Im trying to allow 6to4 though my ipv4 firewall on Debian 6 (Squeeze) but without much luck, it seems most of the syntax used by other OS's isn't quite supported in Debian's iptables.
I'v tried: (I put these before the DROP all INPUT/OUTPUT lines)
$IPT -A INPUT -p ipv6 -j ACCEPT
$IPT -A OUTPUT -p ipv6 -j ACCEPT
Along with a few others but nothing seems to work.