netdev - Re: [RFC net-next 0/6] xdp: make stack perform remove and tests

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Date:   Sat, 25 Nov 2017 17:02:09 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        daniel@...earbox.net, jiri@...nulli.us
Subject: Re: [RFC net-next 0/6] xdp: make stack perform remove and tests

On Thu, Nov 23, 2017 at 06:36:07PM -0800, Jakub Kicinski wrote:
> Hi!
> 
> The purpose of this series is to add a software model of BPF offloads
> to make it easier for everyone to test them and make some of the more
> arcane rules and assumptions more clear.
> 
> The series starts with 3 patches aiming to make XDP handling in the
> drivers less error prone.  Currently driver authors have to remember
> to free XDP programs if XDP is active during unregister.  With this
> series the core will disable XDP on its own.  It will take place
> after close, drivers are not expected to perform reconfiguration
> when disabling XDP on a downed device.
> 
> Next two patches add the software netdev driver.  Last but not least
> there is a python test which exercises all the corner cases which
> came to my mind.
> 
> Test needs to be run as root.  It will print basic information to
> stdout, but can also create a more detailed log of all commands
> when --log option is passed.  Log is in Emacs Org-mode format.
> 
>   ./tools/testing/selftests/bpf/test_offload.py --log /tmp/log
> 
> Something I'm still battling with, and would appreciate help of
> wiser people is that occasionally during the test something makes
> the refcount of init_net drop to 0 :S  I tried to create a simple
> reproducer, but seems like just running the script in the loop is
> the easiest way to go...  Could it have something to do with the
> recent TC work?  The driver is pretty simple and never touches
> ref counts.  The only slightly unusual thing is that the BPF code
> sleeps for a bit on remove in the netdev notifier.

I like the direction.
Patch 3 in particular with auto prog_put is a great idea!
Patch 4 - if you want to do dual gpl+bsd. It's ok and really your call as an author.
Patch 5 - I'm only not excited about debugfs. Can you do the same with tracepoints?
Patch 6 - python 3 is a requirement? or can work with 2.7 ? I don't mind if it's 3+ only.
Just trying to understand the dependencies.
and thanks for adding it to selftests.