netdev - Re: [RFC PATCH 0/2] add ppp_generic ioctl to bridge channels

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Date:   Sun, 15 Nov 2020 12:59:59 +0100
From:   Guillaume Nault <gnault@...hat.com>
To:     Tom Parkin <tparkin@...alix.com>
Cc:     netdev@...r.kernel.org, jchapman@...alix.com
Subject: Re: [RFC PATCH 0/2] add ppp_generic ioctl to bridge channels

On Tue, Nov 10, 2020 at 11:54:07AM +0000, Tom Parkin wrote:
> On  Mon, Nov 09, 2020 at 23:51:53 +0100, Guillaume Nault wrote:
> > BTW, shouldn't we have an "UNBRIDGE" command to remove the bridge
> > between two channels?
> 
> I'm not sure of the usecase for it to be honest.  Do you have
> something specific in mind?

I don't know if there'd be a real production use case. I proposed it
because, in my experience, the diffucult part of any new feature is
the "undo" operation. That's where many race conditions are found.

Having a way to directly revert a BRIDGE operation might help testing
the undo path (otherwise it's just triggered as a side effect of
closing a file descriptor). I personally find that having symmetrical
"do" and "undo" operations helps me thinking precisely about how to
manage concurency. But that's probably a matter of preference. And that
can even be done without exposing the "undo" operation to user space
(it's just more difficult to test).

Anyway, that was just a suggestion. I have no strong opinion.

> Thanks very much for your review and comments, it's much appreciated
> :-)

Thanks! :)