I've created an interface, tun0, which is a pseudo interface (correct term?) to a SLIP connection (created using tunslip6 from the Contiki OS). When I ping6 (ipv6) nodes behing the interface I receive no response. However, I used a small libpcap C program to sniff the tun0 interface and the ping request and responses are visible (could not get tcpdump to behave so I used my own program). So the tunnel interface is working, but someone is filtering the packets, I guess. I am able to ping6 other ipv6 hosts.
I tried to disable the firewall best I could, e.g. like this:
ip6tables -t nat -F
ip6tables -t nat -X
ip6tables -t mangle -F
ip6tables -t mangle -X
ip6tables -P INPUT ACCEPT
ip6tables -P FORWARD ACCEPT
ip6tables -P OUTPUT ACCEPT
But it didn't help. The firewall should not be blocking packets from just this interface anyway should it? Ping6 works on other interfaces. I also tried som TCP and UDP packets with same results.
Who is filtering my packets? (Or is there some other interesting problem stopping the packets from being propagated to the receving application)
Grateful for any ideas,