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

commit 66b13d99d9 (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>

include/net/inet_timewait_sock.h

@@ -134,6 +134,7 @@ struct inet_timewait_sock {
 	struct inet_bind_bucket	*tw_tb;
 	struct hlist_node	tw_death_node;
 };
+#define tw_tclass tw_tos
 
 static inline void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw,
 				      struct hlist_nulls_head *list)

include/net/ipv6.h

@@ -486,7 +486,8 @@ extern int			ip6_rcv_finish(struct sk_buff *skb);
 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,