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net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends
After working on IP defragmentation lately, I found that some large
packets defeat CHECKSUM_COMPLETE optimization because of NIC adding
zero paddings on the last (small) fragment.
While removing the padding with pskb_trim_rcsum(), we set skb->ip_summed
to CHECKSUM_NONE, forcing a full csum validation, even if all prior
fragments had CHECKSUM_COMPLETE set.
We can instead compute the checksum of the part we are trimming,
usually smaller than the part we keep.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 88078d98d1
)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
5123ffdad6
commit
6bf32cda46
2 changed files with 16 additions and 3 deletions
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@ -3135,6 +3135,7 @@ static inline void *skb_push_rcsum(struct sk_buff *skb, unsigned int len)
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return skb->data;
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}
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int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len);
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/**
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* pskb_trim_rcsum - trim received skb and update checksum
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* @skb: buffer to trim
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@ -3148,9 +3149,7 @@ static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
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{
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if (likely(len >= skb->len))
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return 0;
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if (skb->ip_summed == CHECKSUM_COMPLETE)
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skb->ip_summed = CHECKSUM_NONE;
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return __pskb_trim(skb, len);
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return pskb_trim_rcsum_slow(skb, len);
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}
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static inline int __skb_trim_rcsum(struct sk_buff *skb, unsigned int len)
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@ -1839,6 +1839,20 @@ int ___pskb_trim(struct sk_buff *skb, unsigned int len)
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}
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EXPORT_SYMBOL(___pskb_trim);
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/* Note : use pskb_trim_rcsum() instead of calling this directly
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*/
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int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len)
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{
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if (skb->ip_summed == CHECKSUM_COMPLETE) {
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int delta = skb->len - len;
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skb->csum = csum_sub(skb->csum,
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skb_checksum(skb, len, delta, 0));
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}
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return __pskb_trim(skb, len);
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}
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EXPORT_SYMBOL(pskb_trim_rcsum_slow);
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/**
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* __pskb_pull_tail - advance tail of skb header
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* @skb: buffer to reallocate
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