netdev - Re: [PATCH] PPPoL2TP: Add more code snippets

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Message-ID: <ZD5uU8Wrz4cTSwqP@debian>
Date:   Tue, 18 Apr 2023 12:17:55 +0200
From:   Guillaume Nault <gnault@...hat.com>
To:     Samuel Thibault <samuel.thibault@...-lyon.org>,
        James Chapman <jchapman@...alix.com>, tparkin@...alix.com,
        edumazet@...gle.com, davem@...emloft.net, kuba@...nel.org,
        pabeni@...hat.com, corbet@....net, netdev@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PPPoL2TP: Add more code snippets

On Tue, Apr 18, 2023 at 11:11:48AM +0200, Samuel Thibault wrote:
> Guillaume Nault, le mar. 18 avril 2023 11:06:51 +0200, a ecrit:
> > On Tue, Apr 18, 2023 at 10:53:23AM +0200, Samuel Thibault wrote:
> > > Guillaume Nault, le mar. 18 avril 2023 10:34:03 +0200, a ecrit:
> > > > PPPIOCBRIDGECHAN's description
> > > > belongs to Documentation/networking/ppp_generic.rst, where it's already
> > > > documented.
> > > 
> > > Yes but that's hard to find out when you're looking from the L2TP end.
> > 
> > That's why I proposed linking to ppp_generic.rst.
> 
> Yes, but it's still not obvious to L2TP people that it's a ppp channel
> that you have to bridge. Really, having that 20-line snippet available
> would have saved me some head-scratching time.

But the reverse is also true: someone looking at the PPP documentation
is probably not going to realise that PPP sample code have been put in
the L2TP doc.

We can instead add PPP specific code in the PPP documentation. Then add
a line in l2tp.rst saying something like "Handling of the PPP layer is
described in ppp_generic."

If you feel like having sample code for a full example covering the
whole process of creating and setting up the file descriptiors needed
for bridging PPP channels (UDP, L2TP tunnels, L2TP sessions and PPP
channels, and why not PPPoE), then I feel a specific file would be more
indicated, as this would cross several different subsystems.

It'd be okay to to have a few PPP-specific calls in l2tp.rst since
L2TPv2 is tied to PPP and that could give a more complete example of
how to use the L2TP uAPI. But that should be limitted to the most basic
PPP features (creating a channel and a unit).

> Samuel
>