In article <19980913224613.10331@pilhuhn.de>,
	"Heiko W.Rupp" <hwr@pilhuhn.de> writes:
>   Traceroute does not work yet over the tunnel :(

This is AFAIK not a bug in your GRE code. Routing packes through the
tunnel will requires less hops. So if the remote host doesn't use a tunnel
route back it ICMP replies will have a too low TTL to reach your system.

You can watch the same phenomenon with Linux's IPIP tunnel.

-- 
Matthias Scheler                                http://home.owl.de/~tron/