2 * Routines for Token-Ring packet disassembly
3 * Gilbert Ramirez <gram@alumni.rice.edu>
5 * $Id: packet-tr.c,v 1.70 2002/04/14 23:04:04 guy Exp $
7 * Ethereal - Network traffic analyzer
8 * By Gerald Combs <gerald@ethereal.com>
9 * Copyright 1998 Gerald Combs
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version 2
14 * of the License, or (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
30 #ifdef HAVE_SYS_TYPES_H
31 # include <sys/types.h>
37 #include <epan/packet.h>
38 #include "packet-tr.h"
39 #include "packet-llc.h"
41 static int proto_tr = -1;
42 static int hf_tr_dst = -1;
43 static int hf_tr_src = -1;
44 static int hf_tr_addr = -1;
45 static int hf_tr_sr = -1;
46 static int hf_tr_ac = -1;
47 static int hf_tr_priority = -1;
48 static int hf_tr_frame = -1;
49 static int hf_tr_monitor_cnt = -1;
50 static int hf_tr_priority_reservation = -1;
51 static int hf_tr_fc = -1;
52 static int hf_tr_fc_type = -1;
53 static int hf_tr_fc_pcf = -1;
54 static int hf_tr_rif_bytes = -1;
55 static int hf_tr_broadcast = -1;
56 static int hf_tr_max_frame_size = -1;
57 static int hf_tr_direction = -1;
58 static int hf_tr_rif = -1;
59 static int hf_tr_rif_ring = -1;
60 static int hf_tr_rif_bridge = -1;
62 static gint ett_token_ring = -1;
63 static gint ett_token_ring_ac = -1;
64 static gint ett_token_ring_fc = -1;
66 #define TR_MIN_HEADER_LEN 14
67 #define TR_MAX_HEADER_LEN 32
69 static const true_false_string ac_truth = { "Frame", "Token" };
71 static const value_string pcf_vals[] = {
72 { 0, "Normal buffer" },
73 { 1, "Express buffer" },
77 { 5, "Active Monitor Present" },
78 { 6, "Standby Monitor Present" },
82 static const value_string frame_vals[] = {
89 static const value_string broadcast_vals[] = {
90 { 0 << 5, "Non-broadcast" },
91 { 1 << 5, "Non-broadcast" },
92 { 2 << 5, "Non-broadcast" },
93 { 3 << 5, "Non-broadcast" },
94 { 4 << 5, "All-routes broadcast" },
95 { 5 << 5, "All-routes broadcast" },
96 { 6 << 5, "Single-route broadcast" },
97 { 7 << 5, "Single-route broadcast" },
101 static const value_string max_frame_size_vals[] = {
113 static const value_string direction_vals[] = {
114 { 0, "From originating station (-->)" },
115 { 128, "To originating station (<--)" },
119 static dissector_handle_t trmac_handle;
120 static dissector_handle_t llc_handle;
121 static dissector_handle_t data_handle;
124 * DODGY LINUX HACK DODGY LINUX HACK
125 * Linux 2.0.x always passes frames to the Token Ring driver for transmission with
126 * 18 bytes padding for source routing information. Some drivers copy the first
127 * (18 - srlen) bytes up the frame (18 - srlen) bytes thus removing the padding.
128 * Other drivers just make a copy of the entire frame and then hack about with it
129 * so the frame the sniffer gets is fine (just has extra sr routing).
130 * In the first instance (driver hacking frame in situ) the sniffer gets a garbled
132 * This function trys to detect this and returns the offset of where
133 * the frame really starts.
134 * This only detects frames that we have sent ourselves so if we are packet sniffing
135 * on the machine we are watching this is useful.
136 * Compare offset 0 with offset x+1 for a length of x bytes for all value of x = 1 to 18
137 * if match then Linux driver has done in situ source route compression of the crappy
138 * Linux 2.0.x frame so the beginning of the real frame is x bytes in.
139 * (And this real frame x bytes in looks like a proper TR frame that goes on the wire
140 * with none of the Linux idiosyncrasies).
143 int check_for_old_linux_tvb(tvbuff_t *tvb)
148 /* Restrict our looping to the boundaries of the frame */
149 bytes = tvb_length(tvb);
154 data = tvb_get_ptr(tvb, 0, bytes);
156 for(x = 1; x <= bytes-1 ;x++)
158 if (memcmp(&data[0], &data[x], x) == 0)
167 int check_for_old_linux(const u_char * pd)
172 if (memcmp(&pd[0],&pd[x],x) == 0)
182 add_ring_bridge_pairs(int rcf_len, tvbuff_t*, proto_tree *tree);
185 capture_tr(const u_char *pd, int offset, int len, packet_counts *ld) {
187 int source_routed = 0;
190 guint8 trn_rif_bytes;
191 guint8 actual_rif_bytes;
194 /* The trn_hdr struct, as separate variables */
195 guint8 trn_fc; /* field control field */
196 const guint8 *trn_shost; /* source host */
198 if (!BYTES_ARE_IN_FRAME(offset, len, TR_MIN_HEADER_LEN)) {
203 if ((x = check_for_old_linux(pd)))
205 /* Actually packet starts x bytes into what we have got but with all
206 source routing compressed
208 /* pd = &pd[x]; */ offset+=x;
212 trn_fc = pd[offset + 1];
213 trn_shost = &pd[offset + 8];
215 frame_type = (trn_fc & 192) >> 6;
217 /* if the high bit on the first byte of src hwaddr is 1, then
218 this packet is source-routed */
219 source_routed = trn_shost[0] & 128;
221 trn_rif_bytes = pd[offset + 14] & 31;
223 /* the Linux 2.0 TR code strips source-route bits in
224 * order to test for SR. This can be removed from most
225 * packets with oltr, but not all. So, I try to figure out
226 * which packets should have been SR here. I'll check to
227 * see if there's a SNAP or IPX field right after
230 if (!source_routed && trn_rif_bytes > 0) {
231 if (pd[offset + 0x0e] != pd[offset + 0x0f]) {
232 first2_sr = pntohs(&pd[offset + 0xe0 + trn_rif_bytes]);
234 (first2_sr == 0xaaaa &&
235 pd[offset + 0x10 + trn_rif_bytes] == 0x03) ||
237 first2_sr == 0xe0e0 ||
238 first2_sr == 0xe0aa ) {
246 actual_rif_bytes = trn_rif_bytes;
250 actual_rif_bytes = 0;
253 /* this is a silly hack for Linux 2.0.x. Read the comment below,
254 in front of the other #ifdef linux. If we're sniffing our own NIC,
255 we get a full RIF, sometimes with garbage */
256 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
257 (!source_routed && frame_type == 1)) {
258 /* look for SNAP or IPX only */
259 if ( (pd[offset + 0x20] == 0xaa && pd[offset + 0x21] == 0xaa && pd[offset + 0x22] == 03) ||
260 (pd[offset + 0x20] == 0xe0 && pd[offset + 0x21] == 0xe0) ) {
261 actual_rif_bytes = 18;
263 pd[offset + 0x23] == 0 &&
264 pd[offset + 0x24] == 0 &&
265 pd[offset + 0x25] == 0 &&
266 pd[offset + 0x26] == 0x00 &&
267 pd[offset + 0x27] == 0x11) {
269 actual_rif_bytes = 18;
271 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
272 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
273 (i.e. for non SNAP frames e.g. for Netware frames)
274 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
275 bytes as zero frame looks like :-
276 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
277 offset += 8; /* Skip fake LLC and SNAP */
281 offset += actual_rif_bytes + TR_MIN_HEADER_LEN;
283 /* The package is either MAC or LLC */
284 switch (frame_type) {
290 capture_llc(pd, offset, len, ld);
293 /* non-MAC, non-LLC, i.e., "Reserved" */
301 dissect_tr(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
303 proto_tree *tr_tree, *bf_tree;
309 volatile int fixoffset = 0;
310 volatile int source_routed = 0;
311 volatile guint8 trn_rif_bytes;
312 volatile guint8 actual_rif_bytes;
313 volatile guint8 c1_nonsr;
314 volatile guint8 c2_nonsr;
315 volatile guint16 first2_sr;
316 tvbuff_t *volatile tr_tvb;
318 /* The trn_hdr struct, as separate variables */
319 guint8 trn_ac; /* access control field */
320 guint8 trn_fc; /* field control field */
321 const guint8 *trn_dhost; /* destination host */
322 const guint8 *trn_shost; /* source host */
324 /* non-source-routed version of source addr */
325 static guint8 trn_shost_nonsr[6];
328 /* Token-Ring Strings */
329 char *fc[] = { "MAC", "LLC", "Reserved", "Unknown" };
331 if (check_col(pinfo->cinfo, COL_PROTOCOL))
332 col_set_str(pinfo->cinfo, COL_PROTOCOL, "TR");
334 if ((x = check_for_old_linux_tvb((tvbuff_t*) tvb))) {
335 /* Actually packet starts x bytes into what we have got but with all
336 source routing compressed. See comment above */
337 tr_tvb = tvb_new_subset((tvbuff_t*) tvb, x, -1, -1);
344 trn_fc = tvb_get_guint8(tr_tvb, 1);
345 trn_dhost = tvb_get_ptr(tr_tvb, 2, 6);
346 trn_shost = tvb_get_ptr(tr_tvb, 8, 6);
349 memcpy(trn_shost_nonsr, trn_shost, 6);
350 trn_shost_nonsr[0] &= 127;
351 frame_type = (trn_fc & 192) >> 6;
353 if (check_col(pinfo->cinfo, COL_INFO))
354 col_add_fstr(pinfo->cinfo, COL_INFO, "Token-Ring %s", fc[frame_type]);
356 /* if the high bit on the first byte of src hwaddr is 1, then
357 this packet is source-routed */
358 source_routed = trn_shost[0] & 128;
360 trn_rif_bytes = tvb_get_guint8(tr_tvb, 14) & 31;
362 /* the Linux 2.0 TR code strips source-route bits in
363 * order to test for SR. This can be removed from most
364 * packets with oltr, but not all. So, I try to figure out
365 * which packets should have been SR here. I'll check to
366 * see if there's a SNAP or IPX field right after
369 if (frame_type == 1 && !source_routed && trn_rif_bytes > 0) {
372 c1_nonsr = tvb_get_guint8(tr_tvb, 14);
373 c2_nonsr = tvb_get_guint8(tr_tvb, 15);
375 if (c1_nonsr != c2_nonsr) {
377 first2_sr = tvb_get_ntohs(tr_tvb, trn_rif_bytes + 0x0e);
379 if ( ( first2_sr == 0xaaaa &&
380 tvb_get_guint8(tr_tvb, trn_rif_bytes + 0x10) == 0x03) ||
382 first2_sr == 0xe0e0 ||
383 first2_sr == 0xe0aa ) {
390 /* We had no information beyond the TR header. Just assume
391 * this is a normal (non-Linux) TR header. */
398 actual_rif_bytes = trn_rif_bytes;
402 actual_rif_bytes = 0;
405 /* this is a silly hack for Linux 2.0.x. Read the comment below,
406 in front of the other #ifdef linux. If we're sniffing our own NIC,
407 we get a full RIF, sometimes with garbage */
409 if (frame_type == 1 && ( (source_routed && trn_rif_bytes == 2) ||
411 /* look for SNAP or IPX only */
413 (tvb_get_ntohs(tr_tvb, 0x20) == 0xaaaa &&
414 tvb_get_guint8(tr_tvb, 0x22) == 0x03)
416 tvb_get_ntohs(tr_tvb, 0x20) == 0xe0e0 ) {
418 actual_rif_bytes = 18;
421 tvb_get_ntohl(tr_tvb, 0x23) == 0 &&
422 tvb_get_guint8(tr_tvb, 0x27) == 0x11) {
424 actual_rif_bytes = 18;
426 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
427 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
428 (i.e. for non SNAP frames e.g. for Netware frames)
429 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
430 bytes as zero frame looks like :-
431 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
432 fixoffset += 8; /* Skip fake LLC and SNAP */
437 /* We had no information beyond the TR header. Just assume
438 * this is a normal (non-Linux) TR header. */
444 /* XXX - copy it to some buffer associated with "*pinfo", rather than
445 just making "trn_shost_nonsr" static? */
446 SET_ADDRESS(&pinfo->dl_src, AT_ETHER, 6, trn_shost_nonsr);
447 SET_ADDRESS(&pinfo->src, AT_ETHER, 6, trn_shost_nonsr);
448 SET_ADDRESS(&pinfo->dl_dst, AT_ETHER, 6, trn_dhost);
449 SET_ADDRESS(&pinfo->dst, AT_ETHER, 6, trn_dhost);
451 /* protocol analysis tree */
453 /* Create Token-Ring Tree */
454 ti = proto_tree_add_item(tree, proto_tr, tr_tvb, 0, TR_MIN_HEADER_LEN + actual_rif_bytes, FALSE);
455 tr_tree = proto_item_add_subtree(ti, ett_token_ring);
457 /* Create the Access Control bitfield tree */
458 trn_ac = tvb_get_guint8(tr_tvb, 0);
459 ti = proto_tree_add_uint(tr_tree, hf_tr_ac, tr_tvb, 0, 1, trn_ac);
460 bf_tree = proto_item_add_subtree(ti, ett_token_ring_ac);
462 proto_tree_add_uint(bf_tree, hf_tr_priority, tr_tvb, 0, 1, trn_ac);
463 proto_tree_add_boolean(bf_tree, hf_tr_frame, tr_tvb, 0, 1, trn_ac);
464 proto_tree_add_uint(bf_tree, hf_tr_monitor_cnt, tr_tvb, 0, 1, trn_ac);
465 proto_tree_add_uint(bf_tree, hf_tr_priority_reservation, tr_tvb, 0, 1, trn_ac);
467 /* Create the Frame Control bitfield tree */
468 ti = proto_tree_add_uint(tr_tree, hf_tr_fc, tr_tvb, 1, 1, trn_fc);
469 bf_tree = proto_item_add_subtree(ti, ett_token_ring_fc);
471 proto_tree_add_uint(bf_tree, hf_tr_fc_type, tr_tvb, 1, 1, trn_fc);
472 proto_tree_add_uint(bf_tree, hf_tr_fc_pcf, tr_tvb, 1, 1, trn_fc);
473 proto_tree_add_ether(tr_tree, hf_tr_dst, tr_tvb, 2, 6, trn_dhost);
474 proto_tree_add_ether(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost);
475 proto_tree_add_ether_hidden(tr_tree, hf_tr_addr, tr_tvb, 2, 6, trn_dhost);
476 proto_tree_add_ether_hidden(tr_tree, hf_tr_addr, tr_tvb, 8, 6, trn_shost);
478 proto_tree_add_boolean(tr_tree, hf_tr_sr, tr_tvb, 8, 1, source_routed);
480 /* non-source-routed version of src addr */
481 proto_tree_add_ether_hidden(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost_nonsr);
485 rcf1 = tvb_get_guint8(tr_tvb, 14);
486 proto_tree_add_uint(tr_tree, hf_tr_rif_bytes, tr_tvb, 14, 1, trn_rif_bytes);
487 proto_tree_add_uint(tr_tree, hf_tr_broadcast, tr_tvb, 14, 1, rcf1 & 224);
490 rcf2 = tvb_get_guint8(tr_tvb, 15);
491 proto_tree_add_uint(tr_tree, hf_tr_max_frame_size, tr_tvb, 15, 1, rcf2 & 112);
492 proto_tree_add_uint(tr_tree, hf_tr_direction, tr_tvb, 15, 1, rcf2 & 128);
494 /* if we have more than 2 bytes of RIF, then we have
496 if (trn_rif_bytes > 2) {
497 add_ring_bridge_pairs(trn_rif_bytes, tr_tvb, tr_tree);
501 /* Linux 2.0.x has a problem in that the 802.5 code creates
502 an emtpy full (18-byte) RIF area. It's up to the tr driver to
503 either fill it in or remove it before sending the bytes out
504 to the wire. If you run tcpdump on a Linux 2.0.x machine running
505 token-ring, tcpdump will capture these 18 filler bytes. They
506 are filled with garbage. The best way to detect this problem is
507 to know the src hwaddr of the machine from which you were running
508 tcpdump. W/o that, however, I'm guessing that DSAP == SSAP if the
509 frame type is LLC. It's very much a hack. */
510 if (actual_rif_bytes > trn_rif_bytes) {
511 proto_tree_add_text(tr_tree, tr_tvb, TR_MIN_HEADER_LEN + trn_rif_bytes, actual_rif_bytes - trn_rif_bytes,
512 "Empty RIF from Linux 2.0.x driver. The sniffing NIC "
513 "is also running a protocol stack.");
516 proto_tree_add_text(tr_tree, tr_tvb, TR_MIN_HEADER_LEN + 18,8,"Linux 2.0.x fake LLC and SNAP header");
520 next_tvb = tvb_new_subset(tr_tvb, TR_MIN_HEADER_LEN + actual_rif_bytes + fixoffset, -1, -1);
522 /* The package is either MAC or LLC */
523 switch (frame_type) {
526 call_dissector(trmac_handle, next_tvb, pinfo, tree);
529 call_dissector(llc_handle, next_tvb, pinfo, tree);
532 /* non-MAC, non-LLC, i.e., "Reserved" */
533 call_dissector(data_handle,next_tvb, pinfo, tree);
538 /* this routine is taken from the Linux net/802/tr.c code, which shows
539 ring-bridge pairs in the /proc/net/tr_rif virtual file. */
541 add_ring_bridge_pairs(int rcf_len, tvbuff_t *tvb, proto_tree *tree)
544 int segment, brdgnmb, unprocessed_rif;
547 #define RIF_OFFSET 16
548 #define RIF_BYTES_TO_PROCESS 30
550 char buffer[3 + (RIF_BYTES_TO_PROCESS / 2) * 6 + 1];
552 /* Only process so many bytes of RIF, as per TR spec, and not overflow
553 * static buffer above */
554 unprocessed_rif = rcf_len - RIF_BYTES_TO_PROCESS;
555 rcf_len = MIN(rcf_len, RIF_BYTES_TO_PROCESS);
557 /* Ignore the 2 RCF bytes, since they don't make up the ring/bride pairs */
560 for(j = 1; j < rcf_len - 1; j += 2) {
562 segment = tvb_get_ntohs(tvb, RIF_OFFSET) >> 4;
563 size = sprintf(buffer, "%03X",segment);
564 proto_tree_add_uint_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 2, 2, segment);
567 segment = tvb_get_ntohs(tvb, RIF_OFFSET + 1 + j) >> 4;
568 brdgnmb = tvb_get_guint8(tvb, RIF_OFFSET + j) & 0x0f;
569 size = sprintf(buffer+buff_offset, "-%01X-%03X",brdgnmb,segment);
570 proto_tree_add_uint_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 3 + j, 2, segment);
571 proto_tree_add_uint_hidden(tree, hf_tr_rif_bridge, tvb, TR_MIN_HEADER_LEN + 2 + j, 1, brdgnmb);
574 proto_tree_add_string(tree, hf_tr_rif, tvb, TR_MIN_HEADER_LEN + 2, rcf_len, buffer);
576 if (unprocessed_rif > 0) {
577 proto_tree_add_text(tree, tvb, TR_MIN_HEADER_LEN + RIF_BYTES_TO_PROCESS, unprocessed_rif,
578 "Extra RIF bytes beyond spec: %d", unprocessed_rif);
583 proto_register_tr(void)
585 static hf_register_info hf[] = {
587 { "Access Control", "tr.ac", FT_UINT8, BASE_HEX, NULL, 0x0,
591 { "Priority", "tr.priority", FT_UINT8, BASE_DEC, NULL, 0xe0,
595 { "Frame", "tr.frame", FT_BOOLEAN, 8, TFS(&ac_truth), 0x10,
598 { &hf_tr_monitor_cnt,
599 { "Monitor Count", "tr.monitor_cnt", FT_UINT8, BASE_DEC, NULL, 0x08,
602 { &hf_tr_priority_reservation,
603 { "Priority Reservation","tr.priority_reservation", FT_UINT8, BASE_DEC, NULL, 0x07,
607 { "Frame Control", "tr.fc", FT_UINT8, BASE_HEX, NULL, 0x0,
611 { "Frame Type", "tr.frame_type", FT_UINT8, BASE_DEC, VALS(frame_vals), 0xc0,
615 { "Frame PCF", "tr.frame_pcf", FT_UINT8, BASE_DEC, VALS(pcf_vals), 0x0f,
619 { "Destination", "tr.dst", FT_ETHER, BASE_NONE, NULL, 0x0,
620 "Destination Hardware Address", HFILL }},
623 { "Source", "tr.src", FT_ETHER, BASE_NONE, NULL, 0x0,
624 "Source Hardware Address", HFILL }},
627 { "Source or Destination Address", "tr.addr", FT_ETHER, BASE_NONE, NULL, 0x0,
628 "Source or Destination Hardware Address", HFILL }},
631 { "Source Routed", "tr.sr", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
632 "Source Routed", HFILL }},
635 { "RIF Bytes", "tr.rif_bytes", FT_UINT8, BASE_DEC, NULL, 0x0,
636 "Number of bytes in Routing Information Fields, including "
637 "the two bytes of Routing Control Field", HFILL }},
640 { "Broadcast Type", "tr.broadcast", FT_UINT8, BASE_DEC, VALS(broadcast_vals), 0x0,
641 "Type of Token-Ring Broadcast", HFILL }},
643 { &hf_tr_max_frame_size,
644 { "Maximum Frame Size", "tr.max_frame_size", FT_UINT8, BASE_DEC, VALS(max_frame_size_vals),
649 { "Direction", "tr.direction", FT_UINT8, BASE_DEC, VALS(direction_vals), 0x0,
650 "Direction of RIF", HFILL }},
653 { "Ring-Bridge Pairs", "tr.rif", FT_STRING, BASE_NONE, NULL, 0x0,
654 "String representing Ring-Bridge Pairs", HFILL }},
657 { "RIF Ring", "tr.rif.ring", FT_UINT16, BASE_HEX, NULL, 0x0,
661 { "RIF Bridge", "tr.rif.bridge", FT_UINT8, BASE_HEX, NULL, 0x0,
664 static gint *ett[] = {
670 proto_tr = proto_register_protocol("Token-Ring", "Token-Ring", "tr");
671 proto_register_field_array(proto_tr, hf, array_length(hf));
672 proto_register_subtree_array(ett, array_length(ett));
673 register_dissector("tr", dissect_tr, proto_tr);
677 proto_reg_handoff_tr(void)
679 dissector_handle_t tr_handle;
682 * Get handles for the TR MAC and LLC dissectors.
684 trmac_handle = find_dissector("trmac");
685 llc_handle = find_dissector("llc");
686 data_handle = find_dissector("data");
688 tr_handle = find_dissector("tr");
689 dissector_add("wtap_encap", WTAP_ENCAP_TOKEN_RING, tr_handle);