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 /* The message sent when emulating PING */
  37 /* Be nice and tell them it's just a pseudo-ping packet */
  38 static const char icmp_ping_msg[] = "This is a pseudo-PING packet used by Slirp to emulate ICMP ECHO-REQUEST packets.\n";
  39
  40 /* list of actions for icmp_error() on RX of an icmp message */
  41 static const int icmp_flush[19] = {
  42 /*  ECHO REPLY (0)  */   0,
  43                          1,
  44                          1,
  45 /* DEST UNREACH (3) */   1,
  46 /* SOURCE QUENCH (4)*/   1,
  47 /* REDIRECT (5) */       1,
  48                          1,
  49                          1,
  50 /* ECHO (8) */           0,
  51 /* ROUTERADVERT (9) */   1,
  52 /* ROUTERSOLICIT (10) */ 1,
  53 /* TIME EXCEEDED (11) */ 1,
  54 /* PARAMETER PROBLEM (12) */ 1,
  55 /* TIMESTAMP (13) */     0,
  56 /* TIMESTAMP REPLY (14) */ 0,
  57 /* INFO (15) */          0,
  58 /* INFO REPLY (16) */    0,
  59 /* ADDR MASK (17) */     0,
  60 /* ADDR MASK REPLY (18) */ 0
  61 };
  62
  63 /*
  64  * Process a received ICMP message.
  65  */
  66 void
  67 icmp_input(struct mbuf *m, int hlen)
  68 {
  69   register struct icmp *icp;
  70   register struct ip *ip=mtod(m, struct ip *);
  71   int icmplen=ip->ip_len;
  72
  73   DEBUG_CALL("icmp_input");
  74   DEBUG_ARG("m = %lx", (long )m);
  75   DEBUG_ARG("m_len = %d", m->m_len);
  76
  77   /*
  78    * Locate icmp structure in mbuf, and check
  79    * that its not corrupted and of at least minimum length.
  80    */
  81   if (icmplen < ICMP_MINLEN) {          /* min 8 bytes payload */
  82   freeit:
  83     m_freem(m);
  84     goto end_error;
  85   }
  86
  87   m->m_len -= hlen;
  88   m->m_data += hlen;
  89   icp = mtod(m, struct icmp *);
  90   if (cksum(m, icmplen)) {
  91     goto freeit;
  92   }
  93   m->m_len += hlen;
  94   m->m_data -= hlen;
  95
  96   DEBUG_ARG("icmp_type = %d", icp->icmp_type);
  97   switch (icp->icmp_type) {
  98   case ICMP_ECHO:
  99     icp->icmp_type = ICMP_ECHOREPLY;
 100     ip->ip_len += hlen;              /* since ip_input subtracts this */
 101     if (ip->ip_dst.s_addr == vhost_addr.s_addr) {
 102       icmp_reflect(m);
 103     } else {
 104       struct socket *so;
 105       struct sockaddr_in addr;
 106       if ((so = socreate()) == NULL) goto freeit;
 107       if(udp_attach(so) == -1) {
 108         DEBUG_MISC((dfd,"icmp_input udp_attach errno = %d-%s\n",
 109                     errno,strerror(errno)));
 110         sofree(so);
 111         m_free(m);
 112         goto end_error;
 113       }
 114       so->so_m = m;
 115       so->so_faddr = ip->ip_dst;
 116       so->so_fport = htons(7);
 117       so->so_laddr = ip->ip_src;
 118       so->so_lport = htons(9);
 119       so->so_iptos = ip->ip_tos;
 120       so->so_type = IPPROTO_ICMP;
 121       so->so_state = SS_ISFCONNECTED;
 122
 123       /* Send the packet */
 124       addr.sin_family = AF_INET;
 125       if ((so->so_faddr.s_addr & vnetwork_mask.s_addr) ==
 126           vnetwork_addr.s_addr) {
 127         /* It's an alias */
 128         if (so->so_faddr.s_addr == vnameserver_addr.s_addr) {
 129           addr.sin_addr = dns_addr;
 130         } else {
 131           addr.sin_addr = loopback_addr;
 132         }
 133       } else {
 134         addr.sin_addr = so->so_faddr;
 135       }
 136       addr.sin_port = so->so_fport;
 137       if(sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
 138                 (struct sockaddr *)&addr, sizeof(addr)) == -1) {
 139         DEBUG_MISC((dfd,"icmp_input udp sendto tx errno = %d-%s\n",
 140                     errno,strerror(errno)));
 141         icmp_error(m, ICMP_UNREACH,ICMP_UNREACH_NET, 0,strerror(errno));
 142         udp_detach(so);
 143       }
 144     } /* if ip->ip_dst.s_addr == alias_addr.s_addr */
 145     break;
 146   case ICMP_UNREACH:
 147     /* XXX? report error? close socket? */
 148   case ICMP_TIMXCEED:
 149   case ICMP_PARAMPROB:
 150   case ICMP_SOURCEQUENCH:
 151   case ICMP_TSTAMP:
 152   case ICMP_MASKREQ:
 153   case ICMP_REDIRECT:
 154     m_freem(m);
 155     break;
 156
 157   default:
 158     m_freem(m);
 159   } /* swith */
 160
 161 end_error:
 162   /* m is m_free()'d xor put in a socket xor or given to ip_send */
 163   return;
 164 }
 165
 166
 167 /*
 168  *      Send an ICMP message in response to a situation
 169  *
 170  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. MAY send more (we do).
 171  *                      MUST NOT change this header information.
 172  *                      MUST NOT reply to a multicast/broadcast IP address.
 173  *                      MUST NOT reply to a multicast/broadcast MAC address.
 174  *                      MUST reply to only the first fragment.
 175  */
 176 /*
 177  * Send ICMP_UNREACH back to the source regarding msrc.
 178  * mbuf *msrc is used as a template, but is NOT m_free()'d.
 179  * It is reported as the bad ip packet.  The header should
 180  * be fully correct and in host byte order.
 181  * ICMP fragmentation is illegal.  All machines must accept 576 bytes in one
 182  * packet.  The maximum payload is 576-20(ip hdr)-8(icmp hdr)=548
 183  */
 184
 185 #define ICMP_MAXDATALEN (IP_MSS-28)
 186 void
 187 icmp_error(struct mbuf *msrc, u_char type, u_char code, int minsize,
 188            const char *message)
 189 {
 190   unsigned hlen, shlen, s_ip_len;
 191   register struct ip *ip;
 192   register struct icmp *icp;
 193   register struct mbuf *m;
 194
 195   DEBUG_CALL("icmp_error");
 196   DEBUG_ARG("msrc = %lx", (long )msrc);
 197   DEBUG_ARG("msrc_len = %d", msrc->m_len);
 198
 199   if(type!=ICMP_UNREACH && type!=ICMP_TIMXCEED) goto end_error;
 200
 201   /* check msrc */
 202   if(!msrc) goto end_error;
 203   ip = mtod(msrc, struct ip *);
 204 #ifdef DEBUG
 205   { char bufa[20], bufb[20];
 206     strcpy(bufa, inet_ntoa(ip->ip_src));
 207     strcpy(bufb, inet_ntoa(ip->ip_dst));
 208     DEBUG_MISC((dfd, " %.16s to %.16s\n", bufa, bufb));
 209   }
 210 #endif
 211   if(ip->ip_off & IP_OFFMASK) goto end_error;    /* Only reply to fragment 0 */
 212
 213   shlen=ip->ip_hl << 2;
 214   s_ip_len=ip->ip_len;
 215   if(ip->ip_p == IPPROTO_ICMP) {
 216     icp = (struct icmp *)((char *)ip + shlen);
 217     /*
 218      *  Assume any unknown ICMP type is an error. This isn't
 219      *  specified by the RFC, but think about it..
 220      */
 221     if(icp->icmp_type>18 || icmp_flush[icp->icmp_type]) goto end_error;
 222   }
 223
 224   /* make a copy */
 225   if(!(m=m_get())) goto end_error;               /* get mbuf */
 226   { int new_m_size;
 227     new_m_size=sizeof(struct ip )+ICMP_MINLEN+msrc->m_len+ICMP_MAXDATALEN;
 228     if(new_m_size>m->m_size) m_inc(m, new_m_size);
 229   }
 230   memcpy(m->m_data, msrc->m_data, msrc->m_len);
 231   m->m_len = msrc->m_len;                        /* copy msrc to m */
 232
 233   /* make the header of the reply packet */
 234   ip  = mtod(m, struct ip *);
 235   hlen= sizeof(struct ip );     /* no options in reply */
 236
 237   /* fill in icmp */
 238   m->m_data += hlen;
 239   m->m_len -= hlen;
 240
 241   icp = mtod(m, struct icmp *);
 242
 243   if(minsize) s_ip_len=shlen+ICMP_MINLEN;   /* return header+8b only */
 244   else if(s_ip_len>ICMP_MAXDATALEN)         /* maximum size */
 245     s_ip_len=ICMP_MAXDATALEN;
 246
 247   m->m_len=ICMP_MINLEN+s_ip_len;        /* 8 bytes ICMP header */
 248
 249   /* min. size = 8+sizeof(struct ip)+8 */
 250
 251   icp->icmp_type = type;
 252   icp->icmp_code = code;
 253   icp->icmp_id = 0;
 254   icp->icmp_seq = 0;
 255
 256   memcpy(&icp->icmp_ip, msrc->m_data, s_ip_len);   /* report the ip packet */
 257   HTONS(icp->icmp_ip.ip_len);
 258   HTONS(icp->icmp_ip.ip_id);
 259   HTONS(icp->icmp_ip.ip_off);
 260
 261 #ifdef DEBUG
 262   if(message) {           /* DEBUG : append message to ICMP packet */
 263     int message_len;
 264     char *cpnt;
 265     message_len=strlen(message);
 266     if(message_len>ICMP_MAXDATALEN) message_len=ICMP_MAXDATALEN;
 267     cpnt=(char *)m->m_data+m->m_len;
 268     memcpy(cpnt, message, message_len);
 269     m->m_len+=message_len;
 270   }
 271 #endif
 272
 273   icp->icmp_cksum = 0;
 274   icp->icmp_cksum = cksum(m, m->m_len);
 275
 276   m->m_data -= hlen;
 277   m->m_len += hlen;
 278
 279   /* fill in ip */
 280   ip->ip_hl = hlen >> 2;
 281   ip->ip_len = m->m_len;
 282
 283   ip->ip_tos=((ip->ip_tos & 0x1E) | 0xC0);  /* high priority for errors */
 284
 285   ip->ip_ttl = MAXTTL;
 286   ip->ip_p = IPPROTO_ICMP;
 287   ip->ip_dst = ip->ip_src;    /* ip adresses */
 288   ip->ip_src = vhost_addr;
 289
 290   (void ) ip_output((struct socket *)NULL, m);
 291
 292 end_error:
 293   return;
 294 }
 295 #undef ICMP_MAXDATALEN
 296
 297 /*
 298  * Reflect the ip packet back to the source
 299  */
 300 void
 301 icmp_reflect(struct mbuf *m)
 302 {
 303   register struct ip *ip = mtod(m, struct ip *);
 304   int hlen = ip->ip_hl << 2;
 305   int optlen = hlen - sizeof(struct ip );
 306   register struct icmp *icp;
 307
 308   /*
 309    * Send an icmp packet back to the ip level,
 310    * after supplying a checksum.
 311    */
 312   m->m_data += hlen;
 313   m->m_len -= hlen;
 314   icp = mtod(m, struct icmp *);
 315
 316   icp->icmp_cksum = 0;
 317   icp->icmp_cksum = cksum(m, ip->ip_len - hlen);
 318
 319   m->m_data -= hlen;
 320   m->m_len += hlen;
 321
 322   /* fill in ip */
 323   if (optlen > 0) {
 324     /*
 325      * Strip out original options by copying rest of first
 326      * mbuf's data back, and adjust the IP length.
 327      */
 328     memmove((caddr_t)(ip + 1), (caddr_t)ip + hlen,
 329             (unsigned )(m->m_len - hlen));
 330     hlen -= optlen;
 331     ip->ip_hl = hlen >> 2;
 332     ip->ip_len -= optlen;
 333     m->m_len -= optlen;
 334   }
 335
 336   ip->ip_ttl = MAXTTL;
 337   { /* swap */
 338     struct in_addr icmp_dst;
 339     icmp_dst = ip->ip_dst;
 340     ip->ip_dst = ip->ip_src;
 341     ip->ip_src = icmp_dst;
 342   }
 343
 344   (void ) ip_output((struct socket *)NULL, m);
 345 }