skbuff: introduce skb_expand_head()
[ Upstream commit f1260ff15a71b8fc122b2c9abd8a7abffb6e0168 ] Like skb_realloc_headroom(), new helper increases headroom of specified skb. Unlike skb_realloc_headroom(), it does not allocate a new skb if possible; copies skb->sk on new skb when as needed and frees original skb in case of failures. This helps to simplify ip[6]_finish_output2() and a few other similar cases. Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Signed-off-by: David S. Miller <davem@davemloft.net> (cherry picked from commit f1260ff15a71b8fc122b2c9abd8a7abffb6e0168) Signed-off-by: Harshvardhan Jha <harshvardhan.j.jha@oracle.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
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2 changed files with 43 additions and 0 deletions
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@ -1196,6 +1196,7 @@ static inline struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom,
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int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, gfp_t gfp_mask);
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struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
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unsigned int headroom);
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struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom);
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struct sk_buff *skb_copy_expand(const struct sk_buff *skb, int newheadroom,
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int newtailroom, gfp_t priority);
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int __must_check skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,
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@ -1765,6 +1765,48 @@ int __skb_unclone_keeptruesize(struct sk_buff *skb, gfp_t pri)
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return 0;
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}
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/**
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* skb_expand_head - reallocate header of &sk_buff
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* @skb: buffer to reallocate
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* @headroom: needed headroom
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*
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* Unlike skb_realloc_headroom, this one does not allocate a new skb
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* if possible; copies skb->sk to new skb as needed
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* and frees original skb in case of failures.
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*
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* It expect increased headroom and generates warning otherwise.
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*/
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struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom)
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{
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int delta = headroom - skb_headroom(skb);
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if (WARN_ONCE(delta <= 0,
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"%s is expecting an increase in the headroom", __func__))
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return skb;
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/* pskb_expand_head() might crash, if skb is shared */
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if (skb_shared(skb)) {
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struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
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if (likely(nskb)) {
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if (skb->sk)
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skb_set_owner_w(nskb, skb->sk);
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consume_skb(skb);
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} else {
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kfree_skb(skb);
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}
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skb = nskb;
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}
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if (skb &&
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pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) {
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kfree_skb(skb);
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skb = NULL;
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}
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return skb;
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}
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EXPORT_SYMBOL(skb_expand_head);
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/**
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* skb_copy_expand - copy and expand sk_buff
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* @skb: buffer to copy
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