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Subject: Re: Bad DHCP Checksums over VLANs
To: Kurt Jaeger <pi@freebsd.org>
Cc: freebsd-current@freebsd.org, freebsd-net@freebsd.org
References: <9dd3c7f9-d970-5d30-ebf2-c0f40c76011b@vangyzen.net>
 <20180915060615.GF2118@home.opsec.eu>
From: Eric van Gyzen <eric@vangyzen.net>
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Date: Sun, 16 Sep 2018 16:05:41 -0500
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On 9/15/18 1:06 AM, Kurt Jaeger wrote:
> Can you disable all the options of the NIC ?
> 
> ifconfig igb0 -rxcsum -txcsum -wol -tso4 -vlanmtu -vlanhwtag -vlanhwcsum -vlanhwtso
> 
> Try to disable everything that can be disabled, e.g. LRO etc.

Disabling vlanhwtag works around the problem.

Also note that only DHCP traffic has this problem.  If I assign an 
address manually, all traffic flows normally.  Maybe the problem is in 
the BPF send path.

Eric