pppd and AT+WMUX(Multiplex mode)

pppd and AT+WMUX(Multiplex mode)

[Simon Chow]

I am researching how to handle the AT packets and Data packets offered by
the Wavecom GSM modem in AT+WMUX=1 mode. I want to modify the pppd programme
and I think that the tty.c in pppd may be the key to change. The charshunt
function manipulates both the raw bytes sent from and received by the serial
port. However, I am still in an initial stage.

I wonder if the pppd tool can handle the multiplex mode offered by Wavecom
GSM modem. Thanks.

Re: pppd and AT+WMUX(Multiplex mode)

[carlsonj]

Simon Chow writes:
> I am researching how to handle the AT packets and Data packets offered by
> the Wavecom GSM modem in AT+WMUX=1 mode. I want to modify the pppd programme
> and I think that the tty.c in pppd may be the key to change. The charshunt
> function manipulates both the raw bytes sent from and received by the serial
> port. However, I am still in an initial stage.

I don't think that analysis is right.  The charshunt task is invoked
only in a few cases (e.g., where the 'record', 'notty', or 'socket'
options are used), and isn't the normal data path.  The normal data
path is in the kernel, not user space.

> I wonder if the pppd tool can handle the multiplex mode offered by Wavecom
> GSM modem. Thanks.

Not today.  I think you'd have to modify the PPP modules in the Linux
kernel to detect the switching mechanism and feed the data up to pppd
first.  Otherwise, it'll probably be handled as bad PPP frames and
discarded.

-- 
James Carlson                                 <carlsonj@workingcode.com>

Re: pppd and AT+WMUX(Multiplex mode)

[Miguel-Munoz]

Continuing with the same issue...
I´m trying to do the same with the same modem.
I´m thinking in use a 'virtual' ttyS, changing the device driver.
So I would have a point where I could extarct the headers
(data or commands), almost from the port.
Am I wrong?

Thanks

Miguel

----- Original Message ----- 
From: <carlsonj@workingcode.com>
To: "Simon Chow" <simonchow@keytechsys.com.hk>
Cc: <linux-ppp@vger.kernel.org>
Sent: Wednesday, July 21, 2004 5:44 PM
Subject: Re: pppd and AT+WMUX(Multiplex mode)


> Simon Chow writes:
> > I am researching how to handle the AT packets and Data packets offered
by
> > the Wavecom GSM modem in AT+WMUX=1 mode. I want to modify the pppd
programme
> > and I think that the tty.c in pppd may be the key to change. The
charshunt
> > function manipulates both the raw bytes sent from and received by the
serial
> > port. However, I am still in an initial stage.
>
> I don't think that analysis is right.  The charshunt task is invoked
> only in a few cases (e.g., where the 'record', 'notty', or 'socket'
> options are used), and isn't the normal data path.  The normal data
> path is in the kernel, not user space.
>
> > I wonder if the pppd tool can handle the multiplex mode offered by
Wavecom
> > GSM modem. Thanks.
>
> Not today.  I think you'd have to modify the PPP modules in the Linux
> kernel to detect the switching mechanism and feed the data up to pppd
> first.  Otherwise, it'll probably be handled as bad PPP frames and
> discarded.
>
> -- 
> James Carlson                                 <carlsonj@workingcode.com>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-ppp" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: pppd and AT+WMUX(Multiplex mode)

[Simon Chow]

<carlsonj@workingcode.com> wrote in message
news:16638.36676.350168.813237@carlson.workingcode.com...
> Simon Chow writes:
> > I am researching how to handle the AT packets and Data packets offered
by
> > the Wavecom GSM modem in AT+WMUX=1 mode. I want to modify the pppd
programme
> > and I think that the tty.c in pppd may be the key to change. The
charshunt
> > function manipulates both the raw bytes sent from and received by the
serial
> > port. However, I am still in an initial stage.
>
> I don't think that analysis is right.  The charshunt task is invoked
> only in a few cases (e.g., where the 'record', 'notty', or 'socket'
> options are used), and isn't the normal data path.  The normal data
> path is in the kernel, not user space.
>
> > I wonder if the pppd tool can handle the multiplex mode offered by
Wavecom
> > GSM modem. Thanks.
>
> Not today.  I think you'd have to modify the PPP modules in the Linux
> kernel to detect the switching mechanism and feed the data up to pppd
> first.  Otherwise, it'll probably be handled as bad PPP frames and
> discarded.
>
> -- 
> James Carlson                                 <carlsonj@workingcode.com>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-ppp" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>


How about I modify the ppp_async_input function in ppp_async.c to detect the
0xAA and 0xDD, and the ppp_async_push function to encapsulate the PPP frame
with 0xDD?