flow: virtualize flow cache entry methods

This allows to validate the cached object before returning it.
It also allows to destruct object properly, if the last reference
was held in flow cache. This is also a prepartion for caching
bundles in the flow cache.

In return for virtualizing the methods, we save on:
- not having to regenerate the whole flow cache on policy removal:
  each flow matching a killed policy gets refreshed as the getter
  function notices it smartly.
- we do not have to call flow_cache_flush from policy gc, since the
  flow cache now properly deletes the object if it had any references

Signed-off-by: Timo Teras <timo.teras@iki.fi>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 4 deletions

diff --git a/include/net/flow.h b/include/net/flow.h
index 809970b7dfee..bb08692a20b0 100644
--- a/include/net/flow.h
+++ b/include/net/flow.h
@@ -86,11 +86,26 @@ struct flowi {
 
 struct net;
 struct sock;
-typedef int (*flow_resolve_t)(struct net *net, struct flowi *key, u16 family,
-                              u8 dir, void **objp, atomic_t **obj_refp);
+struct flow_cache_ops;
+
+struct flow_cache_object {
+        const struct flow_cache_ops *ops;
+};
+
+struct flow_cache_ops {
+        struct flow_cache_object *(*get)(struct flow_cache_object *);
+        int (*check)(struct flow_cache_object *);
+        void (*delete)(struct flow_cache_object *);
+};
+
+typedef struct flow_cache_object *(*flow_resolve_t)(
+                struct net *net, struct flowi *key, u16 family,
+                u8 dir, struct flow_cache_object *oldobj, void *ctx);
+
+extern struct flow_cache_object *flow_cache_lookup(
+                struct net *net, struct flowi *key, u16 family,
+                u8 dir, flow_resolve_t resolver, void *ctx);
 
-extern void *flow_cache_lookup(struct net *net, struct flowi *key, u16 family,
-                               u8 dir, flow_resolve_t resolver);
 extern void flow_cache_flush(void);
 extern atomic_t flow_cache_genid;