This page describes some IPv6-related issues.

"IPv6: sending pkt_too_big to self"

This is a message that sometimes appears in syslog on a machine with LinuxKernel2.6.

Apparently this is caused by path MTU discovery for paths that use a local tunnel, such as 6to4 or IPSec. This is really just a debugging statement rather than an error, and can be safely ignored.