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, nd_ipv6 *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                         advance = (GET_U_1(cp + 1) + 1) << 3;
  81                         nh = GET_U_1(cp);
  82                         break;
  83
  84                 case IPPROTO_FRAGMENT:
  85                         /*
  86                          * The byte following the next header byte is
  87                          * marked as reserved, and the header is always
  88                          * the same size.
  89                          */
  90                         advance = sizeof(struct ip6_frag);
  91                         nh = GET_U_1(cp);
  92                         break;
  93
  94                 case IPPROTO_ROUTING:
  95                         /*
  96                          * OK, we found it.
  97                          */
  98                         dp = (const struct ip6_rthdr *)cp;
  99                         ND_TCHECK_SIZE(dp);
 100                         len = GET_U_1(dp->ip6r_len);
 101                         switch (GET_U_1(dp->ip6r_type)) {
 102
 103                         case IPV6_RTHDR_TYPE_0:
 104                         case IPV6_RTHDR_TYPE_2:         /* Mobile IPv6 ID-20 */
 105                                 dp0 = (const struct ip6_rthdr0 *)dp;
 106                                 if (len % 2 == 1)
 107                                         goto trunc;
 108                                 len >>= 1;
 109                                 p = (const u_char *) dp0->ip6r0_addr;
 110                                 for (i = 0; i < len; i++) {
 111                                         ND_TCHECK_16(p);
 112                                         dst_addr = (const void *)p;
 113                                         p += 16;
 114                                 }
 115                                 break;
 116                         case IPV6_RTHDR_TYPE_4:
 117                                 /* IPv6 Segment Routing Header (SRH) */
 118                                 srh = (const struct ip6_srh *)dp;
 119                                 if (len % 2 == 1)
 120                                         goto trunc;
 121                                 p = (const u_char *) srh->srh_segments;
 122                                 /*
 123                                  * The list of segments are encoded in the reverse order.
 124                                  * Accordingly, the final DA is encoded in srh_segments[0]
 125                                  */
 126                                 ND_TCHECK_16(p);
 127                                 dst_addr = (const void *)p;
 128                                 break;
 129
 130                         default:
 131                                 break;
 132                         }
 133
 134                         /*
 135                          * Only one routing header to a customer.
 136                          */
 137                         goto done;
 138
 139                 case IPPROTO_AH:
 140                 case IPPROTO_ESP:
 141                 case IPPROTO_IPCOMP:
 142                 default:
 143                         /*
 144                          * AH and ESP are, in the RFCs that describe them,
 145                          * described as being "viewed as an end-to-end
 146                          * payload" "in the IPv6 context, so that they
 147                          * "should appear after hop-by-hop, routing, and
 148                          * fragmentation extension headers".  We assume
 149                          * that's the case, and stop as soon as we see
 150                          * one.  (We can't handle an ESP header in
 151                          * the general case anyway, as its length depends
 152                          * on the encryption algorithm.)
 153                          *
 154                          * IPComp is also "viewed as an end-to-end
 155                          * payload" "in the IPv6 context".
 156                          *
 157                          * All other protocols are assumed to be the final
 158                          * protocol.
 159                          */
 160                         goto done;
 161                 }
 162         }
 163
 164 done:
 165 trunc:
 166         GET_CPY_BYTES(dst, dst_addr, sizeof(nd_ipv6));
 167 }
 168
 169 /*
 170  * Compute a V6-style checksum by building a pseudoheader.
 171  */
 172 uint16_t
 173 nextproto6_cksum(netdissect_options *ndo,
 174                  const struct ip6_hdr *ip6, const uint8_t *data,
 175                  u_int len, u_int covlen, uint8_t next_proto)
 176 {
 177         struct {
 178                 nd_ipv6 ph_src;
 179                 nd_ipv6 ph_dst;
 180                 uint32_t       ph_len;
 181                 uint8_t        ph_zero[3];
 182                 uint8_t        ph_nxt;
 183         } ph;
 184         struct cksum_vec vec[2];
 185         u_int nh;
 186
 187         /* pseudo-header */
 188         memset(&ph, 0, sizeof(ph));
 189         GET_CPY_BYTES(&ph.ph_src, ip6->ip6_src, sizeof(nd_ipv6));
 190         nh = GET_U_1(ip6->ip6_nxt);
 191         switch (nh) {
 192
 193         case IPPROTO_HOPOPTS:
 194         case IPPROTO_DSTOPTS:
 195         case IPPROTO_MOBILITY_OLD:
 196         case IPPROTO_MOBILITY:
 197         case IPPROTO_FRAGMENT:
 198         case IPPROTO_ROUTING:
 199                 /*
 200                  * The next header is either a routing header or a header
 201                  * after which there might be a routing header, so scan
 202                  * for a routing header.
 203                  */
 204                 ip6_finddst(ndo, &ph.ph_dst, ip6);
 205                 break;
 206
 207         default:
 208                 GET_CPY_BYTES(&ph.ph_dst, ip6->ip6_dst, sizeof(nd_ipv6));
 209                 break;
 210         }
 211         ph.ph_len = htonl(len);
 212         ph.ph_nxt = next_proto;
 213
 214         vec[0].ptr = (const uint8_t *)(void *)&ph;
 215         vec[0].len = sizeof(ph);
 216         vec[1].ptr = data;
 217         vec[1].len = covlen;
 218
 219         return in_cksum(vec, 2);
 220 }
 221
 222 /*
 223  * print an IP6 datagram.
 224  */
 225 void
 226 ip6_print(netdissect_options *ndo, const u_char *bp, u_int length)
 227 {
 228         const struct ip6_hdr *ip6;
 229         int advance;
 230         u_int len;
 231         u_int total_advance;
 232         const u_char *cp;
 233         uint32_t payload_len;
 234         uint8_t nh;
 235         int fragmented = 0;
 236         u_int flow;
 237         int found_extension_header;
 238         int found_jumbo;
 239
 240         ndo->ndo_protocol = "ip6";
 241         ip6 = (const struct ip6_hdr *)bp;
 242
 243         ND_TCHECK_SIZE(ip6);
 244         if (length < sizeof (struct ip6_hdr)) {
 245                 ND_PRINT("truncated-ip6 %u", length);
 246                 return;
 247         }
 248
 249         if (!ndo->ndo_eflag)
 250             ND_PRINT("IP6 ");
 251
 252         if (IP6_VERSION(ip6) != 6) {
 253           ND_PRINT("version error: %u != 6", IP6_VERSION(ip6));
 254           return;
 255         }
 256
 257         payload_len = GET_BE_U_2(ip6->ip6_plen);
 258         /*
 259          * RFC 1883 says:
 260          *
 261          * The Payload Length field in the IPv6 header must be set to zero
 262          * in every packet that carries the Jumbo Payload option.  If a
 263          * packet is received with a valid Jumbo Payload option present and
 264          * a non-zero IPv6 Payload Length field, an ICMP Parameter Problem
 265          * message, Code 0, should be sent to the packet's source, pointing
 266          * to the Option Type field of the Jumbo Payload option.
 267          *
 268          * Later versions of the IPv6 spec don't discuss the Jumbo Payload
 269          * option.
 270          *
 271          * If the payload length is 0, we temporarily just set the total
 272          * length to the remaining data in the packet (which, for Ethernet,
 273          * could include frame padding, but if it's a Jumbo Payload frame,
 274          * it shouldn't even be sendable over Ethernet, so we don't worry
 275          * about that), so we can process the extension headers in order
 276          * to *find* a Jumbo Payload hop-by-hop option and, when we've
 277          * processed all the extension headers, check whether we found
 278          * a Jumbo Payload option, and fail if we haven't.
 279          */
 280         if (payload_len != 0) {
 281                 len = payload_len + sizeof(struct ip6_hdr);
 282                 if (length < len)
 283                         ND_PRINT("truncated-ip6 - %u bytes missing!",
 284                                 len - length);
 285         } else
 286                 len = length + sizeof(struct ip6_hdr);
 287
 288         nh = GET_U_1(ip6->ip6_nxt);
 289         if (ndo->ndo_vflag) {
 290             flow = GET_BE_U_4(ip6->ip6_flow);
 291             ND_PRINT("(");
 292             /* RFC 2460 */
 293             if (flow & 0x0ff00000)
 294                 ND_PRINT("class 0x%02x, ", (flow & 0x0ff00000) >> 20);
 295             if (flow & 0x000fffff)
 296                 ND_PRINT("flowlabel 0x%05x, ", flow & 0x000fffff);
 297
 298             ND_PRINT("hlim %u, next-header %s (%u) payload length: %u) ",
 299                          GET_U_1(ip6->ip6_hlim),
 300                          tok2str(ipproto_values,"unknown",nh),
 301                          nh,
 302                          payload_len);
 303         }
 304
 305         /*
 306          * Cut off the snapshot length to the end of the IP payload.
 307          */
 308         if (!nd_push_snaplen(ndo, bp, len)) {
 309                 (*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
 310                         "%s: can't push snaplen on buffer stack", __func__);
 311         }
 312
 313         cp = (const u_char *)ip6;
 314         advance = sizeof(struct ip6_hdr);
 315         total_advance = 0;
 316         /* Process extension headers */
 317         found_extension_header = 0;
 318         found_jumbo = 0;
 319         while (cp < ndo->ndo_snapend && advance > 0) {
 320                 if (len < (u_int)advance)
 321                         goto trunc;
 322                 cp += advance;
 323                 len -= advance;
 324                 total_advance += advance;
 325
 326                 if (cp == (const u_char *)(ip6 + 1) &&
 327                     nh != IPPROTO_TCP && nh != IPPROTO_UDP &&
 328                     nh != IPPROTO_DCCP && nh != IPPROTO_SCTP) {
 329                         ND_PRINT("%s > %s: ", GET_IP6ADDR_STRING(ip6->ip6_src),
 330                                      GET_IP6ADDR_STRING(ip6->ip6_dst));
 331                 }
 332
 333                 switch (nh) {
 334
 335                 case IPPROTO_HOPOPTS:
 336                         advance = hbhopt_process(ndo, cp, &found_jumbo, &payload_len);
 337                         if (advance < 0) {
 338                                 nd_pop_packet_info(ndo);
 339                                 return;
 340                         }
 341                         found_extension_header = 1;
 342                         nh = GET_U_1(cp);
 343                         break;
 344
 345                 case IPPROTO_DSTOPTS:
 346                         advance = dstopt_process(ndo, cp);
 347                         if (advance < 0) {
 348                                 nd_pop_packet_info(ndo);
 349                                 return;
 350                         }
 351                         found_extension_header = 1;
 352                         nh = GET_U_1(cp);
 353                         break;
 354
 355                 case IPPROTO_FRAGMENT:
 356                         advance = frag6_print(ndo, cp, (const u_char *)ip6);
 357                         if (advance < 0 || ndo->ndo_snapend <= cp + advance) {
 358                                 nd_pop_packet_info(ndo);
 359                                 return;
 360                         }
 361                         found_extension_header = 1;
 362                         nh = GET_U_1(cp);
 363                         fragmented = 1;
 364                         break;
 365
 366                 case IPPROTO_MOBILITY_OLD:
 367                 case IPPROTO_MOBILITY:
 368                         /*
 369                          * XXX - we don't use "advance"; RFC 3775 says that
 370                          * the next header field in a mobility header
 371                          * should be IPPROTO_NONE, but speaks of
 372                          * the possibility of a future extension in
 373                          * which payload can be piggybacked atop a
 374                          * mobility header.
 375                          */
 376                         advance = mobility_print(ndo, cp, (const u_char *)ip6);
 377                         if (advance < 0) {
 378                                 nd_pop_packet_info(ndo);
 379                                 return;
 380                         }
 381                         found_extension_header = 1;
 382                         nh = GET_U_1(cp);
 383                         nd_pop_packet_info(ndo);
 384                         return;
 385
 386                 case IPPROTO_ROUTING:
 387                         ND_TCHECK_1(cp);
 388                         advance = rt6_print(ndo, cp, (const u_char *)ip6);
 389                         if (advance < 0) {
 390                                 nd_pop_packet_info(ndo);
 391                                 return;
 392                         }
 393                         found_extension_header = 1;
 394                         nh = GET_U_1(cp);
 395                         break;
 396
 397                 default:
 398                         /*
 399                          * Not an extension header; hand off to the
 400                          * IP protocol demuxer.
 401                          */
 402                         if (found_jumbo) {
 403                                 /*
 404                                  * We saw a Jumbo Payload option.
 405                                  * Set the length to the payload length
 406                                  * plus the IPv6 header length, and
 407                                  * change the snapshot length accordingly.
 408                                  *
 409                                  * But make sure it's not shorter than
 410                                  * the total number of bytes we've
 411                                  * processed so far.
 412                                  */
 413                                 len = payload_len + sizeof(struct ip6_hdr);
 414                                 if (len < total_advance)
 415                                         goto trunc;
 416                                 if (length < len)
 417                                         ND_PRINT("truncated-ip6 - %u bytes missing!",
 418                                                 len - length);
 419                                 nd_change_snaplen(ndo, bp, len);
 420
 421                                 /*
 422                                  * Now subtract the length of the IPv6
 423                                  * header plus extension headers to get
 424                                  * the payload length.
 425                                  */
 426                                 len -= total_advance;
 427                         } else {
 428                                 /*
 429                                  * We didn't see a Jumbo Payload option;
 430                                  * was the payload length zero?
 431                                  */
 432                                 if (payload_len == 0) {
 433                                         /*
 434                                          * Yes.  If we found an extension
 435                                          * header, treat that as a truncated
 436                                          * packet header, as there was
 437                                          * no payload to contain an
 438                                          * extension header.
 439                                          */
 440                                         if (found_extension_header)
 441                                                 goto trunc;
 442
 443                                         /*
 444                                          * OK, we didn't see any extension
 445                                          * header, but that means we have
 446                                          * no payload, so set the length
 447                                          * to the IPv6 header length,
 448                                          * and change the snapshot length
 449                                          * accordingly.
 450                                          */
 451                                         len = sizeof(struct ip6_hdr);
 452                                         nd_change_snaplen(ndo, bp, len);
 453
 454                                         /*
 455                                          * Now subtract the length of
 456                                          * the IPv6 header plus extension
 457                                          * headers (there weren't any, so
 458                                          * that's just the IPv6 header
 459                                          * length) to get the payload length.
 460                                          */
 461                                         len -= total_advance;
 462                                 }
 463                         }
 464                         ip_demux_print(ndo, cp, len, 6, fragmented,
 465                                        GET_U_1(ip6->ip6_hlim), nh, bp);
 466                         nd_pop_packet_info(ndo);
 467                         return;
 468                 }
 469
 470                 /* ndo_protocol reassignment after xxx_print() calls */
 471                 ndo->ndo_protocol = "ip6";
 472         }
 473
 474         nd_pop_packet_info(ndo);
 475         return;
 476 trunc:
 477         nd_print_trunc(ndo);
 478 }