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

From: Stephen Hemminger <[email-masked]>
Date: Tue, 12 Dec 2017 14:01:27 -0800

On Tue, 12 Dec 2017 11:00:38 -0800
Ed Swierk <[email-masked]> wrote:

> On Tue, Dec 12, 2017 at 10:34 AM, Stephen Hemminger
> <[email-masked]> 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

Maybe add a netem impairment that does padding?