_faddr;
 100
 101     insque(so, &so->slirp->icmp);
 102
 103     if (sendto(so->s, m->m_data + hlen, m->m_len - hlen, 0,
 104                (struct sockaddr *)&addr, sizeof(addr)) == -1) {
 105         DEBUG_MISC("icmp_input icmp sendto tx errno = %d-%s",
 106                    errno, strerror(errno));
 107         icmp_send_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0, strerror(errno));
 108         icmp_detach(so);
 109     }
 110
 111     return 0;
 112 }
 113
 114 void icmp_detach(struct socket *so)
 115 {
 116     so->slirp->cb->unregister_poll_fd(so->s, so->slirp->opaque);
 117     closesocket(so->s);
 118     sofree(so);
 119 }
 120
 121 /*
 122  * Process a received ICMP message.
 123  */
 124 void
 125 icmp_input(struct mbuf *m, int hlen)
 126 {
 127   register struct icmp *icp;
 128   register struct ip *ip=mtod(m, struct ip *);
 129   int icmplen=ip->ip_len;
 130   Slirp *slirp = m->slirp;
 131
 132   DEBUG_CALL("icmp_input");
 133   DEBUG_ARG("m = %p", m);
 134   DEBUG_ARG("m_len = %d", m->m_len);
 135
 136   /*
 137    * Locate icmp structure in mbuf, and check
 138    * that its not corrupted and of at least minimum length.
 139    */
 140   if (icmplen < ICMP_MINLEN) {          /* min 8 bytes payload */
 141   freeit:
 142     m_free(m);
 143     goto end_error;
 144   }
 145
 146   m->m_len -= hlen;
 147   m->m_data += hlen;
 148   icp = mtod(m, struct icmp *);
 149   if (cksum(m, icmplen)) {
 150     goto freeit;
 151   }
 152   m->m_len += hlen;
 153   m->m_data -= hlen;
 154
 155   DEBUG_ARG("icmp_type = %d", icp->icmp_type);
 156   switch (icp->icmp_type) {
 157   case ICMP_ECHO:
 158     ip->ip_len += hlen;              /* since ip_input subtracts this */
 159     if (ip->ip_dst.s_addr == slirp->vhost_addr.s_addr ||
 160         ip->ip_dst.s_addr == slirp->vnameserver_addr.s_addr) {
 161         icmp_reflect(m);
 162     } else if (slirp->restricted) {
 163         goto freeit;
 164     } else {
 165       struct socket *so;
 166       struct sockaddr_storage addr;
 167       so = socreate(slirp);
 168       if (icmp_send(so, m, hlen) == 0) {
 169         return;
 170       }
 171       if (udp_attach(so, AF_INET) == -1) {
 172         DEBUG_MISC("icmp_input udp_attach errno = %d-%s",
 173                errno,strerror(errno));
 174         sofree(so);
 175         m_free(m);
 176         goto end_error;
 177       }
 178       so->so_m = m;
 179       so->so_ffamily = AF_INET;
 180       so->so_faddr = ip->ip_dst;
 181       so->so_fport = htons(7);
 182       so->so_lfamily = AF_INET;
 183       so->so_laddr = ip->ip_src;
 184       so->so_lport = htons(9);
 185       so->so_iptos = ip->ip_tos;
 186       so->so_type = IPPROTO_ICMP;
 187       so->so_state = SS_ISFCONNECTED;
 188
 189       /* Send the packet */
 190       addr = so->fhost.ss;
 191       sotranslate_out(so, &addr);
 192
 193       if(sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
 194                 (struct sockaddr *)&addr, sockaddr_size(&addr)) == -1) {
 195         DEBUG_MISC("icmp_input udp sendto tx errno = %d-%s",
 196                errno,strerror(errno));
 197         icmp_send_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0, strerror(errno));
 198         udp_detach(so);
 199       }
 200     } /* if ip->ip_dst.s_addr == alias_addr.s_addr */
 201     break;
 202   case ICMP_UNREACH:
 203     /* XXX? report error? close socket? */
 204   case ICMP_TIMXCEED:
 205   case ICMP_PARAMPROB:
 206   case ICMP_SOURCEQUENCH:
 207   case ICMP_TSTAMP:
 208   case ICMP_MASKREQ:
 209   case ICMP_REDIRECT:
 210     m_free(m);
 211     break;
 212
 213   default:
 214     m_free(m);
 215   } /* swith */
 216
 217 end_error:
 218   /* m is m_free()'d xor put in a socket xor or given to ip_send */
 219   return;
 220 }
 221
 222
 223 /*
 224  *      Send an ICMP message in response to a situation
 225  *
 226  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
 227  *                      MUST NOT change this header information.
 228  *                      MUST NOT reply to a multicast/broadcast IP address.
 229  *                      MUST NOT reply to a multicast/broadcast MAC address.
 230  *                      MUST reply to only the first fragment.
 231  */
 232 /*
 233  * Send ICMP_UNREACH back to the source regarding msrc.
 234  * mbuf *msrc is used as a template, but is NOT m_free()'d.
 235  * It is reported as the bad ip packet.  The header should
 236  * be fully correct and in host byte order.
 237  * ICMP fragmentation is illegal.  All machines must accept 576 bytes in one
 238  * packet.  The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
 239  */
 240
 241 #define ICMP_MAXDATALEN (IP_MSS-28)
 242 void
 243 icmp_send_error(struct mbuf *msrc, uint8_t type, uint8_t code, int minsize,
 244            const char *message)
 245 {
 246   unsigned hlen, shlen, s_ip_len;
 247   register struct ip *ip;
 248   register struct icmp *icp;
 249   register struct mbuf *m;
 250
 251   DEBUG_CALL("icmp_send_error");
 252   DEBUG_ARG("msrc = %p", msrc);
 253   DEBUG_ARG("msrc_len = %d", msrc->m_len);
 254
 255   if(type!=ICMP_UNREACH && type!=ICMP_TIMXCEED) goto end_error;
 256
 257   /* check msrc */
 258   if(!msrc) goto end_error;
 259   ip = mtod(msrc, struct ip *);
 260   if (slirp_debug & DBG_MISC) {
 261     char bufa[20], bufb[20];
 262     strcpy(bufa, inet_ntoa(ip->ip_src));
 263     strcpy(bufb, inet_ntoa(ip->ip_dst));
 264     DEBUG_MISC(" %.16s to %.16s", bufa, bufb);
 265   }
 266   if(ip->ip_off & IP_OFFMASK) goto end_error;    /* Only reply to fragment 0 */
 267
 268   /* Do not reply to source-only IPs */
 269   if ((ip->ip_src.s_addr & htonl(~(0xf << 28))) == 0) {
 270       goto end_error;
 271   }
 272
 273   shlen=ip->ip_hl << 2;
 274   s_ip_len=ip->ip_len;
 275   if(ip->ip_p == IPPROTO_ICMP) {
 276     icp = (struct icmp *)((char *)ip + shlen);
 277     /*
 278      *  Assume any unknown ICMP type is an error. This isn't
 279      *  specified by the RFC, but think about it..
 280      */
 281     if(icp->icmp_type>18 || icmp_flush[icp->icmp_type]) goto end_error;
 282   }
 283
 284   /* make a copy */
 285   m = m_get(msrc->slirp);
 286   if (!m) {
 287       goto end_error;
 288   }
 289
 290   { int new_m_size;
 291     new_m_size=sizeof(struct ip )+ICMP_MINLEN+msrc->m_len+ICMP_MAXDATALEN;
 292     if(new_m_size>m->m_size) m_inc(m, new_m_size);
 293   }
 294   memcpy(m->m_data, msrc->m_data, msrc->m_len);
 295   m->m_len = msrc->m_len;                        /* copy msrc to m */
 296
 297   /* make the header of the reply packet */
 298   ip  = mtod(m, struct ip *);
 299   hlen= sizeof(struct ip );     /* no options in reply */
 300
 301   /* fill in icmp */
 302   m->m_data += hlen;
 303   m->m_len -= hlen;
 304
 305   icp = mtod(m, struct icmp *);
 306
 307   if(minsize) s_ip_len=shlen+ICMP_MINLEN;   /* return header+8b only */
 308   else if(s_ip_len>ICMP_MAXDATALEN)         /* maximum size */
 309     s_ip_len=ICMP_MAXDATALEN;
 310
 311   m->m_len=ICMP_MINLEN+s_ip_len;        /* 8 bytes ICMP header */
 312
 313   /* min. size = 8+sizeof(struct ip)+8 */
 314
 315   icp->icmp_type = type;
 316   icp->icmp_code = code;
 317   icp->icmp_id = 0;
 318   icp->icmp_seq = 0;
 319
 320   memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len);   /* report the ip packet */
 321   HTONS(icp->icmp_ip.ip_len);
 322   HTONS(icp->icmp_ip.ip_id);
 323   HTONS(icp->icmp_ip.ip_off);
 324
 325   if (message && WITH_ICMP_ERROR_MSG) { /* append message to ICMP packet */
 326     int message_len;
 327     char *cpnt;
 328     message_len=strlen(message);
 329     if(message_len>ICMP_MAXDATALEN) message_len=ICMP_MAXDATALEN;
 330     cpnt=(char *)m->m_data+m->m_len;
 331     memcpy(cpnt, message, message_len);
 332     m->m_len+=message_len;
 333   }
 334
 335   icp->icmp_cksum = 0;
 336   icp->icmp_cksum = cksum(m, m->m_len);
 337
 338   m->m_data -= hlen;
 339   m->m_len += hlen;
 340
 341   /* fill in ip */
 342   ip->ip_hl = hlen >> 2;
 343   ip->ip_len = m->m_len;
 344
 345   ip->ip_tos=((ip->ip_tos & 0x1E) | 0xC0);  /* high priority for errors */
 346
 347   ip->ip_ttl = MAXTTL;
 348   ip->ip_p = IPPROTO_ICMP;
 349   ip->ip_dst = ip->ip_src;    /* ip addresses */
 350   ip->ip_src = m->slirp->vhost_addr;
 351
 352   (void ) ip_output((struct socket *)NULL, m);
 353
 354 end_error:
 355   return;
 356 }
 357 #undef ICMP_MAXDATALEN
 358
 359 /*
 360  * Reflect the ip packet back to the source
 361  */
 362 void
 363 icmp_reflect(struct mbuf *m)
 364 {
 365   register struct ip *ip = mtod(m, struct ip *);
 366   int hlen = ip->ip_hl << 2;
 367   int optlen = hlen - sizeof(struct ip );
 368   register struct icmp *icp;
 369
 370   /*
 371    * Send an icmp packet back to the ip level,
 372    * after supplying a checksum.
 373    */
 374   m->m_data += hlen;
 375   m->m_len -= hlen;
 376   icp = mtod(m, struct icmp *);
 377
 378   icp->icmp_type = ICMP_ECHOREPLY;
 379   icp->icmp_cksum = 0;
 380   icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
 381
 382   m->m_data -= hlen;
 383   m->m_len += hlen;
 384
 385   /* fill in ip */
 386   if (optlen > 0) {
 387     /*
 388      * Strip out original options by copying rest of first
 389      * mbuf's data back, and adjust the IP length.
 390      */
 391     memmove((char *)(ip + 1), (char *)ip + hlen,
 392             (unsigned )(m->m_len - hlen));
 393     hlen -= optlen;
 394     ip->ip_hl = hlen >> 2;
 395     ip->ip_len -= optlen;
 396     m->m_len -= optlen;
 397   }
 398
 399   ip->ip_ttl = MAXTTL;
 400   { /* swap */
 401     struct in_addr icmp_dst;
 402     icmp_dst = ip->ip_dst;
 403     ip->ip_dst = ip->ip_src;
 404     ip->ip_src = icmp_dst;
 405   }
 406
 407   (void ) ip_output((struct socket *)NULL, m);
 408 }
 409
 410 void icmp_receive(struct socket *so)
 411 {
 412     struct mbuf *m = so->so_m;
 413     struct ip *ip = mtod(m, struct ip *);
 414     int hlen = ip->ip_hl << 2;
 415     uint8_t error_code;
 416     struct icmp *icp;
 417     int id, len;
 418
 419     m->m_data += hlen;
 420     m->m_len -= hlen;
 421     icp = mtod(m, struct icmp *);
 422
 423     id = icp->icmp_id;
 424     len = recv(so->s, icp, M_ROOM(m), 0);
 425     /*
 426      * The behavior of reading SOCK_DGRAM+IPPROTO_ICMP sockets is inconsistent
 427      * between host OSes.  On Linux, only the ICMP header and payload is
 428      * included.  On macOS/Darwin, the socket acts like a raw socket and
 429      * includes the IP header as well.  On other BSDs, SOCK_DGRAM+IPPROTO_ICMP
 430      * sockets aren't supported at all, so we treat them like raw sockets.  It
 431      * isn't possible to detect this difference at runtime, so we must use an
 432      * #ifdef to determine if we need to remove the IP header.
 433      */
 434 #ifdef CONFIG_BSD
 435     if (len >= sizeof(struct ip)) {
 436         struct ip *inner_ip = mtod(m, struct ip *);
 437         int inner_hlen = inner_ip->ip_hl << 2;
 438         if (inner_hlen > len) {
 439             len = -1;
 440             errno = -EINVAL;
 441         } else {
 442             len -= inner_hlen;
 443             memmove(icp, (unsigned char *)icp + inner_hlen, len);
 444         }
 445     } else {
 446       len = -1;
 447       errno = -EINVAL;
 448     }
 449 #endif
 450     icp->icmp_id = id;
 451
 452     m->m_data -= hlen;
 453     m->m_len += hlen;
 454
 455     if (len == -1 || len == 0) {
 456         if (errno == ENETUNREACH) {
 457             error_code = ICMP_UNREACH_NET;
 458         } else {
 459             error_code = ICMP_UNREACH_HOST;
 460         }
 461         DEBUG_MISC(" udp icmp rx errno = %d-%s", errno,
 462                    strerror(errno));
 463         icmp_send_error(so->so_m, ICMP_UNREACH, error_code, 0, strerror(errno));
 464     } else {
 465         icmp_reflect(so->so_m);
 466         so->so_m = NULL; /* Don't m_free() it again! */
 467     }
 468     icmp_detach(so);
 469 }