ipv6: tcp: fix TCLASS value in ACK messages sent from TIME_WAIT

commit 66b13d99d96a (ipv4: tcp: fix TOS value in ACK messages sent from
TIME_WAIT) fixed IPv4 only.

This part is for the IPv6 side, adding a tclass param to ip6_xmit()

We alias tw_tclass and tw_tos, if socket family is INET6.

[ if sockets is ipv4-mapped, only IP_TOS socket option is used to fill
TOS field, TCLASS is not taken into account ]

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 3b5ac1f..a366a8a 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -486,7 +486,8 @@
 extern int			ip6_xmit(struct sock *sk,
 					 struct sk_buff *skb,
 					 struct flowi6 *fl6,
-					 struct ipv6_txoptions *opt);
+					 struct ipv6_txoptions *opt,
+					 int tclass);
 
 extern int			ip6_nd_hdr(struct sock *sk,
 					   struct sk_buff *skb,