udp: add encap_destroy callback

Users of udp encapsulation currently have an encap_rcv callback which they can
use to hook into the udp receive path.

In situations where a encapsulation user allocates resources associated with a
udp encap socket, it may be convenient to be able to also hook the proto
.destroy operation.  For example, if an encap user holds a reference to the
udp socket, the destroy hook might be used to relinquish this reference.

This patch adds a socket destroy hook into udp, which is set and enabled
in the same way as the existing encap_rcv hook.

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/udp.h b/include/linux/udp.h
index 9d81de123c90..42278bbf7a88 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -68,6 +68,7 @@ struct udp_sock {
          * For encapsulation sockets.
          */
         int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);
+        void (*encap_destroy)(struct sock *sk);
 };
 
 static inline struct udp_sock *udp_sk(const struct sock *sk)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 265c42cf963c..0a073a263720 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1762,9 +1762,16 @@ int udp_rcv(struct sk_buff *skb)
 
 void udp_destroy_sock(struct sock *sk)
 {
+        struct udp_sock *up = udp_sk(sk);
         bool slow = lock_sock_fast(sk);
         udp_flush_pending_frames(sk);
         unlock_sock_fast(sk, slow);
+        if (static_key_false(&udp_encap_needed) && up->encap_type) {
+                void (*encap_destroy)(struct sock *sk);
+                encap_destroy = ACCESS_ONCE(up->encap_destroy);
+                if (encap_destroy)
+                        encap_destroy(sk);
+        }
 }
 
 /*
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 599e1ba6d1ce..d8e5e852fc7a 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1285,10 +1285,18 @@ do_confirm:
 
 void udpv6_destroy_sock(struct sock *sk)
 {
+        struct udp_sock *up = udp_sk(sk);
         lock_sock(sk);
         udp_v6_flush_pending_frames(sk);
         release_sock(sk);
 
+        if (static_key_false(&udpv6_encap_needed) && up->encap_type) {
+                void (*encap_destroy)(struct sock *sk);
+                encap_destroy = ACCESS_ONCE(up->encap_destroy);
+                if (encap_destroy)
+                        encap_destroy(sk);
+        }
+
         inet6_destroy_sock(sk);
 }