Handle unicast packets larger than PMTU in switch mode.

If PMTUDiscovery is enabled, and we see a unicast packet that is larger than
the path MTU in switch mode, treat it just like we would do in router mode.

diff --git a/src/route.c b/src/route.c
index e79fae5..d748db1 100644 (file)
--- a/src/route.c
+++ b/src/route.c
@@ -94,6 +94,13 @@ static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
        } else
                return true;
 }
+
+static void swap_mac_addresses(vpn_packet_t *packet) {
+       mac_t tmp;
+       memcpy(&tmp, &packet->data[0], sizeof tmp);
+       memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
+       memcpy(&packet->data[6], &tmp, sizeof tmp);
+}
        
 static void learn_mac(mac_t *address)
 {
@@ -160,40 +167,6 @@ void age_subnets(void)
        }
 }
 
-static void route_mac(node_t *source, vpn_packet_t *packet)
-{
-       subnet_t *subnet;
-       mac_t dest;
-
-       cp();
-
-
-       /* Learn source address */
-
-       if(source == myself) {
-               mac_t src;
-               memcpy(&src, &packet->data[6], sizeof src);
-               learn_mac(&src);
-       }
-
-       /* Lookup destination address */
-
-       memcpy(&dest, &packet->data[0], sizeof dest);
-       subnet = lookup_subnet_mac(&dest);
-
-       if(!subnet) {
-               broadcast_packet(source, packet);
-               return;
-       }
-
-       if(subnet->owner == source) {
-               ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
-               return;
-       }
-
-       send_packet(subnet->owner, packet);
-}
-
 /* RFC 792 */
 
 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
@@ -210,6 +183,10 @@ static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t
        
        cp();
 
+       /* Swap Ethernet source and destination addresses */
+
+       swap_mac_addresses(packet);
+
        /* Copy headers from packet into properly aligned structs on the stack */
 
        memcpy(&ip, packet->data + ether_size, ip_size);
@@ -406,6 +383,10 @@ static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t
        
        cp();
 
+       /* Swap Ethernet source and destination addresses */
+
+       swap_mac_addresses(packet);
+
        /* Copy headers from packet to structs on the stack */
 
        memcpy(&ip6, packet->data + ether_size, ip6_size);
@@ -743,6 +724,64 @@ static void route_arp(node_t *source, vpn_packet_t *packet)
        send_packet(source, packet);
 }
 
+static void route_mac(node_t *source, vpn_packet_t *packet)
+{
+       subnet_t *subnet;
+       mac_t dest;
+
+       cp();
+
+
+       /* Learn source address */
+
+       if(source == myself) {
+               mac_t src;
+               memcpy(&src, &packet->data[6], sizeof src);
+               learn_mac(&src);
+       }
+
+       /* Lookup destination address */
+
+       memcpy(&dest, &packet->data[0], sizeof dest);
+       subnet = lookup_subnet_mac(&dest);
+
+       if(!subnet) {
+               broadcast_packet(source, packet);
+               return;
+       }
+
+       if(subnet->owner == source) {
+               ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
+               return;
+       }
+
+       // Handle packets larger than PMTU
+
+       node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
+       
+       if(via && packet->len > via->mtu && via != myself) {
+               ifdebug(TRAFFIC) logger(LOG_INFO, _("Packet for %s (%s) length %d larger than MTU %d"), subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
+               uint16_t type = packet->data[12] << 8 | packet->data[13];
+               if(type == ETH_P_IP) {
+                       if(packet->data[20] & 0x40) {
+                               packet->len = via->mtu;
+                               route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
+                       } else {
+                               fragment_ipv4_packet(via, packet);
+                       }
+               } else if(type == ETH_P_IPV6) {
+                       packet->len = via->mtu;
+                       route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
+               } else
+                       ifdebug(TRAFFIC) logger(LOG_INFO, _("Large packet of unhandled type %hx dropped"), type);
+
+               return;
+       }
+
+       send_packet(subnet->owner, packet);
+}
+
+
 void route(node_t *source, vpn_packet_t *packet)
 {
        cp();
@@ -753,9 +792,8 @@ void route(node_t *source, vpn_packet_t *packet)
        switch (routing_mode) {
                case RMODE_ROUTER:
                        {
-                               uint16_t type;
+                               uint16_t type = packet->data[12] << 8 | packet->data[13];
 
-                               type = ntohs(*((uint16_t *)(&packet->data[12])));
                                switch (type) {
                                        case ETH_P_ARP:
                                                route_arp(source, packet);