netdev - Re: Stack sends oversize UDP packet to the driver

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Message-ID: <CACKFLi=O8fDPbtPeiPcrkSxp3U5EgNzhOsU9yJ3c-cU01p-dhQ@mail.gmail.com>
Date:   Wed, 30 Jan 2019 01:07:18 -0800
From:   Michael Chan <michael.chan@...adcom.com>
To:     Mahesh Bandewar (महेश बंडेवार) 
        <maheshb@...gle.com>
Cc:     Daniel Axtens <dja@...ens.net>, Netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: Stack sends oversize UDP packet to the driver

On Tue, Jan 22, 2019 at 10:29 AM Mahesh Bandewar (महेश बंडेवार)
<maheshb@...gle.com> wrote:

>
> The idea behind the fix is very simple and it is to create a dst-only
> (unregistered) device with a very low MTU and use it instead of 'lo'
> while invalidating the dst. This would make it *not* forward packets
> to driver which might need fragmentation.
>

We tested the 2 patches many times and including an overnight test.  I
can confirm that the oversize UDP packets are no longer seen with the
patches applied.  However, I don't see the blackhole xmit function
getting called to free the SKBs though.

Thanks.