Re: [PATCH] ppp: implement MRU option

[Denis Kenzior <denkenz@gmail.com>]

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Hi Kristen,

> On Thu, 22 Apr 2010 15:16:58 -0500
> 
> Denis Kenzior <denkenz@gmail.com> wrote:
> > Hi Kristen,
> >
> > > @@ -80,7 +88,7 @@ static gboolean ppp_net_callback(GIOChannel *channel,
> > >  GIOCondition cond,
> > >
> > >  	if (cond & G_IO_IN) {
> > >  		/* leave space to add PPP protocol field */
> > > -		status = g_io_channel_read_chars(channel, buf + 2, MAX_PACKET,
> > > +		status = g_io_channel_read_chars(channel, buf + 2, net->mtu,
> > >  				&bytes_read, &error);
> > >  		if (bytes_read > 0) {
> > >  			ppp->proto = htons(PPP_IP_PROTO);
> >
> > So I actually have a concern here.  Quoting RFC 1332 Section 2.1:
> > "Exactly one IP packet is encapsulated in the Information field of PPP
> >    Data Link Layer frames where the Protocol field indicates type hex
> >    0021 (Internet Protocol)."
> >
> > However, you're not changing the physical MTU of the TUN/TAP interface,
> > so in effect you are mangling the packets that are larger than net->mtu. 
> > These packets will most likely simply be discarded leading to lots of
> > fun.
> 
> We can add an ioctl to change the MTU during ppp_net_set_mtu(), which
> should hopefully resolve this.
> 

Yep, my thinking as well.  Can you send a patch?

Thanks,
-Denis