flowcache: Make flow cache name space aware

Inserting a entry into flowcache, or flushing flowcache should be based
on per net scope. The reason to do so is flushing operation from fat
netns crammed with flow entries will also making the slim netns with only
a few flow cache entries go away in original implementation.

Since flowcache is tightly coupled with IPsec, so it would be easier to
put flow cache global parameters into xfrm namespace part. And one last
thing needs to do is bumping flow cache genid, and flush flow cache should
also be made in per net style.

Signed-off-by: Fan Du <fan.du@windriver.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/include/net/flowcache.h b/include/net/flowcache.h
new file mode 100644
index 0000000..c8f665e
--- /dev/null
+++ b/include/net/flowcache.h
@@ -0,0 +1,25 @@
+#ifndef _NET_FLOWCACHE_H
+#define _NET_FLOWCACHE_H
+
+#include <linux/interrupt.h>
+#include <linux/types.h>
+#include <linux/timer.h>
+#include <linux/notifier.h>
+
+struct flow_cache_percpu {
+	struct hlist_head		*hash_table;
+	int				hash_count;
+	u32				hash_rnd;
+	int				hash_rnd_recalc;
+	struct tasklet_struct		flush_tasklet;
+};
+
+struct flow_cache {
+	u32				hash_shift;
+	struct flow_cache_percpu __percpu *percpu;
+	struct notifier_block		hotcpu_notifier;
+	int				low_watermark;
+	int				high_watermark;
+	struct timer_list		rnd_timer;
+};
+#endif	/* _NET_FLOWCACHE_H */