netdev - Re: [PATCH] bnx2x: drop packets where gso

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Message-ID: <1505745775.29839.16.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 18 Sep 2017 07:42:55 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Daniel Axtens <dja@...ens.net>
Cc:     netdev@...r.kernel.org, tlfalcon@...ux.vnet.ibm.com,
        Yuval.Mintz@...ium.com, ariel.elior@...ium.com,
        everest-linux-l2@...ium.com, jay.vosburgh@...onical.com
Subject: Re: [PATCH] bnx2x: drop packets where gso_size is too big for
 hardware

On Mon, 2017-09-18 at 14:41 +1000, Daniel Axtens wrote:
> Hi Eric,
...
> So I've been experimenting with this and reading through the core
> networking code. If my understanding is correct, disabling GSO will
> cause the packet to be segmented, but it will be segemented into
> gso_size+header length packets. So in this case (~10kB gso_size) the
> resultant packets will still be too big - although at least they don't
> cause a crash in that case.

You describe a bug in core networking stack then.

When we perform software segmentation, we must do the check against
route mtu, and drop the offending frame, and send an ICMP back
eventually.