Subject: [PATCH net-next 1/2] lwtunnel: Add destroy state operation

From: Tom Herbert <[email-masked]>
Date: Thu, 13 Oct 2016 17:57:42 -0700

Users of lwt tunnels may set up some secondary state in build_state
function. Add a corresponding destroy_state function to allow users to
clean up state. This destroy state function is called from lwstate_free.
Also, we now free lwstate using kfree_rcu so user can assume structure
is not freed before rcu.

Signed-off-by: Tom Herbert <[email-masked]>
---
 include/net/lwtunnel.h |  7 +++----
 net/core/lwtunnel.c    | 13 +++++++++++++
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/include/net/lwtunnel.h b/include/net/lwtunnel.h
index ea3f80f..119b11b 100644
--- a/include/net/lwtunnel.h
+++ b/include/net/lwtunnel.h
@@ -29,6 +29,7 @@ struct lwtunnel_state {
 	int		(*orig_input)(struct sk_buff *);
 	int             len;
 	__u16		headroom;
+	struct		rcu_head rcu;
 	__u8            data[0];
 };
 
@@ -43,13 +44,11 @@ struct lwtunnel_encap_ops {
 	int (*get_encap_size)(struct lwtunnel_state *lwtstate);
 	int (*cmp_encap)(struct lwtunnel_state *a, struct lwtunnel_state *b);
 	int (*xmit)(struct sk_buff *skb);
+	void (*destroy_state)(struct lwtunnel_state *lws);
 };
 
 #ifdef CONFIG_LWTUNNEL
-static inline void lwtstate_free(struct lwtunnel_state *lws)
-{
-	kfree(lws);
-}
+void lwtstate_free(struct lwtunnel_state *lws);
 
 static inline struct lwtunnel_state *
 lwtstate_get(struct lwtunnel_state *lws)
diff --git a/net/core/lwtunnel.c b/net/core/lwtunnel.c
index e5f84c2..7401474 100644
--- a/net/core/lwtunnel.c
+++ b/net/core/lwtunnel.c
@@ -130,6 +130,19 @@ int lwtunnel_build_state(struct net_device *dev, u16 encap_type,
 }
 EXPORT_SYMBOL(lwtunnel_build_state);
 
+void  lwtstate_free(struct lwtunnel_state *lws)
+{
+	const struct lwtunnel_encap_ops *ops = lwtun_encaps[lws->type];
+
+	if (ops->destroy_state) {
+		ops->destroy_state(lws);
+		kfree_rcu(lws, rcu);
+	} else {
+		kfree(lws);
+	}
+}
+EXPORT_SYMBOL(lwtstate_free);
+
 int lwtunnel_fill_encap(struct sk_buff *skb, struct lwtunnel_state *lwtstate)
 {
 	const struct lwtunnel_encap_ops *ops;
-- 
2.9.3