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-rw-r--r--epan/dissectors/packet-tpkt.c395
1 files changed, 395 insertions, 0 deletions
diff --git a/epan/dissectors/packet-tpkt.c b/epan/dissectors/packet-tpkt.c
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+++ b/epan/dissectors/packet-tpkt.c
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+/* packet-tpkt.c
+ *
+ * Routine to check for RFC 1006 TPKT header and to dissect TPKT header
+ * Copyright 2000, Philips Electronics N.V.
+ * Andreas Sikkema <h323@ramdyne.nl>
+ *
+ * Routine to dissect RFC 1006 TPKT packet containing OSI TP PDU
+ * Copyright 2001, Martin Thomas <Martin_A_Thomas@yahoo.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 <stdio.h>
+#include <string.h>
+
+#include "packet-tpkt.h"
+#include "packet-frame.h"
+#include "prefs.h"
+
+/* TPKT header fields */
+static int proto_tpkt = -1;
+static protocol_t *proto_tpkt_ptr;
+static int hf_tpkt_version = -1;
+static int hf_tpkt_reserved = -1;
+static int hf_tpkt_length = -1;
+
+/* TPKT fields defining a sub tree */
+static gint ett_tpkt = -1;
+
+/* desegmentation of OSI over TPKT over TCP */
+static gboolean tpkt_desegment = TRUE;
+
+#define TCP_PORT_TPKT 102
+
+/* find the dissector for OSI TP (aka COTP) */
+static dissector_handle_t osi_tp_handle;
+
+/*
+ * Check whether this could be a TPKT-encapsulated PDU.
+ * Returns -1 if it's not, and the PDU length from the TPKT header
+ * if it is.
+ *
+ * "min_len" is the minimum length of the PDU; the length field in the
+ * TPKT header must be at least "4+min_len" in order for this to be a
+ * valid TPKT PDU for the protocol in question.
+ */
+int
+is_tpkt(tvbuff_t *tvb, int min_len)
+{
+ guint16 pkt_len;
+
+ /*
+ * If TPKT is disabled, don't dissect it, just return -1, meaning
+ * "this isn't TPKT".
+ */
+ if (!proto_is_protocol_enabled(proto_tpkt_ptr))
+ return -1;
+
+ /* There should at least be 4 bytes left in the frame */
+ if (!tvb_bytes_exist(tvb, 0, 4))
+ return -1; /* there aren't */
+
+ /*
+ * The first octet should be 3 and the second one should be 0
+ * The H.323 implementers guide suggests that this might not
+ * always be the case....
+ */
+ if (!(tvb_get_guint8(tvb, 0) == 3 && tvb_get_guint8(tvb, 1) == 0))
+ return -1; /* they're not */
+
+ /*
+ * Get the length from the TPKT header. Make sure it's large
+ * enough.
+ */
+ pkt_len = tvb_get_ntohs(tvb, 2);
+ if (pkt_len < 4 + min_len)
+ return -1; /* it's not */
+
+ /*
+ * Return the length from the header.
+ */
+ return pkt_len;
+}
+
+/*
+ * Dissect TPKT-encapsulated data in a TCP stream.
+ */
+void
+dissect_tpkt_encap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
+ gboolean desegment, dissector_handle_t subdissector_handle)
+{
+ proto_item *ti = NULL;
+ proto_tree *tpkt_tree = NULL;
+ volatile int offset = 0;
+ int length_remaining;
+ int data_len;
+ volatile int length;
+ tvbuff_t *next_tvb;
+ const char *saved_proto;
+
+ /*
+ * If we're reassembling segmented TPKT PDUs, empty the COL_INFO
+ * column, so subdissectors can append information
+ * without having to worry about emptying the column.
+ *
+ * We use "col_add_str()" because the subdissector
+ * might be appending information to the column, in
+ * which case we'd have to zero the buffer out explicitly
+ * anyway.
+ */
+ if (tpkt_desegment && check_col(pinfo->cinfo, COL_INFO))
+ col_add_str(pinfo->cinfo, COL_INFO, "");
+
+ while (tvb_reported_length_remaining(tvb, offset) != 0) {
+ /*
+ * Is the first byte of this putative TPKT header
+ * a valid TPKT version number, i.e. 3?
+ */
+ if (tvb_get_guint8(tvb, offset) != 3) {
+ /*
+ * No, so don't assume this is a TPKT header;
+ * we might be in the middle of TPKT data,
+ * so don't get the length and don't try to
+ * do reassembly.
+ */
+ if (check_col(pinfo->cinfo, COL_PROTOCOL))
+ col_set_str(pinfo->cinfo, COL_PROTOCOL, "TPKT");
+ if (check_col(pinfo->cinfo, COL_INFO))
+ col_set_str(pinfo->cinfo, COL_INFO, "Continuation");
+ if (tree) {
+ ti = proto_tree_add_item(tree, proto_tpkt, tvb,
+ offset, -1, FALSE);
+ tpkt_tree = proto_item_add_subtree(ti, ett_tpkt);
+
+ proto_tree_add_text(tpkt_tree, tvb, offset, -1,
+ "Continuation data");
+ }
+ return;
+ }
+
+ length_remaining = tvb_length_remaining(tvb, offset);
+
+ /*
+ * Can we do reassembly?
+ */
+ if (desegment && pinfo->can_desegment) {
+ /*
+ * Yes - is the TPKT header split across segment
+ * boundaries?
+ */
+ if (length_remaining < 4) {
+ /*
+ * Yes. Tell the TCP dissector where
+ * the data for this message starts in
+ * the data it handed us, and how many
+ * more bytes we need, and return.
+ */
+ pinfo->desegment_offset = offset;
+ pinfo->desegment_len = 4 - length_remaining;
+ return;
+ }
+ }
+
+ /*
+ * Get the length from the TPKT header.
+ */
+ data_len = tvb_get_ntohs(tvb, offset + 2);
+
+ /*
+ * Can we do reassembly?
+ */
+ if (desegment && pinfo->can_desegment) {
+ /*
+ * Yes - is the payload split across segment
+ * boundaries?
+ */
+ if (length_remaining < data_len) {
+ /*
+ * Yes. Tell the TCP dissector where
+ * the data for this message starts in
+ * the data it handed us, and how many
+ * more bytes we need, and return.
+ */
+ pinfo->desegment_offset = offset;
+ pinfo->desegment_len =
+ data_len - length_remaining;
+ return;
+ }
+ }
+
+ /*
+ * Dissect the TPKT header.
+ * Save and restore "pinfo->current_proto".
+ */
+ saved_proto = pinfo->current_proto;
+ pinfo->current_proto = "TPKT";
+
+ if (check_col(pinfo->cinfo, COL_PROTOCOL))
+ col_set_str(pinfo->cinfo, COL_PROTOCOL, "TPKT");
+ /*
+ * Don't add the TPKT header information if we're
+ * reassembling segmented TPKT PDUs or if this
+ * PDU isn't reassembled.
+ *
+ * XXX - the first is so that subdissectors can append
+ * information without getting TPKT stuff in the middle;
+ * why the second?
+ */
+ if (!tpkt_desegment && !pinfo->fragmented
+ && check_col(pinfo->cinfo, COL_INFO)) {
+ col_add_fstr(pinfo->cinfo, COL_INFO,
+ "TPKT Data length = %u", data_len);
+ }
+
+ if (tree) {
+ ti = proto_tree_add_item(tree, proto_tpkt, tvb,
+ offset, 4, FALSE);
+ tpkt_tree = proto_item_add_subtree(ti, ett_tpkt);
+
+ /* Version */
+ proto_tree_add_item(tpkt_tree, hf_tpkt_version, tvb,
+ offset, 1, FALSE);
+
+ /* Reserved octet*/
+ proto_tree_add_item(tpkt_tree, hf_tpkt_reserved, tvb,
+ offset + 1, 1, FALSE);
+
+ /* Length */
+ proto_tree_add_uint(tpkt_tree, hf_tpkt_length, tvb,
+ offset + 2, 2, data_len);
+ }
+ pinfo->current_proto = saved_proto;
+
+ /* Skip the TPKT header. */
+ offset += 4;
+ data_len -= 4;
+
+ /*
+ * Construct a tvbuff containing the amount of the payload
+ * we have available. Make its reported length the
+ * amount of data in this TPKT packet.
+ *
+ * XXX - if reassembly isn't enabled. the subdissector
+ * will throw a BoundsError exception, rather than a
+ * ReportedBoundsError exception. We really want
+ * a tvbuff where the length is "length", the reported
+ * length is "plen + 2", and the "if the snapshot length
+ * were infinite" length were the minimum of the
+ * reported length of the tvbuff handed to us and "plen+2",
+ * with a new type of exception thrown if the offset is
+ * within the reported length but beyond that third length,
+ * with that exception getting the "Unreassembled Packet"
+ * error.
+ */
+ length = length_remaining - 4;
+ if (length > data_len)
+ length = data_len;
+ next_tvb = tvb_new_subset(tvb, offset, length, data_len);
+
+ /*
+ * Call the subdissector.
+ *
+ * Catch the ReportedBoundsError exception; if this
+ * particular message happens to get a ReportedBoundsError
+ * exception, that doesn't mean that we should stop
+ * dissecting TPKT messages within this frame or chunk
+ * of reassembled data.
+ *
+ * If it gets a BoundsError, we can stop, as there's nothing
+ * more to see, so we just re-throw it.
+ */
+ TRY {
+ call_dissector(subdissector_handle, next_tvb, pinfo,
+ tree);
+ }
+ CATCH(BoundsError) {
+ RETHROW;
+ }
+ CATCH(ReportedBoundsError) {
+ show_reported_bounds_error(tvb, pinfo, tree);
+ }
+ ENDTRY;
+
+ /*
+ * Skip the payload.
+ */
+ offset += length;
+ }
+}
+
+/*
+ * Dissect RFC 1006 TPKT, which wraps a TPKT header around an OSI TP
+ * PDU.
+ */
+static void
+dissect_tpkt(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+{
+ dissect_tpkt_encap(tvb, pinfo, tree, tpkt_desegment, osi_tp_handle);
+}
+
+void
+proto_register_tpkt(void)
+{
+ static hf_register_info hf[] =
+ {
+ {
+ &hf_tpkt_version,
+ {
+ "Version",
+ "tpkt.version",
+ FT_UINT8,
+ BASE_DEC,
+ NULL,
+ 0x0,
+ "", HFILL
+ }
+ },
+ {
+ &hf_tpkt_reserved,
+ {
+ "Reserved",
+ "tpkt.reserved",
+ FT_UINT8,
+ BASE_DEC,
+ NULL,
+ 0x0,
+ "", HFILL
+ }
+ },
+ {
+ &hf_tpkt_length,
+ {
+ "Length",
+ "tpkt.length",
+ FT_UINT16,
+ BASE_DEC,
+ NULL,
+ 0x0,
+ "", HFILL
+ }
+ },
+ };
+
+ static gint *ett[] =
+ {
+ &ett_tpkt,
+ };
+ module_t *tpkt_module;
+
+ proto_tpkt = proto_register_protocol("TPKT", "TPKT", "tpkt");
+ proto_tpkt_ptr = find_protocol_by_id(proto_tpkt);
+ proto_register_field_array(proto_tpkt, hf, array_length(hf));
+ proto_register_subtree_array(ett, array_length(ett));
+
+ tpkt_module = prefs_register_protocol(proto_tpkt, NULL);
+ prefs_register_bool_preference(tpkt_module, "desegment",
+ "Desegment all TPKT messages spanning multiple TCP segments",
+ "Whether the TPKT dissector should desegment all messages spanning multiple TCP segments",
+ &tpkt_desegment);
+}
+
+void
+proto_reg_handoff_tpkt(void)
+{
+ dissector_handle_t tpkt_handle;
+
+ osi_tp_handle = find_dissector("ositp");
+ tpkt_handle = create_dissector_handle(dissect_tpkt, proto_tpkt);
+ dissector_add("tcp.port", TCP_PORT_TPKT, tpkt_handle);
+}
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