Merge branch 'l2tp'

Tom Parkin says:

====================
This l2tp bugfix patchset addresses a number of issues.

The first five patches in the series prevent l2tp sessions pinning an l2tp
tunnel open.  This occurs because the l2tp tunnel is torn down in the tunnel
socket destructor, but each session holds a tunnel socket reference which
prevents tunnels with sessions being deleted.  The solution I've implemented
here involves adding a .destroy hook to udp code, as discussed previously on
netdev[1].

The subsequent seven patches address futher bugs exposed by fixing the problem
above, or exposed through stress testing the implementation above.  Patch 11
(avoid deadlock in l2tp stats update) isn't directly related to tunnel/session
lifetimes, but it does prevent deadlocks on i386 kernels running on 64 bit
hardware.

This patchset has been tested on 32 and 64 bit preempt/non-preempt kernels,
using iproute2, openl2tp, and custom-made stress test code.

[1] http://comments.gmane.org/gmane.linux.network/259169
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

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)

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);
+	}
 }
 
 /*

net/ipv6/udp.c

@@ -1285,10 +1285,18 @@ int udpv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 
 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);
 }