[-next] Regression: ssh log in slowdown

[Tom Herbert]

>
> I assume this is the series "[PATCH 0/4] Checksum fixes"
> (marc.info/?l=linux-netdev&m=140261417832399&w=2)?
>
Yes.

> As I'm not subscribed to netdev, I cannot reply to that thread.
>
> "[PATCH 1/4] net: Fix save software checksum complete" fixes the issue
> for me.
> However, "[PATCH 2/4] udp: call __skb_checksum_complete when doing full
> checksum" reintroduces the exact same bad behavior :-(
>
This implies the problem is happening in UDP path. AFAICT skb->csum is 
correct, and I don't seem to be able to reproduce the issue on my setup. 
It is possible that an skb copy is happening in which case we don't copy
csum_valid so that checksum_unnecessary would fail in this case.

Can you try with the patch below. Thanks!

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index bf92824..9cd5344 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -689,6 +689,9 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
 	new->ooo_okay		= old->ooo_okay;
 	new->no_fcs		= old->no_fcs;
 	new->encapsulation	= old->encapsulation;
+	new->encap_hdr_csum	= old->encap_hdr_csum;
+	new->csum_valid		= old->csum_valid;
+	new->csum_complete_sw	= old->csum_complete_sw;
 #ifdef CONFIG_XFRM
 	new->sp			= secpath_get(old->sp);
 #endif
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