netdev - Re: UDP packets arriving on wrong sockets

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Message-ID: <20180803041911.GA30724@canndrew.org>
Date:   Fri, 3 Aug 2018 00:19:11 -0400
From:   Andrew Cann <shum@...ndrew.org>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: UDP packets arriving on wrong sockets

On Thu, Aug 02, 2018 at 11:21:41AM -0400, Willem de Bruijn wrote:
> You have two sockets bound to the same address and port? Is this using
> SO_REUSEPORT?

Yes, this is using SO_REUSEPORT.

My colleague wrote a python reproducer for this here:
https://gist.github.com/povilasb/53f1c802dbc2aca36a0ffa5b4cb95536

If you run server.py, then client.py, you should see packets arriving at
opposite sockets about half the time. My kernel version is NixOS 4.14.51, he
tested on two different machines - a debian 4.9.0 and fedora 28 4.17.2. We can
reproduce this on all kernels we tested.

Thanks in advance for any help you can give :)

 - Andrew

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