[IPV6]: Generalise some functions

Using sk->sk_protocol instead of IPPROTO_TCP.

Will be used by DCCPv6 in the next changesets.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
5 files changed