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Commit 0ebd0ac5 authored by Patrick McHardy's avatar Patrick McHardy Committed by David S. Miller
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net: add function to allocate sk_buff head without data area 



Add a function to allocate a sk_buff head without any data. This will
be used by memory mapped netlink to attach data from the mmaped area
to the skb.

Additionally change skb_release_all() to check whether the skb has a
data area to allow the skb destructor to clear the data pointer in case
only a head has been allocated.

Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e32123e5

include/linux/skbuff.h

+6 −0
Original line number Diff line number Diff line
@@ -651,6 +651,12 @@ static inline struct sk_buff *alloc_skb_fclone(unsigned int size, 
	return __alloc_skb(size, priority, SKB_ALLOC_FCLONE, NUMA_NO_NODE);

}



extern struct sk_buff *__alloc_skb_head(gfp_t priority, int node);

static inline struct sk_buff *alloc_skb_head(gfp_t priority)

{

	return __alloc_skb_head(priority, -1);

}



extern struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);

extern int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask);

extern struct sk_buff *skb_clone(struct sk_buff *skb,

net/core/skbuff.c

+29 −1
Original line number Diff line number Diff line
@@ -179,6 +179,33 @@ out: 
 *

 */



struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)

{

	struct sk_buff *skb;



	/* Get the HEAD */

	skb = kmem_cache_alloc_node(skbuff_head_cache,

				    gfp_mask & ~__GFP_DMA, node);

	if (!skb)

		goto out;



	/*

	 * Only clear those fields we need to clear, not those that we will

	 * actually initialise below. Hence, don't put any more fields after

	 * the tail pointer in struct sk_buff!

	 */

	memset(skb, 0, offsetof(struct sk_buff, tail));

	skb->data = NULL;

	skb->truesize = sizeof(struct sk_buff);

	atomic_set(&skb->users, 1);



#ifdef NET_SKBUFF_DATA_USES_OFFSET

	skb->mac_header = ~0U;

#endif

out:

	return skb;

}



/**

 *	__alloc_skb	-	allocate a network buffer

 *	@size: size to allocate
@@ -584,6 +611,7 @@ static void skb_release_head_state(struct sk_buff *skb) 
static void skb_release_all(struct sk_buff *skb)

{

	skb_release_head_state(skb);

	if (likely(skb->data))

		skb_release_data(skb);

}