2 * Routines for Token-Ring packet disassembly
3 * Gilbert Ramirez <gram@xiexie.org>
5 * $Id: packet-tr.c,v 1.36 2000/03/20 22:22:45 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 guint8 trn_shost[6]; /* 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 memcpy(&trn_fc, &pd[offset + 1], sizeof(guint8));
181 memcpy(trn_shost, &pd[offset + 8], 6 * sizeof(guint8));
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;
284 /* The trn_hdr struct, as separate variables */
285 guint8 trn_ac; /* access control field */
286 guint8 trn_fc; /* field control field */
287 guint8 trn_dhost[6]; /* destination host */
288 guint8 trn_shost[6]; /* source host */
289 guint16 trn_rcf; /* routing control field */
290 guint16 trn_rseg[8]; /* routing registers */
292 /* non-source-routed version of source addr */
293 static guint8 trn_shost_nonsr[6];
296 /* Token-Ring Strings */
297 char *fc[] = { "MAC", "LLC", "Reserved", "Unknown" };
299 if (!BYTES_ARE_IN_FRAME(offset, TR_MIN_HEADER_LEN)) {
300 dissect_data(pd, offset, fd, tree);
304 if ((x = check_for_old_linux(pd)))
306 /* Actually packet starts x bytes into what we have got but with all
307 source routing compressed. See comment above */
314 memcpy(&trn_ac, &pd[offset+0], sizeof(guint8));
315 memcpy(&trn_fc, &pd[offset+1], sizeof(guint8));
316 memcpy(trn_dhost, &pd[offset+2], 6 * sizeof(guint8));
317 memcpy(trn_shost, &pd[offset+8], 6 * sizeof(guint8));
318 memcpy(&trn_rcf, &pd[offset+14], sizeof(guint16));
319 memcpy(trn_rseg, &pd[offset+16], 8 * sizeof(guint16));
321 memcpy(trn_shost_nonsr, &pd[offset+8], 6 * sizeof(guint8));
322 trn_shost_nonsr[0] &= 127;
323 frame_type = (trn_fc & 192) >> 6;
325 /* if the high bit on the first byte of src hwaddr is 1, then
326 this packet is source-routed */
327 source_routed = trn_shost[0] & 128;
329 trn_rif_bytes = pd[offset+14] & 31;
331 /* sometimes we have a RCF but no RIF... half source-routed? */
332 /* I'll check for 2 bytes of RIF and the 0x70 byte */
333 if (!source_routed && trn_rif_bytes > 0) {
334 if (trn_rif_bytes == 2) {
337 /* the Linux 2.0 TR code strips source-route bits in
338 * order to test for SR. This can be removed from most
339 * packets with oltr, but not all. So, I try to figure out
340 * which packets should have been SR here. I'll check to
341 * see if there's a SNAP or IPX field right after
345 pd[offset + 0x0e + trn_rif_bytes] == 0xaa &&
346 pd[offset + 0x0f + trn_rif_bytes] == 0xaa &&
347 pd[offset + 0x10 + trn_rif_bytes] == 0x03) ||
349 pd[offset + 0x0e + trn_rif_bytes] == 0xe0 &&
350 pd[offset + 0x0f + trn_rif_bytes] == 0xe0) ) {
355 printf("0e+%d = %02X 0f+%d = %02X\n", trn_rif_bytes,
356 pd[offset + 0x0e + trn_rif_bytes],
358 pd[offset + 0x0f + trn_rif_bytes]);
364 actual_rif_bytes = trn_rif_bytes;
368 actual_rif_bytes = 0;
371 /* this is a silly hack for Linux 2.0.x. Read the comment below,
372 in front of the other #ifdef linux. If we're sniffing our own NIC,
373 we get a full RIF, sometimes with garbage */
374 if ((source_routed && trn_rif_bytes == 2 && frame_type == 1) ||
375 (!source_routed && frame_type == 1)) {
376 /* look for SNAP or IPX only */
377 if ( (pd[offset + 0x20] == 0xaa &&
378 pd[offset + 0x21] == 0xaa &&
379 pd[offset + 0x22] == 03)
381 (pd[offset + 0x20] == 0xe0 &&
382 pd[offset + 0x21] == 0xe0) ) {
384 actual_rif_bytes = 18;
393 actual_rif_bytes = 18;
395 /* Linux 2.0.x also requires drivers pass up a fake SNAP and LLC header before th
396 real LLC hdr for all Token Ring frames that arrive with DSAP and SSAP != 0xAA
397 (i.e. for non SNAP frames e.g. for Netware frames)
398 the fake SNAP header has the ETH_P_TR_802_2 ether type (0x0011) and the protocol id
399 bytes as zero frame looks like :-
400 TR Header | Fake LLC | Fake SNAP | Wire LLC | Rest of data */
401 fixoffset += 8; /* Skip fake LLC and SNAP */
405 /* XXX - copy it to some buffer associated with "pi", rather than
406 just making "trn_shost_nonsr" static? */
407 SET_ADDRESS(&pi.dl_src, AT_ETHER, 6, &trn_shost_nonsr[0]);
408 SET_ADDRESS(&pi.src, AT_ETHER, 6, &trn_shost_nonsr[0]);
409 SET_ADDRESS(&pi.dl_dst, AT_ETHER, 6, &pd[offset + 2]);
410 SET_ADDRESS(&pi.dst, AT_ETHER, 6, &pd[offset + 2]);
412 /* information window */
413 if (check_col(fd, COL_PROTOCOL))
414 col_add_str(fd, COL_PROTOCOL, "TR");
415 if (check_col(fd, COL_INFO))
416 col_add_fstr(fd, COL_INFO, "Token-Ring %s", fc[frame_type]);
418 /* protocol analysis tree */
420 /* Create Token-Ring Tree */
421 ti = proto_tree_add_item(tree, proto_tr, offset, 14 + actual_rif_bytes, NULL);
422 tr_tree = proto_item_add_subtree(ti, ett_token_ring);
424 /* Create the Access Control bitfield tree */
425 ti = proto_tree_add_item(tr_tree, hf_tr_ac, offset, 1, trn_ac);
426 bf_tree = proto_item_add_subtree(ti, ett_token_ring_ac);
428 proto_tree_add_item(bf_tree, hf_tr_priority, offset, 1, trn_ac);
429 proto_tree_add_item(bf_tree, hf_tr_frame, offset, 1, trn_ac);
430 proto_tree_add_item(bf_tree, hf_tr_monitor_cnt, offset, 1, trn_ac);
431 proto_tree_add_item(bf_tree, hf_tr_priority_reservation, offset, 1, trn_ac);
433 /* Create the Frame Control bitfield tree */
434 ti = proto_tree_add_item(tr_tree, hf_tr_fc, offset + 1, 1, trn_fc);
435 bf_tree = proto_item_add_subtree(ti, ett_token_ring_fc);
437 proto_tree_add_item(bf_tree, hf_tr_fc_type, offset + 1, 1, trn_fc);
438 proto_tree_add_item(bf_tree, hf_tr_fc_pcf, offset + 1, 1, trn_fc);
439 proto_tree_add_item(tr_tree, hf_tr_dst, offset + 2, 6, trn_dhost);
440 proto_tree_add_item(tr_tree, hf_tr_src, offset + 8, 6, trn_shost);
441 proto_tree_add_item_hidden(tr_tree, hf_tr_addr, offset + 2, 6, trn_dhost);
442 proto_tree_add_item_hidden(tr_tree, hf_tr_addr, offset + 8, 6, trn_shost);
444 proto_tree_add_item_hidden(tr_tree, hf_tr_sr, offset + 8, 1, source_routed);
446 /* non-source-routed version of src addr */
447 proto_tree_add_item_hidden(tr_tree, hf_tr_src, offset + 8, 6, trn_shost_nonsr);
451 proto_tree_add_item(tr_tree, hf_tr_rif_bytes, offset + 14, 1, trn_rif_bytes);
452 proto_tree_add_item(tr_tree, hf_tr_broadcast, offset + 14, 1, pd[offset + 14] & 224);
455 proto_tree_add_item(tr_tree, hf_tr_max_frame_size, offset + 15, 1, pd[offset + 15] & 112);
456 proto_tree_add_item(tr_tree, hf_tr_direction, offset + 15, 1, pd[offset + 15] & 128);
458 /* if we have more than 2 bytes of RIF, then we have
460 if ((trn_rif_bytes > 2) && BYTES_ARE_IN_FRAME(offset + 14, trn_rif_bytes)) {
461 add_ring_bridge_pairs(trn_rif_bytes,
462 pd, offset, tr_tree);
466 /* Linux 2.0.x has a problem in that the 802.5 code creates
467 an emtpy full (18-byte) RIF area. It's up to the tr driver to
468 either fill it in or remove it before sending the bytes out
469 to the wire. If you run tcpdump on a Linux 2.0.x machine running
470 token-ring, tcpdump will capture these 18 filler bytes. They
471 are filled with garbage. The best way to detect this problem is
472 to know the src hwaddr of the machine from which you were running
473 tcpdump. W/o that, however, I'm guessing that DSAP == SSAP if the
474 frame type is LLC. It's very much a hack. -- Gilbert Ramirez */
475 if (actual_rif_bytes > trn_rif_bytes) {
476 proto_tree_add_text(tr_tree, 14 + trn_rif_bytes, actual_rif_bytes - trn_rif_bytes,
477 "Empty RIF from Linux 2.0.x driver. The sniffing NIC "
478 "is also running a protocol stack.");
481 proto_tree_add_text(tr_tree, 14 + 18,8,"Linux 2.0.x fake LLC and SNAP header");
484 offset += 14 + actual_rif_bytes + fixoffset;
486 if (IS_DATA_IN_FRAME(offset)) {
487 /* The package is either MAC or LLC */
488 switch (frame_type) {
491 dissect_trmac(pd, offset, fd, tree);
494 dissect_llc(pd, offset, fd, tree);
497 /* non-MAC, non-LLC, i.e., "Reserved" */
498 dissect_data(pd, offset, fd, tree);
504 /* this routine is taken from the Linux net/802/tr.c code, which shows
505 ring-bridge pairs in the /proc/net/tr_rif virtual file. */
507 add_ring_bridge_pairs(int rcf_len, const u_char *pd, int offset, proto_tree *tree)
510 int segment, brdgnmb, unprocessed_rif;
513 #define RIF_BYTES_TO_PROCESS 30
515 char buffer[3 + (RIF_BYTES_TO_PROCESS / 2) * 6 + 1];
517 /* Only process so many bytes of RIF, as per TR spec, and not overflow
518 * static buffer above */
519 unprocessed_rif = rcf_len - RIF_BYTES_TO_PROCESS;
520 rcf_len = MIN(rcf_len, RIF_BYTES_TO_PROCESS);
522 /* Ignore the 2 RCF bytes, since they don't make up the ring/bride pairs */
525 for(j = 1; j < rcf_len - 1; j += 2) {
527 segment=pntohs(&pd[offset + 16]) >> 4;
528 size = sprintf(buffer, "%03X",segment);
529 proto_tree_add_item_hidden(tree, hf_tr_rif_ring, offset + 16, 2, segment);
532 segment=pntohs(&pd[offset+17+j]) >> 4;
533 brdgnmb=pd[offset+16+j] & 0x0f;
534 size = sprintf(buffer+buff_offset, "-%01X-%03X",brdgnmb,segment);
535 proto_tree_add_item_hidden(tree, hf_tr_rif_ring, offset+17+j, 2, segment);
536 proto_tree_add_item_hidden(tree, hf_tr_rif_bridge, offset+16+j, 1, brdgnmb);
539 proto_tree_add_item(tree, hf_tr_rif, offset+16, rcf_len, buffer);
541 if (unprocessed_rif > 0) {
542 proto_tree_add_text(tree, offset+14+RIF_BYTES_TO_PROCESS, unprocessed_rif,
543 "Extra RIF bytes beyond spec: %d", unprocessed_rif);
548 proto_register_tr(void)
550 static hf_register_info hf[] = {
552 { "Access Control", "tr.ac", FT_UINT8, BASE_HEX, NULL, 0x0,
556 { "Priority", "tr.priority", FT_UINT8, BASE_DEC, NULL, 0xe0,
560 { "Frame", "tr.frame", FT_BOOLEAN, 8, TFS(&ac_truth), 0x10,
563 { &hf_tr_monitor_cnt,
564 { "Monitor Count", "tr.monitor_cnt", FT_UINT8, BASE_DEC, NULL, 0x08,
567 { &hf_tr_priority_reservation,
568 { "Priority Reservation","tr.priority_reservation", FT_UINT8, BASE_DEC, NULL, 0x07,
572 { "Frame Control", "tr.fc", FT_UINT8, BASE_HEX, NULL, 0x0,
576 { "Frame Type", "tr.frame_type", FT_UINT8, BASE_DEC, VALS(frame_vals), 0xc0,
580 { "Frame PCF", "tr.frame_pcf", FT_UINT8, BASE_DEC, VALS(pcf_vals), 0x0f,
584 { "Destination", "tr.dst", FT_ETHER, BASE_NONE, NULL, 0x0,
585 "Destination Hardware Address" }},
588 { "Source", "tr.src", FT_ETHER, BASE_NONE, NULL, 0x0,
589 "Source Hardware Address" }},
592 { "Source or Destination Address", "tr.addr", FT_ETHER, BASE_NONE, NULL, 0x0,
593 "Source or Destination Hardware Address" }},
596 { "Source Routed", "tr.sr", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
600 { "RIF Bytes", "tr.rif_bytes", FT_UINT8, BASE_DEC, NULL, 0x0,
601 "Number of bytes in Routing Information Fields, including "
602 "the two bytes of Routing Control Field" }},
605 { "Broadcast Type", "tr.broadcast", FT_UINT8, BASE_DEC, VALS(broadcast_vals), 0x0,
606 "Type of Token-Ring Broadcast" }},
608 { &hf_tr_max_frame_size,
609 { "Maximum Frame Size", "tr.max_frame_size", FT_UINT8, BASE_DEC, VALS(max_frame_size_vals),
614 { "Direction", "tr.direction", FT_UINT8, BASE_DEC, VALS(direction_vals), 0x0,
615 "Direction of RIF" }},
618 { "Ring-Bridge Pairs", "tr.rif", FT_STRING, BASE_NONE, NULL, 0x0,
619 "String representing Ring-Bridge Pairs" }},
622 { "RIF Ring", "tr.rif.ring", FT_UINT16, BASE_HEX, NULL, 0x0,
626 { "RIF Bridge", "tr.rif.bridge", FT_UINT8, BASE_HEX, NULL, 0x0,
629 static gint *ett[] = {
635 proto_tr = proto_register_protocol("Token-Ring", "tr");
636 proto_register_field_array(proto_tr, hf, array_length(hf));
637 proto_register_subtree_array(ett, array_length(ett));