[lwip-users] lwip PPP stack, which authentication is used for GPRS APN

[Wagner Hans-Jörg]

Hi Clive and other lwip users

I am looking for tools to investigate in PPP (over serial port) protocol 
handling, espacially the PAP and CHAP mechanism. As I read, there are several 
different CHAP standards (MD5 and a windows proprietary one as I understood 
Clive). Please read further explanations, what Im planning to do.

I plan now to use lwip with uCOSII on an MPC555 platform (I know this is an old 
one, but its still used in our products).

The TCP/IP/PPP stack is used to make a gprs connection from our MPC555. For 
this we use a bluetooth OEM module and a bluetooth enabled mobile phone.

Today I made a trace with the sysutil/netmon V3.02 from Microsoft, whats going 
on, if I make a GPRS connection with a standard modem driver, the OEM bluetooth 
module and the mobile phone (btw I had success). However, its very akward to 
identify relevant protocol fields in a hex trace. I could identify the PPP 
authentification start protocol (according to the PPP RFC it starts with 0x7E, 
0xFF, then the CHAP or PAP relevant part was 0x23 0xC0 0x21)
The RFC tells 0xC021 is PAP and 0xC023 is CHAP. However I dont know, if PPP 
over serial line transmitts MS Byte or LS Byte first for 16bit values. So I 
dont know if my windows PC used CHAP or PAP to authenticate with the GPRS APN.

Does anybody know, how to trace serial line PPP protocols and analyze it with 
windows tools (already parsing and commenting relevant protocol fields). Has 
ethereal the ability to trace the serial line (how) or is it just intendet to 
use with ethernet network interfaces?

BTW: Which CHAP standard is supported by the LWIP and how can I check in the 
PPP frame, if its a MD5 or a windows proprietary standard? Or does somebody 
even know, if there is a common standard used by GPRS APNs, or is it GPRS 
provider dependent?

Regards
Hans-Joerg

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