datapath: Backport: vxlan: interpret IP headers for ECN correctly

Upstream commit:
    When looking for outer IP header, use the actual socket address family, not
    the address family of the default destination which is not set for metadata
    based interfaces (and doesn't have to match the address family of the
    received packet even if it was set).

    Fix also the misleading comment.

    Signed-off-by: Jiri Benc <jbenc@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Upstream: ce212d0f6f5 ("vxlan: interpret IP headers for ECN correctly")
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Jesse Gross <jesse@kernel.org>

datapath/linux/compat/vxlan.c

@@ -824,7 +824,6 @@ static void vxlan_rcv(struct vxlan_sock *vs, struct sk_buff *skb,
 #endif
 	union vxlan_addr saddr;
 	int err = 0;
-	union vxlan_addr *remote_ip;
 
 	/* For flow based devices, map all packets to VNI 0 */
 	if (vs->flags & VXLAN_F_COLLECT_METADATA)
@@ -835,7 +834,6 @@ static void vxlan_rcv(struct vxlan_sock *vs, struct sk_buff *skb,
 	if (!vxlan)
 		goto drop;
 
-	remote_ip = &vxlan->default_dst.remote_ip;
 	skb_reset_mac_header(skb);
 	skb_scrub_packet(skb, !net_eq(vxlan->net, dev_net(vxlan->dev)));
 	skb->protocol = eth_type_trans(skb, vxlan->dev);
@@ -845,8 +843,8 @@ static void vxlan_rcv(struct vxlan_sock *vs, struct sk_buff *skb,
 	if (ether_addr_equal(eth_hdr(skb)->h_source, vxlan->dev->dev_addr))
 		goto drop;
 
-	/* Re-examine inner Ethernet packet */
-	if (remote_ip->sa.sa_family == AF_INET) {
+	/* Get data from the outer IP header */
+	if (vxlan_get_sk_family(vs) == AF_INET) {
 		oip = ip_hdr(skb);
 		saddr.sin.sin_addr.s_addr = oip->saddr;
 		saddr.sa.sa_family = AF_INET;