From owner-freebsd-net@freebsd.org  Tue Sep 26 09:46:03 2017
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Subject: Re: igb(4) txcsum6 broken in few cases
To: Sepherosa Ziehau <sepherosa@gmail.com>
Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
References: <4cdc0f02-0ec4-4f1a-f14a-d4eeef78cbe0@kornberger.name>
 <CAMOc5cxY7ykP1sr+t4C-4PfphSYCNHr2iBciua6s1R0rANhhPA@mail.gmail.com>
From: Julian Kornberger <jk@kornberger.name>
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Date: Tue, 26 Sep 2017 11:45:55 +0200
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Hi Sepherosa,

I attached a dump. I can provide bigger dumps, but not in public, 
because they might contain sensitive data.
The outgoing UDP packets are created by my fastd kernel module [1] that 
is a simple UDP tunneling protocol that encapsulates IP packets using 
M_PREPEND. Some code is similar to if_vxlan.c.

ICMPv4 echo requests inside of the tunnel lead to invalid checksums in > 
95% of the cases. But also other packets types are affected.

[1] https://github.com/digineo/fastd/blob/master/kmod/fastd.c

Regards,
Julian


On 26.09.2017 07:10, Sepherosa Ziehau wrote:
> It will be more than helpful, if you can provides tcpdumps.