Re: [PATCH] PPPoL2TP: Add more code snippets

Samuel Thibault
2023-04-18T09:11:57Z

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:
> > > 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.
>
> connect() failed. You can't do anything with this socket.

Ah, you were talking about the failure case, ok.

> > > > +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.
>
> 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.

Samuel