net: ipv6: tcp reset, icmp need to consider L3 domain

Responses for packets to unused ports are getting lost with L3 domains.

IPv4 has ip_send_unicast_reply for sending TCP responses which accounts
for L3 domains; update the IPv6 counterpart tcp_v6_send_response.
For icmp the L3 master check needs to be moved up in icmp6_send
to properly respond to UDP packets to a port with no listener.

Fixes: ca254490 ("net: Add VRF support to IPv6 stack")
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/icmp.c

@@ -445,6 +445,8 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
 
 	if (__ipv6_addr_needs_scope_id(addr_type))
 		iif = skb->dev->ifindex;
+	else
+		iif = l3mdev_master_ifindex(skb->dev);
 
 	/*
 	 *	Must not send error if the source does not uniquely
@@ -499,9 +501,6 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
 	else if (!fl6.flowi6_oif)
 		fl6.flowi6_oif = np->ucast_oif;
 
-	if (!fl6.flowi6_oif)
-		fl6.flowi6_oif = l3mdev_master_ifindex(skb->dev);
-
 	dst = icmpv6_route_lookup(net, skb, sk, &fl6);
 	if (IS_ERR(dst))
 		goto out;

net/ipv6/tcp_ipv6.c

@@ -810,8 +810,13 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
 	fl6.flowi6_proto = IPPROTO_TCP;
 	if (rt6_need_strict(&fl6.daddr) && !oif)
 		fl6.flowi6_oif = tcp_v6_iif(skb);
-	else
+	else {
+		if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
+			oif = skb->skb_iif;
+
 		fl6.flowi6_oif = oif;
+	}
+
 	fl6.flowi6_mark = IP6_REPLY_MARK(net, skb->mark);
 	fl6.fl6_dport = t1->dest;
 	fl6.fl6_sport = t1->source;