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[lwip-users] PPP no IP address assigned

From: Michael Waeber
Subject: [lwip-users] PPP no IP address assigned
Date: Wed, 01 Apr 2015 08:47:03 +0200
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0

Hi all

I try to integrate PPP with a GPRS modem in our system. lwIP works well
for ethernet in our system since 3 years. Since PPP is currently
actively developed I've upgraded from 1.4.1 to current Master

The modem is connected to GPRS, then the PPP session is started. The
communication parameters are negotiated successfully (LCP). The
authentication is OK: Login OK. Now lwIP sends a Configuration request

ff 03 80 21 01 01 00 16 03 06 00 00 00 00 81 06 00 00 00 00 83 06 00 00
00 00 6e db 7e

Interpreted (Wireshark):
Protocol: Internet Protocol Control Protocol (0x8021)
Options: (18 bytes), IP address, Primary DNS Server IP Address,
Secondary DNS Server IP Address
IP address:
Primary DNS Server IP Address:
Secondary DNS Server IP Address:

After this frame the communication is dead, no answer received, no other
frame sent.

I've tried using various combinations of
- No auth, PAP, Chap
- With/without VJ header compression

a) Has anybody a hint why it does not work? I think the provider should
   send a IPCP Configuration Request/Ack/Nack?

b) I do not receive a callback (see pppos_create()). After a long
   timeout I try to restart, but without success: The stack is in a
   deadlock, I can't close the session. ppp_close(m_pSelf->ppp, true)
   does not give a callback either. So the only solution is to reset the
   whole system. How do I reset a hanging PPP session if no
   communication happens?

Best regards

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