forked from osmocom/wireshark
0f2584c4d2
- in dissect_tpkt_encap() only check the desegment flag passed in the function. svn path=/trunk/; revision=16016
401 lines
10 KiB
C
401 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 <epan/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 (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_item_set_text(ti, "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 (!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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proto_item_set_text(ti, "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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proto_item_append_text(ti, ", Version: 3");
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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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proto_item_append_text(ti, ", Length: %u", 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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"Version, only version 3 is defined", 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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"Reserved, should be 0", 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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"Length of data unit, including this header", 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 - ISO on TCP - RFC1006", "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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