220 lines
6.4 KiB
C
220 lines
6.4 KiB
C
/* packet-xot.c
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* Routines for X.25 over TCP dissection (RFC 1613)
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*
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* Copyright 2000, Paul Ionescu <paul@acorp.ro>
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*
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* $Id: packet-xot.c,v 1.10 2002/04/09 08:15:02 guy Exp $
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*
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* Ethereal - Network traffic analyzer
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* By Gerald Combs <gerald@ethereal.com>
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* Copyright 1998 Gerald Combs
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#ifdef HAVE_CONFIG_H
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# include "config.h"
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#endif
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#include <stdio.h>
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#include <stdlib.h>
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#include <ctype.h>
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#include <string.h>
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#include <glib.h>
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#include <epan/packet.h>
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#include "packet-frame.h"
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#include "prefs.h"
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#define TCP_PORT_XOT 1998
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static gint proto_xot = -1;
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static gint hf_xot_version = -1;
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static gint hf_xot_length = -1;
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static gint ett_xot = -1;
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/* desegmentation of X.25 over TCP */
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static gboolean xot_desegment = TRUE;
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static dissector_handle_t x25_handle;
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static void dissect_xot(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
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{
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volatile int offset = 0;
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int length_remaining;
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guint16 version;
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guint16 plen;
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int length;
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proto_item *ti;
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proto_tree *xot_tree;
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tvbuff_t *next_tvb;
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while (tvb_reported_length_remaining(tvb, offset) != 0) {
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length_remaining = tvb_length_remaining(tvb, offset);
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/*
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* Can we do reassembly?
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*/
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if (xot_desegment && pinfo->can_desegment) {
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/*
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* Yes - is the X.25-over-TCP header split across segment boundaries?
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*/
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if (length_remaining < 4) {
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/*
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* Yes. Tell the TCP dissector where the data for this message
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* starts in the data it handed us, and how many
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* more bytes we need, and return.
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*/
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pinfo->desegment_offset = offset;
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pinfo->desegment_len = 4 - length_remaining;
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return;
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}
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}
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/*
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* Get the length of the XOT packet.
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*/
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version = tvb_get_ntohs(tvb, offset + 0);
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if (version != 0)
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return;
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plen = tvb_get_ntohs(tvb, offset + 2);
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/*
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* Can we do reassembly?
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*/
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if (xot_desegment && pinfo->can_desegment) {
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/*
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* Yes - is the XOT packet split across segment boundaries?
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*/
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if (length_remaining < plen + 4) {
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/*
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* Yes. Tell the TCP dissector where the data for this message
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* starts in the data it handed us, and how many more bytes we
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* need, and return.
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*/
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pinfo->desegment_offset = offset;
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pinfo->desegment_len = (plen + 4) - length_remaining;
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return;
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}
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}
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/*
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* Dissect the X.25-over-TCP packet.
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*
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* Catch the ReportedBoundsError exception; if this particular message
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* happens to get a ReportedBoundsError exception, that doesn't mean
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* that we should stop dissecting X.25-over-TCP messages within this
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* frame or chunk of reassembled data.
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*
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* If it gets a BoundsError, we can stop, as there's nothing more to see,
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* so we just re-throw it.
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*/
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TRY {
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if (check_col(pinfo->cinfo, COL_PROTOCOL))
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col_set_str(pinfo->cinfo, COL_PROTOCOL, "XOT");
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if (check_col(pinfo->cinfo, COL_INFO))
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col_add_fstr(pinfo->cinfo, COL_INFO, "XOT Version = %u, size = %u",
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version,plen );
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if (tree) {
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ti = proto_tree_add_protocol_format(tree, proto_xot, tvb, offset, 4,
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"X.25 over TCP");
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xot_tree = proto_item_add_subtree(ti, ett_xot);
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proto_tree_add_uint(xot_tree, hf_xot_version, tvb, offset, 2, version);
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proto_tree_add_uint(xot_tree, hf_xot_length, tvb, offset + 2, 2, plen);
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}
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/*
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* Construct a tvbuff containing the amount of the payload we have
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* available. Make its reported length the amount of data in the
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* X.25-over-TCP packet.
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*
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* XXX - if reassembly isn't enabled. the subdissector will throw a
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* BoundsError exception, rather than a ReportedBoundsError exception.
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* We really want a tvbuff where the length is "length", the reported
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* length is "plen + 4", and the "if the snapshot length were infinite"
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* length is the minimum of the reported length of the tvbuff handed
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* to us and "plen+4", with a new type of exception thrown if the offset
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* is within the reported length but beyond that third length, with that
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* exception getting the "Unreassembled Packet" error.
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*/
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length = length_remaining - 4;
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if (length > plen)
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length = plen;
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next_tvb = tvb_new_subset(tvb, offset + 4, length, plen);
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call_dissector(x25_handle,next_tvb,pinfo,tree);
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}
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CATCH(BoundsError) {
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RETHROW;
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}
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CATCH(ReportedBoundsError) {
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show_reported_bounds_error(tvb, pinfo, tree);
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}
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ENDTRY;
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/*
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* Skip the X.25-over-TCP header and the payload.
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*/
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offset += plen + 4;
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}
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}
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/* Register the protocol with Ethereal */
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void
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proto_register_xot(void)
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{
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static hf_register_info hf[] = {
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{ &hf_xot_version,
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{ "Version", "xot.version", FT_UINT16, BASE_DEC,
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NULL, 0, "Version of X.25 over TCP protocol", HFILL }},
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{ &hf_xot_length,
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{ "Length", "xot.length", FT_UINT16, BASE_DEC,
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NULL, 0, "Length of X.25 over TCP packet", HFILL }}
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};
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static gint *ett[] = {
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&ett_xot,
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};
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module_t *xot_module;
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proto_xot = proto_register_protocol("X.25 over TCP", "XOT", "xot");
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proto_register_field_array(proto_xot, hf, array_length(hf));
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proto_register_subtree_array(ett, array_length(ett));
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xot_module = prefs_register_protocol(proto_xot, NULL);
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prefs_register_bool_preference(xot_module, "desegment",
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"Desegment all X.25-over-TCP messages spanning multiple TCP segments",
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"Whether the X.25-over-TCP dissector should desegment all messages spanning multiple TCP segments",
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&xot_desegment);
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}
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void
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proto_reg_handoff_xot(void)
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{
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dissector_handle_t xot_handle;
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/*
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* Get a handle for the X.25 dissector.
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*/
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x25_handle = find_dissector("x.25");
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xot_handle = create_dissector_handle(dissect_xot, proto_xot);
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dissector_add("tcp.port", TCP_PORT_XOT, xot_handle);
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}
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