278 lines
7.4 KiB
C
278 lines
7.4 KiB
C
/* follow.c
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*
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* $Id: follow.c,v 1.20 1999/12/10 04:25:59 gram Exp $
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*
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* Copyright 1998 Mike Hall <mlh@io.com>
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*
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* Ethereal - Network traffic analyzer
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* By Gerald Combs <gerald@zing.org>
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* Copyright 1998 Gerald Combs
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*
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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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*/
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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 <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#ifdef HAVE_SYS_TYPES_H
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# include <sys/types.h>
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#endif
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#include <glib.h>
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#include "packet.h"
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#include "follow.h"
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extern FILE* data_out_file;
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gboolean incomplete_tcp_stream = FALSE;
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static guint32 ip_address[2];
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static u_int tcp_port[2];
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static int check_fragments( int, tcp_stream_chunk * );
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static void write_packet_data( tcp_stream_chunk *, const char * );
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/* this will build libpcap filter text that will only
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pass the packets related to the stream. There is a
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chance that two streams could intersect, but not a
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very good one */
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char*
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build_follow_filter( packet_info *pi ) {
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char* buf = malloc(1024);
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if( pi->net_src.type == AT_IPv4 && pi->net_dst.type == AT_IPv4
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&& pi->ipproto == 6 ) {
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/* TCP over IPv4 */
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sprintf( buf,
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"(ip.addr eq %s and ip.addr eq %s) and (tcp.port eq %d and tcp.port eq %d)",
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ip_to_str( pi->net_src.data),
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ip_to_str( pi->net_dst.data),
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pi->srcport, pi->destport );
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}
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else {
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free( buf );
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return NULL;
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}
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memcpy(&ip_address[0], pi->net_src.data, sizeof ip_address[0]);
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memcpy(&ip_address[1], pi->net_dst.data, sizeof ip_address[1]);
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tcp_port[0] = pi->srcport;
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tcp_port[1] = pi->destport;
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return buf;
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}
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/* here we are going to try and reconstruct the data portion of a TCP
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session. We will try and handle duplicates, TCP fragments, and out
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of order packets in a smart way. */
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static tcp_frag *frags[2] = { 0, 0};
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static u_long seq[2];
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static guint32 src[2] = { 0, 0 };
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void
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reassemble_tcp( u_long sequence, u_long length, const char* data,
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u_long data_length, int synflag, address *net_src,
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address *net_dst, u_int srcport, u_int dstport,
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guint32 secs, guint32 usecs) {
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guint32 srcx, dstx;
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int src_index, j, first = 0;
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u_long newseq;
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tcp_frag *tmp_frag;
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tcp_stream_chunk sc;
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src_index = -1;
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/* first check if this packet should be processed */
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if (net_src->type != AT_IPv4 || net_dst->type != AT_IPv4)
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return;
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memcpy(&srcx, net_src->data, sizeof srcx);
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memcpy(&dstx, net_dst->data, sizeof dstx);
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if ((srcx != ip_address[0] && srcx != ip_address[1]) ||
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(dstx != ip_address[0] && dstx != ip_address[1]) ||
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(srcport != tcp_port[0] && srcport != tcp_port[1]) ||
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(dstport != tcp_port[0] && dstport != tcp_port[1]))
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return;
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/* Initialize our stream chunk. This data gets written to disk. */
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sc.src_addr = srcx;
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sc.src_port = srcport;
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sc.secs = secs;
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sc.usecs = usecs;
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sc.dlen = data_length;
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/* first we check to see if we have seen this src ip before. */
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for( j=0; j<2; j++ ) {
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if( src[j] == srcx ) {
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src_index = j;
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}
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}
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/* we didn't find it if src_index == -1 */
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if( src_index < 0 ) {
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/* assign it to a src_index and get going */
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for( j=0; j<2; j++ ) {
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if( src[j] == 0 ) {
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src[j] = srcx;
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src_index = j;
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first = 1;
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break;
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}
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}
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}
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if( src_index < 0 ) {
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fprintf( stderr, "ERROR in reassemble_tcp: Too many addresses!\n");
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return;
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}
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if( data_length < length ) {
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incomplete_tcp_stream = TRUE;
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}
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/* now that we have filed away the srcs, lets get the sequence number stuff
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figured out */
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if( first ) {
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/* this is the first time we have seen this src's sequence number */
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seq[src_index] = sequence + length;
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if( synflag ) {
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seq[src_index]++;
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}
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/* write out the packet data */
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write_packet_data( &sc, data );
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return;
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}
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/* if we are here, we have already seen this src, let's
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try and figure out if this packet is in the right place */
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if( sequence < seq[src_index] ) {
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/* this sequence number seems dated, but
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check the end to make sure it has no more
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info than we have already seen */
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newseq = sequence + length;
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if( newseq > seq[src_index] ) {
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u_long new_len;
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/* this one has more than we have seen. let's get the
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payload that we have not seen. */
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new_len = seq[src_index] - sequence;
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if ( data_length <= new_len ) {
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data = NULL;
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data_length = 0;
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incomplete_tcp_stream = TRUE;
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} else {
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data += new_len;
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data_length -= new_len;
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}
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sequence = seq[src_index];
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length = newseq - seq[src_index];
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/* this will now appear to be right on time :) */
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}
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}
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if ( sequence == seq[src_index] ) {
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/* right on time */
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seq[src_index] += length;
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if( synflag ) seq[src_index]++;
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if( data ) {
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write_packet_data( &sc, data );
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}
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/* done with the packet, see if it caused a fragment to fit */
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while( check_fragments( src_index, &sc ) )
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;
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}
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else {
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/* out of order packet */
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if( sequence > seq[src_index] ) {
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tmp_frag = (tcp_frag *)malloc( sizeof( tcp_frag ) );
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tmp_frag->data = (u_char *)malloc( data_length );
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tmp_frag->seq = sequence;
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tmp_frag->len = length;
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tmp_frag->data_len = data_length;
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memcpy( tmp_frag->data, data, data_length );
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if( frags[src_index] ) {
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tmp_frag->next = frags[src_index];
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} else {
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tmp_frag->next = NULL;
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}
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frags[src_index] = tmp_frag;
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}
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}
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} /* end reassemble_tcp */
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/* here we search through all the frag we have collected to see if
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one fits */
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static int
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check_fragments( int index, tcp_stream_chunk *sc ) {
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tcp_frag *prev = NULL;
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tcp_frag *current;
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current = frags[index];
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while( current ) {
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if( current->seq == seq[index] ) {
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/* this fragment fits the stream */
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if( current->data ) {
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sc->dlen = current->data_len;
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write_packet_data( sc, current->data );
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}
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seq[index] += current->len;
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if( prev ) {
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prev->next = current->next;
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} else {
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frags[index] = current->next;
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}
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free( current->data );
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free( current );
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return 1;
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}
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prev = current;
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current = current->next;
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}
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return 0;
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}
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/* this should always be called before we start to reassemble a stream */
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void
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reset_tcp_reassembly() {
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tcp_frag *current, *next;
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int i;
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incomplete_tcp_stream = FALSE;
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for( i=0; i<2; i++ ) {
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seq[i] = 0;
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src[i] = 0;
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ip_address[i] = 0;
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tcp_port[i] = 0;
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current = frags[i];
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while( current ) {
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next = current->next;
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free( current->data );
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free( current );
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current = next;
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}
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frags[i] = NULL;
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}
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}
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static void
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write_packet_data( tcp_stream_chunk *sc, const char *data ) {
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fwrite( sc, 1, sizeof(tcp_stream_chunk), data_out_file );
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fwrite( data, 1, sc->dlen, data_out_file );
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}
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