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/net/sctp/ipv6.c b/net/sctp/ipv6.c
index aabaee4..8104278 100644
--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -243,7 +243,7 @@
 	if (!(transport->param_flags & SPP_PMTUD_ENABLE))
 		skb->local_df = 1;
 
-	return ip6_xmit(sk, skb, &fl6, np->opt);
+	return ip6_xmit(sk, skb, &fl6, np->opt, np->tclass);
 }
 
 /* Returns the dst cache entry for the given source and destination ip