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: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index a92d9e7..898cf5c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -179,6 +179,33 @@
*
*/
+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
@@ -584,7 +611,8 @@
static void skb_release_all(struct sk_buff *skb)
{
skb_release_head_state(skb);
- skb_release_data(skb);
+ if (likely(skb->data))
+ skb_release_data(skb);
}
/**