dccp: Per-socket initialisation of feature negotiation

This provides feature-negotiation initialisation for both DCCP sockets
and DCCP request_sockets, to support feature negotiation during
connection setup.

It also resolves a FIXME regarding the congestion control
initialisation.

Thanks to Wei Yongjun for help with the IPv6 side of this patch.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index d0bd348..1cdf4ae 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -193,6 +193,7 @@
 
 	dccp_init_xmit_timers(sk);
 
+	INIT_LIST_HEAD(&dp->dccps_featneg);
 	/*
 	 * FIXME: We're hardcoding the CCID, and doing this at this point makes
 	 * the listening (master) sock get CCID control blocks, which is not