Support MSS clamping for IP in IP (RFC 2003) packets.

This change allows tinc MSS clamping to operate on TCP streams that are
inside an IP in IP tunnel.

diff --git a/src/route.c b/src/route.c
index a130e69..92dc1cd 100644 (file)
--- a/src/route.c
+++ b/src/route.c
@@ -406,6 +406,15 @@ static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *pac
                type = DATA(packet)[16] << 8 | DATA(packet)[17];
        }
 
+       /* IP in IP (RFC 2003) packet */
+       if(type == ETH_P_IP && DATA(packet)[start + 9] == 4) {
+               start += 20;
+       }
+
+       if(packet->len <= start + 20) {
+               return;
+       }
+
        if(type == ETH_P_IP && DATA(packet)[start + 9] == 6) {
                start += (DATA(packet)[start] & 0xf) * 4;
        } else if(type == ETH_P_IPV6 && DATA(packet)[start + 6] == 6) {