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Re: [lwip-users] Acknowledge Problem

From: Sergio R. Caprile
Subject: Re: [lwip-users] Acknowledge Problem
Date: Mon, 18 Apr 2016 11:18:34 -0300
User-agent: Mozilla/5.0 (Windows NT 6.1; rv:38.0) Gecko/20100101 Thunderbird/38.7.2

>> Did you check that with a known-good application ?
> *Not yet.*

Well..., you should. Did I say 'should' ? You _must_

>> What version of lwIP are you using ?
> *We used lwip 1.4.1 and also
> source from git.savannah.gnu.org (commit #70f3e5e). In both versions
> the problem exists.*

I would say that "you experience this behaviour when running either version", I wouldn't blame lwIP for it, not yet.

>> Do you use an OS ? NO_SYS=?
> *FreeRTOS*

>> What API are you using ?
> *I have to check this.*

>> Do you honor the threading rules ?
> *I have to check this.*

Well, if you don't honor threading rules, you will experience all kind of strange and faulty behaviour, and that won't be lwIP's fault, so... you should start here.

>> Do you know there are web servers in the contrib tree ?
> *Yes, we are using netcon*

You are running a port over FreeRTOS, you should(must) have NO_SYS=0, basic functions must run on one thread, I mean, no rx interrupts and lwIP core on a thread. Netconn apps may run on a separate thread (but I'm not versed in netconn) The delay you describe has been observed in some ports that poll the rx driver and forget to remove all frames from it (ST?) The delays I observe are consistent with this, the server seems to answer "one frame off", and then in frame 57, an XID comes in and stacks one extra frame in the Eth controller memory, probably causing a frame loss, and later there ARP requests, what makes this even worse. I may be wrong, but...

You say you are using the 'netcon' webserver (do you mean 'netconn' ?)
However, your capture file shows the server responds with "Server: lwIP/1.3.1 (http://savannah.nongnu.org/projects/lwip)", and that belongs to fsdata.c, which is from the RAW API webserver. Besides, the netconn web server does not serve files.
You should know what you are using, in order to use it properly.

If you are indeed using the RAW API webserver, that server runs quite more than OK. If you are running 'a' netconn server, that server is not lwIP code.

Your problem, then, I bet, lies on a faulty port, please check what I already suggested you should check (and you did not). If, after that, you still have problems, please open a new thread and include your API, RTOS and port provider description in the subject.

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