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RE: Need help for TCP/IP over PPP via GSM modem


Hello, Matt:
   Yes, by channging wo->neg_asyncmap from 0 to 1 in lcp_init fixed my
problem. Now I can ping (google.com) and the call of connect() is also
working. Great!
   I really appreciate your help and have a nice weekend!

Weili


-----Original Message-----
From: Matt Jerdonek [mailto:maj1224@yahoo.com] 
Sent: Friday, December 03, 2004 12:49 PM
To: Weili Yao; ecos-discuss@sources.redhat.com
Subject: Re: [ECOS] Need help for TCP/IP over PPP via GSM modem

We just finished testing TCP/IP over PPP with a GSM modem.  There was
one problem that we encountered that might explain what you're seeing
...

The eCos PPP stack does not negotiate ACCM.  Our GSM provider had a bug
in their PPP server that caused their ACCM to default to zero when the
peer did not negotiate ACCM (it should have defaulted to 0xFFFFFFFF).
This would cause the PPP stack in eCos to think the incoming PPP frames
had a bad checksum, and discard them.  We fixed the problem by turning
on ACCM negotiation in the PPP stack (Set
wo->neg_asyncmap to 1 in lcp_init).  There is a more
complete patch that is submitted to fix this issue, but it has not yet
been committed.

Hope this helps,
-- Matt

--- Weili Yao <weili_yao@trimble.com> wrote:

> Hello, there:
>     I am using Redhat ECOS for our TCP/IP over PPP connection via GSM 
> modem. The ECOS source was downloaded from CVS about two months ago. 
> The GSM service provider is Cingular Wireless with GPRS enabled. The 
> problem is after PPP connection established, I was not able to ping or

> connect to anywhere. It failed at recvfrom() with return -1 when used 
> in the
> ping_host(...) (see ppp_updown.c). The TCP/IP
> connect() API call waits
> forever. But the same source code (only with different serial port on 
> the device) works with serial cable connected to my Linux box. With 
> that serial cable attached to Linux, I was able to do ping and to call

> connect().
>     Can anybody there help me with this problem? It seems to me that 
> with wireless modem PPP connection, the TCP/IP code does not work. By 
> the way, even though it failed at recvfrom() in the ping, I do see the

> ICMP echo back in the port driver, and the echo data is correct, but 
> that incoming data is not used by recvfrom(). Why?
> Look at the routing
> table, the local device IP address is assigned to:
> 10.216.27.198, but
> the remote (at Cingular) IP address is:
> 66.102.185.195. Does this have
> any conflict? These IP addresses are assigned automatically during PPP

> connection.
> 
>     The following is the details how to set the PPP connection and 
> what the routing table is. Please let me know if you need more 
> information. I really appreciate your help with this problem.
> 
> For the PPP connection, I am using:
>     user name: WAP@CINGULARGPRS.COM
>     password: CINGULAR1
> After using AT commands(baud rate is configured as
> 115200) :
>     AT+CGDCONT=1,"IP","WAP.CINGULAR"
>     ATD*99***1#
> by supplying above user name and password in the CHAP, the PPP 
> connection has been established.
>  
> After PPP connection established, I used ECOS API:
> show_network_tables(printf)  to check the network information and I 
> got the following routing table:
> "Routing tables " 
> 
> "Destination       Gateway          Mask       Flags
>       Interface " 
> 
> 0.0.0.0           66.102.185.195   0.0.0.0      UGS 
>        ppp0
> 
> 66.102.185.195    10.216.27.198                 UH  
>        ppp0
> 
> 127.0.0.0         127.0.0.1        255.0.0.0    UG  
>        lo0
> 
> 127.0.0.1         127.0.0.1                     UH  
>        lo0
> 
> Interface statistics
> 
> lo0
> 
>     IP: 127.0.0.1, Broadcast: 127.0.0.1, Netmask:
> 255.0.0.0
> 
>         UP, LOOPBACK, RUNNING, MULTICAST
> 
>     MTU: 16384, Metric: 0
> 
>        Rx - Packets: 0, Bytes: 0,
> 
>        Tx - Packets: 0, Bytes: 0
> 
> ppp0
> 
>      IP: 10.216.27.198, Broadcast: 66.102.185.195,
> Netmask: 255.0.0.0
> 
>          UP, RUNNING, MULTICAST
> 
>      MTU: 1500, Metric: 0,
> 
>          Rx - Packets: 0, Bytes: 0" 
> 
>          Tx - Packets: 0, Bytes: 0
> 
> ============
> Thank you a lot!
> 
> Weili Yao
> 
> 
> 
> --
> Before posting, please read the FAQ:
> http://ecos.sourceware.org/fom/ecos
> and search the list archive:
> http://ecos.sourceware.org/ml/ecos-discuss
> 
> 



		
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