xfrm: Honor original L3 slave device in xfrmi policy lookup

[ Upstream commit 025c65e119bf58b610549ca359c9ecc5dee6a8d2 ]

If an xfrmi is associated to a vrf layer 3 master device,
xfrm_policy_check() fails after traffic decapsulation. The input
interface is replaced by the layer 3 master device, and hence
xfrmi_decode_session() can't match the xfrmi anymore to satisfy
policy checking.

Extend ingress xfrmi lookup to honor the original layer 3 slave
device, allowing xfrm interfaces to operate within a vrf domain.

Fixes: f203b76d7809 ("xfrm: Add virtual xfrm interfaces")
Signed-off-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 3e966c6..4ddd2b1 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -295,7 +295,8 @@
 };
 
 struct xfrm_if_cb {
-	struct xfrm_if	*(*decode_session)(struct sk_buff *skb);
+	struct xfrm_if	*(*decode_session)(struct sk_buff *skb,
+					   unsigned short family);
 };
 
 void xfrm_if_register_cb(const struct xfrm_if_cb *ifcb);