slirp/src/ip_icmp.c

   1 /* SPDX-License-Identifier: BSD-3-Clause */
   2 /*
   3  * Copyright (c) 1982, 1986, 1988, 1993
   4  *      The Regents of the University of California.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  * 3. Neither the name of the University nor the names of its contributors
  15  *    may be used to endorse or promote products derived from this software
  16  *    without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGE.
  29  *
  30  *      @(#)ip_icmp.c   8.2 (Berkeley) 1/4/94
  31  * ip_icmp.c,v 1.7 1995/05/30 08:09:42 rgrimes Exp
  32  */
  33
  34 #include "slirp.h"
  35 #include "ip_icmp.h"
  36
  37 #ifndef WITH_ICMP_ERROR_MSG
  38 #define WITH_ICMP_ERROR_MSG 0
  39 #endif
  40
  41 /* The message sent when emulating PING */
  42 /* Be nice and tell them it's just a pseudo-ping packet */
  43 static const char icmp_ping_msg[] = "This is a pseudo-PING packet used by Slirp to emulate ICMP ECHO-REQUEST packets.\n";
  44
  45 /* list of actions for icmp_send_error() on RX of an icmp message */
  46 static const int icmp_flush[19] = {
  47 /*  ECHO REPLY (0)  */   0,
  48                          1,
  49                          1,
  50 /* DEST UNREACH (3) */   1,
  51 /* SOURCE QUENCH (4)*/   1,
  52 /* REDIRECT (5) */       1,
  53                          1,
  54                          1,
  55 /* ECHO (8) */           0,
  56 /* ROUTERADVERT (9) */   1,
  57 /* ROUTERSOLICIT (10) */ 1,
  58 /* TIME EXCEEDED (11) */ 1,
  59 /* PARAMETER PROBLEM (12) */ 1,
  60 /* TIMESTAMP (13) */     0,
  61 /* TIMESTAMP REPLY (14) */ 0,
  62 /* INFO (15) */          0,
  63 /* INFO REPLY (16) */    0,
  64 /* ADDR MASK (17) */     0,
  65 /* ADDR MASK REPLY (18) */ 0
  66 };
  67
  68 void icmp_init(Slirp *slirp)
  69 {
  70     slirp->icmp.so_next = slirp->icmp.so_prev = &slirp->icmp;
  71     slirp->icmp_last_so = &slirp->icmp;
  72 }
  73
  74 void icmp_cleanup(Slirp *slirp)
  75 {
  76     while (slirp->icmp.so_next != &slirp->icmp) {
  77         icmp_detach(slirp->icmp.so_next);
  78     }
  79 }
  80
  81 static int icmp_send(struct socket *so, struct mbuf *m, int hlen)
  82 {
  83     struct ip *ip = mtod(m, struct ip *);
  84     struct sockaddr_in addr;
  85
  86     so->s = slirp_socket(AF_INET, SOCK_DGRAM, IPPROTO_ICMP);
  87     if (so->s == -1) {
  88         return -1;
  89     }
  90
  91     so->so_m = m;
  92     so->so_faddr = ip->ip_dst;
  93     so->so_laddr = ip->ip_src;
  94     so->so_iptos = ip->ip_tos;
  95     so->so_type = IPPROTO_ICMP;
  96     so->so_state = SS_ISFCONNECTED;
  97     so->so_expire = curtime + SO_EXPIRE;
  98
  99     addr.sin_family = AF_INET;
 100     addr.sin_addr = so->so_faddr;
 101
 102     insque(so, &so->slirp->icmp);
 103
 104     if (sendto(so->s, m->m_data + hlen, m->m_len - hlen, 0,
 105                (struct sockaddr *)&addr, sizeof(addr)) == -1) {
 106         DEBUG_MISC("icmp_input icmp sendto tx errno = %d-%s",
 107                    errno, strerror(errno));
 108         icmp_send_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0, strerror(errno));
 109         icmp_detach(so);
 110     }
 111
 112     return 0;
 113 }
 114
 115 void icmp_detach(struct socket *so)
 116 {
 117     so->slirp->cb->unregister_poll_fd(so->s, so->slirp->opaque);
 118     closesocket(so->s);
 119     sofree(so);
 120 }
 121
 122 /*
 123  * Process a received ICMP message.
 124  */
 125 void
 126 icmp_input(struct mbuf *m, int hlen)
 127 {
 128   register struct icmp *icp;
 129   register struct ip *ip=mtod(m, struct ip *);
 130   int icmplen=ip->ip_len;
 131   Slirp *slirp = m->slirp;
 132
 133   DEBUG_CALL("icmp_input");
 134   DEBUG_ARG("m = %p", m);
 135   DEBUG_ARG("m_len = %d", m->m_len);
 136
 137   /*
 138    * Locate icmp structure in mbuf, and check
 139    * that its not corrupted and of at least minimum length.
 140    */
 141   if (icmplen < ICMP_MINLEN) {          /* min 8 bytes payload */
 142   freeit:
 143     m_free(m);
 144     goto end_error;
 145   }
 146
 147   m->m_len -= hlen;
 148   m->m_data += hlen;
 149   icp = mtod(m, struct icmp *);
 150   if (cksum(m, icmplen)) {
 151     goto freeit;
 152   }
 153   m->m_len += hlen;
 154   m->m_data -= hlen;
 155
 156   DEBUG_ARG("icmp_type = %d", icp->icmp_type);
 157   switch (icp->icmp_type) {
 158   case ICMP_ECHO:
 159     ip->ip_len += hlen;              /* since ip_input subtracts this */
 160     if (ip->ip_dst.s_addr == slirp->vhost_addr.s_addr ||
 161         ip->ip_dst.s_addr == slirp->vnameserver_addr.s_addr) {
 162         icmp_reflect(m);
 163     } else if (slirp->restricted) {
 164         goto freeit;
 165     } else {
 166       struct socket *so;
 167       struct sockaddr_storage addr;
 168       so = socreate(slirp);
 169       if (icmp_send(so, m, hlen) == 0) {
 170         return;
 171       }
 172       if (udp_attach(so, AF_INET) == -1) {
 173         DEBUG_MISC("icmp_input udp_attach errno = %d-%s",
 174                errno,strerror(errno));
 175         sofree(so);
 176         m_free(m);
 177         goto end_error;
 178       }
 179       so->so_m = m;
 180       so->so_ffamily = AF_INET;
 181       so->so_faddr = ip->ip_dst;
 182       so->so_fport = htons(7);
 183       so->so_lfamily = AF_INET;
 184       so->so_laddr = ip->ip_src;
 185       so->so_lport = htons(9);
 186       so->so_iptos = ip->ip_tos;
 187       so->so_type = IPPROTO_ICMP;
 188       so->so_state = SS_ISFCONNECTED;
 189
 190       /* Send the packet */
 191       addr = so->fhost.ss;
 192       sotranslate_out(so, &addr);
 193
 194       if(sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
 195                 (struct sockaddr *)&addr, sockaddr_size(&addr)) == -1) {
 196         DEBUG_MISC("icmp_input udp sendto tx errno = %d-%s",
 197                errno,strerror(errno));
 198         icmp_send_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0, strerror(errno));
 199         udp_detach(so);
 200       }
 201     } /* if ip->ip_dst.s_addr == alias_addr.s_addr */
 202     break;
 203   case ICMP_UNREACH:
 204     /* XXX? report error? close socket? */
 205   case ICMP_TIMXCEED:
 206   case ICMP_PARAMPROB:
 207   case ICMP_SOURCEQUENCH:
 208   case ICMP_TSTAMP:
 209   case ICMP_MASKREQ:
 210   case ICMP_REDIRECT:
 211     m_free(m);
 212     break;
 213
 214   default:
 215     m_free(m);
 216   } /* swith */
 217
 218 end_error:
 219   /* m is m_free()'d xor put in a socket xor or given to ip_send */
 220   return;
 221 }
 222
 223
 224 /*
 225  *      Send an ICMP message in response to a situation
 226  *
 227  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
 228  *                      MUST NOT change this header information.
 229  *                      MUST NOT reply to a multicast/broadcast IP address.
 230  *                      MUST NOT reply to a multicast/broadcast MAC address.
 231  *                      MUST reply to only the first fragment.
 232  */
 233 /*
 234  * Send ICMP_UNREACH back to the source regarding msrc.
 235  * mbuf *msrc is used as a template, but is NOT m_free()'d.
 236  * It is reported as the bad ip packet.  The header should
 237  * be fully correct and in host byte order.
 238  * ICMP fragmentation is illegal.  All machines must accept 576 bytes in one
 239  * packet.  The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
 240  */
 241
 242 #define ICMP_MAXDATALEN (IP_MSS-28)
 243 void
 244 icmp_send_error(struct mbuf *msrc, uint8_t type, uint8_t code, int minsize,
 245            const char *message)
 246 {
 247   unsigned hlen, shlen, s_ip_len;
 248   register struct ip *ip;
 249   register struct icmp *icp;
 250   register struct mbuf *m;
 251
 252   DEBUG_CALL("icmp_send_error");
 253   DEBUG_ARG("msrc = %p", msrc);
 254   DEBUG_ARG("msrc_len = %d", msrc->m_len);
 255
 256   if(type!=ICMP_UNREACH && type!=ICMP_TIMXCEED) goto end_error;
 257
 258   /* check msrc */
 259   if(!msrc) goto end_error;
 260   ip = mtod(msrc, struct ip *);
 261   if (slirp_debug & DBG_MISC) {
 262     char bufa[20], bufb[20];
 263     strcpy(bufa, inet_ntoa(ip->ip_src));
 264     strcpy(bufb, inet_ntoa(ip->ip_dst));
 265     DEBUG_MISC(" %.16s to %.16s", bufa, bufb);
 266   }
 267   if(ip->ip_off & IP_OFFMASK) goto end_error;    /* Only reply to fragment 0 */
 268
 269   /* Do not reply to source-only IPs */
 270   if ((ip->ip_src.s_addr & htonl(~(0xf << 28))) == 0) {
 271       goto end_error;
 272   }
 273
 274   shlen=ip->ip_hl << 2;
 275   s_ip_len=ip->ip_len;
 276   if(ip->ip_p == IPPROTO_ICMP) {
 277     icp = (struct icmp *)((char *)ip + shlen);
 278     /*
 279      *  Assume any unknown ICMP type is an error. This isn't
 280      *  specified by the RFC, but think about it..
 281      */
 282     if(icp->icmp_type>18 || icmp_flush[icp->icmp_type]) goto end_error;
 283   }
 284
 285   /* make a copy */
 286   m = m_get(msrc->slirp);
 287   if (!m) {
 288       goto end_error;
 289   }
 290
 291   { int new_m_size;
 292     new_m_size=sizeof(struct ip )+ICMP_MINLEN+msrc->m_len+ICMP_MAXDATALEN;
 293     if(new_m_size>m->m_size) m_inc(m, new_m_size);
 294   }
 295   memcpy(m->m_data, msrc->m_data, msrc->m_len);
 296   m->m_len = msrc->m_len;                        /* copy msrc to m */
 297
 298   /* make the header of the reply packet */
 299   ip  = mtod(m, struct ip *);
 300   hlen= sizeof(struct ip );     /* no options in reply */
 301
 302   /* fill in icmp */
 303   m->m_data += hlen;
 304   m->m_len -= hlen;
 305
 306   icp = mtod(m, struct icmp *);
 307
 308   if(minsize) s_ip_len=shlen+ICMP_MINLEN;   /* return header+8b only */
 309   else if(s_ip_len>ICMP_MAXDATALEN)         /* maximum size */
 310     s_ip_len=ICMP_MAXDATALEN;
 311
 312   m->m_len=ICMP_MINLEN+s_ip_len;        /* 8 bytes ICMP header */
 313
 314   /* min. size = 8+sizeof(struct ip)+8 */
 315
 316   icp->icmp_type = type;
 317   icp->icmp_code = code;
 318   icp->icmp_id = 0;
 319   icp->icmp_seq = 0;
 320
 321   memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len);   /* report the ip packet */
 322   HTONS(icp->icmp_ip.ip_len);
 323   HTONS(icp->icmp_ip.ip_id);
 324   HTONS(icp->icmp_ip.ip_off);
 325
 326   if (message && WITH_ICMP_ERROR_MSG) { /* append message to ICMP packet */
 327     int message_len;
 328     char *cpnt;
 329     message_len=strlen(message);
 330     if(message_len>ICMP_MAXDATALEN) message_len=ICMP_MAXDATALEN;
 331     cpnt=(char *)m->m_data+m->m_len;
 332     memcpy(cpnt, message, message_len);
 333     m->m_len+=message_len;
 334   }
 335
 336   icp->icmp_cksum = 0;
 337   icp->icmp_cksum = cksum(m, m->m_len);
 338
 339   m->m_data -= hlen;
 340   m->m_len += hlen;
 341
 342   /* fill in ip */
 343   ip->ip_hl = hlen >> 2;
 344   ip->ip_len = m->m_len;
 345
 346   ip->ip_tos=((ip->ip_tos & 0x1E) | 0xC0);  /* high priority for errors */
 347
 348   ip->ip_ttl = MAXTTL;
 349   ip->ip_p = IPPROTO_ICMP;
 350   ip->ip_dst = ip->ip_src;    /* ip addresses */
 351   ip->ip_src = m->slirp->vhost_addr;
 352
 353   (void ) ip_output((struct socket *)NULL, m);
 354
 355 end_error:
 356   return;
 357 }
 358 #undef ICMP_MAXDATALEN
 359
 360 /*
 361  * Reflect the ip packet back to the source
 362  */
 363 void
 364 icmp_reflect(struct mbuf *m)
 365 {
 366   register struct ip *ip = mtod(m, struct ip *);
 367   int hlen = ip->ip_hl << 2;
 368   int optlen = hlen - sizeof(struct ip );
 369   register struct icmp *icp;
 370
 371   /*
 372    * Send an icmp packet back to the ip level,
 373    * after supplying a checksum.
 374    */
 375   m->m_data += hlen;
 376   m->m_len -= hlen;
 377   icp = mtod(m, struct icmp *);
 378
 379   icp->icmp_type = ICMP_ECHOREPLY;
 380   icp->icmp_cksum = 0;
 381   icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
 382
 383   m->m_data -= hlen;
 384   m->m_len += hlen;
 385
 386   /* fill in ip */
 387   if (optlen > 0) {
 388     /*
 389      * Strip out original options by copying rest of first
 390      * mbuf's data back, and adjust the IP length.
 391      */
 392     memmove((char *)(ip + 1), (char *)ip + hlen,
 393             (unsigned )(m->m_len - hlen));
 394     hlen -= optlen;
 395     ip->ip_hl = hlen >> 2;
 396     ip->ip_len -= optlen;
 397     m->m_len -= optlen;
 398   }
 399
 400   ip->ip_ttl = MAXTTL;
 401   { /* swap */
 402     struct in_addr icmp_dst;
 403     icmp_dst = ip->ip_dst;
 404     ip->ip_dst = ip->ip_src;
 405     ip->ip_src = icmp_dst;
 406   }
 407
 408   (void ) ip_output((struct socket *)NULL, m);
 409 }
 410
 411 void icmp_receive(struct socket *so)
 412 {
 413     struct mbuf *m = so->so_m;
 414     struct ip *ip = mtod(m, struct ip *);
 415     int hlen = ip->ip_hl << 2;
 416     uint8_t error_code;
 417     struct icmp *icp;
 418     int id, len;
 419
 420     m->m_data += hlen;
 421     m->m_len -= hlen;
 422     icp = mtod(m, struct icmp *);
 423
 424     id = icp->icmp_id;
 425     len = recv(so->s, icp, M_ROOM(m), 0);
 426     /*
 427      * The behavior of reading SOCK_DGRAM+IPPROTO_ICMP sockets is inconsistent
 428      * between host OSes.  On Linux, only the ICMP header and payload is
 429      * included.  On macOS/Darwin, the socket acts like a raw socket and
 430      * includes the IP header as well.  On other BSDs, SOCK_DGRAM+IPPROTO_ICMP
 431      * sockets aren't supported at all, so we treat them like raw sockets.  It
 432      * isn't possible to detect this difference at runtime, so we must use an
 433      * #ifdef to determine if we need to remove the IP header.
 434      */
 435 #ifdef CONFIG_BSD
 436     if (len >= sizeof(struct ip)) {
 437         struct ip *inner_ip = mtod(m, struct ip *);
 438         int inner_hlen = inner_ip->ip_hl << 2;
 439         if (inner_hlen > len) {
 440             len = -1;
 441             errno = -EINVAL;
 442         } else {
 443             len -= inner_hlen;
 444             memmove(icp, (unsigned char *)icp + inner_hlen, len);
 445         }
 446     } else {
 447       len = -1;
 448       errno = -EINVAL;
 449     }
 450 #endif
 451     icp->icmp_id = id;
 452
 453     m->m_data -= hlen;
 454     m->m_len += hlen;
 455
 456     if (len == -1 || len == 0) {
 457         if (errno == ENETUNREACH) {
 458             error_code = ICMP_UNREACH_NET;
 459         } else {
 460             error_code = ICMP_UNREACH_HOST;
 461         }
 462         DEBUG_MISC(" udp icmp rx errno = %d-%s", errno,
 463                    strerror(errno));
 464         icmp_send_error(so->so_m, ICMP_UNREACH, error_code, 0, strerror(errno));
 465     } else {
 466         icmp_reflect(so->so_m);
 467         so->so_m = NULL; /* Don't m_free() it again! */
 468     }
 469     icmp_detach(so);
 470 }