2 * Routines for Token-Ring packet disassembly
3 * Gilbert Ramirez <gram@xiexie.org>
5 * $Id: packet-tr.c,v 1.39 2000/05/11 22:04:17 gram 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-llc.h"
39 #include "packet-trmac.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[] = {
112 static const value_string direction_vals[] = {
113 { 0, "From originating station (-->)" },
114 { 128, "To originating station (<--)" },
119 * DODGY LINUX HACK DODGY LINUX HACK
120 * Linux 2.0.x always passes frames to the Token Ring driver for transmission with
121 * 18 bytes padding for source routing information. Some drivers copy the first
122 * (18 - srlen) bytes up the frame (18 - srlen) bytes thus removing the padding.
123 * Other drivers just make a copy of the entire frame and then hack about with it
124 * so the frame the sniffer gets is fine (just has extra sr routing).
125 * In the first instance (driver hacking frame in situ) the sniffer gets a garbled
127 * This function trys to detect this and returns the offset of where
128 * the frame really starts.
129 * This only detects frames that we have sent ourselves so if we are packet sniffing
130 * on the machine we are watching this is useful.
131 * Compare offset 0 with offset x+1 for a length of x bytes for all value of x = 1 to 18
132 * if match then Linux driver has done in situ source route compression of the crappy
133 * Linux 2.0.x frame so the beginning of the real frame is x bytes in.
134 * (And this real frame x bytes in looks like a proper TR frame that goes on the wire
135 * with none of the Linux idiosyncrasies).
137 int check_for_old_linux(const u_char * pd)
142 if (memcmp(&pd[0],&pd[x],x) == 0)
151 add_ring_bridge_pairs(int rcf_len, const u_char *pd, int offset, proto_tree *tree);
154 capture_tr(const u_char *pd, int offset, packet_counts *ld) {
156 int source_routed = 0;
159 guint8 trn_rif_bytes;
160 guint8 actual_rif_bytes;
162 /* The trn_hdr struct, as separate variables */
163 guint8 trn_fc; /* field control field */
164 const guint8 *trn_shost; /* source host */
166 if (!BYTES_ARE_IN_FRAME(offset, TR_MIN_HEADER_LEN)) {
171 if ((x = check_for_old_linux(pd)))
173 /* Actually packet starts x bytes into what we have got but with all
174 source routing compressed
176 /* pd = &pd[x]; */ offset+=x;
180 trn_fc = pd[offset + 1];
181 trn_shost = &pd[offset + 8];
183 frame_type = (trn_fc & 192) >> 6;
185 /* if the high bit on the first byte of src hwaddr is 1, then
186 this packet is source-routed */
187 source_routed = trn_shost[0] & 128;
189 trn_rif_bytes = pd[offset + 14] & 31;
191 /* sometimes we have a RCF but no RIF... half source-routed? */
192 if (!source_routed && trn_rif_bytes > 0) {
193 /* I'll check for 2 bytes of RIF and mark the packet as source
194 * routed even though I'm not sure _what_ that kind of packet is */
195 if (trn_rif_bytes == 2) {
198 /* the Linux 2.0 TR code strips source-route bits in
199 * order to test for SR. This can be removed from most
200 * packets with oltr, but not all. So, I try to figure out
201 * which packets should have been SR here. I'll check to
202 * see if there's a SNAP or IPX field right after
206 pd[offset + 0x0e + trn_rif_bytes] == 0xaa &&
207 pd[offset + 0x0f + trn_rif_bytes] == 0xaa &&
208 pd[offset + 0x10 + trn_rif_bytes] == 0x03) ||
210 pd[offset + 0x0e + trn_rif_bytes] == 0xe0 &&
211 pd[offset + 0x0f + trn_rif_bytes] == 0xe0) ) {
219 actual_rif_bytes = trn_rif_bytes;
223 actual_rif_bytes = 0;
226 /* this is a silly hack for Linux 2.0.x. Read the comment below,
227 in front of the other #ifdef linux. If we're sniffing our own NIC,
228 we get a full RIF, sometimes with garbage */
229 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
230 (!source_routed && frame_type == 1)) {
231 /* look for SNAP or IPX only */
232 if ( (pd[offset + 0x20] == 0xaa && pd[offset + 0x21] == 0xaa && pd[offset + 0x22] == 03) ||
233 (pd[offset + 0x20] == 0xe0 && pd[offset + 0x21] == 0xe0) ) {
234 actual_rif_bytes = 18;
236 pd[offset + 0x23] == 0 &&
237 pd[offset + 0x24] == 0 &&
238 pd[offset + 0x25] == 0 &&
239 pd[offset + 0x26] == 0x00 &&
240 pd[offset + 0x27] == 0x11) {
242 actual_rif_bytes = 18;
244 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
245 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
246 (i.e. for non SNAP frames e.g. for Netware frames)
247 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
248 bytes as zero frame looks like :-
249 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
250 offset += 8; /* Skip fake LLC and SNAP */
254 offset += actual_rif_bytes + 14;
256 /* The package is either MAC or LLC */
257 switch (frame_type) {
263 capture_llc(pd, offset, ld);
266 /* non-MAC, non-LLC, i.e., "Reserved" */
274 dissect_tr(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
276 proto_tree *tr_tree, *bf_tree;
279 int source_routed = 0;
281 guint8 trn_rif_bytes;
282 guint8 actual_rif_bytes;
285 /* The trn_hdr struct, as separate variables */
286 guint8 trn_ac; /* access control field */
287 guint8 trn_fc; /* field control field */
288 const guint8 *trn_dhost; /* destination host */
289 const guint8 *trn_shost; /* source host */
291 /* non-source-routed version of source addr */
292 static guint8 trn_shost_nonsr[6];
295 /* Token-Ring Strings */
296 char *fc[] = { "MAC", "LLC", "Reserved", "Unknown" };
298 if (!BYTES_ARE_IN_FRAME(offset, TR_MIN_HEADER_LEN)) {
299 dissect_data(pd, offset, fd, tree);
303 if ((x = check_for_old_linux(pd)))
305 /* Actually packet starts x bytes into what we have got but with all
306 source routing compressed. See comment above */
312 trn_fc = pd[offset+1];
313 trn_dhost = &pd[offset+2];
314 trn_shost = &pd[offset+8];
316 memcpy(trn_shost_nonsr, trn_shost, 6 * sizeof(guint8));
317 trn_shost_nonsr[0] &= 127;
318 frame_type = (trn_fc & 192) >> 6;
320 /* if the high bit on the first byte of src hwaddr is 1, then
321 this packet is source-routed */
322 source_routed = trn_shost[0] & 128;
324 trn_rif_bytes = pd[offset+14] & 31;
326 /* sometimes we have a RCF but no RIF... half source-routed? */
327 /* I'll check for 2 bytes of RIF and the 0x70 byte */
328 if (!source_routed && trn_rif_bytes > 0) {
329 if (trn_rif_bytes == 2) {
332 /* the Linux 2.0 TR code strips source-route bits in
333 * order to test for SR. This can be removed from most
334 * packets with oltr, but not all. So, I try to figure out
335 * which packets should have been SR here. I'll check to
336 * see if there's a SNAP or IPX field right after
340 pd[offset + 0x0e + trn_rif_bytes] == 0xaa &&
341 pd[offset + 0x0f + trn_rif_bytes] == 0xaa &&
342 pd[offset + 0x10 + trn_rif_bytes] == 0x03) ||
344 pd[offset + 0x0e + trn_rif_bytes] == 0xe0 &&
345 pd[offset + 0x0f + trn_rif_bytes] == 0xe0) ) {
350 printf("0e+%d = %02X 0f+%d = %02X\n", trn_rif_bytes,
351 pd[offset + 0x0e + trn_rif_bytes],
353 pd[offset + 0x0f + trn_rif_bytes]);
359 actual_rif_bytes = trn_rif_bytes;
363 actual_rif_bytes = 0;
366 /* this is a silly hack for Linux 2.0.x. Read the comment below,
367 in front of the other #ifdef linux. If we're sniffing our own NIC,
368 we get a full RIF, sometimes with garbage */
369 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
370 (!source_routed && frame_type == 1)) {
371 /* look for SNAP or IPX only */
372 if ( (pd[offset + 0x20] == 0xaa &&
373 pd[offset + 0x21] == 0xaa &&
374 pd[offset + 0x22] == 03)
376 (pd[offset + 0x20] == 0xe0 &&
377 pd[offset + 0x21] == 0xe0) ) {
379 actual_rif_bytes = 18;
388 actual_rif_bytes = 18;
390 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
391 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
392 (i.e. for non SNAP frames e.g. for Netware frames)
393 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
394 bytes as zero frame looks like :-
395 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
396 fixoffset += 8; /* Skip fake LLC and SNAP */
400 /* XXX - copy it to some buffer associated with "pi", rather than
401 just making "trn_shost_nonsr" static? */
402 SET_ADDRESS(&pi.dl_src, AT_ETHER, 6, trn_shost_nonsr);
403 SET_ADDRESS(&pi.src, AT_ETHER, 6, trn_shost_nonsr);
404 SET_ADDRESS(&pi.dl_dst, AT_ETHER, 6, trn_dhost);
405 SET_ADDRESS(&pi.dst, AT_ETHER, 6, trn_dhost);
407 /* information window */
408 if (check_col(fd, COL_PROTOCOL))
409 col_add_str(fd, COL_PROTOCOL, "TR");
410 if (check_col(fd, COL_INFO))
411 col_add_fstr(fd, COL_INFO, "Token-Ring %s", fc[frame_type]);
413 /* protocol analysis tree */
415 /* Create Token-Ring Tree */
416 ti = proto_tree_add_item(tree, proto_tr, NullTVB, offset, 14 + actual_rif_bytes, NULL);
417 tr_tree = proto_item_add_subtree(ti, ett_token_ring);
419 /* Create the Access Control bitfield tree */
420 trn_ac = pd[offset+0];
421 ti = proto_tree_add_item(tr_tree, hf_tr_ac, NullTVB, offset, 1, trn_ac);
422 bf_tree = proto_item_add_subtree(ti, ett_token_ring_ac);
424 proto_tree_add_item(bf_tree, hf_tr_priority, NullTVB, offset, 1, trn_ac);
425 proto_tree_add_item(bf_tree, hf_tr_frame, NullTVB, offset, 1, trn_ac);
426 proto_tree_add_item(bf_tree, hf_tr_monitor_cnt, NullTVB, offset, 1, trn_ac);
427 proto_tree_add_item(bf_tree, hf_tr_priority_reservation, NullTVB, offset, 1, trn_ac);
429 /* Create the Frame Control bitfield tree */
430 ti = proto_tree_add_item(tr_tree, hf_tr_fc, NullTVB, offset + 1, 1, trn_fc);
431 bf_tree = proto_item_add_subtree(ti, ett_token_ring_fc);
433 proto_tree_add_item(bf_tree, hf_tr_fc_type, NullTVB, offset + 1, 1, trn_fc);
434 proto_tree_add_item(bf_tree, hf_tr_fc_pcf, NullTVB, offset + 1, 1, trn_fc);
435 proto_tree_add_item(tr_tree, hf_tr_dst, NullTVB, offset + 2, 6, trn_dhost);
436 proto_tree_add_item(tr_tree, hf_tr_src, NullTVB, offset + 8, 6, trn_shost);
437 proto_tree_add_item_hidden(tr_tree, hf_tr_addr, NullTVB, offset + 2, 6, trn_dhost);
438 proto_tree_add_item_hidden(tr_tree, hf_tr_addr, NullTVB, offset + 8, 6, trn_shost);
440 proto_tree_add_item(tr_tree, hf_tr_sr, NullTVB, offset + 8, 1, source_routed);
442 /* non-source-routed version of src addr */
443 proto_tree_add_item_hidden(tr_tree, hf_tr_src, NullTVB, offset + 8, 6, trn_shost_nonsr);
447 proto_tree_add_item(tr_tree, hf_tr_rif_bytes, NullTVB, offset + 14, 1, trn_rif_bytes);
448 proto_tree_add_item(tr_tree, hf_tr_broadcast, NullTVB, offset + 14, 1, pd[offset + 14] & 224);
451 proto_tree_add_item(tr_tree, hf_tr_max_frame_size, NullTVB, offset + 15, 1, pd[offset + 15] & 112);
452 proto_tree_add_item(tr_tree, hf_tr_direction, NullTVB, offset + 15, 1, pd[offset + 15] & 128);
454 /* if we have more than 2 bytes of RIF, then we have
456 if ((trn_rif_bytes > 2) && BYTES_ARE_IN_FRAME(offset + 14, trn_rif_bytes)) {
457 add_ring_bridge_pairs(trn_rif_bytes,
458 pd, offset, tr_tree);
462 /* Linux 2.0.x has a problem in that the 802.5 code creates
463 an emtpy full (18-byte) RIF area. It's up to the tr driver to
464 either fill it in or remove it before sending the bytes out
465 to the wire. If you run tcpdump on a Linux 2.0.x machine running
466 token-ring, tcpdump will capture these 18 filler bytes. They
467 are filled with garbage. The best way to detect this problem is
468 to know the src hwaddr of the machine from which you were running
469 tcpdump. W/o that, however, I'm guessing that DSAP == SSAP if the
470 frame type is LLC. It's very much a hack. -- Gilbert Ramirez */
471 if (actual_rif_bytes > trn_rif_bytes) {
472 proto_tree_add_text(tr_tree, NullTVB, 14 + trn_rif_bytes, actual_rif_bytes - trn_rif_bytes,
473 "Empty RIF from Linux 2.0.x driver. The sniffing NIC "
474 "is also running a protocol stack.");
477 proto_tree_add_text(tr_tree, NullTVB, 14 + 18,8,"Linux 2.0.x fake LLC and SNAP header");
480 offset += 14 + actual_rif_bytes + fixoffset;
482 if (IS_DATA_IN_FRAME(offset)) {
483 next_tvb = tvb_new_subset(pi.compat_top_tvb, offset, -1);
484 /* The package is either MAC or LLC */
485 switch (frame_type) {
488 dissect_trmac(pd, offset, fd, tree);
491 dissect_llc(next_tvb, &pi, tree);
494 /* non-MAC, non-LLC, i.e., "Reserved" */
495 dissect_data_tvb(next_tvb, &pi, tree);
501 /* this routine is taken from the Linux net/802/tr.c code, which shows
502 ring-bridge pairs in the /proc/net/tr_rif virtual file. */
504 add_ring_bridge_pairs(int rcf_len, const u_char *pd, int offset, proto_tree *tree)
507 int segment, brdgnmb, unprocessed_rif;
510 #define RIF_BYTES_TO_PROCESS 30
512 char buffer[3 + (RIF_BYTES_TO_PROCESS / 2) * 6 + 1];
514 /* Only process so many bytes of RIF, as per TR spec, and not overflow
515 * static buffer above */
516 unprocessed_rif = rcf_len - RIF_BYTES_TO_PROCESS;
517 rcf_len = MIN(rcf_len, RIF_BYTES_TO_PROCESS);
519 /* Ignore the 2 RCF bytes, since they don't make up the ring/bride pairs */
522 for(j = 1; j < rcf_len - 1; j += 2) {
524 segment=pntohs(&pd[offset + 16]) >> 4;
525 size = sprintf(buffer, "%03X",segment);
526 proto_tree_add_item_hidden(tree, hf_tr_rif_ring, NullTVB, offset + 16, 2, segment);
529 segment=pntohs(&pd[offset+17+j]) >> 4;
530 brdgnmb=pd[offset+16+j] & 0x0f;
531 size = sprintf(buffer+buff_offset, "-%01X-%03X",brdgnmb,segment);
532 proto_tree_add_item_hidden(tree, hf_tr_rif_ring, NullTVB, offset+17+j, 2, segment);
533 proto_tree_add_item_hidden(tree, hf_tr_rif_bridge, NullTVB, offset+16+j, 1, brdgnmb);
536 proto_tree_add_item(tree, hf_tr_rif, NullTVB, offset+16, rcf_len, buffer);
538 if (unprocessed_rif > 0) {
539 proto_tree_add_text(tree, NullTVB, offset+14+RIF_BYTES_TO_PROCESS, unprocessed_rif,
540 "Extra RIF bytes beyond spec: %d", unprocessed_rif);
545 proto_register_tr(void)
547 static hf_register_info hf[] = {
549 { "Access Control", "tr.ac", FT_UINT8, BASE_HEX, NULL, 0x0,
553 { "Priority", "tr.priority", FT_UINT8, BASE_DEC, NULL, 0xe0,
557 { "Frame", "tr.frame", FT_BOOLEAN, 8, TFS(&ac_truth), 0x10,
560 { &hf_tr_monitor_cnt,
561 { "Monitor Count", "tr.monitor_cnt", FT_UINT8, BASE_DEC, NULL, 0x08,
564 { &hf_tr_priority_reservation,
565 { "Priority Reservation","tr.priority_reservation", FT_UINT8, BASE_DEC, NULL, 0x07,
569 { "Frame Control", "tr.fc", FT_UINT8, BASE_HEX, NULL, 0x0,
573 { "Frame Type", "tr.frame_type", FT_UINT8, BASE_DEC, VALS(frame_vals), 0xc0,
577 { "Frame PCF", "tr.frame_pcf", FT_UINT8, BASE_DEC, VALS(pcf_vals), 0x0f,
581 { "Destination", "tr.dst", FT_ETHER, BASE_NONE, NULL, 0x0,
582 "Destination Hardware Address" }},
585 { "Source", "tr.src", FT_ETHER, BASE_NONE, NULL, 0x0,
586 "Source Hardware Address" }},
589 { "Source or Destination Address", "tr.addr", FT_ETHER, BASE_NONE, NULL, 0x0,
590 "Source or Destination Hardware Address" }},
593 { "Source Routed", "tr.sr", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
597 { "RIF Bytes", "tr.rif_bytes", FT_UINT8, BASE_DEC, NULL, 0x0,
598 "Number of bytes in Routing Information Fields, including "
599 "the two bytes of Routing Control Field" }},
602 { "Broadcast Type", "tr.broadcast", FT_UINT8, BASE_DEC, VALS(broadcast_vals), 0x0,
603 "Type of Token-Ring Broadcast" }},
605 { &hf_tr_max_frame_size,
606 { "Maximum Frame Size", "tr.max_frame_size", FT_UINT8, BASE_DEC, VALS(max_frame_size_vals),
611 { "Direction", "tr.direction", FT_UINT8, BASE_DEC, VALS(direction_vals), 0x0,
612 "Direction of RIF" }},
615 { "Ring-Bridge Pairs", "tr.rif", FT_STRING, BASE_NONE, NULL, 0x0,
616 "String representing Ring-Bridge Pairs" }},
619 { "RIF Ring", "tr.rif.ring", FT_UINT16, BASE_HEX, NULL, 0x0,
623 { "RIF Bridge", "tr.rif.bridge", FT_UINT8, BASE_HEX, NULL, 0x0,
626 static gint *ett[] = {
632 proto_tr = proto_register_protocol("Token-Ring", "tr");
633 proto_register_field_array(proto_tr, hf, array_length(hf));
634 proto_register_subtree_array(ett, array_length(ett));