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skb: add helpers to allocate ext independently from sk_buff

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Currently we can allocate the extension only after the skb,
this change allows the user to do the opposite, will simplify
allocation failure handling from MPTCP.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2020-01-09 07:59:24 -08:00 committed by David S. Miller
parent e66b2f31a0
commit 8b69a80381
2 changed files with 36 additions and 2 deletions
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3
include/linux/skbuff.h
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@ -4120,6 +4120,9 @@ struct skb_ext {
char data[0] __aligned(8);
};
struct skb_ext *__skb_ext_alloc(void);
void *__skb_ext_set(struct sk_buff *skb, enum skb_ext_id id,
struct skb_ext *ext);
void *skb_ext_add(struct sk_buff *skb, enum skb_ext_id id);
void __skb_ext_del(struct sk_buff *skb, enum skb_ext_id id);
void __skb_ext_put(struct skb_ext *ext);

35
net/core/skbuff.c
View File

@ -5987,7 +5987,14 @@ static void *skb_ext_get_ptr(struct skb_ext *ext, enum skb_ext_id id)
return (void *)ext + (ext->offset[id] * SKB_EXT_ALIGN_VALUE);
}
static struct skb_ext *skb_ext_alloc(void)
/**
* __skb_ext_alloc - allocate a new skb extensions storage
*
* Returns the newly allocated pointer. The pointer can later attached to a
* skb via __skb_ext_set().
* Note: caller must handle the skb_ext as an opaque data.
*/
struct skb_ext *__skb_ext_alloc(void)
{
struct skb_ext *new = kmem_cache_alloc(skbuff_ext_cache, GFP_ATOMIC);
@ -6027,6 +6034,30 @@ static struct skb_ext *skb_ext_maybe_cow(struct skb_ext *old,
return new;
}
/**
* __skb_ext_set - attach the specified extension storage to this skb
* @skb: buffer
* @id: extension id
* @ext: extension storage previously allocated via __skb_ext_alloc()
*
* Existing extensions, if any, are cleared.
*
* Returns the pointer to the extension.
*/
void *__skb_ext_set(struct sk_buff *skb, enum skb_ext_id id,
struct skb_ext *ext)
{
unsigned int newlen, newoff = SKB_EXT_CHUNKSIZEOF(*ext);
skb_ext_put(skb);
newlen = newoff + skb_ext_type_len[id];
ext->chunks = newlen;
ext->offset[id] = newoff;
skb->extensions = ext;
skb->active_extensions = 1 << id;
return skb_ext_get_ptr(ext, id);
}
/**
* skb_ext_add - allocate space for given extension, COW if needed
* @skb: buffer
@ -6060,7 +6091,7 @@ void *skb_ext_add(struct sk_buff *skb, enum skb_ext_id id)
} else {
newoff = SKB_EXT_CHUNKSIZEOF(*new);
new = skb_ext_alloc();
new = __skb_ext_alloc();
if (!new)
return NULL;
}