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Date:   Tue, 18 Apr 2023 10:53:23 +0200
From:   Samuel Thibault <samuel.thibault@ens-lyon.org>
To:     Guillaume Nault <gnault@redhat.com>
Cc:     James Chapman <jchapman@katalix.com>, tparkin@katalix.com,
        edumazet@google.com, davem@davemloft.net, kuba@kernel.org,
        pabeni@redhat.com, corbet@lwn.net, netdev@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] PPPoL2TP: Add more code snippets
Message-ID: <20230418085323.h6xij7w6d2o4kxxi@begin>
Mail-Followup-To: Samuel Thibault <samuel.thibault@ens-lyon.org>,
        Guillaume Nault <gnault@redhat.com>,
        James Chapman <jchapman@katalix.com>, tparkin@katalix.com,
        edumazet@google.com, davem@davemloft.net, kuba@kernel.org,
        pabeni@redhat.com, corbet@lwn.net, netdev@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20230416220704.xqk4q6uwjbujnqpv@begin>
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Guillaume Nault, le mar. 18 avril 2023 10:34:03 +0200, a ecrit:
> On Mon, Apr 17, 2023 at 12:07:04AM +0200, Samuel Thibault wrote:
> >          sax.sa_family = AF_PPPOX;
> >          sax.sa_protocol = PX_PROTO_OL2TP;
> >          sax.pppol2tp.fd = tunnel_fd;
> > @@ -406,12 +407,64 @@ Sample userspace code:
> >          /* session_fd is the fd of the session's PPPoL2TP socket.
> >           * tunnel_fd is the fd of the tunnel UDP / L2TPIP socket.
> >           */
> > -        fd = connect(session_fd, (struct sockaddr *)&sax, sizeof(sax));
> > -        if (fd < 0 ) {
> > +        ret = connect(session_fd, (struct sockaddr *)&sax, sizeof(sax));
> > +        if (ret < 0 ) {
> 
> Now you also need to close session_fd.

? No, we need it for PPPIOCGCHAN, and also PPPIOCGL2TPSTATS.

I'll put return session_fd instead.

> > +The ppp<ifunit> interface can then be configured as usual with SIOCSIFMTU,
> > +SIOCSIFADDR, SIOCSIFDSTADDR, SIOCSIFNETMASK, and activated by setting IFF_UP
> > +with SIOCSIFFLAGS
> > +
> > +  - Tunnel switching is supported by bridging channels::
> 
> This is a PPP feature not an L2TP one.
> 
> 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.

> If necessary, you can link to ppp_generic.rst here.
> 
> Also, calling this feature 'tunnel switching' is misleading.

That's how I have seen it is called in L2TP jargon.

Samuel