-void receive_udppacket(node_t * n, vpn_packet_t * inpkt)
-{
- vpn_packet_t pkt1, pkt2;
- vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
- int nextpkt = 0;
- vpn_packet_t *outpkt = pkt[0];
- int outlen, outpad;
- long int complen = MTU + 12;
- EVP_CIPHER_CTX ctx;
- char hmac[EVP_MAX_MD_SIZE];
-
- cp();
-
- /* Check the message authentication code */
-
- if(myself->digest && myself->maclength) {
- inpkt->len -= myself->maclength;
- HMAC(myself->digest, myself->key, myself->keylength,
- (char *) &inpkt->seqno, inpkt->len, hmac, NULL);
-
- if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, myself->maclength)) {
- if(debug_lvl >= DEBUG_TRAFFIC)
- syslog(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
- n->name, n->hostname);
- return;
- }
- }
+ Probes are sent in batches of at least three, with random sizes between the
+ lower and upper boundaries for the MTU thus far discovered.
+
+ After the initial discovery, a fourth packet is added to each batch with a
+ size larger than the currently known PMTU, to test if the PMTU has increased.
+
+ In case local discovery is enabled, another packet is added to each batch,
+ which will be broadcast to the local network.