2 * Routines for Token-Ring packet disassembly
3 * Gilbert Ramirez <gram@xiexie.org>
5 * $Id: packet-tr.c,v 1.42 2000/05/19 05:29:43 guy Exp $
7 * Ethereal - Network traffic analyzer
8 * By Gerald Combs <gerald@zing.org>
9 * Copyright 1998 Gerald Combs
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation; either version 2
15 * of the License, or (at your option) any later version.
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with this program; if not, write to the Free Software
24 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
31 #ifdef HAVE_SYS_TYPES_H
32 # include <sys/types.h>
38 #include "packet-tr.h"
39 #include "packet-llc.h"
40 #include "packet-trmac.h"
42 static int proto_tr = -1;
43 static int hf_tr_dst = -1;
44 static int hf_tr_src = -1;
45 static int hf_tr_addr = -1;
46 static int hf_tr_sr = -1;
47 static int hf_tr_ac = -1;
48 static int hf_tr_priority = -1;
49 static int hf_tr_frame = -1;
50 static int hf_tr_monitor_cnt = -1;
51 static int hf_tr_priority_reservation = -1;
52 static int hf_tr_fc = -1;
53 static int hf_tr_fc_type = -1;
54 static int hf_tr_fc_pcf = -1;
55 static int hf_tr_rif_bytes = -1;
56 static int hf_tr_broadcast = -1;
57 static int hf_tr_max_frame_size = -1;
58 static int hf_tr_direction = -1;
59 static int hf_tr_rif = -1;
60 static int hf_tr_rif_ring = -1;
61 static int hf_tr_rif_bridge = -1;
63 static gint ett_token_ring = -1;
64 static gint ett_token_ring_ac = -1;
65 static gint ett_token_ring_fc = -1;
67 #define TR_MIN_HEADER_LEN 14
68 #define TR_MAX_HEADER_LEN 32
70 static const true_false_string ac_truth = { "Frame", "Token" };
72 static const value_string pcf_vals[] = {
73 { 0, "Normal buffer" },
74 { 1, "Express buffer" },
78 { 5, "Active Monitor Present" },
79 { 6, "Standby Monitor Present" },
83 static const value_string frame_vals[] = {
90 static const value_string broadcast_vals[] = {
91 { 0 << 5, "Non-broadcast" },
92 { 1 << 5, "Non-broadcast" },
93 { 2 << 5, "Non-broadcast" },
94 { 3 << 5, "Non-broadcast" },
95 { 4 << 5, "All-routes broadcast" },
96 { 5 << 5, "All-routes broadcast" },
97 { 6 << 5, "Single-route broadcast" },
98 { 7 << 5, "Single-route broadcast" },
102 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 (<--)" },
120 * DODGY LINUX HACK DODGY LINUX HACK
121 * Linux 2.0.x always passes frames to the Token Ring driver for transmission with
122 * 18 bytes padding for source routing information. Some drivers copy the first
123 * (18 - srlen) bytes up the frame (18 - srlen) bytes thus removing the padding.
124 * Other drivers just make a copy of the entire frame and then hack about with it
125 * so the frame the sniffer gets is fine (just has extra sr routing).
126 * In the first instance (driver hacking frame in situ) the sniffer gets a garbled
128 * This function trys to detect this and returns the offset of where
129 * the frame really starts.
130 * This only detects frames that we have sent ourselves so if we are packet sniffing
131 * on the machine we are watching this is useful.
132 * Compare offset 0 with offset x+1 for a length of x bytes for all value of x = 1 to 18
133 * if match then Linux driver has done in situ source route compression of the crappy
134 * Linux 2.0.x frame so the beginning of the real frame is x bytes in.
135 * (And this real frame x bytes in looks like a proper TR frame that goes on the wire
136 * with none of the Linux idiosyncrasies).
138 int check_for_old_linux_tvb(tvbuff_t *tvb)
143 /* Restrict our looping to the boundaries of the frame */
144 bytes = tvb_length(tvb);
149 data = tvb_get_ptr(tvb, 0, bytes);
151 for(x = 1; x <= bytes-1 ;x++)
153 if (memcmp(&data[0], &data[x], x) == 0)
161 int check_for_old_linux(const u_char * pd)
166 if (memcmp(&pd[0],&pd[x],x) == 0)
176 add_ring_bridge_pairs(int rcf_len, tvbuff_t*, proto_tree *tree);
179 capture_tr(const u_char *pd, int offset, packet_counts *ld) {
181 int source_routed = 0;
184 guint8 trn_rif_bytes;
185 guint8 actual_rif_bytes;
187 /* The trn_hdr struct, as separate variables */
188 guint8 trn_fc; /* field control field */
189 const guint8 *trn_shost; /* source host */
191 if (!BYTES_ARE_IN_FRAME(offset, TR_MIN_HEADER_LEN)) {
196 if ((x = check_for_old_linux(pd)))
198 /* Actually packet starts x bytes into what we have got but with all
199 source routing compressed
201 /* pd = &pd[x]; */ offset+=x;
205 trn_fc = pd[offset + 1];
206 trn_shost = &pd[offset + 8];
208 frame_type = (trn_fc & 192) >> 6;
210 /* if the high bit on the first byte of src hwaddr is 1, then
211 this packet is source-routed */
212 source_routed = trn_shost[0] & 128;
214 trn_rif_bytes = pd[offset + 14] & 31;
216 /* sometimes we have a RCF but no RIF... half source-routed? */
217 if (!source_routed && trn_rif_bytes > 0) {
218 /* I'll check for 2 bytes of RIF and mark the packet as source
219 * routed even though I'm not sure _what_ that kind of packet is */
220 if (trn_rif_bytes == 2) {
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
231 pd[offset + 0x0e + trn_rif_bytes] == 0xaa &&
232 pd[offset + 0x0f + trn_rif_bytes] == 0xaa &&
233 pd[offset + 0x10 + trn_rif_bytes] == 0x03) ||
235 pd[offset + 0x0e + trn_rif_bytes] == 0xe0 &&
236 pd[offset + 0x0f + trn_rif_bytes] == 0xe0) ) {
244 actual_rif_bytes = trn_rif_bytes;
248 actual_rif_bytes = 0;
251 /* this is a silly hack for Linux 2.0.x. Read the comment below,
252 in front of the other #ifdef linux. If we're sniffing our own NIC,
253 we get a full RIF, sometimes with garbage */
254 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
255 (!source_routed && frame_type == 1)) {
256 /* look for SNAP or IPX only */
257 if ( (pd[offset + 0x20] == 0xaa && pd[offset + 0x21] == 0xaa && pd[offset + 0x22] == 03) ||
258 (pd[offset + 0x20] == 0xe0 && pd[offset + 0x21] == 0xe0) ) {
259 actual_rif_bytes = 18;
261 pd[offset + 0x23] == 0 &&
262 pd[offset + 0x24] == 0 &&
263 pd[offset + 0x25] == 0 &&
264 pd[offset + 0x26] == 0x00 &&
265 pd[offset + 0x27] == 0x11) {
267 actual_rif_bytes = 18;
269 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
270 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
271 (i.e. for non SNAP frames e.g. for Netware frames)
272 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
273 bytes as zero frame looks like :-
274 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
275 offset += 8; /* Skip fake LLC and SNAP */
279 offset += actual_rif_bytes + TR_MIN_HEADER_LEN;
281 /* The package is either MAC or LLC */
282 switch (frame_type) {
288 capture_llc(pd, offset, ld);
291 /* non-MAC, non-LLC, i.e., "Reserved" */
299 dissect_tr(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
301 proto_tree *tr_tree, *bf_tree;
307 const guint8* next_pd;
309 volatile int fixoffset = 0;
310 volatile int source_routed = 0;
311 volatile guint8 trn_rif_bytes;
312 volatile guint8 actual_rif_bytes;
314 /* I make tr_tvb static because I need to set it before any TRY block.
315 * If tr_tvb were not static, the possibility exists that the value
316 * I give to tr_tvb would be clobbered. */
317 static tvbuff_t *tr_tvb = NULL;
319 /* The trn_hdr struct, as separate variables */
320 guint8 trn_ac; /* access control field */
321 guint8 trn_fc; /* field control field */
322 const guint8 *trn_dhost; /* destination host */
323 const guint8 *trn_shost; /* source host */
325 /* non-source-routed version of source addr */
326 static guint8 trn_shost_nonsr[6];
329 /* Token-Ring Strings */
330 char *fc[] = { "MAC", "LLC", "Reserved", "Unknown" };
332 pinfo->current_proto = "Token-Ring";
334 if (check_col(pinfo->fd, COL_PROTOCOL))
335 col_add_str(pinfo->fd, COL_PROTOCOL, "TR");
337 if ((x = check_for_old_linux_tvb((tvbuff_t*) tvb))) {
338 /* Actually packet starts x bytes into what we have got but with all
339 source routing compressed. See comment above */
340 tr_tvb = tvb_new_subset((tvbuff_t*) tvb, x, -1, -1);
347 trn_fc = tvb_get_guint8(tr_tvb, 1);
348 trn_dhost = tvb_get_ptr(tr_tvb, 2, 6);
349 trn_shost = tvb_get_ptr(tr_tvb, 8, 6);
352 memcpy(trn_shost_nonsr, trn_shost, 6);
353 trn_shost_nonsr[0] &= 127;
354 frame_type = (trn_fc & 192) >> 6;
356 if (check_col(pinfo->fd, COL_INFO))
357 col_add_fstr(pinfo->fd, COL_INFO, "Token-Ring %s", fc[frame_type]);
359 /* if the high bit on the first byte of src hwaddr is 1, then
360 this packet is source-routed */
361 source_routed = trn_shost[0] & 128;
363 trn_rif_bytes = tvb_get_guint8(tr_tvb, 14) & 31;
365 /* sometimes we have a RCF but no RIF... half source-routed? */
366 /* I'll check for 2 bytes of RIF and the 0x70 byte */
367 if (!source_routed && trn_rif_bytes > 0) {
368 if (trn_rif_bytes == 2) {
371 /* the Linux 2.0 TR code strips source-route bits in
372 * order to test for SR. This can be removed from most
373 * packets with oltr, but not all. So, I try to figure out
374 * which packets should have been SR here. I'll check to
375 * see if there's a SNAP or IPX field right after
380 if ( ( tvb_get_ntohs(tr_tvb, trn_rif_bytes + 0x0e) == 0xaaaa &&
381 tvb_get_guint8(tr_tvb, trn_rif_bytes + 0x10) == 0x03) ||
383 tvb_get_ntohs(tr_tvb, trn_rif_bytes + 0x0e) == 0xe0e0 ) {
389 /* We had no information beyond the TR header. Just assume
390 * 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 ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
410 (!source_routed && frame_type == 1)) {
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 "pi", rather than
445 just making "trn_shost_nonsr" static? */
446 SET_ADDRESS(&pi.dl_src, AT_ETHER, 6, trn_shost_nonsr);
447 SET_ADDRESS(&pi.src, AT_ETHER, 6, trn_shost_nonsr);
448 SET_ADDRESS(&pi.dl_dst, AT_ETHER, 6, trn_dhost);
449 SET_ADDRESS(&pi.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, NULL);
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_item(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_item(bf_tree, hf_tr_priority, tr_tvb, 0, 1, trn_ac);
463 proto_tree_add_item(bf_tree, hf_tr_frame, tr_tvb, 0, 1, trn_ac);
464 proto_tree_add_item(bf_tree, hf_tr_monitor_cnt, tr_tvb, 0, 1, trn_ac);
465 proto_tree_add_item(bf_tree, hf_tr_priority_reservation, tr_tvb, 0, 1, trn_ac);
467 /* Create the Frame Control bitfield tree */
468 ti = proto_tree_add_item(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_item(bf_tree, hf_tr_fc_type, tr_tvb, 1, 1, trn_fc);
472 proto_tree_add_item(bf_tree, hf_tr_fc_pcf, tr_tvb, 1, 1, trn_fc);
473 proto_tree_add_item(tr_tree, hf_tr_dst, tr_tvb, 2, 6, trn_dhost);
474 proto_tree_add_item(tr_tree, hf_tr_src, tr_tvb, 8, 6, trn_shost);
475 proto_tree_add_item_hidden(tr_tree, hf_tr_addr, tr_tvb, 2, 6, trn_dhost);
476 proto_tree_add_item_hidden(tr_tree, hf_tr_addr, tr_tvb, 8, 6, trn_shost);
478 proto_tree_add_item(tr_tree, hf_tr_sr, tr_tvb, 8, 1, source_routed);
480 /* non-source-routed version of src addr */
481 proto_tree_add_item_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_item(tr_tree, hf_tr_rif_bytes, tr_tvb, 14, 1, trn_rif_bytes);
487 proto_tree_add_item(tr_tree, hf_tr_broadcast, tr_tvb, 14, 1, rcf1 & 224);
490 rcf2 = tvb_get_guint8(tr_tvb, 15);
491 proto_tree_add_item(tr_tree, hf_tr_max_frame_size, tr_tvb, 15, 1, rcf2 & 112);
492 proto_tree_add_item(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");
522 next_tvb = tvb_new_subset(tr_tvb, TR_MIN_HEADER_LEN + actual_rif_bytes + fixoffset, -1, -1);
523 tvb_compat(next_tvb, &next_pd, &next_offset);
525 /* The package is either MAC or LLC */
526 switch (frame_type) {
529 dissect_trmac(next_pd, next_offset, pinfo->fd, tree);
532 dissect_llc(next_tvb, pinfo, tree);
535 /* non-MAC, non-LLC, i.e., "Reserved" */
536 dissect_data_tvb(next_tvb, pinfo, tree);
541 /* this routine is taken from the Linux net/802/tr.c code, which shows
542 ring-bridge pairs in the /proc/net/tr_rif virtual file. */
544 add_ring_bridge_pairs(int rcf_len, tvbuff_t *tvb, proto_tree *tree)
547 int segment, brdgnmb, unprocessed_rif;
550 #define RIF_OFFSET 16
551 #define RIF_BYTES_TO_PROCESS 30
553 char buffer[3 + (RIF_BYTES_TO_PROCESS / 2) * 6 + 1];
555 /* Only process so many bytes of RIF, as per TR spec, and not overflow
556 * static buffer above */
557 unprocessed_rif = rcf_len - RIF_BYTES_TO_PROCESS;
558 rcf_len = MIN(rcf_len, RIF_BYTES_TO_PROCESS);
560 /* Ignore the 2 RCF bytes, since they don't make up the ring/bride pairs */
563 for(j = 1; j < rcf_len - 1; j += 2) {
565 segment = tvb_get_ntohs(tvb, RIF_OFFSET) >> 4;
566 size = sprintf(buffer, "%03X",segment);
567 proto_tree_add_item_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 2, 2, segment);
570 segment = tvb_get_ntohs(tvb, RIF_OFFSET + 1 + j) >> 4;
571 brdgnmb = tvb_get_guint8(tvb, RIF_OFFSET + j) & 0x0f;
572 size = sprintf(buffer+buff_offset, "-%01X-%03X",brdgnmb,segment);
573 proto_tree_add_item_hidden(tree, hf_tr_rif_ring, tvb, TR_MIN_HEADER_LEN + 3 + j, 2, segment);
574 proto_tree_add_item_hidden(tree, hf_tr_rif_bridge, tvb, TR_MIN_HEADER_LEN + 2 + j, 1, brdgnmb);
577 proto_tree_add_item(tree, hf_tr_rif, tvb, TR_MIN_HEADER_LEN + 2, rcf_len, buffer);
579 if (unprocessed_rif > 0) {
580 proto_tree_add_text(tree, tvb, TR_MIN_HEADER_LEN + RIF_BYTES_TO_PROCESS, unprocessed_rif,
581 "Extra RIF bytes beyond spec: %d", unprocessed_rif);
586 proto_register_tr(void)
588 static hf_register_info hf[] = {
590 { "Access Control", "tr.ac", FT_UINT8, BASE_HEX, NULL, 0x0,
594 { "Priority", "tr.priority", FT_UINT8, BASE_DEC, NULL, 0xe0,
598 { "Frame", "tr.frame", FT_BOOLEAN, 8, TFS(&ac_truth), 0x10,
601 { &hf_tr_monitor_cnt,
602 { "Monitor Count", "tr.monitor_cnt", FT_UINT8, BASE_DEC, NULL, 0x08,
605 { &hf_tr_priority_reservation,
606 { "Priority Reservation","tr.priority_reservation", FT_UINT8, BASE_DEC, NULL, 0x07,
610 { "Frame Control", "tr.fc", FT_UINT8, BASE_HEX, NULL, 0x0,
614 { "Frame Type", "tr.frame_type", FT_UINT8, BASE_DEC, VALS(frame_vals), 0xc0,
618 { "Frame PCF", "tr.frame_pcf", FT_UINT8, BASE_DEC, VALS(pcf_vals), 0x0f,
622 { "Destination", "tr.dst", FT_ETHER, BASE_NONE, NULL, 0x0,
623 "Destination Hardware Address" }},
626 { "Source", "tr.src", FT_ETHER, BASE_NONE, NULL, 0x0,
627 "Source Hardware Address" }},
630 { "Source or Destination Address", "tr.addr", FT_ETHER, BASE_NONE, NULL, 0x0,
631 "Source or Destination Hardware Address" }},
634 { "Source Routed", "tr.sr", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
638 { "RIF Bytes", "tr.rif_bytes", FT_UINT8, BASE_DEC, NULL, 0x0,
639 "Number of bytes in Routing Information Fields, including "
640 "the two bytes of Routing Control Field" }},
643 { "Broadcast Type", "tr.broadcast", FT_UINT8, BASE_DEC, VALS(broadcast_vals), 0x0,
644 "Type of Token-Ring Broadcast" }},
646 { &hf_tr_max_frame_size,
647 { "Maximum Frame Size", "tr.max_frame_size", FT_UINT8, BASE_DEC, VALS(max_frame_size_vals),
652 { "Direction", "tr.direction", FT_UINT8, BASE_DEC, VALS(direction_vals), 0x0,
653 "Direction of RIF" }},
656 { "Ring-Bridge Pairs", "tr.rif", FT_STRING, BASE_NONE, NULL, 0x0,
657 "String representing Ring-Bridge Pairs" }},
660 { "RIF Ring", "tr.rif.ring", FT_UINT16, BASE_HEX, NULL, 0x0,
664 { "RIF Bridge", "tr.rif.bridge", FT_UINT8, BASE_HEX, NULL, 0x0,
667 static gint *ett[] = {
673 proto_tr = proto_register_protocol("Token-Ring", "tr");
674 proto_register_field_array(proto_tr, hf, array_length(hf));
675 proto_register_subtree_array(ett, array_length(ett));