3 * $Id: follow.c,v 1.2 1998/09/27 22:12:25 gerald 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.
36 extern FILE* data_out_file;
38 /* this will build libpcap filter text that will only
39 pass the packets related to the stream. There is a
40 chance that two streams could intersect, but not a
43 build_follow_filter( packet_info *pi ) {
44 char* buf = malloc(1024);
45 if( pi->ipproto == 6 ) {
47 sprintf( buf, "host %s and host %s and (ip proto \\tcp) and (port %d and port %d)",
48 pi->srcip, pi->destip, pi->srcport, pi->destport );
57 /* here we are going to try and reconstruct the data portion of a TCP
58 session. We will try and handle duplicates, TCP fragments, and out
59 of order packets in a smart way. */
61 static tcp_frag *frags[2] = { 0, 0};
63 static u_long src[2] = { 0, 0 };
66 reassemble_tcp( u_long sequence, u_long length, const char* data, int synflag, u_long srcx ) {
67 int src_index, j, first = 0;
71 /* first we check to see if we have seen this src ip before. */
72 for( j=0; j<2; j++ ) {
73 if( src[j] == srcx ) {
77 /* we didn't find it if src_index == -1 */
79 /* assign it to a src_index and get going */
80 for( j=0; j<2; j++ ) {
90 fprintf( stderr, "ERROR in reassemble_tcp: Too many addresses!\n");
93 /* now that we have filed away the srcs, lets get the sequence number stuff
96 /* this is the first time we have seen this src's sequence number */
97 seq[src_index] = sequence + length;
101 /* write out the packet data */
102 write_packet_data( data, length );
105 /* if we are here, we have already seen this src, let's
106 try and figure out if this packet is in the right place */
107 if( sequence < seq[src_index] ) {
108 /* this sequence number seems dated, but
109 check the end to make sure it has no more
110 info than we have already seen */
111 newseq = sequence + length;
112 if( newseq > seq[src_index] ) {
113 /* this one has more than we have seen. let's get the
114 payload that we have not seen. */
115 data += ( seq[src_index] - sequence );
116 sequence = seq[src_index];
117 length = newseq - seq[src_index];
118 /* this will now appear to be right on time :) */
121 if ( sequence == seq[src_index] ) {
123 seq[src_index] += length;
124 if( synflag ) seq[src_index]++;
125 write_packet_data( data, length );
126 /* done with the packet, see if it caused a fragment to fit */
127 while( check_fragments( src_index ) )
131 /* out of order packet */
132 if( sequence > seq[src_index] ) {
133 tmp_frag = (tcp_frag *)malloc( sizeof( tcp_frag ) );
134 tmp_frag->data = (u_char *)malloc( length );
135 tmp_frag->seq = sequence;
136 tmp_frag->len = length;
137 bcopy( data, tmp_frag->data, length );
138 if( frags[src_index] ) {
139 tmp_frag->next = frags[src_index];
141 tmp_frag->next = NULL;
143 frags[src_index] = tmp_frag;
146 } /* end reassemble_tcp */
148 /* here we search through all the frag we have collected to see if
151 check_fragments( int index ) {
152 tcp_frag *prev = NULL;
154 current = frags[index];
156 if( current->seq == seq[index] ) {
157 /* this fragment fits the stream */
158 write_packet_data( current->data, current->len );
159 seq[index] += current->len;
161 prev->next = current->next;
163 src[index] = current->next;
165 free( current->data );
170 current = current->next;
175 /* this should always be called before we start to reassemble a stream */
177 reset_tcp_reassembly() {
178 tcp_frag *current, *next;
180 for( i=0; i<2; i++ ) {
185 next = current->next;
186 free( current->data );
195 write_packet_data( const u_char* data, int length ) {
196 fwrite( data, 1, length, data_out_file );