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