2 * Routines for Token-Ring packet disassembly
3 * Gilbert Ramirez <gram@xiexie.org>
5 * $Id: packet-tr.c,v 1.63 2001/07/03 04:56:46 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>
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;
123 * DODGY LINUX HACK DODGY LINUX HACK
124 * Linux 2.0.x always passes frames to the Token Ring driver for transmission with
125 * 18 bytes padding for source routing information. Some drivers copy the first
126 * (18 - srlen) bytes up the frame (18 - srlen) bytes thus removing the padding.
127 * Other drivers just make a copy of the entire frame and then hack about with it
128 * so the frame the sniffer gets is fine (just has extra sr routing).
129 * In the first instance (driver hacking frame in situ) the sniffer gets a garbled
131 * This function trys to detect this and returns the offset of where
132 * the frame really starts.
133 * This only detects frames that we have sent ourselves so if we are packet sniffing
134 * on the machine we are watching this is useful.
135 * Compare offset 0 with offset x+1 for a length of x bytes for all value of x = 1 to 18
136 * if match then Linux driver has done in situ source route compression of the crappy
137 * Linux 2.0.x frame so the beginning of the real frame is x bytes in.
138 * (And this real frame x bytes in looks like a proper TR frame that goes on the wire
139 * with none of the Linux idiosyncrasies).
141 int check_for_old_linux_tvb(tvbuff_t *tvb)
146 /* Restrict our looping to the boundaries of the frame */
147 bytes = tvb_length(tvb);
152 data = tvb_get_ptr(tvb, 0, bytes);
154 for(x = 1; x <= bytes-1 ;x++)
156 if (memcmp(&data[0], &data[x], x) == 0)
164 int check_for_old_linux(const u_char * pd)
169 if (memcmp(&pd[0],&pd[x],x) == 0)
179 add_ring_bridge_pairs(int rcf_len, tvbuff_t*, proto_tree *tree);
182 capture_tr(const u_char *pd, int offset, packet_counts *ld) {
184 int source_routed = 0;
187 guint8 trn_rif_bytes;
188 guint8 actual_rif_bytes;
191 /* The trn_hdr struct, as separate variables */
192 guint8 trn_fc; /* field control field */
193 const guint8 *trn_shost; /* source host */
195 if (!BYTES_ARE_IN_FRAME(offset, TR_MIN_HEADER_LEN)) {
200 if ((x = check_for_old_linux(pd)))
202 /* Actually packet starts x bytes into what we have got but with all
203 source routing compressed
205 /* pd = &pd[x]; */ offset+=x;
209 trn_fc = pd[offset + 1];
210 trn_shost = &pd[offset + 8];
212 frame_type = (trn_fc & 192) >> 6;
214 /* if the high bit on the first byte of src hwaddr is 1, then
215 this packet is source-routed */
216 source_routed = trn_shost[0] & 128;
218 trn_rif_bytes = pd[offset + 14] & 31;
220 /* the Linux 2.0 TR code strips source-route bits in
221 * order to test for SR. This can be removed from most
222 * packets with oltr, but not all. So, I try to figure out
223 * which packets should have been SR here. I'll check to
224 * see if there's a SNAP or IPX field right after
227 if (!source_routed && trn_rif_bytes > 0) {
228 if (pd[offset + 0x0e] != pd[offset + 0x0f]) {
229 first2_sr = pntohs(&pd[offset + 0xe0 + trn_rif_bytes]);
231 (first2_sr == 0xaaaa &&
232 pd[offset + 0x10 + trn_rif_bytes] == 0x03) ||
234 first2_sr == 0xe0e0 ||
235 first2_sr == 0xe0aa ) {
243 actual_rif_bytes = trn_rif_bytes;
247 actual_rif_bytes = 0;
250 /* this is a silly hack for Linux 2.0.x. Read the comment below,
251 in front of the other #ifdef linux. If we're sniffing our own NIC,
252 we get a full RIF, sometimes with garbage */
253 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
254 (!source_routed && frame_type == 1)) {
255 /* look for SNAP or IPX only */
256 if ( (pd[offset + 0x20] == 0xaa && pd[offset + 0x21] == 0xaa && pd[offset + 0x22] == 03) ||
257 (pd[offset + 0x20] == 0xe0 && pd[offset + 0x21] == 0xe0) ) {
258 actual_rif_bytes = 18;
260 pd[offset + 0x23] == 0 &&
261 pd[offset + 0x24] == 0 &&
262 pd[offset + 0x25] == 0 &&
263 pd[offset + 0x26] == 0x00 &&
264 pd[offset + 0x27] == 0x11) {
266 actual_rif_bytes = 18;
268 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
269 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
270 (i.e. for non SNAP frames e.g. for Netware frames)
271 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
272 bytes as zero frame looks like :-
273 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
274 offset += 8; /* Skip fake LLC and SNAP */
278 offset += actual_rif_bytes + TR_MIN_HEADER_LEN;
280 /* The package is either MAC or LLC */
281 switch (frame_type) {
287 capture_llc(pd, offset, ld);
290 /* non-MAC, non-LLC, i.e., "Reserved" */
298 dissect_tr(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
300 proto_tree *tr_tree, *bf_tree;
306 volatile int fixoffset = 0;
307 volatile int source_routed = 0;
308 volatile guint8 trn_rif_bytes;
309 volatile guint8 actual_rif_bytes;
310 volatile guint8 c1_nonsr;
311 volatile guint8 c2_nonsr;
312 volatile guint16 first2_sr;
313 tvbuff_t *volatile tr_tvb;
315 /* The trn_hdr struct, as separate variables */
316 guint8 trn_ac; /* access control field */
317 guint8 trn_fc; /* field control field */
318 const guint8 *trn_dhost; /* destination host */
319 const guint8 *trn_shost; /* source host */
321 /* non-source-routed version of source addr */
322 static guint8 trn_shost_nonsr[6];
325 /* Token-Ring Strings */
326 char *fc[] = { "MAC", "LLC", "Reserved", "Unknown" };
328 if (check_col(pinfo->fd, COL_PROTOCOL))
329 col_set_str(pinfo->fd, COL_PROTOCOL, "TR");
331 if ((x = check_for_old_linux_tvb((tvbuff_t*) tvb))) {
332 /* Actually packet starts x bytes into what we have got but with all
333 source routing compressed. See comment above */
334 tr_tvb = tvb_new_subset((tvbuff_t*) tvb, x, -1, -1);
341 trn_fc = tvb_get_guint8(tr_tvb, 1);
342 trn_dhost = tvb_get_ptr(tr_tvb, 2, 6);
343 trn_shost = tvb_get_ptr(tr_tvb, 8, 6);
346 memcpy(trn_shost_nonsr, trn_shost, 6);
347 trn_shost_nonsr[0] &= 127;
348 frame_type = (trn_fc & 192) >> 6;
350 if (check_col(pinfo->fd, COL_INFO))
351 col_add_fstr(pinfo->fd, COL_INFO, "Token-Ring %s", fc[frame_type]);
353 /* if the high bit on the first byte of src hwaddr is 1, then
354 this packet is source-routed */
355 source_routed = trn_shost[0] & 128;
357 trn_rif_bytes = tvb_get_guint8(tr_tvb, 14) & 31;
359 /* the Linux 2.0 TR code strips source-route bits in
360 * order to test for SR. This can be removed from most
361 * packets with oltr, but not all. So, I try to figure out
362 * which packets should have been SR here. I'll check to
363 * see if there's a SNAP or IPX field right after
366 if (frame_type == 1 && !source_routed && trn_rif_bytes > 0) {
369 c1_nonsr = tvb_get_guint8(tr_tvb, 14);
370 c2_nonsr = tvb_get_guint8(tr_tvb, 15);
372 if (c1_nonsr != c2_nonsr) {
374 first2_sr = tvb_get_ntohs(tr_tvb, trn_rif_bytes + 0x0e);
376 if ( ( first2_sr == 0xaaaa &&
377 tvb_get_guint8(tr_tvb, trn_rif_bytes + 0x10) == 0x03) ||
379 first2_sr == 0xe0e0 ||
380 first2_sr == 0xe0aa ) {
387 /* We had no information beyond the TR header. Just assume
388 * this is a normal (non-Linux) TR header. */
395 actual_rif_bytes = trn_rif_bytes;
399 actual_rif_bytes = 0;
402 /* this is a silly hack for Linux 2.0.x. Read the comment below,
403 in front of the other #ifdef linux. If we're sniffing our own NIC,
404 we get a full RIF, sometimes with garbage */
406 if (frame_type == 1 && ( (source_routed && trn_rif_bytes == 2) ||
408 /* look for SNAP or IPX only */
410 (tvb_get_ntohs(tr_tvb, 0x20) == 0xaaaa &&
411 tvb_get_guint8(tr_tvb, 0x22) == 0x03)
413 tvb_get_ntohs(tr_tvb, 0x20) == 0xe0e0 ) {
415 actual_rif_bytes = 18;
418 tvb_get_ntohl(tr_tvb, 0x23) == 0 &&
419 tvb_get_guint8(tr_tvb, 0x27) == 0x11) {
421 actual_rif_bytes = 18;
423 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
424 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
425 (i.e. for non SNAP frames e.g. for Netware frames)
426 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
427 bytes as zero frame looks like :-
428 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
429 fixoffset += 8; /* Skip fake LLC and SNAP */
434 /* We had no information beyond the TR header. Just assume
435 * this is a normal (non-Linux) TR header. */
441 /* XXX - copy it to some buffer associated with "*pinfo", rather than
442 just making "trn_shost_nonsr" static? */
443 SET_ADDRESS(&pinfo->dl_src, AT_ETHER, 6, trn_shost_nonsr);
444 SET_ADDRESS(&pinfo->src, AT_ETHER, 6, trn_shost_nonsr);
445 SET_ADDRESS(&pinfo->dl_dst, AT_ETHER, 6, trn_dhost);
446 SET_ADDRESS(&pinfo->dst, AT_ETHER, 6, trn_dhost);
448 /* protocol analysis tree */
450 /* Create Token-Ring Tree */
451 ti = proto_tree_add_item(tree, proto_tr, tr_tvb, 0, TR_MIN_HEADER_LEN + actual_rif_bytes, FALSE);
452 tr_tree = proto_item_add_subtree(ti, ett_token_ring);
454 /* Create the Access Control bitfield tree */
455 trn_ac = tvb_get_guint8(tr_tvb, 0);
456 ti = proto_tree_add_uint(tr_tree, hf_tr_ac, tr_tvb, 0, 1, trn_ac);
457 bf_tree = proto_item_add_subtree(ti, ett_token_ring_ac);
459 proto_tree_add_uint(bf_tree, hf_tr_priority, tr_tvb, 0, 1, trn_ac);
460 proto_tree_add_boolean(bf_tree, hf_tr_frame, tr_tvb, 0, 1, trn_ac);
461 proto_tree_add_uint(bf_tree, hf_tr_monitor_cnt, tr_tvb, 0, 1, trn_ac);
462 proto_tree_add_uint(bf_tree, hf_tr_priority_reservation, tr_tvb, 0, 1, trn_ac);
464 /* Create the Frame Control bitfield tree */
465 ti = proto_tree_add_uint(tr_tree, hf_tr_fc, tr_tvb, 1, 1, trn_fc);
466 bf_tree = proto_item_add_subtree(ti, ett_token_ring_fc);
468 proto_tree_add_uint(bf_tree, hf_tr_fc_type, tr_tvb, 1, 1, trn_fc);
469 proto_tree_add_uint(bf_tree, hf_tr_fc_pcf, tr_tvb, 1, 1, trn_fc);
470 proto_tree_add_ether(tr_tree, hf_tr_dst, tr_tvb, 2, 6, trn_dhost);
471 proto_tree_add_ether(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost);
472 proto_tree_add_ether_hidden(tr_tree, hf_tr_addr, tr_tvb, 2, 6, trn_dhost);
473 proto_tree_add_ether_hidden(tr_tree, hf_tr_addr, tr_tvb, 8, 6, trn_shost);
475 proto_tree_add_boolean(tr_tree, hf_tr_sr, tr_tvb, 8, 1, source_routed);
477 /* non-source-routed version of src addr */
478 proto_tree_add_ether_hidden(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost_nonsr);
482 rcf1 = tvb_get_guint8(tr_tvb, 14);
483 proto_tree_add_uint(tr_tree, hf_tr_rif_bytes, tr_tvb, 14, 1, trn_rif_bytes);
484 proto_tree_add_uint(tr_tree, hf_tr_broadcast, tr_tvb, 14, 1, rcf1 & 224);
487 rcf2 = tvb_get_guint8(tr_tvb, 15);
488 proto_tree_add_uint(tr_tree, hf_tr_max_frame_size, tr_tvb, 15, 1, rcf2 & 112);
489 proto_tree_add_uint(tr_tree, hf_tr_direction, tr_tvb, 15, 1, rcf2 & 128);
491 /* if we have more than 2 bytes of RIF, then we have
493 if (trn_rif_bytes > 2) {
494 add_ring_bridge_pairs(trn_rif_bytes, tr_tvb, tr_tree);
498 /* Linux 2.0.x has a problem in that the 802.5 code creates
499 an emtpy full (18-byte) RIF area. It's up to the tr driver to
500 either fill it in or remove it before sending the bytes out
501 to the wire. If you run tcpdump on a Linux 2.0.x machine running
502 token-ring, tcpdump will capture these 18 filler bytes. They
503 are filled with garbage. The best way to detect this problem is
504 to know the src hwaddr of the machine from which you were running
505 tcpdump. W/o that, however, I'm guessing that DSAP == SSAP if the
506 frame type is LLC. It's very much a hack. */
507 if (actual_rif_bytes > trn_rif_bytes) {
508 proto_tree_add_text(tr_tree, tr_tvb, TR_MIN_HEADER_LEN + trn_rif_bytes, actual_rif_bytes - trn_rif_bytes,
509 "Empty RIF from Linux 2.0.x driver. The sniffing NIC "
510 "is also running a protocol stack.");
513 proto_tree_add_text(tr_tree, tr_tvb, TR_MIN_HEADER_LEN + 18,8,"Linux 2.0.x fake LLC and SNAP header");
517 next_tvb = tvb_new_subset(tr_tvb, TR_MIN_HEADER_LEN + actual_rif_bytes + fixoffset, -1, -1);
519 /* The package is either MAC or LLC */
520 switch (frame_type) {
523 call_dissector(trmac_handle, next_tvb, pinfo, tree);
526 call_dissector(llc_handle, next_tvb, pinfo, tree);
529 /* non-MAC, non-LLC, i.e., "Reserved" */
530 dissect_data(next_tvb, 0, pinfo, tree);
535 /* this routine is taken from the Linux net/802/tr.c code, which shows
536 ring-bridge pairs in the /proc/net/tr_rif virtual file. */
538 add_ring_bridge_pairs(int rcf_len, tvbuff_t *tvb, proto_tree *tree)
541 int segment, brdgnmb, unprocessed_rif;
544 #define RIF_OFFSET 16
545 #define RIF_BYTES_TO_PROCESS 30
547 char buffer[3 + (RIF_BYTES_TO_PROCESS / 2) * 6 + 1];
549 /* Only process so many bytes of RIF, as per TR spec, and not overflow
550 * static buffer above */
551 unprocessed_rif = rcf_len - RIF_BYTES_TO_PROCESS;
552 rcf_len = MIN(rcf_len, RIF_BYTES_TO_PROCESS);
554 /* Ignore the 2 RCF bytes, since they don't make up the ring/bride pairs */
557 for(j = 1; j < rcf_len - 1; j += 2) {
559 segment = tvb_get_ntohs(tvb, RIF_OFFSET) >> 4;
560 size = sprintf(buffer, "%03X",segment);
561 proto_tree_add_uint_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 2, 2, segment);
564 segment = tvb_get_ntohs(tvb, RIF_OFFSET + 1 + j) >> 4;
565 brdgnmb = tvb_get_guint8(tvb, RIF_OFFSET + j) & 0x0f;
566 size = sprintf(buffer+buff_offset, "-%01X-%03X",brdgnmb,segment);
567 proto_tree_add_uint_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 3 + j, 2, segment);
568 proto_tree_add_uint_hidden(tree, hf_tr_rif_bridge, tvb, TR_MIN_HEADER_LEN + 2 + j, 1, brdgnmb);
571 proto_tree_add_string(tree, hf_tr_rif, tvb, TR_MIN_HEADER_LEN + 2, rcf_len, buffer);
573 if (unprocessed_rif > 0) {
574 proto_tree_add_text(tree, tvb, TR_MIN_HEADER_LEN + RIF_BYTES_TO_PROCESS, unprocessed_rif,
575 "Extra RIF bytes beyond spec: %d", unprocessed_rif);
580 proto_register_tr(void)
582 static hf_register_info hf[] = {
584 { "Access Control", "tr.ac", FT_UINT8, BASE_HEX, NULL, 0x0,
588 { "Priority", "tr.priority", FT_UINT8, BASE_DEC, NULL, 0xe0,
592 { "Frame", "tr.frame", FT_BOOLEAN, 8, TFS(&ac_truth), 0x10,
595 { &hf_tr_monitor_cnt,
596 { "Monitor Count", "tr.monitor_cnt", FT_UINT8, BASE_DEC, NULL, 0x08,
599 { &hf_tr_priority_reservation,
600 { "Priority Reservation","tr.priority_reservation", FT_UINT8, BASE_DEC, NULL, 0x07,
604 { "Frame Control", "tr.fc", FT_UINT8, BASE_HEX, NULL, 0x0,
608 { "Frame Type", "tr.frame_type", FT_UINT8, BASE_DEC, VALS(frame_vals), 0xc0,
612 { "Frame PCF", "tr.frame_pcf", FT_UINT8, BASE_DEC, VALS(pcf_vals), 0x0f,
616 { "Destination", "tr.dst", FT_ETHER, BASE_NONE, NULL, 0x0,
617 "Destination Hardware Address", HFILL }},
620 { "Source", "tr.src", FT_ETHER, BASE_NONE, NULL, 0x0,
621 "Source Hardware Address", HFILL }},
624 { "Source or Destination Address", "tr.addr", FT_ETHER, BASE_NONE, NULL, 0x0,
625 "Source or Destination Hardware Address", HFILL }},
628 { "Source Routed", "tr.sr", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
629 "Source Routed", HFILL }},
632 { "RIF Bytes", "tr.rif_bytes", FT_UINT8, BASE_DEC, NULL, 0x0,
633 "Number of bytes in Routing Information Fields, including "
634 "the two bytes of Routing Control Field", HFILL }},
637 { "Broadcast Type", "tr.broadcast", FT_UINT8, BASE_DEC, VALS(broadcast_vals), 0x0,
638 "Type of Token-Ring Broadcast", HFILL }},
640 { &hf_tr_max_frame_size,
641 { "Maximum Frame Size", "tr.max_frame_size", FT_UINT8, BASE_DEC, VALS(max_frame_size_vals),
646 { "Direction", "tr.direction", FT_UINT8, BASE_DEC, VALS(direction_vals), 0x0,
647 "Direction of RIF", HFILL }},
650 { "Ring-Bridge Pairs", "tr.rif", FT_STRING, BASE_NONE, NULL, 0x0,
651 "String representing Ring-Bridge Pairs", HFILL }},
654 { "RIF Ring", "tr.rif.ring", FT_UINT16, BASE_HEX, NULL, 0x0,
658 { "RIF Bridge", "tr.rif.bridge", FT_UINT8, BASE_HEX, NULL, 0x0,
661 static gint *ett[] = {
667 proto_tr = proto_register_protocol("Token-Ring", "Token-Ring", "tr");
668 proto_register_field_array(proto_tr, hf, array_length(hf));
669 proto_register_subtree_array(ett, array_length(ett));
670 register_dissector("tr", dissect_tr, proto_tr);
674 proto_reg_handoff_tr(void)
677 * Get handles for the TR MAC and LLC dissectors.
679 trmac_handle = find_dissector("trmac");
680 llc_handle = find_dissector("llc");
682 dissector_add("wtap_encap", WTAP_ENCAP_TOKEN_RING, dissect_tr,