Re: [lwip-users] PPP - TCP

[Sylvain Rochet]

Hi Norberto,

On Fri, Jan 15, 2016 at 03:35:06PM -0200, Norberto R. de Goes Jr. wrote:
> Hi Sylvain.
> 
> How I told you, I am facing problems with TCP-PPP in lwip scenario.
> Then I decided use just a raw lwip code to reproduce the problem and, if it
> is possible, could you use it to reproduce in your environment.
> 
> I fetched my git repositoy today (15/jan). Hashs:
>   - lwip:               e033866651903f4b12e6af074180272c5aadc553
>   - lwip-contrib:  ddff8d34d0e7e5f417926aed032067e75c28a447
> 
> and I changed a little bit two files (attached).
>   - ports/unix/proj/unixsim/lwipopts.h
>   - ports/unix/proj/unixsim/simhost.c
> 
> The "simhost" then was compiled using the original makefile:
>   > cd .../lwip-contrib/ports/unix/proj/unixsim
>   > make
> 
> I have two VM´s (Ubuntu) in a Win-7 server. In the VM#1, I run the pppd
> (linux), passive mode. Just after, the simhost app is executed in VM#2.
> The link ppp is established, with no problem.
> 
> The simhost already implements a TCP echo server (reply). At VM#1, the echo
> client app (use the TCP linux stack, no lwip) is executed. The TCP
> connection is established.
> 
> After 3 or 4 string messages exchanged the lwip reports error and the TCP
> connection going to down. The client reports "Resource temporarily
> unavailable" and  the simhost app sometimes shut down.
> 
> I apologize for my insistence, but we are in great need of a help.
> Thanks.

From a quick look on what you changed in the unixsim project, the added 
ppp_loop_thread() function is using the lwIP PPP raw API, which is not 
thread safe.

Please try using pppos_input_sys() instead of pppos_input(). FYI that's 
properly documented into lwip/doc/ppp.txt, section "3 PPPoS input path 
(raw API, IRQ safe API, TCPIP API)".

Sylvain

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