udp: avoid csum_partial() for validated skb
In commit e6afc8ace6dd5 ("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>
diff --git a/include/net/udp.h b/include/net/udp.h
index ae07f37..8894d71 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -160,8 +160,8 @@
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);