Improvements for PMTU discovery and IPv4 packet fragmentation.

src/graph.c

@@ -17,7 +17,7 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
-    $Id: graph.c,v 1.1.2.33 2003/12/20 21:25:17 guus Exp $
+    $Id: graph.c,v 1.1.2.34 2003/12/22 11:04:16 guus Exp $
 */
 
 /* We need to generate two trees from the graph:
@@ -231,9 +231,9 @@ void sssp_bfs(void)
 					avl_insert_node(node_udp_tree, node);
 
 					if(e->to->options & OPTION_PMTU_DISCOVERY) {
-						e->to->mtu = MTU;
 						e->to->mtuprobes = 0;
-						e->to->probedmtu = 0;
+						e->to->minmtu = 0;
+						e->to->maxmtu = MTU;
 						if(e->to->status.validkey)
 							send_mtu_probe(e->to);
 					}
@@ -270,6 +270,10 @@ void sssp_bfs(void)
 			n->status.validkey = false;
 			n->status.waitingforkey = false;
 
+			n->maxmtu = MTU;
+			n->minmtu = 0;
+			n->mtuprobes = 0;
+
 			asprintf(&envp[0], "NETNAME=%s", netname ? : "");
 			asprintf(&envp[1], "DEVICE=%s", device ? : "");
 			asprintf(&envp[2], "INTERFACE=%s", iface ? : "");

src/net_packet.c

@@ -17,7 +17,7 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
-    $Id: net_packet.c,v 1.1.2.46 2003/12/20 21:09:33 guus Exp $
+    $Id: net_packet.c,v 1.1.2.47 2003/12/22 11:04:16 guus Exp $
 */
 
 #include "system.h"
@@ -47,6 +47,10 @@
 #include "utils.h"
 #include "xalloc.h"
 
+#ifdef WSAEMSGSIZE
+#define EMSGSIZE WSAEMSGSIZE
+#endif
+
 int keylifetime = 0;
 int keyexpires = 0;
 EVP_CIPHER_CTX packet_ctx;
@@ -64,20 +68,21 @@ void send_mtu_probe(node_t *n)
 	cp();
 
 	n->mtuprobes++;
+	n->mtuevent = NULL;
 
-	if(n->mtuprobes >= 10 && !n->probedmtu) {
+	if(n->mtuprobes >= 10 && !n->minmtu) {
 		ifdebug(TRAFFIC) logger(LOG_INFO, _("No response to MTU probes from %s (%s)"), n->name, n->hostname);
 		return;
 	}
 
 	for(i = 0; i < 3; i++) {
-		if(n->mtuprobes >= 30 || n->probedmtu >= n->mtu) {
+		if(n->mtuprobes >= 30 || n->minmtu >= n->maxmtu) {
-			n->mtu = n->probedmtu;
+			n->mtu = n->minmtu;
 			ifdebug(TRAFFIC) logger(LOG_INFO, _("Fixing MTU of %s (%s) to %d after %d probes"), n->name, n->hostname, n->mtu, n->mtuprobes);
 			return;
 		}
 
-		len = n->probedmtu + 1 + random() % (n->mtu - n->probedmtu);
+		len = n->minmtu + 1 + random() % (n->maxmtu - n->minmtu);
 		if(len < 64)
 			len = 64;
 		
@@ -104,8 +109,8 @@ void mtu_probe_h(node_t *n, vpn_packet_t *packet) {
 		packet->data[0] = 1;
 		send_packet(n, packet);
 	} else {
-		if(n->probedmtu < packet->len)
+		if(n->minmtu < packet->len)
-			n->probedmtu = packet->len;
+			n->minmtu = packet->len;
 	}
 }
 
@@ -386,6 +391,8 @@ static void send_udppacket(node_t *n, vpn_packet_t *inpkt)
 	if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
 		logger(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name, n->hostname, strerror(errno));
 		if(errno == EMSGSIZE) {
+			if(n->maxmtu >= origlen)
+				n->maxmtu = origlen - 1;
 			if(n->mtu >= origlen)
 				n->mtu = origlen - 1;
 		}

src/net_socket.c

@@ -17,7 +17,7 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
-    $Id: net_socket.c,v 1.1.2.37 2003/12/20 21:09:33 guus Exp $
+    $Id: net_socket.c,v 1.1.2.38 2003/12/22 11:04:16 guus Exp $
 */
 
 #include "system.h"
@@ -163,13 +163,9 @@ int setup_vpn_in_socket(const sockaddr_t *sa)
 	{
 		bool choice;
 
-		if(sa->sa.sa_family == AF_INET && get_config_bool(lookup_config(myself->connection->config_tree, "PMTUDiscovery"), &choice) && choice) {
+		if(get_config_bool(lookup_config(myself->connection->config_tree, "PMTUDiscovery"), &choice) && choice) {
 			option = IP_PMTUDISC_DO;
-			if(setsockopt(nfd, SOL_IP, IP_MTU_DISCOVER, &option, sizeof(option))) {
+			setsockopt(nfd, SOL_IP, IP_MTU_DISCOVER, &option, sizeof(option));
-				closesocket(nfd);
-				logger(LOG_ERR, _("Can't set PMTU discovery mode: %s"), strerror(errno));
-				return -1;
-			}
 		}
 	}
 #endif
@@ -178,13 +174,9 @@ int setup_vpn_in_socket(const sockaddr_t *sa)
 	{
 		bool choice;
 
-		if(sa->sa.sa_family == AF_INET6 && get_config_bool(lookup_config(myself->connection->config_tree, "PMTUDiscovery"), &choice) && choice) {
+		if(get_config_bool(lookup_config(myself->connection->config_tree, "PMTUDiscovery"), &choice) && choice) {
 			option = IPV6_PMTUDISC_DO;
-			if(setsockopt(nfd, SOL_IPV6, IPV6_MTU_DISCOVER, &option, sizeof(option))) {
+			setsockopt(nfd, SOL_IPV6, IPV6_MTU_DISCOVER, &option, sizeof(option));
-				closesocket(nfd);
-				logger(LOG_ERR, _("Can't set PMTU discovery mode: %s"), strerror(errno));
-				return -1;
-			}
 		}
 	}
 #endif

src/node.c

@@ -17,7 +17,7 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
-    $Id: node.c,v 1.1.2.30 2003/12/20 21:25:17 guus Exp $
+    $Id: node.c,v 1.1.2.31 2003/12/22 11:04:16 guus Exp $
 */
 
 #include "system.h"
@@ -81,6 +81,7 @@ node_t *new_node(void)
 	n->queue = list_alloc((list_action_t) free);
 	EVP_CIPHER_CTX_init(&n->packet_ctx);
 	n->mtu = MTU;
+	n->maxmtu = MTU;
 
 	return n;
 }
@@ -110,6 +111,9 @@ void free_node(node_t *n)
 	sockaddrfree(&n->address);
 
 	EVP_CIPHER_CTX_cleanup(&n->packet_ctx);
+
+	if(n->mtuevent)
+		event_del(n->mtuevent);
 	
 	free(n);
 }
@@ -180,11 +184,11 @@ void dump_nodes(void)
 
 	for(node = node_tree->head; node; node = node->next) {
 		n = node->data;
-		logger(LOG_DEBUG, _(" %s at %s cipher %d digest %d maclength %d compression %d options %lx status %04x nexthop %s via %s probedmtu %d"),
+		logger(LOG_DEBUG, _(" %s at %s cipher %d digest %d maclength %d compression %d options %lx status %04x nexthop %s via %s pmtu %d (min %d max %d)"),
 			   n->name, n->hostname, n->cipher ? n->cipher->nid : 0,
 			   n->digest ? n->digest->type : 0, n->maclength, n->compression,
 			   n->options, *(uint32_t *)&n->status, n->nexthop ? n->nexthop->name : "-",
-			   n->via ? n->via->name : "-", n->probedmtu);
+			   n->via ? n->via->name : "-", n->mtu, n->minmtu, n->maxmtu);
 	}
 
 	logger(LOG_DEBUG, _("End of nodes."));

src/node.h

@@ -17,7 +17,7 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
-    $Id: node.h,v 1.1.2.30 2003/12/20 19:47:52 guus Exp $
+    $Id: node.h,v 1.1.2.31 2003/12/22 11:04:16 guus Exp $
 */
 
 #ifndef __TINC_NODE_H__
@@ -74,7 +74,8 @@ typedef struct node_t {
 	unsigned char late[16];			/* Bitfield marking late packets */
 
 	length_t mtu;				/* Maximum size of packets to send to this node */
-	length_t probedmtu;			/* Probed MTU */
+	length_t minmtu;			/* Probed minimum MTU */
+	length_t maxmtu;			/* Probed maximum MTU */
 	int mtuprobes;				/* Number of probes */
 	event_t *mtuevent;			/* Probe event */
 } node_t;

src/protocol_auth.c

@@ -17,7 +17,7 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
-    $Id: protocol_auth.c,v 1.1.4.33 2003/12/20 21:25:17 guus Exp $
+    $Id: protocol_auth.c,v 1.1.4.34 2003/12/22 11:04:16 guus Exp $
 */
 
 #include "system.h"
@@ -479,6 +479,8 @@ bool send_ack(connection_t *c)
 	if((get_config_bool(lookup_config(c->config_tree, "PMTUDiscovery"), &choice) && choice) || myself->options & OPTION_PMTU_DISCOVERY)
 		c->options |= OPTION_PMTU_DISCOVERY;
 
+	get_config_int(lookup_config(c->config_tree, "Weight"), &c->estimated_weight);
+
 	return send_request(c, "%d %s %d %lx", ACK, myport, c->estimated_weight, c->options);
 }
 
@@ -519,7 +521,7 @@ bool ack_h(connection_t *c)
 {
 	char hisport[MAX_STRING_SIZE];
 	char *hisaddress, *dummy;
-	int weight;
+	int weight, mtu;
 	long int options;
 	node_t *n;
 
@@ -554,6 +556,12 @@ bool ack_h(connection_t *c)
 	c->node = n;
 	c->options |= options;
 
+	if(get_config_int(lookup_config(c->config_tree, "PMTU"), &mtu) && mtu < n->mtu)
+		n->mtu = mtu;
+
+	if(get_config_int(lookup_config(myself->connection->config_tree, "PMTU"), &mtu) && mtu < n->mtu)
+		n->mtu = mtu;
+
 	/* Activate this connection */
 
 	c->allow_request = ALL;

src/route.c

@@ -17,7 +17,7 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
-    $Id: route.c,v 1.1.2.73 2003/12/20 21:25:17 guus Exp $
+    $Id: route.c,v 1.1.2.74 2003/12/22 11:04:17 guus Exp $
 */
 
 #include "system.h"
@@ -276,6 +276,58 @@ static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t
 	send_packet(source, packet);
 }
 
+/* RFC 791 */
+
+static __inline__ void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
+	struct ip ip;
+	vpn_packet_t fragment;
+	int len, maxlen, todo;
+	uint8_t *offset;
+	uint16_t ip_off, origf;
+	
+	cp();
+
+	memcpy(&ip, packet->data + ether_size, ip_size);
+	fragment.priority = packet->priority;
+
+	if(ip.ip_hl != ip_size / 4)
+		return;
+	
+	todo = ntohs(ip.ip_len) - ip_size;
+
+	if(ether_size + ip_size + todo != packet->len) {
+		ifdebug(TRAFFIC) logger(LOG_WARNING, _("Length of packet (%d) doesn't match length in IPv4 header (%d)"), packet->len, ether_size + ip_size + todo);
+		return;
+	}
+
+	ifdebug(TRAFFIC) logger(LOG_INFO, _("Fragmenting packet of %d bytes to %s (%s)"), packet->len, dest->name, dest->hostname);
+
+	offset = packet->data + ether_size + ip_size;
+	maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
+	ip_off = ntohs(ip.ip_off);
+	origf = ip_off & ~IP_OFFMASK;
+	ip_off &= IP_OFFMASK;
+	
+	while(todo) {
+		len = todo > maxlen ? maxlen : todo;
+		memcpy(fragment.data + ether_size + ip_size, offset, len);
+		todo -= len;
+		offset += len;
+
+		ip.ip_len = htons(ip_size + len);
+		ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
+		ip.ip_sum = 0;
+		ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
+		memcpy(fragment.data, packet->data, ether_size);
+		memcpy(fragment.data + ether_size, &ip, ip_size);
+		fragment.len = ether_size + ip_size + len;
+
+		send_packet(dest, &fragment);
+
+		ip_off += len / 8;
+	}	
+}
+
 static __inline__ void route_ipv4_unicast(node_t *source, vpn_packet_t *packet)
 {
 	subnet_t *subnet;
@@ -304,16 +356,21 @@ static __inline__ void route_ipv4_unicast(node_t *source, vpn_packet_t *packet)
 	if(!subnet->owner->status.reachable)
 		route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 
-	if(subnet->owner->options & OPTION_PMTU_DISCOVERY && packet->len > subnet->owner->mtu && subnet->owner != myself) {
-		ifdebug(TRAFFIC) logger(LOG_INFO, _("Packet for %s (%s) length %d larger than MTU %d"), subnet->owner->name, subnet->owner->hostname, packet->len, subnet->owner->mtu);
-		packet->len = subnet->owner->mtu;
-		route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
-		return;
-	}
-
 	if(priorityinheritance)
 		packet->priority = packet->data[15];
 
+	if(subnet->owner->options & OPTION_PMTU_DISCOVERY && packet->len > subnet->owner->mtu && subnet->owner != myself) {
+		ifdebug(TRAFFIC) logger(LOG_INFO, _("Packet for %s (%s) length %d larger than MTU %d"), subnet->owner->name, subnet->owner->hostname, packet->len, subnet->owner->mtu);
+		if(packet->data[20] & 0x40) {
+			packet->len = subnet->owner->mtu;
+			route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
+		} else {
+			fragment_ipv4_packet(subnet->owner, packet);
+		}
+
+		return;
+	}
+
 	send_packet(subnet->owner, packet);
 }