void backtracking(node_t *currentNode, connection_t *currentSolution, connection_t *globalSolution)
{
//Move to the neighbors
int i;
for(i = 0; i < currentNode->n_neighbors; i++) {
//Check if solution
if(currentNode->neighbors[i] == currentSolution->destination &&
currentNode->n_connections[i]) {
backtracking_compareSolutions(globalSolution, currentSolution);
continue;
}
//If no more connections, skip to next neighbor
if(!node_use_connection(currentNode, currentNode->neighbors[i]->name))
continue;
//Move forward
connection_push(currentSolution, currentNode->neighbors[i]);
backtracking(currentNode->neighbors[i], currentSolution, globalSolution);
//Move backwards
connection_pop(currentSolution);
node_free_connection(currentNode, currentNode->neighbors[i]->name);
}
}
/* process_packet:
* Callback which processes a packet captured by libpcap. */
void process_packet(u_char *user, const struct pcap_pkthdr *hdr, const u_char *pkt)
{
struct tcphdr tcp;
int off, len, delta;
connection *C, c;
struct sockaddr_storage src, dst;
struct sockaddr *s, *d;
uint8_t proto;
s = (struct sockaddr *)&src;
d = (struct sockaddr *)&dst;
if (handle_link_layer(&datalink_info, pkt, hdr->caplen, &proto, &off))
return;
if (layer3_find_tcp(pkt, proto, &off, s, d, &tcp))
return;
len = hdr->caplen - off;
/* XXX fragmented packets and other nasties. */
/* try to find the connection slot associated with this. */
C = find_connection(s, d);
/* no connection at all, so we need to allocate one. */
if (!C) {
log_msg(LOG_INFO, "new connection: %s", connection_string(s,d));
C = alloc_connection();
*C = connection_new(s, d);
/* This might or might not be an entirely new connection (SYN flag
* set). Either way we need a sequence number to start at. */
(*C)->isn = ntohl(tcp.th_seq);
}
/* Now we need to process this segment. */
c = *C;
delta = 0;/*tcp.syn ? 1 : 0;*/
/* NB (STD0007):
* SEG.LEN = the number of octets occupied by the data in the
* segment (counting SYN and FIN) */
#if 0
if (tcp.syn)
/* getting a new isn. */
c->isn = htonl(tcp.seq);
#endif
if (tcp.th_flags & TH_RST) {
/* Looks like this connection is bogus, and so might be a
* connection going the other way. */
log_msg(LOG_INFO, "connection reset: %s", connection_string(s, d));
connection_delete(c);
*C = NULL;
if ((C = find_connection(d, s))) {
connection_delete(*C);
*C = NULL;
}
return;
}
if (len > 0) {
/* We have some data in the packet. If this data occurred after
* the first data we collected for this connection, then save it
* so that we can look for images. Otherwise, discard it. */
unsigned int offset;
offset = ntohl(tcp.th_seq);
/* Modulo 2**32 arithmetic; offset = seq - isn + delta. */
if (offset < (c->isn + delta))
offset = 0xffffffff - (c->isn + delta - offset);
else
offset -= c->isn + delta;
if (offset > c->len + WRAPLEN) {
/* Out-of-order packet. */
log_msg(LOG_INFO, "out of order packet: %s", connection_string(s, d));
} else {
connection_push(c, pkt + off, offset, len);
extract_media(c);
}
}
if (tcp.th_flags & TH_FIN) {
/* Connection closing; mark it as closed, but let sweep_connections
* free it if appropriate. */
log_msg(LOG_INFO, "connection closing: %s, %d bytes transferred", connection_string(s, d), c->len);
c->fin = 1;
}
/* sweep out old connections */
sweep_connections();
}