From 04a4bb55bcf35b63d40fd2725e58599ff8310dd7 Mon Sep 17 00:00:00 2001 From: Lennert Buytenhek Date: Wed, 1 Oct 2008 02:33:12 -0700 Subject: [PATCH] net: add skb_recycle_check() to enable netdriver skb recycling This patch adds skb_recycle_check(), which can be used by a network driver after transmitting an skb to check whether this skb can be recycled as a receive buffer. skb_recycle_check() checks that the skb is not shared or cloned, and that it is linear and its head portion large enough (as determined by the driver) to be recycled as a receive buffer. If these conditions are met, it does any necessary reference count dropping and cleans up the skbuff as if it just came from __alloc_skb(). Signed-off-by: Lennert Buytenhek Signed-off-by: David S. Miller --- include/linux/skbuff.h | 2 ++ net/core/skbuff.c | 41 +++++++++++++++++++++++++++++++++++++++-- 2 files changed, 41 insertions(+), 2 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index a19ea43fea02..720b688c22b6 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -383,6 +383,8 @@ static inline struct sk_buff *alloc_skb_fclone(unsigned int size, return __alloc_skb(size, priority, 1, -1); } +extern int skb_recycle_check(struct sk_buff *skb, int skb_size); + extern struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src); extern struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t priority); diff --git a/net/core/skbuff.c b/net/core/skbuff.c index ca1ccdf1ef76..2c218a0808b4 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -363,8 +363,7 @@ static void kfree_skbmem(struct sk_buff *skb) } } -/* Free everything but the sk_buff shell. */ -static void skb_release_all(struct sk_buff *skb) +static void skb_release_head_state(struct sk_buff *skb) { dst_release(skb->dst); #ifdef CONFIG_XFRM @@ -388,6 +387,12 @@ static void skb_release_all(struct sk_buff *skb) skb->tc_verd = 0; #endif #endif +} + +/* Free everything but the sk_buff shell. */ +static void skb_release_all(struct sk_buff *skb) +{ + skb_release_head_state(skb); skb_release_data(skb); } @@ -424,6 +429,38 @@ void kfree_skb(struct sk_buff *skb) __kfree_skb(skb); } +int skb_recycle_check(struct sk_buff *skb, int skb_size) +{ + struct skb_shared_info *shinfo; + + if (skb_is_nonlinear(skb) || skb->fclone != SKB_FCLONE_UNAVAILABLE) + return 0; + + skb_size = SKB_DATA_ALIGN(skb_size + NET_SKB_PAD); + if (skb_end_pointer(skb) - skb->head < skb_size) + return 0; + + if (skb_shared(skb) || skb_cloned(skb)) + return 0; + + skb_release_head_state(skb); + shinfo = skb_shinfo(skb); + atomic_set(&shinfo->dataref, 1); + shinfo->nr_frags = 0; + shinfo->gso_size = 0; + shinfo->gso_segs = 0; + shinfo->gso_type = 0; + shinfo->ip6_frag_id = 0; + shinfo->frag_list = NULL; + + memset(skb, 0, offsetof(struct sk_buff, tail)); + skb_reset_tail_pointer(skb); + skb->data = skb->head + NET_SKB_PAD; + + return 1; +} +EXPORT_SYMBOL(skb_recycle_check); + static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old) { new->tstamp = old->tstamp; -- 2.20.1