[PATCH v2] xfrm: fix inbound ipv4/udp/esp packets to UDPv6 dualstack sockets

["Maciej Żenczykowski" <maze@google.com>]

Before Linux v5.8 an AF_INET6 SOCK_DGRAM (udp/udplite) socket
with SOL_UDP, UDP_ENCAP, UDP_ENCAP_ESPINUDP{,_NON_IKE} enabled
would just unconditionally use xfrm4_udp_encap_rcv(), afterwards
such a socket would use the newly added xfrm6_udp_encap_rcv()
which only handles IPv6 packets.

Cc: Sabrina Dubroca <sd@queasysnail.net>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Benedict Wong <benedictwong@google.com>
Cc: Yan Yan <evitayan@google.com>
Fixes: 0146dca70b87 ('xfrm: add support for UDPv6 encapsulation of ESP')
Signed-off-by: Maciej Żenczykowski <maze@google.com>
---
 net/ipv4/xfrm4_input.c | 1 +
 net/ipv6/xfrm6_input.c | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/net/ipv4/xfrm4_input.c b/net/ipv4/xfrm4_input.c
index ad2afeef4f10..eac206a290d0 100644
--- a/net/ipv4/xfrm4_input.c
+++ b/net/ipv4/xfrm4_input.c
@@ -164,6 +164,7 @@ int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
 	kfree_skb(skb);
 	return 0;
 }
+EXPORT_SYMBOL(xfrm4_udp_encap_rcv);
 
 int xfrm4_rcv(struct sk_buff *skb)
 {
diff --git a/net/ipv6/xfrm6_input.c b/net/ipv6/xfrm6_input.c
index 04cbeefd8982..4907ab241d6b 100644
--- a/net/ipv6/xfrm6_input.c
+++ b/net/ipv6/xfrm6_input.c
@@ -86,6 +86,9 @@ int xfrm6_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
 	__be32 *udpdata32;
 	__u16 encap_type = up->encap_type;
 
+	if (skb->protocol == htons(ETH_P_IP))
+		return xfrm4_udp_encap_rcv(sk, skb);
+
 	/* if this is not encapsulated socket, then just return now */
 	if (!encap_type)
 		return 1;
-- 
2.41.0.rc0.172.g3f132b7071-goog