Re: [lwip-users] Debug pppos packet loss issue

[Sylvain Rochet]

Hi Axel,

On Thu, Mar 02, 2017 at 08:55:15PM +0800, Axel Lin wrote:
> Hi,
> I'm using current lwIP master tree.
> 
> I got my device connect to internet via 4G/LTE module now (by PPPoS).
> However, I found sometimes download file size mismatch when
> try to download some files (about 100KB) from http server.
> 
> I tried enable PPP_DEBUG / PRINTPKT_SUPPORT / PPP_PROTOCOLNAME /
> LWIP_STATS_DISPLAY, but I don't see any unusual things.
> 
> The only strange thing is in download success case, the download speed 
> is fast. In download file mismatch (seems some packet lost) case, the 
> download speed is very low. Any hint to debug such issue?

HTTP uses TCP so whatever happens you shouldn't have a size mismatch.

As usual, for the must common lwIP misuse, if you are using an OS, you 
must not call RAW API outside the lwIP TCPIP thread and since you are 
using PPPoS you must use the thread-safe PPPoS input API (see PPP 
documentation).

Sylvain