Re: [lwip-users] Advise on PPPoS implementation

[Sylvain Rochet]

Hi,

On Thu, Nov 02, 2017 at 05:02:36PM +0000, Raivis wrote:
> That's a very good, point, I've been so frustrated that it didn't occur to
> me that I can just print the packet in my serial function.
> 
> Apologies I somehow over glanced your suggestion before.
> 
> I enabled the PPP_DEBUG and PRINTPKT_SUPPORT, and removed all filters from
> ppp_dump_packet() in utils.c, leaving just "pp_dbglog()"  function call.
> 
> 
> From my inexperienced point of view, the PPP side seems to work fine I
> guess.

It is, pppos_netif_output() is the last step in the lwIP PPP stack, it 
means (if it succeed, which is the case here), that your serial output 
callback was called.


> Is it something to do with netif?

I don't understand to which scope this question apply; The netif is 
properly configured for me, we can undoubtfuly see the TCP SYN attempt 
in the debug log, meaning the packet goes down all the stack up to your 
serial low level writer.

If you are talking about your low level flow serial driver, it looks 
fine from here, you already said you saw the TCP packet properly sent on 
wire.

However, there might be some missing dark magic in your dialup 
chatscript ("AT" commands) before starting the PPP session. Your modem 
accepts the PPP session and set a apparently usable IP address so it 
should work but, well, some of these modems (all?), especially cellular 
ones, have some quirks[*] in their firmwares.

   [*] I'm saving a strong word here


Maybe you could try with UDP first instead of TCP; I don't think it 
would help in this case but we never know.


Sylvain

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