xfrm: support sending NAT keepalives in ESP in UDP states

Add the ability to send out RFC-3948 NAT keepalives from the xfrm stack.

To use, Userspace sets an XFRM_NAT_KEEPALIVE_INTERVAL integer property when
creating XFRM outbound states which denotes the number of seconds between
keepalive messages.

Keepalive messages are sent from a per net delayed work which iterates over
the xfrm states. The logic is guarded by the xfrm state spinlock due to the
xfrm state walk iterator.

Possible future enhancements:

- Adding counters to keep track of sent keepalives.
- deduplicate NAT keepalives between states sharing the same nat keepalive
  parameters.
- provisioning hardware offloads for devices capable of implementing this.
- revise xfrm state list to use an rcu list in order to avoid running this
  under spinlock.

Suggested-by: Paul Wouters <[email protected]>
Tested-by: Paul Wouters <[email protected]>
Tested-by: Antony Antony <[email protected]>
Signed-off-by: Eyal Birger <[email protected]>
Signed-off-by: Steffen Klassert <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
index 423b52eca908..d489d9250bff 100644
--- a/include/net/netns/xfrm.h
+++ b/include/net/netns/xfrm.h
@@ -83,6 +83,7 @@ struct netns_xfrm {
 
 	spinlock_t xfrm_policy_lock;
 	struct mutex xfrm_cfg_mutex;
+	struct delayed_work	nat_keepalive_work;
 };
 
 #endif