2 * Routines for the Generic Routing Encapsulation (GRE) protocol
3 * Brad Robel-Forrest <brad.robel-forrest@watchguard.com>
5 * $Id: packet-gre.c,v 1.43 2001/04/23 18:11:01 guy Exp $
7 * Ethereal - Network traffic analyzer
8 * By Gerald Combs <gerald@ethereal.com>
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>
35 #ifdef HAVE_NETINET_IN_H
36 #include <netinet/in.h>
40 #include "packet-wccp.h"
46 static int proto_gre = -1;
47 static int hf_gre_proto = -1;
49 static gint ett_gre = -1;
50 static gint ett_gre_flags = -1;
51 static gint ett_gre_wccp2_redirect_header = -1;
53 static dissector_table_t gre_dissector_table;
55 /* bit positions for flags in header */
61 #define GH_B_RECUR 0x0700
62 #define GH_P_A 0x0080 /* only in special PPTPized GRE header */
63 #define GH_P_FLAGS 0x0078 /* only in special PPTPized GRE header */
64 #define GH_R_FLAGS 0x00F8
65 #define GH_B_VER 0x0007
67 static void add_flags_and_ver(proto_tree *, guint16, tvbuff_t *, int, int);
68 static void dissect_gre_wccp2_redirect_header(tvbuff_t *, int, proto_tree *);
70 static const value_string typevals[] = {
71 { ETHERTYPE_PPP, "PPP" },
72 { ETHERTYPE_IP, "IP" },
74 { ETHERTYPE_IPX, "IPX"},
75 { ETHERTYPE_ETHBRIDGE, "Transparent Ethernet bridging" },
76 { GRE_FR, "Frame Relay"},
81 dissect_gre(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
84 guint16 flags_and_ver;
86 gboolean is_ppp = FALSE;
87 gboolean is_wccp2 = FALSE;
90 proto_tree *gre_tree = NULL;
95 flags_and_ver = tvb_get_ntohs(tvb, offset);
96 type = tvb_get_ntohs(tvb, offset + sizeof(flags_and_ver));
98 if (check_col(pinfo->fd, COL_PROTOCOL))
99 col_set_str(pinfo->fd, COL_PROTOCOL, "GRE");
101 if (check_col(pinfo->fd, COL_INFO)) {
102 col_add_fstr(pinfo->fd, COL_INFO, "Encapsulated %s",
103 val_to_str(type, typevals, "0x%04X (unknown)"));
106 if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R)
108 if (flags_and_ver & GH_B_K)
110 if (flags_and_ver & GH_B_S)
115 if (flags_and_ver & GH_P_A)
121 /* WCCP2 puts an extra 4 octets into the header, but uses the same
122 encapsulation type; if it looks as if the first octet of the packet
123 isn't the beginning of an IPv4 header, assume it's WCCP2. */
124 if ((tvb_get_guint8(tvb, offset + sizeof(flags_and_ver) + sizeof(type)) & 0xF0) != 0x40) {
132 ti = proto_tree_add_protocol_format(tree, proto_gre, tvb, offset, len,
133 "Generic Routing Encapsulation (%s)",
134 val_to_str(type, typevals, "0x%04X - unknown"));
135 gre_tree = proto_item_add_subtree(ti, ett_gre);
136 add_flags_and_ver(gre_tree, flags_and_ver, tvb, offset, is_ppp);
138 offset += sizeof(flags_and_ver);
141 proto_tree_add_uint(gre_tree, hf_gre_proto, tvb, offset, sizeof(type), type);
143 offset += sizeof(type);
145 if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
147 guint length, reported_length;
149 guint16 cksum, computed_cksum;
151 cksum = tvb_get_ntohs(tvb, offset);
152 length = tvb_length(tvb);
153 reported_length = tvb_reported_length(tvb);
154 if ((flags_and_ver & GH_B_C) && !pinfo->fragmented
155 && length >= reported_length) {
156 /* The Checksum Present bit is set, and the packet isn't part of a
157 fragmented datagram and isn't truncated, so we can checksum it. */
159 cksum_vec[0].ptr = tvb_get_ptr(tvb, 0, reported_length);
160 cksum_vec[0].len = reported_length;
161 computed_cksum = in_cksum(cksum_vec, 1);
162 if (computed_cksum == 0) {
163 proto_tree_add_text(gre_tree, tvb, offset, 2,
164 "Checksum: 0x%04x (correct)", cksum);
166 proto_tree_add_text(gre_tree, tvb, offset, 2,
167 "Checksum: 0x%04x (incorrect, should be 0x%04x)",
168 cksum, in_cksum_shouldbe(cksum, computed_cksum));
171 proto_tree_add_text(gre_tree, tvb, offset, 2,
172 "Checksum: 0x%04x", cksum);
178 if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
180 proto_tree_add_text(gre_tree, tvb, offset, 2,
181 "Offset: %u", tvb_get_ntohs(tvb, offset));
186 if (flags_and_ver & GH_B_K) {
189 proto_tree_add_text(gre_tree, tvb, offset, 2,
190 "Payload length: %u", tvb_get_ntohs(tvb, offset));
194 proto_tree_add_text(gre_tree, tvb, offset, 2,
195 "Call ID: %u", tvb_get_ntohs(tvb, offset));
201 proto_tree_add_text(gre_tree, tvb, offset, 4,
202 "Key: %u", tvb_get_ntohl(tvb, offset));
208 if (flags_and_ver & GH_B_S) {
210 proto_tree_add_text(gre_tree, tvb, offset, 4,
211 "Sequence number: %u", tvb_get_ntohl(tvb, offset));
216 if (is_ppp && flags_and_ver & GH_P_A) {
218 proto_tree_add_text(gre_tree, tvb, offset, 4,
219 "Acknowledgement number: %u", tvb_get_ntohl(tvb, offset));
224 if (flags_and_ver & GH_B_R) {
226 sre_af = tvb_get_ntohs(tvb, offset);
228 proto_tree_add_text(gre_tree, tvb, offset, sizeof(guint16),
229 "Address family: %u", sre_af);
231 offset += sizeof(guint16);
233 proto_tree_add_text(gre_tree, tvb, offset, 1,
234 "SRE offset: %u", tvb_get_guint8(tvb, offset));
236 offset += sizeof(guint8);
237 sre_length = tvb_get_guint8(tvb, offset);
239 proto_tree_add_text(gre_tree, tvb, offset, sizeof(guint8),
240 "SRE length: %u", sre_length);
242 offset += sizeof(guint8);
243 if (sre_af == 0 && sre_length == 0)
245 offset += sre_length;
249 if (type == GRE_WCCP) {
252 dissect_gre_wccp2_redirect_header(tvb, offset, gre_tree);
256 next_tvb = tvb_new_subset(tvb, offset, -1, -1);
257 if (!dissector_try_port(gre_dissector_table, type, next_tvb, pinfo, tree))
258 dissect_data(next_tvb, 0, pinfo, gre_tree);
262 add_flags_and_ver(proto_tree *tree, guint16 flags_and_ver, tvbuff_t *tvb,
263 int offset, int is_ppp)
266 proto_tree * fv_tree;
267 int nbits = sizeof(flags_and_ver) * 8;
269 ti = proto_tree_add_text(tree, tvb, offset, 2,
270 "Flags and version: %#04x", flags_and_ver);
271 fv_tree = proto_item_add_subtree(ti, ett_gre_flags);
273 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
274 decode_boolean_bitfield(flags_and_ver, GH_B_C, nbits,
275 "Checksum", "No checksum"));
276 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
277 decode_boolean_bitfield(flags_and_ver, GH_B_R, nbits,
278 "Routing", "No routing"));
279 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
280 decode_boolean_bitfield(flags_and_ver, GH_B_K, nbits,
282 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
283 decode_boolean_bitfield(flags_and_ver, GH_B_S, nbits,
284 "Sequence number", "No sequence number"));
285 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
286 decode_boolean_bitfield(flags_and_ver, GH_B_s, nbits,
287 "Strict source route", "No strict source route"));
288 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
289 decode_numeric_bitfield(flags_and_ver, GH_B_RECUR, nbits,
290 "Recursion control: %u"));
292 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
293 decode_boolean_bitfield(flags_and_ver, GH_P_A, nbits,
294 "Acknowledgment number", "No acknowledgment number"));
295 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
296 decode_numeric_bitfield(flags_and_ver, GH_P_FLAGS, nbits,
300 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
301 decode_numeric_bitfield(flags_and_ver, GH_R_FLAGS, nbits,
305 proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
306 decode_numeric_bitfield(flags_and_ver, GH_B_VER, nbits,
311 dissect_gre_wccp2_redirect_header(tvbuff_t *tvb, int offset, proto_tree *tree)
314 proto_tree * rh_tree;
317 ti = proto_tree_add_text(tree, tvb, offset, 4, "Redirect header");
318 rh_tree = proto_item_add_subtree(ti, ett_gre_wccp2_redirect_header);
320 rh_flags = tvb_get_guint8(tvb, offset);
321 proto_tree_add_text(rh_tree, tvb, offset, 1, "%s",
322 decode_boolean_bitfield(rh_flags, 0x80, 8,
323 "Dynamic service", "Well-known service"));
324 proto_tree_add_text(rh_tree, tvb, offset, 1, "%s",
325 decode_boolean_bitfield(rh_flags, 0x40, 8,
326 "Alternative bucket used", "Alternative bucket not used"));
328 proto_tree_add_text(rh_tree, tvb, offset + 1, 1, "Service ID: %s",
329 val_to_str(tvb_get_guint8(tvb, offset + 1), service_id_vals, "Unknown (0x%02X)"));
331 proto_tree_add_text(rh_tree, tvb, offset + 2, 1, "Alternative bucket index: %u",
332 tvb_get_guint8(tvb, offset + 2));
333 proto_tree_add_text(rh_tree, tvb, offset + 3, 1, "Primary bucket index: %u",
334 tvb_get_guint8(tvb, offset + 3));
338 proto_register_gre(void)
340 static hf_register_info hf[] = {
342 { "Protocol Type", "gre.proto", FT_UINT16, BASE_HEX, VALS(typevals), 0x0,
343 "The protocol that is GRE encapsulated"}
346 static gint *ett[] = {
349 &ett_gre_wccp2_redirect_header,
352 proto_gre = proto_register_protocol("Generic Routing Encapsulation",
354 proto_register_field_array(proto_gre, hf, array_length(hf));
355 proto_register_subtree_array(ett, array_length(ett));
357 /* subdissector code */
358 gre_dissector_table = register_dissector_table("gre.proto");
362 proto_reg_handoff_gre(void)
364 dissector_add("ip.proto", IP_PROTO_GRE, dissect_gre, proto_gre);