/* packet-xot.c * Routines for X.25 over TCP dissection (RFC 1613) * * Copyright 2000, Paul Ionescu * * $Id: packet-xot.c,v 1.11 2002/08/28 21:00:40 jmayer Exp $ * * Ethereal - Network traffic analyzer * By Gerald Combs * 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 #include #include #include #include #include #include "packet-frame.h" #include "prefs.h" #define TCP_PORT_XOT 1998 static gint proto_xot = -1; static gint hf_xot_version = -1; static gint hf_xot_length = -1; static gint ett_xot = -1; /* desegmentation of X.25 over TCP */ static gboolean xot_desegment = TRUE; static dissector_handle_t x25_handle; static void dissect_xot(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) { volatile int offset = 0; int length_remaining; guint16 version; guint16 plen; int length; proto_item *ti; proto_tree *xot_tree; tvbuff_t *next_tvb; while (tvb_reported_length_remaining(tvb, offset) != 0) { length_remaining = tvb_length_remaining(tvb, offset); /* * Can we do reassembly? */ if (xot_desegment && pinfo->can_desegment) { /* * Yes - is the X.25-over-TCP 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 of the XOT packet. */ version = tvb_get_ntohs(tvb, offset + 0); if (version != 0) return; plen = tvb_get_ntohs(tvb, offset + 2); /* * Can we do reassembly? */ if (xot_desegment && pinfo->can_desegment) { /* * Yes - is the XOT packet split across segment boundaries? */ if (length_remaining < plen + 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 = (plen + 4) - length_remaining; return; } } /* * Dissect the X.25-over-TCP packet. * * Catch the ReportedBoundsError exception; if this particular message * happens to get a ReportedBoundsError exception, that doesn't mean * that we should stop dissecting X.25-over-TCP 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 { if (check_col(pinfo->cinfo, COL_PROTOCOL)) col_set_str(pinfo->cinfo, COL_PROTOCOL, "XOT"); if (check_col(pinfo->cinfo, COL_INFO)) col_add_fstr(pinfo->cinfo, COL_INFO, "XOT Version = %u, size = %u", version,plen ); if (tree) { ti = proto_tree_add_protocol_format(tree, proto_xot, tvb, offset, 4, "X.25 over TCP"); xot_tree = proto_item_add_subtree(ti, ett_xot); proto_tree_add_uint(xot_tree, hf_xot_version, tvb, offset, 2, version); proto_tree_add_uint(xot_tree, hf_xot_length, tvb, offset + 2, 2, plen); } /* * Construct a tvbuff containing the amount of the payload we have * available. Make its reported length the amount of data in the * X.25-over-TCP 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 + 4", and the "if the snapshot length were infinite" * length is the minimum of the reported length of the tvbuff handed * to us and "plen+4", 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 > plen) length = plen; next_tvb = tvb_new_subset(tvb, offset + 4, length, plen); call_dissector(x25_handle,next_tvb,pinfo,tree); } CATCH(BoundsError) { RETHROW; } CATCH(ReportedBoundsError) { show_reported_bounds_error(tvb, pinfo, tree); } ENDTRY; /* * Skip the X.25-over-TCP header and the payload. */ offset += plen + 4; } } /* Register the protocol with Ethereal */ void proto_register_xot(void) { static hf_register_info hf[] = { { &hf_xot_version, { "Version", "xot.version", FT_UINT16, BASE_DEC, NULL, 0, "Version of X.25 over TCP protocol", HFILL }}, { &hf_xot_length, { "Length", "xot.length", FT_UINT16, BASE_DEC, NULL, 0, "Length of X.25 over TCP packet", HFILL }} }; static gint *ett[] = { &ett_xot, }; module_t *xot_module; proto_xot = proto_register_protocol("X.25 over TCP", "XOT", "xot"); proto_register_field_array(proto_xot, hf, array_length(hf)); proto_register_subtree_array(ett, array_length(ett)); xot_module = prefs_register_protocol(proto_xot, NULL); prefs_register_bool_preference(xot_module, "desegment", "Desegment all X.25-over-TCP messages spanning multiple TCP segments", "Whether the X.25-over-TCP dissector should desegment all messages spanning multiple TCP segments", &xot_desegment); } void proto_reg_handoff_xot(void) { dissector_handle_t xot_handle; /* * Get a handle for the X.25 dissector. */ x25_handle = find_dissector("x.25"); xot_handle = create_dissector_handle(dissect_xot, proto_xot); dissector_add("tcp.port", TCP_PORT_XOT, xot_handle); }