[PATCHv3 net-next 1/2] udp: call udp_encap_enable for v6 sockets when enabling encap

[Xin Long]

When enabling encap for a ipv6 socket without udp_encap_needed_key
increased, UDP GRO won't work for v4 mapped v6 address packets as
sk will be NULL in udp4_gro_receive().

This patch is to enable it by increasing udp_encap_needed_key for
v6 sockets in udp_tunnel_encap_enable(), and correspondingly
decrease udp_encap_needed_key in udpv6_destroy_sock().

v1->v2:
  - add udp_encap_disable() and export it.

Signed-off-by: Xin Long <lucien....@gmail.com>
---
 include/net/udp.h        | 1 +
 include/net/udp_tunnel.h | 3 +--
 net/ipv4/udp.c           | 6 ++++++
 net/ipv6/udp.c           | 4 +++-
 4 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/net/udp.h b/include/net/udp.h
index 877832b..1e7b6cd 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -467,6 +467,7 @@ void udp_init(void);
 
 DECLARE_STATIC_KEY_FALSE(udp_encap_needed_key);
 void udp_encap_enable(void);
+void udp_encap_disable(void);
 #if IS_ENABLED(CONFIG_IPV6)
 DECLARE_STATIC_KEY_FALSE(udpv6_encap_needed_key);
 void udpv6_encap_enable(void);
diff --git a/include/net/udp_tunnel.h b/include/net/udp_tunnel.h
index 282d10e..afc7ce7 100644
--- a/include/net/udp_tunnel.h
+++ b/include/net/udp_tunnel.h
@@ -181,9 +181,8 @@ static inline void udp_tunnel_encap_enable(struct socket 
*sock)
 #if IS_ENABLED(CONFIG_IPV6)
        if (sock->sk->sk_family == PF_INET6)
                ipv6_stub->udpv6_encap_enable();
-       else
 #endif
-               udp_encap_enable();
+       udp_encap_enable();
 }
 
 #define UDP_TUNNEL_NIC_MAX_TABLES      4
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 7103b0a..28bfe60 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -596,6 +596,12 @@ void udp_encap_enable(void)
 }
 EXPORT_SYMBOL(udp_encap_enable);
 
+void udp_encap_disable(void)
+{
+       static_branch_dec(&udp_encap_needed_key);
+}
+EXPORT_SYMBOL(udp_encap_disable);
+
 /* Handler for tunnels with arbitrary destination ports: no socket lookup, go
  * through error handlers in encapsulations looking for a match.
  */
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index b9f3dfd..d754292 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1608,8 +1608,10 @@ void udpv6_destroy_sock(struct sock *sk)
                        if (encap_destroy)
                                encap_destroy(sk);
                }
-               if (up->encap_enabled)
+               if (up->encap_enabled) {
                        static_branch_dec(&udpv6_encap_needed_key);
+                       udp_encap_disable();
+               }
        }
 
        inet6_destroy_sock(sk);
-- 
2.1.0