aboutsummaryrefslogtreecommitdiffstats
path: root/epan/dissectors/packet-gre.c
diff options
context:
space:
mode:
Diffstat (limited to 'epan/dissectors/packet-gre.c')
-rw-r--r--epan/dissectors/packet-gre.c388
1 files changed, 388 insertions, 0 deletions
diff --git a/epan/dissectors/packet-gre.c b/epan/dissectors/packet-gre.c
new file mode 100644
index 0000000000..b7a29f575c
--- /dev/null
+++ b/epan/dissectors/packet-gre.c
@@ -0,0 +1,388 @@
+/* packet-gre.c
+ * Routines for the Generic Routing Encapsulation (GRE) protocol
+ * Brad Robel-Forrest <brad.robel-forrest@watchguard.com>
+ *
+ * $Id$
+ *
+ * Ethereal - Network traffic analyzer
+ * By Gerald Combs <gerald@ethereal.com>
+ * Copyright 1998 Gerald Combs
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <glib.h>
+#include <epan/packet.h>
+#include "packet-wccp.h"
+#include "in_cksum.h"
+#include "etypes.h"
+#include "greproto.h"
+#include "ipproto.h"
+#include "llcsaps.h"
+
+/*
+ * See RFC 1701 "Generic Routing Encapsulation (GRE)", RFC 1702
+ * "Generic Routing Encapsulation over IPv4 networks", RFC 2637
+ * "Point-to-Point Tunneling Protocol (PPTP)", RFC 2784 "Generic
+ * Routing Encapsulation (GRE)", RFC 2890 "Key and Sequence
+ * Number Extensions to GRE" and draft-ietf-mpls-in-ip-or-gre-07.txt
+ * "Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE)".
+ */
+
+static int proto_gre = -1;
+static int hf_gre_proto = -1;
+
+static gint ett_gre = -1;
+static gint ett_gre_flags = -1;
+static gint ett_gre_wccp2_redirect_header = -1;
+
+static dissector_table_t gre_dissector_table;
+static dissector_handle_t data_handle;
+
+/* bit positions for flags in header */
+#define GH_B_C 0x8000
+#define GH_B_R 0x4000
+#define GH_B_K 0x2000
+#define GH_B_S 0x1000
+#define GH_B_s 0x0800
+#define GH_B_RECUR 0x0700
+#define GH_P_A 0x0080 /* only in special PPTPized GRE header */
+#define GH_P_FLAGS 0x0078 /* only in special PPTPized GRE header */
+#define GH_R_FLAGS 0x00F8
+#define GH_B_VER 0x0007
+
+static void add_flags_and_ver(proto_tree *, guint16, tvbuff_t *, int, int);
+static void dissect_gre_wccp2_redirect_header(tvbuff_t *, int, proto_tree *);
+
+static const value_string typevals[] = {
+ { ETHERTYPE_PPP, "PPP" },
+ { ETHERTYPE_IP, "IP" },
+ { SAP_OSINL5, "OSI"},
+ { GRE_WCCP, "WCCP"},
+ { ETHERTYPE_IPX, "IPX"},
+ { ETHERTYPE_ETHBRIDGE, "Transparent Ethernet bridging" },
+ { GRE_FR, "Frame Relay"},
+ { ETHERTYPE_IPv6, "IPv6" },
+ { ETHERTYPE_MPLS, "MPLS label switched packet" },
+ { 0, NULL }
+};
+
+static void
+dissect_gre(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+{
+ int offset = 0;
+ guint16 flags_and_ver;
+ guint16 type;
+ gboolean is_ppp = FALSE;
+ gboolean is_wccp2 = FALSE;
+ guint len = 4;
+ proto_item *ti;
+ proto_tree *gre_tree = NULL;
+ guint16 sre_af;
+ guint8 sre_length;
+ tvbuff_t *next_tvb;
+
+ flags_and_ver = tvb_get_ntohs(tvb, offset);
+ type = tvb_get_ntohs(tvb, offset + sizeof(flags_and_ver));
+
+ if (check_col(pinfo->cinfo, COL_PROTOCOL))
+ col_set_str(pinfo->cinfo, COL_PROTOCOL, "GRE");
+
+ if (check_col(pinfo->cinfo, COL_INFO)) {
+ col_add_fstr(pinfo->cinfo, COL_INFO, "Encapsulated %s",
+ val_to_str(type, typevals, "0x%04X (unknown)"));
+ }
+
+ if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R)
+ len += 4;
+ if (flags_and_ver & GH_B_K)
+ len += 4;
+ if (flags_and_ver & GH_B_S)
+ len += 4;
+ switch (type) {
+
+ case ETHERTYPE_PPP:
+ if (flags_and_ver & GH_P_A)
+ len += 4;
+ is_ppp = TRUE;
+ break;
+
+ case GRE_WCCP:
+ /* WCCP2 puts an extra 4 octets into the header, but uses the same
+ encapsulation type; if it looks as if the first octet of the packet
+ isn't the beginning of an IPv4 header, assume it's WCCP2. */
+ if ((tvb_get_guint8(tvb, offset + sizeof(flags_and_ver) + sizeof(type)) & 0xF0) != 0x40) {
+ len += 4;
+ is_wccp2 = TRUE;
+ }
+ break;
+ }
+
+ if (tree) {
+ ti = proto_tree_add_protocol_format(tree, proto_gre, tvb, offset, len,
+ "Generic Routing Encapsulation (%s)",
+ val_to_str(type, typevals, "0x%04X - unknown"));
+ gre_tree = proto_item_add_subtree(ti, ett_gre);
+ add_flags_and_ver(gre_tree, flags_and_ver, tvb, offset, is_ppp);
+ }
+ offset += sizeof(flags_and_ver);
+
+ if (tree) {
+ proto_tree_add_uint(gre_tree, hf_gre_proto, tvb, offset, sizeof(type), type);
+ }
+ offset += sizeof(type);
+
+ if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
+ if (tree) {
+ guint length, reported_length;
+ vec_t cksum_vec[1];
+ guint16 cksum, computed_cksum;
+
+ cksum = tvb_get_ntohs(tvb, offset);
+ length = tvb_length(tvb);
+ reported_length = tvb_reported_length(tvb);
+ if ((flags_and_ver & GH_B_C) && !pinfo->fragmented
+ && length >= reported_length) {
+ /* The Checksum Present bit is set, and the packet isn't part of a
+ fragmented datagram and isn't truncated, so we can checksum it. */
+
+ cksum_vec[0].ptr = tvb_get_ptr(tvb, 0, reported_length);
+ cksum_vec[0].len = reported_length;
+ computed_cksum = in_cksum(cksum_vec, 1);
+ if (computed_cksum == 0) {
+ proto_tree_add_text(gre_tree, tvb, offset, 2,
+ "Checksum: 0x%04x (correct)", cksum);
+ } else {
+ proto_tree_add_text(gre_tree, tvb, offset, 2,
+ "Checksum: 0x%04x (incorrect, should be 0x%04x)",
+ cksum, in_cksum_shouldbe(cksum, computed_cksum));
+ }
+ } else {
+ proto_tree_add_text(gre_tree, tvb, offset, 2,
+ "Checksum: 0x%04x", cksum);
+ }
+ }
+ offset += 2;
+ }
+
+ if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
+ if (tree) {
+ proto_tree_add_text(gre_tree, tvb, offset, 2,
+ "Offset: %u", tvb_get_ntohs(tvb, offset));
+ }
+ offset += 2;
+ }
+
+ if (flags_and_ver & GH_B_K) {
+ if (is_ppp) {
+ if (tree) {
+ proto_tree_add_text(gre_tree, tvb, offset, 2,
+ "Payload length: %u", tvb_get_ntohs(tvb, offset));
+ }
+ offset += 2;
+ if (tree) {
+ proto_tree_add_text(gre_tree, tvb, offset, 2,
+ "Call ID: %u", tvb_get_ntohs(tvb, offset));
+ }
+ offset += 2;
+ }
+ else {
+ if (tree) {
+ proto_tree_add_text(gre_tree, tvb, offset, 4,
+ "Key: %u", tvb_get_ntohl(tvb, offset));
+ }
+ offset += 4;
+ }
+ }
+
+ if (flags_and_ver & GH_B_S) {
+ if (tree) {
+ proto_tree_add_text(gre_tree, tvb, offset, 4,
+ "Sequence number: %u", tvb_get_ntohl(tvb, offset));
+ }
+ offset += 4;
+ }
+
+ if (is_ppp && flags_and_ver & GH_P_A) {
+ if (tree) {
+ proto_tree_add_text(gre_tree, tvb, offset, 4,
+ "Acknowledgement number: %u", tvb_get_ntohl(tvb, offset));
+ }
+ offset += 4;
+ }
+
+ if (flags_and_ver & GH_B_R) {
+ for (;;) {
+ sre_af = tvb_get_ntohs(tvb, offset);
+ if (tree) {
+ proto_tree_add_text(gre_tree, tvb, offset, sizeof(guint16),
+ "Address family: %u", sre_af);
+ }
+ offset += sizeof(guint16);
+ if (tree) {
+ proto_tree_add_text(gre_tree, tvb, offset, 1,
+ "SRE offset: %u", tvb_get_guint8(tvb, offset));
+ }
+ offset += sizeof(guint8);
+ sre_length = tvb_get_guint8(tvb, offset);
+ if (tree) {
+ proto_tree_add_text(gre_tree, tvb, offset, sizeof(guint8),
+ "SRE length: %u", sre_length);
+ }
+ offset += sizeof(guint8);
+ if (sre_af == 0 && sre_length == 0)
+ break;
+ offset += sre_length;
+ }
+ }
+
+ if (type == GRE_WCCP) {
+ if (is_wccp2) {
+ if (tree)
+ dissect_gre_wccp2_redirect_header(tvb, offset, gre_tree);
+ offset += 4;
+ }
+ }
+
+ /* If the S bit is not set, this packet might not have a payload, so
+ check whether there's any data left, first.
+
+ XXX - the S bit isn't in RFC 2784, which deprecates that bit
+ and some other bits in RFC 1701 and says that they should be
+ zero for RFC 2784-compliant GRE; as such, the absence of the
+ S bit doesn't necessarily mean there's no payload. */
+ if (!(flags_and_ver & GH_B_S)) {
+ if (tvb_reported_length_remaining(tvb, offset) <= 0)
+ return; /* no payload */
+ }
+ next_tvb = tvb_new_subset(tvb, offset, -1, -1);
+ if (!dissector_try_port(gre_dissector_table, type, next_tvb, pinfo, tree))
+ call_dissector(data_handle,next_tvb, pinfo, gre_tree);
+}
+
+static void
+add_flags_and_ver(proto_tree *tree, guint16 flags_and_ver, tvbuff_t *tvb,
+ int offset, int is_ppp)
+{
+ proto_item * ti;
+ proto_tree * fv_tree;
+ int nbits = sizeof(flags_and_ver) * 8;
+
+ ti = proto_tree_add_text(tree, tvb, offset, 2,
+ "Flags and version: %#04x", flags_and_ver);
+ fv_tree = proto_item_add_subtree(ti, ett_gre_flags);
+
+ proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
+ decode_boolean_bitfield(flags_and_ver, GH_B_C, nbits,
+ "Checksum", "No checksum"));
+ proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
+ decode_boolean_bitfield(flags_and_ver, GH_B_R, nbits,
+ "Routing", "No routing"));
+ proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
+ decode_boolean_bitfield(flags_and_ver, GH_B_K, nbits,
+ "Key", "No key"));
+ proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
+ decode_boolean_bitfield(flags_and_ver, GH_B_S, nbits,
+ "Sequence number", "No sequence number"));
+ proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
+ decode_boolean_bitfield(flags_and_ver, GH_B_s, nbits,
+ "Strict source route", "No strict source route"));
+ proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
+ decode_numeric_bitfield(flags_and_ver, GH_B_RECUR, nbits,
+ "Recursion control: %u"));
+ if (is_ppp) {
+ proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
+ decode_boolean_bitfield(flags_and_ver, GH_P_A, nbits,
+ "Acknowledgment number", "No acknowledgment number"));
+ proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
+ decode_numeric_bitfield(flags_and_ver, GH_P_FLAGS, nbits,
+ "Flags: %u"));
+ }
+ else {
+ proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
+ decode_numeric_bitfield(flags_and_ver, GH_R_FLAGS, nbits,
+ "Flags: %u"));
+ }
+
+ proto_tree_add_text(fv_tree, tvb, offset, sizeof(flags_and_ver), "%s",
+ decode_numeric_bitfield(flags_and_ver, GH_B_VER, nbits,
+ "Version: %u"));
+ }
+
+static void
+dissect_gre_wccp2_redirect_header(tvbuff_t *tvb, int offset, proto_tree *tree)
+{
+ proto_item * ti;
+ proto_tree * rh_tree;
+ guint8 rh_flags;
+
+ ti = proto_tree_add_text(tree, tvb, offset, 4, "Redirect header");
+ rh_tree = proto_item_add_subtree(ti, ett_gre_wccp2_redirect_header);
+
+ rh_flags = tvb_get_guint8(tvb, offset);
+ proto_tree_add_text(rh_tree, tvb, offset, 1, "%s",
+ decode_boolean_bitfield(rh_flags, 0x80, 8,
+ "Dynamic service", "Well-known service"));
+ proto_tree_add_text(rh_tree, tvb, offset, 1, "%s",
+ decode_boolean_bitfield(rh_flags, 0x40, 8,
+ "Alternative bucket used", "Alternative bucket not used"));
+
+ proto_tree_add_text(rh_tree, tvb, offset + 1, 1, "Service ID: %s",
+ val_to_str(tvb_get_guint8(tvb, offset + 1), service_id_vals, "Unknown (0x%02X)"));
+ if (rh_flags & 0x40)
+ proto_tree_add_text(rh_tree, tvb, offset + 2, 1, "Alternative bucket index: %u",
+ tvb_get_guint8(tvb, offset + 2));
+ proto_tree_add_text(rh_tree, tvb, offset + 3, 1, "Primary bucket index: %u",
+ tvb_get_guint8(tvb, offset + 3));
+}
+
+void
+proto_register_gre(void)
+{
+ static hf_register_info hf[] = {
+ { &hf_gre_proto,
+ { "Protocol Type", "gre.proto", FT_UINT16, BASE_HEX, VALS(typevals), 0x0,
+ "The protocol that is GRE encapsulated", HFILL }
+ },
+ };
+ static gint *ett[] = {
+ &ett_gre,
+ &ett_gre_flags,
+ &ett_gre_wccp2_redirect_header,
+ };
+
+ proto_gre = proto_register_protocol("Generic Routing Encapsulation",
+ "GRE", "gre");
+ proto_register_field_array(proto_gre, hf, array_length(hf));
+ proto_register_subtree_array(ett, array_length(ett));
+
+ /* subdissector code */
+ gre_dissector_table = register_dissector_table("gre.proto",
+ "GRE protocol type", FT_UINT16, BASE_HEX);
+}
+
+void
+proto_reg_handoff_gre(void)
+{
+ dissector_handle_t gre_handle;
+
+ gre_handle = create_dissector_handle(dissect_gre, proto_gre);
+ dissector_add("ip.proto", IP_PROTO_GRE, gre_handle);
+ data_handle = find_dissector("data");
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-04-16 12:12:12 +0000