The Tcpdump Group git mirrors - tcpdump/blob - print-ip6.c

   1 /*
   2  * Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994
   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: (1) source code distributions
   7  * retain the above copyright notice and this paragraph in its entirety, (2)
   8  * distributions including binary code include the above copyright notice and
   9  * this paragraph in its entirety in the documentation or other materials
  10  * provided with the distribution, and (3) all advertising materials mentioning
  11  * features or use of this software display the following acknowledgement:
  12  * ``This product includes software developed by the University of California,
  13  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  14  * the University nor the names of its contributors may be used to endorse
  15  * or promote products derived from this software without specific prior
  16  * written permission.
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  18  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  */
  21
  22 /* \summary: IPv6 printer */
  23
  24 #ifdef HAVE_CONFIG_H
  25 #include <config.h>
  26 #endif
  27
  28 #include "netdissect-stdinc.h"
  29
  30 #include <string.h>
  31
  32 #include "netdissect.h"
  33 #include "addrtoname.h"
  34 #include "extract.h"
  35
  36 #include "ip6.h"
  37 #include "ipproto.h"
  38
  39 /*
  40  * If routing headers are presend and valid, set dst to the final destination.
  41  * Otherwise, set it to the IPv6 destination.
  42  *
  43  * This is used for UDP and TCP pseudo-header in the checksum
  44  * calculation.
  45  */
  46 static void
  47 ip6_finddst(netdissect_options *ndo, struct in6_addr *dst,
  48             const struct ip6_hdr *ip6)
  49 {
  50         const u_char *cp;
  51         u_int advance;
  52         u_int nh;
  53         const void *dst_addr;
  54         const struct ip6_rthdr *dp;
  55         const struct ip6_rthdr0 *dp0;
  56         const struct ip6_srh *srh;
  57         const u_char *p;
  58         int i, len;
  59
  60         cp = (const u_char *)ip6;
  61         advance = sizeof(struct ip6_hdr);
  62         nh = GET_U_1(ip6->ip6_nxt);
  63         dst_addr = (const void *)ip6->ip6_dst;
  64
  65         while (cp < ndo->ndo_snapend) {
  66                 cp += advance;
  67
  68                 switch (nh) {
  69
  70                 case IPPROTO_HOPOPTS:
  71                 case IPPROTO_DSTOPTS:
  72                 case IPPROTO_MOBILITY_OLD:
  73                 case IPPROTO_MOBILITY:
  74                         /*
  75                          * These have a header length byte, following
  76                          * the next header byte, giving the length of
  77                          * the header, in units of 8 octets, excluding
  78                          * the first 8 octets.
  79                          */
  80                         ND_TCHECK_2(cp);
  81                         advance = (GET_U_1(cp + 1) + 1) << 3;
  82                         nh = GET_U_1(cp);
  83                         break;
  84
  85                 case IPPROTO_FRAGMENT:
  86                         /*
  87                          * The byte following the next header byte is
  88                          * marked as reserved, and the header is always
  89                          * the same size.
  90                          */
  91                         ND_TCHECK_1(cp);
  92                         advance = sizeof(struct ip6_frag);
  93                         nh = GET_U_1(cp);
  94                         break;
  95
  96                 case IPPROTO_ROUTING:
  97                         /*
  98                          * OK, we found it.
  99                          */
 100                         dp = (const struct ip6_rthdr *)cp;
 101                         ND_TCHECK_SIZE(dp);
 102                         len = GET_U_1(dp->ip6r_len);
 103                         switch (GET_U_1(dp->ip6r_type)) {
 104
 105                         case IPV6_RTHDR_TYPE_0:
 106                         case IPV6_RTHDR_TYPE_2:         /* Mobile IPv6 ID-20 */
 107                                 dp0 = (const struct ip6_rthdr0 *)dp;
 108                                 if (len % 2 == 1)
 109                                         goto trunc;
 110                                 len >>= 1;
 111                                 p = (const u_char *) dp0->ip6r0_addr;
 112                                 for (i = 0; i < len; i++) {
 113                                         ND_TCHECK_16(p);
 114                                         dst_addr = (const void *)p;
 115                                         p += 16;
 116                                 }
 117                                 break;
 118                         case IPV6_RTHDR_TYPE_4:
 119                                 /* IPv6 Segment Routing Header (SRH) */
 120                                 srh = (const struct ip6_srh *)dp;
 121                                 if (len % 2 == 1)
 122                                         goto trunc;
 123                                 p = (const u_char *) srh->srh_segments;
 124                                 /*
 125                                  * The list of segments are encoded in the reverse order.
 126                                  * Accordingly, the final DA is encoded in srh_segments[0]
 127                                  */
 128                                 ND_TCHECK_16(p);
 129                                 dst_addr = (const void *)p;
 130                                 break;
 131
 132                         default:
 133                                 break;
 134                         }
 135
 136                         /*
 137                          * Only one routing header to a customer.
 138                          */
 139                         goto done;
 140
 141                 case IPPROTO_AH:
 142                 case IPPROTO_ESP:
 143                 case IPPROTO_IPCOMP:
 144                 default:
 145                         /*
 146                          * AH and ESP are, in the RFCs that describe them,
 147                          * described as being "viewed as an end-to-end
 148                          * payload" "in the IPv6 context, so that they
 149                          * "should appear after hop-by-hop, routing, and
 150                          * fragmentation extension headers".  We assume
 151                          * that's the case, and stop as soon as we see
 152                          * one.  (We can't handle an ESP header in
 153                          * the general case anyway, as its length depends
 154                          * on the encryption algorithm.)
 155                          *
 156                          * IPComp is also "viewed as an end-to-end
 157                          * payload" "in the IPv6 context".
 158                          *
 159                          * All other protocols are assumed to be the final
 160                          * protocol.
 161                          */
 162                         goto done;
 163                 }
 164         }
 165
 166 done:
 167 trunc:
 168         UNALIGNED_MEMCPY(dst, dst_addr, sizeof(nd_ipv6));
 169 }
 170
 171 /*
 172  * Compute a V6-style checksum by building a pseudoheader.
 173  */
 174 uint16_t
 175 nextproto6_cksum(netdissect_options *ndo,
 176                  const struct ip6_hdr *ip6, const uint8_t *data,
 177                  u_int len, u_int covlen, uint8_t next_proto)
 178 {
 179         struct {
 180                 struct in6_addr ph_src;
 181                 struct in6_addr ph_dst;
 182                 uint32_t       ph_len;
 183                 uint8_t        ph_zero[3];
 184                 uint8_t        ph_nxt;
 185         } ph;
 186         struct cksum_vec vec[2];
 187         u_int nh;
 188
 189         /* pseudo-header */
 190         memset(&ph, 0, sizeof(ph));
 191         UNALIGNED_MEMCPY(&ph.ph_src, ip6->ip6_src, sizeof (struct in6_addr));
 192         nh = GET_U_1(ip6->ip6_nxt);
 193         switch (nh) {
 194
 195         case IPPROTO_HOPOPTS:
 196         case IPPROTO_DSTOPTS:
 197         case IPPROTO_MOBILITY_OLD:
 198         case IPPROTO_MOBILITY:
 199         case IPPROTO_FRAGMENT:
 200         case IPPROTO_ROUTING:
 201                 /*
 202                  * The next header is either a routing header or a header
 203                  * after which there might be a routing header, so scan
 204                  * for a routing header.
 205                  */
 206                 ip6_finddst(ndo, &ph.ph_dst, ip6);
 207                 break;
 208
 209         default:
 210                 UNALIGNED_MEMCPY(&ph.ph_dst, ip6->ip6_dst,
 211                                  sizeof (struct in6_addr));
 212                 break;
 213         }
 214         ph.ph_len = htonl(len);
 215         ph.ph_nxt = next_proto;
 216
 217         vec[0].ptr = (const uint8_t *)(void *)&ph;
 218         vec[0].len = sizeof(ph);
 219         vec[1].ptr = data;
 220         vec[1].len = covlen;
 221
 222         return in_cksum(vec, 2);
 223 }
 224
 225 /*
 226  * print an IP6 datagram.
 227  */
 228 void
 229 ip6_print(netdissect_options *ndo, const u_char *bp, u_int length)
 230 {
 231         const struct ip6_hdr *ip6;
 232         int advance;
 233         u_int len;
 234         u_int total_advance;
 235         const u_char *cp;
 236         uint32_t payload_len;
 237         uint8_t nh;
 238         int fragmented = 0;
 239         u_int flow;
 240         int found_extension_header;
 241         int found_jumbo;
 242
 243         ndo->ndo_protocol = "ip6";
 244         ip6 = (const struct ip6_hdr *)bp;
 245
 246         ND_TCHECK_SIZE(ip6);
 247         if (length < sizeof (struct ip6_hdr)) {
 248                 ND_PRINT("truncated-ip6 %u", length);
 249                 return;
 250         }
 251
 252         if (!ndo->ndo_eflag)
 253             ND_PRINT("IP6 ");
 254
 255         if (IP6_VERSION(ip6) != 6) {
 256           ND_PRINT("version error: %u != 6", IP6_VERSION(ip6));
 257           return;
 258         }
 259
 260         payload_len = GET_BE_U_2(ip6->ip6_plen);
 261         /*
 262          * RFC 1883 says:
 263          *
 264          * The Payload Length field in the IPv6 header must be set to zero
 265          * in every packet that carries the Jumbo Payload option.  If a
 266          * packet is received with a valid Jumbo Payload option present and
 267          * a non-zero IPv6 Payload Length field, an ICMP Parameter Problem
 268          * message, Code 0, should be sent to the packet's source, pointing
 269          * to the Option Type field of the Jumbo Payload option.
 270          *
 271          * Later versions of the IPv6 spec don't discuss the Jumbo Payload
 272          * option.
 273          *
 274          * If the payload length is 0, we temporarily just set the total
 275          * length to the remaining data in the packet (which, for Ethernet,
 276          * could include frame padding, but if it's a Jumbo Payload frame,
 277          * it shouldn't even be sendable over Ethernet, so we don't worry
 278          * about that), so we can process the extension headers in order
 279          * to *find* a Jumbo Payload hop-by-hop option and, when we've
 280          * processed all the extension headers, check whether we found
 281          * a Jumbo Payload option, and fail if we haven't.
 282          */
 283         if (payload_len != 0) {
 284                 len = payload_len + sizeof(struct ip6_hdr);
 285                 if (length < len)
 286                         ND_PRINT("truncated-ip6 - %u bytes missing!",
 287                                 len - length);
 288         } else
 289                 len = length + sizeof(struct ip6_hdr);
 290
 291         nh = GET_U_1(ip6->ip6_nxt);
 292         if (ndo->ndo_vflag) {
 293             flow = GET_BE_U_4(ip6->ip6_flow);
 294             ND_PRINT("(");
 295 #if 0
 296             /* rfc1883 */
 297             if (flow & 0x0f000000)
 298                 ND_PRINT("pri 0x%02x, ", (flow & 0x0f000000) >> 24);
 299             if (flow & 0x00ffffff)
 300                 ND_PRINT("flowlabel 0x%06x, ", flow & 0x00ffffff);
 301 #else
 302             /* RFC 2460 */
 303             if (flow & 0x0ff00000)
 304                 ND_PRINT("class 0x%02x, ", (flow & 0x0ff00000) >> 20);
 305             if (flow & 0x000fffff)
 306                 ND_PRINT("flowlabel 0x%05x, ", flow & 0x000fffff);
 307 #endif
 308
 309             ND_PRINT("hlim %u, next-header %s (%u) payload length: %u) ",
 310                          GET_U_1(ip6->ip6_hlim),
 311                          tok2str(ipproto_values,"unknown",nh),
 312                          nh,
 313                          payload_len);
 314         }
 315
 316         /*
 317          * Cut off the snapshot length to the end of the IP payload.
 318          */
 319         nd_push_snapend(ndo, bp + len);
 320
 321         cp = (const u_char *)ip6;
 322         advance = sizeof(struct ip6_hdr);
 323         total_advance = 0;
 324         /* Process extension headers */
 325         found_extension_header = 0;
 326         found_jumbo = 0;
 327         while (cp < ndo->ndo_snapend && advance > 0) {
 328                 if (len < (u_int)advance)
 329                         goto trunc;
 330                 cp += advance;
 331                 len -= advance;
 332                 total_advance += advance;
 333
 334                 if (cp == (const u_char *)(ip6 + 1) &&
 335                     nh != IPPROTO_TCP && nh != IPPROTO_UDP &&
 336                     nh != IPPROTO_DCCP && nh != IPPROTO_SCTP) {
 337                         ND_PRINT("%s > %s: ", ip6addr_string(ndo, ip6->ip6_src),
 338                                      ip6addr_string(ndo, ip6->ip6_dst));
 339                 }
 340
 341                 switch (nh) {
 342
 343                 case IPPROTO_HOPOPTS:
 344                         advance = hbhopt_process(ndo, cp, &found_jumbo, &payload_len);
 345                         if (advance < 0) {
 346                                 nd_pop_packet_info(ndo);
 347                                 return;
 348                         }
 349                         found_extension_header = 1;
 350                         nh = GET_U_1(cp);
 351                         break;
 352
 353                 case IPPROTO_DSTOPTS:
 354                         advance = dstopt_process(ndo, cp);
 355                         if (advance < 0) {
 356                                 nd_pop_packet_info(ndo);
 357                                 return;
 358                         }
 359                         found_extension_header = 1;
 360                         nh = GET_U_1(cp);
 361                         break;
 362
 363                 case IPPROTO_FRAGMENT:
 364                         advance = frag6_print(ndo, cp, (const u_char *)ip6);
 365                         if (advance < 0 || ndo->ndo_snapend <= cp + advance) {
 366                                 nd_pop_packet_info(ndo);
 367                                 return;
 368                         }
 369                         found_extension_header = 1;
 370                         nh = GET_U_1(cp);
 371                         fragmented = 1;
 372                         break;
 373
 374                 case IPPROTO_MOBILITY_OLD:
 375                 case IPPROTO_MOBILITY:
 376                         /*
 377                          * XXX - we don't use "advance"; RFC 3775 says that
 378                          * the next header field in a mobility header
 379                          * should be IPPROTO_NONE, but speaks of
 380                          * the possiblity of a future extension in
 381                          * which payload can be piggybacked atop a
 382                          * mobility header.
 383                          */
 384                         advance = mobility_print(ndo, cp, (const u_char *)ip6);
 385                         if (advance < 0) {
 386                                 nd_pop_packet_info(ndo);
 387                                 return;
 388                         }
 389                         found_extension_header = 1;
 390                         nh = GET_U_1(cp);
 391                         nd_pop_packet_info(ndo);
 392                         return;
 393
 394                 case IPPROTO_ROUTING:
 395                         ND_TCHECK_1(cp);
 396                         advance = rt6_print(ndo, cp, (const u_char *)ip6);
 397                         if (advance < 0) {
 398                                 nd_pop_packet_info(ndo);
 399                                 return;
 400                         }
 401                         found_extension_header = 1;
 402                         nh = GET_U_1(cp);
 403                         break;
 404
 405                 default:
 406                         /*
 407                          * Not an extension header; hand off to the
 408                          * IP protocol demuxer.
 409                          */
 410                         if (found_jumbo) {
 411                                 /*
 412                                  * We saw a Jumbo Payload option.
 413                                  * Set the length to the payload length
 414                                  * plus the IPv6 header length, and
 415                                  * change the snapshot length accordingly.
 416                                  */
 417                                 len = payload_len + sizeof(struct ip6_hdr);
 418                                 if (length < len)
 419                                         ND_PRINT("truncated-ip6 - %u bytes missing!",
 420                                                 len - length);
 421                                 nd_change_snapend(ndo, bp + len);
 422
 423                                 /*
 424                                  * Now subtract the length of the IPv6
 425                                  * header plus extension headers to get
 426                                  * the payload length.
 427                                  */
 428                                 len -= total_advance;
 429                         } else {
 430                                 /*
 431                                  * We didn't see a Jumbo Payload option;
 432                                  * was the payload length zero?
 433                                  */
 434                                 if (payload_len == 0) {
 435                                         /*
 436                                          * Yes.  If we found an extension
 437                                          * header, treat that as a truncated
 438                                          * packet header, as there was
 439                                          * no payload to contain an
 440                                          * extension header.
 441                                          */
 442                                         if (found_extension_header)
 443                                                 goto trunc;
 444
 445                                         /*
 446                                          * OK, we didn't see any extnesion
 447                                          * header, but that means we have
 448                                          * no payload, so set the length
 449                                          * to the IPv6 header length,
 450                                          * and change the snapshot length
 451                                          * accordingly.
 452                                          */
 453                                         len = sizeof(struct ip6_hdr);
 454                                         nd_change_snapend(ndo, bp + len);
 455
 456                                         /*
 457                                          * Now subtract the length of
 458                                          * the IPv6 header plus extension
 459                                          * headers (there weren't any, so
 460                                          * that's just the IPv6 header
 461                                          * length) to get the payload length.
 462                                          */
 463                                         len -= total_advance;
 464                                 }
 465                         }
 466                         ip_print_demux(ndo, cp, len, 6, fragmented,
 467                             GET_U_1(ip6->ip6_hlim), nh, bp);
 468                         nd_pop_packet_info(ndo);
 469                         return;
 470                 }
 471
 472                 /* ndo_protocol reassignment after xxx_print() calls */
 473                 ndo->ndo_protocol = "ip6";
 474         }
 475
 476         nd_pop_packet_info(ndo);
 477         return;
 478 trunc:
 479         nd_print_trunc(ndo);
 480 }