Re: ppp

[Denis Kenzior <denkenz@gmail.com>]

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Hi Ryan,

> Hello,
>
> We need a ppp interface for our modem. I was told on the chat forum that
> a tap/tun device was to be used. Has anyone else started with this or
> thought how to implement this?

We're currently working on a userspace ppp implementation that will integrate 
with GAtChat.  The goal here is to make it integrate well with the current 
multiplexed channel capability in GAtMux/GatChat and not need to involve an 
external daemon.

>
> After reading briefly the code from pppd, the implementation, for a
> first draft, is pretty straight forward (w/o encryption, etc. in
> userspace). "Just" dial the apn, and hand over the tty fd to ppp via ioctl.
>

Unfortunately it is not that simple.  pppd requires a proper kernel file 
descriptor to hand off to the kernel ppp line discipline.  In our userspace 
implementation that is not the case.  1 kernel file descriptor is shared by 
potentially many GAtChat channels using a multiplexing protocol.  Hence why we 
can't reuse the kernel implementation.

Regards,
-Denis