[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [lwip-users] Help with PPP connection - modem disconnects for no obv

From: Patrick Klos
Subject: Re: [lwip-users] Help with PPP connection - modem disconnects for no obvious reason...
Date: Wed, 20 Mar 2019 14:19:48 -0400
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.3

On 3/20/2019 1:48 PM, Sylvain Rochet wrote:
Hi Patrick,

Hi Sylvain,

On Wed, Mar 20, 2019 at 01:20:02PM -0400, Patrick Klos wrote:
For whatever reason, you're not responding to the CHAP challenges.

Are you dialing into an ISP (which would require authentication) or into
another system configured to be a "server"?  Either way, the peer is
expecting you to have a username and password of some kind, but you're not
responding to their challenges.
Well, that's just PPP to a cellular modem, PPP link is only between the
device and the cellular modem to de/serialize IP packets on a serial
link. That's why authentication is never required, cellular modems
usually add some kind of fake authentication to support PPP clients
where authentication can't be disabled.

OK, but that just begs the question "why is the modem asking for CHAP authentication"?  Maybe that's how GSM modems work?  Anyway, let's explore the CHAP process further.

Also, what version of LwIP are you using?  I can't find some of these debug
strings (like "CHAP Challenge") in my (2.1.2) sources. And are you sure all
your modules were compiled with PPP_DEBUG defined as non-zero?
"CHAP Challenge" is from "CHAP" from chap_protent and "Challenge" from

Oops... sorry, I didn't notice that.

Debugging seem pretty well enabled, for once in a while I have no clue
what is wrong here, usually it's straightforward from the trace but here
it really isn't.

If all the debugging is enabled, I'm curious why we don't see a CHAP Response being sent out?  I would suggest adding a few PPPDEBUG statements to chap_input() (especially the few places where is silently returns) and chap_respond() and see what that reveals?


reply via email to

[Prev in Thread] Current Thread [Next in Thread]