[INET]: Consolidate xxx_frag_alloc()

Just perform the kzalloc() allocation and setup common
fields in the inet_frag_queue(). Then return the result
to the caller to initialize the rest.

The inet_frag_alloc() may return NULL, so check the 
return value before doing the container_of(). This looks 
ugly, but the xxx_frag_alloc() will be removed soon.

The xxx_expire() timer callbacks are patches, 
because the argument is now the inet_frag_queue, not 
the protocol specific queue.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index 133e187..412b858 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -43,6 +43,7 @@
 	void			(*skb_free)(struct sk_buff *);
 	int			(*equal)(struct inet_frag_queue *q1,
 					 struct inet_frag_queue *q2);
+	void			(*frag_expire)(unsigned long data);
 };
 
 void inet_frags_init(struct inet_frags *);
@@ -54,6 +55,7 @@
 int inet_frag_evictor(struct inet_frags *f);
 struct inet_frag_queue *inet_frag_intern(struct inet_frag_queue *q,
 		struct inet_frags *f, unsigned int hash);
+struct inet_frag_queue *inet_frag_alloc(struct inet_frags *f);
 
 static inline void inet_frag_put(struct inet_frag_queue *q, struct inet_frags *f)
 {