netdev - Re: WARN trace - skb_warn_bad_offload - vxlan - large udp packet

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Message-ID: <568DCF2B.2090502@stressinduktion.org>
Date:	Thu, 7 Jan 2016 03:36:27 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	"Nelson, Shannon" <shannon.nelson@...el.com>,
	Tom Herbert <tom@...bertland.com>,
	Jesse Gross <jesse@...ira.com>, Jiri Benc <jbenc@...hat.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: WARN trace - skb_warn_bad_offload - vxlan - large udp packet -
 udp checksum disabled

On 15.12.2015 02:35, Nelson, Shannon wrote:
> Using a slightly modified version of udpspam (see diff below - hopefully not mangled by corporate email servers), where I set the SO_NO_CHECK socket option and can specify a large buffer size, I can reliably get the following WARN trace.  I have reproduced this on both ixgbe and i40e drivers using "udpspam-no-check <target-ip> 6000".
>
> It looks to me like this is in the Tx path before we get to the actual NIC drivers, but I may be wrong.

Does UFO offloading on the tunnel interface fix this error?

ethtool -K vxlan ufo off

If yes we can't feed SO_NO_CHECK udp packets into UFO as gso/ufo 
requires CHECKSUM_PARTIAL (or add some more logic into the skb or query 
socket status from skb_gso_segment).

Thanks,
Hannes

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