IPv6: Can't ping anything - "Operation not permitted"

Question

I've been working on getting IPv6 support into my network, and had everything working properly for a short while. The server is running Ubuntu Server 8.10.

Now however whenever I attempt to do anything related to IPv6 on the server, I get "Operation not permitted". This is coming from things like wide-dhcpv6-client (when trying to get an IPv6 address from the ISP) and radvd - both log errors of this type into syslog.

Even pinging the loopback interface fails:

xxx@gordon:~$ ping6 ::1
PING ::1(::1) 56 data bytes
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted
^C
--- ::1 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2014ms

xxx@gordon:~$ sudo ping6 ::1
sudo: unable to resolve host gordon
PING ::1(::1) 56 data bytes
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted
^C
--- ::1 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2014ms

As you can see, I have attempted pinging as root, as most of the material I've found on the internet points to a permission problem. However, that has not helped.

Any hints to getting unstuck would be appreciated.

Answer 1

Easy answer: somehow ip6tables had been configured to reject all packets, so reconfiguring back to ACCEPT solved the problem:

ip6tables -P INPUT ACCEPT
ip6tables -P OUTPUT ACCEPT
ip6tables -P FORWARD ACCEPT