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udp: avoid csum_partial() for validated skb

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In commit e6afc8ace6 ("udp: remove headers from UDP packets before
queueing"), udp_csum_pull_header() helper was added but missed fact
that CHECKSUM_UNNECESSARY packets were now converted to CHECKSUM_NONE
and skb->csum_valid was set to 1 for them.

Since csum_partial() is quite expensive, even for 8-byte area, it is
worth adding a test.

We also can use skb->data instead of udp_hdr() as we are pulling
UDP headers, as it is sightly faster.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-05-31 15:22:41 -07:00 committed by David S. Miller
parent 524c6f691b
commit 595d0b2946
1 changed files with 2 additions and 2 deletions
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4
include/net/udp.h
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@ -160,8 +160,8 @@ void udp_set_csum(bool nocheck, struct sk_buff *skb,
static inline void udp_csum_pull_header(struct sk_buff *skb)
{
if (skb->ip_summed == CHECKSUM_NONE)
skb->csum = csum_partial(udp_hdr(skb), sizeof(struct udphdr),
if (!skb->csum_valid && skb->ip_summed == CHECKSUM_NONE)
skb->csum = csum_partial(skb->data, sizeof(struct udphdr),
skb->csum);
skb_pull_rcsum(skb, sizeof(struct udphdr));
UDP_SKB_CB(skb)->cscov -= sizeof(struct udphdr);