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| author | Eric Dumazet <edumazet@google.com> | 2018-04-18 11:43:15 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-04-19 13:44:11 -0400 |
| commit | 88078d98d1bb085d72af8437707279e203524fa5 (patch) | |
| tree | bf20f9ebb371aa14ce699ad9be0afc093babd04b | |
| parent | 292eba02dbb4c41da840e462e51ee97d80d873d1 (diff) | |
| download | linux-88078d98d1bb085d72af8437707279e203524fa5.tar.gz linux-88078d98d1bb085d72af8437707279e203524fa5.tar.bz2 linux-88078d98d1bb085d72af8437707279e203524fa5.zip | |
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>
| -rw-r--r-- | include/linux/skbuff.h | 5 | ||||
| -rw-r--r-- | net/core/skbuff.c | 14 |
2 files changed, 16 insertions, 3 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 9065477ed255..d274059529eb 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -3131,6 +3131,7 @@ static inline void *skb_push_rcsum(struct sk_buff *skb, unsigned int len) return skb->data; } +int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len); /** * pskb_trim_rcsum - trim received skb and update checksum * @skb: buffer to trim @@ -3144,9 +3145,7 @@ static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len) { if (likely(len >= skb->len)) return 0; - if (skb->ip_summed == CHECKSUM_COMPLETE) - skb->ip_summed = CHECKSUM_NONE; - return __pskb_trim(skb, len); + return pskb_trim_rcsum_slow(skb, len); } static inline int __skb_trim_rcsum(struct sk_buff *skb, unsigned int len) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 345b51837ca8..ff49e352deea 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1839,6 +1839,20 @@ done: } EXPORT_SYMBOL(___pskb_trim); +/* Note : use pskb_trim_rcsum() instead of calling this directly + */ +int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len) +{ + if (skb->ip_summed == CHECKSUM_COMPLETE) { + int delta = skb->len - len; + + skb->csum = csum_sub(skb->csum, + skb_checksum(skb, len, delta, 0)); + } + return __pskb_trim(skb, len); +} +EXPORT_SYMBOL(pskb_trim_rcsum_slow); + /** * __pskb_pull_tail - advance tail of skb header * @skb: buffer to reallocate |