netdev - Re: [PATCH] veth: Optionally pad packets to minimum Ethernet length

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Date:   Tue, 12 Dec 2017 11:00:38 -0800
From:   Ed Swierk <eswierk@...portsystems.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Dan Williams <dcbw@...hat.com>,
        netdev <netdev@...r.kernel.org>,
        Benjamin Warren <ben@...portsystems.com>,
        Keith Holleman <holleman@...portsystems.com>
Subject: Re: [PATCH] veth: Optionally pad packets to minimum Ethernet length

On Tue, Dec 12, 2017 at 10:34 AM, Stephen Hemminger
<stephen@...workplumber.org> wrote:
> Why not add to netdevsim rather than cluttering up a normal driver
> with test support.  We just pulled a bunch of test stuff out of dummy
> for the same reason.

My test setup to trigger an openvswitch conntrack issue
(https://marc.info/?l=linux-netdev&m=151309548725627) involves a lot
of moving parts:

[netns-a: vetha1] - [vetha0] - [ovsbr0] - [vethb0] - [netns-b: vethb1]

with nc client and server in netns-a and -b, and tweaks like turning
off tcp_timestamps to make sure the packets in the TCP stream are
small enough to reproduce the problem. A simpler, less fragile test
setup would be valuable, especially if it ends up as an automated
regression test.

Could netdevsim be useful for that? Are there any existing tests
producing TCP traffic that might serve as an example?

--Ed