Hi, I would like to know why ip_tunnel_ioctl() enforces the DF bit whenever the tunnel device has a fixed TTL set. The same restriction is enforced by iproute2 (iptunnel.c and link_iptnl.c).
Ideally I would like to use an IPIP tunnel with a fixed TTL but no DF bit set. Otherwise for non-TCP packets that are larger than the PMTU size the kernel will send ICMP packets to end systems. However these ICMP packets are ignored by the end system since the original packets didn't have the DF bit set. As a result, non-TCP packets larger than the PMTU are being dropped. Regards Alex
