forked from osmocom/wireshark
d530bd4e14
I (hopefully) didn't changed any protocol fields or preference file names, but only the GUI labels appearing in the protocol display and the protocol preferences. Also added a note to the protocol preferences (where appropriate), that you have to enable "Allow subdissectors to reassemble TCP streams" at the corresponding protocol settings for TCP reassembling to take effect. If you encounter any mistakes I've made here, please let me know... svn path=/trunk/; revision=11784
397 lines
10 KiB
C
397 lines
10 KiB
C
/* packet-tpkt.c
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*
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* Routine to check for RFC 1006 TPKT header and to dissect TPKT header
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* Copyright 2000, Philips Electronics N.V.
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* Andreas Sikkema <h323@ramdyne.nl>
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*
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* Routine to dissect RFC 1006 TPKT packet containing OSI TP PDU
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* Copyright 2001, Martin Thomas <Martin_A_Thomas@yahoo.com>
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*
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* $Id$
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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 <glib.h>
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#include <epan/packet.h>
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#include <stdio.h>
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#include <string.h>
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#include "packet-tpkt.h"
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#include "packet-frame.h"
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#include "prefs.h"
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/* TPKT header fields */
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static int proto_tpkt = -1;
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static protocol_t *proto_tpkt_ptr;
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static int hf_tpkt_version = -1;
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static int hf_tpkt_reserved = -1;
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static int hf_tpkt_length = -1;
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/* TPKT fields defining a sub tree */
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static gint ett_tpkt = -1;
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/* desegmentation of OSI over TPKT over TCP */
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static gboolean tpkt_desegment = TRUE;
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#define TCP_PORT_TPKT 102
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/* find the dissector for OSI TP (aka COTP) */
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static dissector_handle_t osi_tp_handle;
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/*
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* Check whether this could be a TPKT-encapsulated PDU.
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* Returns -1 if it's not, and the PDU length from the TPKT header
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* if it is.
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*
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* "min_len" is the minimum length of the PDU; the length field in the
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* TPKT header must be at least "4+min_len" in order for this to be a
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* valid TPKT PDU for the protocol in question.
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*/
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int
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is_tpkt(tvbuff_t *tvb, int min_len)
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{
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guint16 pkt_len;
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/*
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* If TPKT is disabled, don't dissect it, just return -1, meaning
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* "this isn't TPKT".
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*/
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if (!proto_is_protocol_enabled(proto_tpkt_ptr))
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return -1;
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/* There should at least be 4 bytes left in the frame */
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if (!tvb_bytes_exist(tvb, 0, 4))
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return -1; /* there aren't */
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/*
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* The first octet should be 3 and the second one should be 0
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* The H.323 implementers guide suggests that this might not
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* always be the case....
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*/
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if (!(tvb_get_guint8(tvb, 0) == 3 && tvb_get_guint8(tvb, 1) == 0))
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return -1; /* they're not */
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/*
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* Get the length from the TPKT header. Make sure it's large
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* enough.
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*/
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pkt_len = tvb_get_ntohs(tvb, 2);
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if (pkt_len < 4 + min_len)
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return -1; /* it's not */
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/*
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* Return the length from the header.
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*/
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return pkt_len;
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}
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/*
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* Dissect TPKT-encapsulated data in a TCP stream.
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*/
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void
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dissect_tpkt_encap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
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gboolean desegment, dissector_handle_t subdissector_handle)
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{
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proto_item *ti = NULL;
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proto_tree *tpkt_tree = NULL;
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volatile int offset = 0;
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int length_remaining;
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int data_len;
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volatile int length;
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tvbuff_t *next_tvb;
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const char *saved_proto;
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/*
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* If we're reassembling segmented TPKT PDUs, empty the COL_INFO
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* column, so subdissectors can append information
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* without having to worry about emptying the column.
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*
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* We use "col_add_str()" because the subdissector
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* might be appending information to the column, in
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* which case we'd have to zero the buffer out explicitly
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* anyway.
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*/
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if (tpkt_desegment && check_col(pinfo->cinfo, COL_INFO))
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col_add_str(pinfo->cinfo, COL_INFO, "");
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while (tvb_reported_length_remaining(tvb, offset) != 0) {
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/*
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* Is the first byte of this putative TPKT header
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* a valid TPKT version number, i.e. 3?
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*/
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if (tvb_get_guint8(tvb, offset) != 3) {
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/*
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* No, so don't assume this is a TPKT header;
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* we might be in the middle of TPKT data,
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* so don't get the length and don't try to
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* do reassembly.
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*/
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if (check_col(pinfo->cinfo, COL_PROTOCOL))
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col_set_str(pinfo->cinfo, COL_PROTOCOL, "TPKT");
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if (check_col(pinfo->cinfo, COL_INFO))
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col_set_str(pinfo->cinfo, COL_INFO, "Continuation");
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if (tree) {
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ti = proto_tree_add_item(tree, proto_tpkt, tvb,
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offset, -1, FALSE);
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tpkt_tree = proto_item_add_subtree(ti, ett_tpkt);
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proto_tree_add_text(tpkt_tree, tvb, offset, -1,
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"Continuation data");
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}
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return;
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}
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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 (desegment && pinfo->can_desegment) {
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/*
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* Yes - is the TPKT header split across segment
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* 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
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* the data for this message starts in
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* 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 from the TPKT header.
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*/
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data_len = 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 (desegment && pinfo->can_desegment) {
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/*
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* Yes - is the payload split across segment
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* boundaries?
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*/
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if (length_remaining < data_len) {
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/*
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* Yes. Tell the TCP dissector where
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* the data for this message starts in
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* 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 =
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data_len - 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 TPKT header.
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* Save and restore "pinfo->current_proto".
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*/
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saved_proto = pinfo->current_proto;
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pinfo->current_proto = "TPKT";
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if (check_col(pinfo->cinfo, COL_PROTOCOL))
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col_set_str(pinfo->cinfo, COL_PROTOCOL, "TPKT");
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/*
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* Don't add the TPKT header information if we're
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* reassembling segmented TPKT PDUs or if this
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* PDU isn't reassembled.
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*
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* XXX - the first is so that subdissectors can append
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* information without getting TPKT stuff in the middle;
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* why the second?
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*/
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if (!tpkt_desegment && !pinfo->fragmented
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&& check_col(pinfo->cinfo, COL_INFO)) {
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col_add_fstr(pinfo->cinfo, COL_INFO,
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"TPKT Data length = %u", data_len);
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}
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if (tree) {
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ti = proto_tree_add_item(tree, proto_tpkt, tvb,
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offset, 4, FALSE);
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tpkt_tree = proto_item_add_subtree(ti, ett_tpkt);
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/* Version */
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proto_tree_add_item(tpkt_tree, hf_tpkt_version, tvb,
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offset, 1, FALSE);
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/* Reserved octet*/
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proto_tree_add_item(tpkt_tree, hf_tpkt_reserved, tvb,
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offset + 1, 1, FALSE);
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/* Length */
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proto_tree_add_uint(tpkt_tree, hf_tpkt_length, tvb,
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offset + 2, 2, data_len);
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}
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pinfo->current_proto = saved_proto;
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/* Skip the TPKT header. */
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offset += 4;
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data_len -= 4;
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/*
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* Construct a tvbuff containing the amount of the payload
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* we have available. Make its reported length the
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* amount of data in this TPKT packet.
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*
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* XXX - if reassembly isn't enabled. the subdissector
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* will throw a BoundsError exception, rather than a
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* ReportedBoundsError exception. We really want
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* a tvbuff where the length is "length", the reported
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* length is "plen + 2", and the "if the snapshot length
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* were infinite" length were the minimum of the
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* reported length of the tvbuff handed to us and "plen+2",
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* with a new type of exception thrown if the offset is
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* within the reported length but beyond that third length,
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* with that exception getting the "Unreassembled Packet"
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* error.
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*/
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length = length_remaining - 4;
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if (length > data_len)
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length = data_len;
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next_tvb = tvb_new_subset(tvb, offset, length, data_len);
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/*
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* Call the subdissector.
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*
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* Catch the ReportedBoundsError exception; if this
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* particular message happens to get a ReportedBoundsError
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* exception, that doesn't mean that we should stop
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* dissecting TPKT messages within this frame or chunk
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* of reassembled data.
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*
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* If it gets a BoundsError, we can stop, as there's nothing
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* more to see, so we just re-throw it.
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*/
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TRY {
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call_dissector(subdissector_handle, next_tvb, pinfo,
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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 payload.
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*/
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offset += length;
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}
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}
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/*
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* Dissect RFC 1006 TPKT, which wraps a TPKT header around an OSI TP
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* PDU.
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*/
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static void
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dissect_tpkt(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
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{
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dissect_tpkt_encap(tvb, pinfo, tree, tpkt_desegment, osi_tp_handle);
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}
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void
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proto_register_tpkt(void)
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{
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static hf_register_info hf[] =
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{
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{
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&hf_tpkt_version,
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{
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"Version",
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"tpkt.version",
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FT_UINT8,
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BASE_DEC,
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NULL,
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0x0,
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"", HFILL
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}
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},
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{
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&hf_tpkt_reserved,
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{
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"Reserved",
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"tpkt.reserved",
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FT_UINT8,
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BASE_DEC,
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NULL,
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0x0,
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"", HFILL
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}
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},
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{
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&hf_tpkt_length,
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{
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"Length",
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"tpkt.length",
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FT_UINT16,
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BASE_DEC,
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NULL,
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0x0,
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"", HFILL
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}
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},
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};
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static gint *ett[] =
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{
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&ett_tpkt,
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};
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module_t *tpkt_module;
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proto_tpkt = proto_register_protocol("TPKT", "TPKT", "tpkt");
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proto_tpkt_ptr = find_protocol_by_id(proto_tpkt);
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proto_register_field_array(proto_tpkt, hf, array_length(hf));
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proto_register_subtree_array(ett, array_length(ett));
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tpkt_module = prefs_register_protocol(proto_tpkt, NULL);
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prefs_register_bool_preference(tpkt_module, "desegment",
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"Reassemble TPKT messages spanning multiple TCP segments",
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"Whether the TPKT dissector should reassemble messages spanning multiple TCP segments. "
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"To use this option, you must also enable \"Allow subdissectors to reassemble TCP streams\" in the TCP protocol settings.",
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&tpkt_desegment);
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}
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void
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proto_reg_handoff_tpkt(void)
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{
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dissector_handle_t tpkt_handle;
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osi_tp_handle = find_dissector("ositp");
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tpkt_handle = create_dissector_handle(dissect_tpkt, proto_tpkt);
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dissector_add("tcp.port", TCP_PORT_TPKT, tpkt_handle);
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}
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