3 * $Id: follow.c,v 1.12 1999/07/17 04:19:02 gram Exp $
5 * Copyright 1998 Mike Hall <mlh@io.com>
7 * Ethereal - Network traffic analyzer
8 * By Gerald Combs <gerald@zing.org>
9 * Copyright 1998 Gerald Combs
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation; either version 2
15 * of the License, or (at your option) any later version.
17 * This program is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with this program; if not, write to the Free Software
24 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
40 #ifdef HAVE_SYS_TYPES_H
41 # include <sys/types.h>
49 extern FILE* data_out_file;
51 gboolean incomplete_tcp_stream = FALSE;
53 static int check_fragments( int );
54 static void write_packet_data( const u_char *, int );
56 /* this will build libpcap filter text that will only
57 pass the packets related to the stream. There is a
58 chance that two streams could intersect, but not a
61 build_follow_filter( packet_info *pi ) {
62 char* buf = malloc(1024);
63 if( pi->ipproto == 6 ) {
65 sprintf( buf, "(ip.addr eq %s and ip.addr eq %s) and (tcp.port eq %d and tcp.port eq %d)",
66 pi->srcip, pi->destip, pi->srcport, pi->destport );
75 /* here we are going to try and reconstruct the data portion of a TCP
76 session. We will try and handle duplicates, TCP fragments, and out
77 of order packets in a smart way. */
79 static tcp_frag *frags[2] = { 0, 0};
81 static u_long src[2] = { 0, 0 };
84 reassemble_tcp( u_long sequence, u_long length, const char* data, u_long data_length, int synflag, u_long srcx ) {
85 int src_index, j, first = 0;
89 /* first we check to see if we have seen this src ip before. */
90 for( j=0; j<2; j++ ) {
91 if( src[j] == srcx ) {
95 /* we didn't find it if src_index == -1 */
97 /* assign it to a src_index and get going */
98 for( j=0; j<2; j++ ) {
107 if( src_index < 0 ) {
108 fprintf( stderr, "ERROR in reassemble_tcp: Too many addresses!\n");
112 if( data_length < length ) {
113 incomplete_tcp_stream = TRUE;
116 /* now that we have filed away the srcs, lets get the sequence number stuff
119 /* this is the first time we have seen this src's sequence number */
120 seq[src_index] = sequence + length;
124 /* write out the packet data */
125 write_packet_data( data, data_length );
128 /* if we are here, we have already seen this src, let's
129 try and figure out if this packet is in the right place */
130 if( sequence < seq[src_index] ) {
131 /* this sequence number seems dated, but
132 check the end to make sure it has no more
133 info than we have already seen */
134 newseq = sequence + length;
135 if( newseq > seq[src_index] ) {
138 /* this one has more than we have seen. let's get the
139 payload that we have not seen. */
141 new_len = seq[src_index] - sequence;
143 if ( data_length <= new_len ) {
146 incomplete_tcp_stream = TRUE;
149 data_length -= new_len;
151 sequence = seq[src_index];
152 length = newseq - seq[src_index];
154 /* this will now appear to be right on time :) */
157 if ( sequence == seq[src_index] ) {
159 seq[src_index] += length;
160 if( synflag ) seq[src_index]++;
162 write_packet_data( data, data_length );
164 /* done with the packet, see if it caused a fragment to fit */
165 while( check_fragments( src_index ) )
169 /* out of order packet */
170 if( sequence > seq[src_index] ) {
171 tmp_frag = (tcp_frag *)malloc( sizeof( tcp_frag ) );
172 tmp_frag->data = (u_char *)malloc( data_length );
173 tmp_frag->seq = sequence;
174 tmp_frag->len = length;
175 tmp_frag->data_len = data_length;
176 memcpy( tmp_frag->data, data, data_length );
177 if( frags[src_index] ) {
178 tmp_frag->next = frags[src_index];
180 tmp_frag->next = NULL;
182 frags[src_index] = tmp_frag;
185 } /* end reassemble_tcp */
187 /* here we search through all the frag we have collected to see if
190 check_fragments( int index ) {
191 tcp_frag *prev = NULL;
193 current = frags[index];
195 if( current->seq == seq[index] ) {
196 /* this fragment fits the stream */
197 if( current->data ) {
198 write_packet_data( current->data, current->data_len );
200 seq[index] += current->len;
202 prev->next = current->next;
204 frags[index] = current->next;
206 free( current->data );
211 current = current->next;
216 /* this should always be called before we start to reassemble a stream */
218 reset_tcp_reassembly() {
219 tcp_frag *current, *next;
221 incomplete_tcp_stream = FALSE;
222 for( i=0; i<2; i++ ) {
227 next = current->next;
228 free( current->data );
237 write_packet_data( const u_char* data, int length ) {
238 fwrite( data, 1, length, data_out_file );