xfrm: Use VRF master index if output device is enslaved

Directs route lookups to VRF table. Compiles out if NET_VRF is not
enabled. With this patch able to successfully bring up ipsec tunnels
in VRFs, even with duplicate network configuration.

Signed-off-by: David Ahern <[e-mail]>
Acked-by: Nikolay Aleksandrov <[e-mail]>
Acked-by: Steffen Klassert <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/xfrm4_policy.c

···
 #include <net/dst.h>
 #include <net/xfrm.h>
 #include <net/ip.h>
+#include <net/vrf.h>
 
 static struct xfrm_policy_afinfo xfrm4_policy_afinfo;
 
···
 	struct flowi4 *fl4 = &fl->u.ip4;
 	int oif = 0;
 
-	if (skb_dst(skb))
-		oif = skb_dst(skb)->dev->ifindex;
+	if (skb_dst(skb)) {
+		oif = vrf_master_ifindex(skb_dst(skb)->dev) ?
+			: skb_dst(skb)->dev->ifindex;
+	}
 
 	memset(fl4, 0, sizeof(struct flowi4));
 	fl4->flowi4_mark = skb->mark;

net/ipv6/xfrm6_policy.c

···
 #include <net/ip.h>
 #include <net/ipv6.h>
 #include <net/ip6_route.h>
+#include <net/vrf.h>
 #if IS_ENABLED(CONFIG_IPV6_MIP6)
 #include <net/mip6.h>
 #endif
···
 
 	nexthdr = nh[nhoff];
 
-	if (skb_dst(skb))
-		oif = skb_dst(skb)->dev->ifindex;
+	if (skb_dst(skb)) {
+		oif = vrf_master_ifindex(skb_dst(skb)->dev) ?
+			: skb_dst(skb)->dev->ifindex;
+	}
 
 	memset(fl6, 0, sizeof(struct flowi6));
 	fl6->flowi6_mark = skb->mark;