Small fixes for PMTU discovery.

[oweals/tinc.git] / src / route.c

diff --git a/src/route.c b/src/route.c
index 367926ea035fd0b102cd4b83baf59c85201438df..8f238e2cca36ad356206b338490cdbe3b5512ba4 100644 (file)
--- a/src/route.c
+++ b/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 1.1.2.75 2003/12/24 10:48:15 guus Exp $
 */
 
 #include "system.h"
@@ -276,9 +276,62 @@ 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;
+       node_t *via;
 
        cp();
 
@@ -304,16 +357,23 @@ 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];
 
+       via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
+       
+       if(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);
+               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);
+               }
+
+               return;
+       }
+
        send_packet(subnet->owner, packet);
 }
 
@@ -409,6 +469,7 @@ static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t
 static __inline__ void route_ipv6_unicast(node_t *source, vpn_packet_t *packet)
 {
        subnet_t *subnet;
+       node_t *via;
 
        cp();
 
@@ -437,10 +498,12 @@ static __inline__ void route_ipv6_unicast(node_t *source, vpn_packet_t *packet)
 
        if(!subnet->owner->status.reachable)
                route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
+
+       via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
        
-       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;
+       if(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);
+               packet->len = via->mtu;
                route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
                return;
        }