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Re: [lwip-users] Lwip 1.4.0 issue with Large Packets when Receiving on L

From: Sergio R. Caprile
Subject: Re: [lwip-users] Lwip 1.4.0 issue with Large Packets when Receiving on LWIP
Date: Fri, 13 May 2016 10:47:23 -0300
User-agent: Mozilla/5.0 (Windows NT 6.1; rv:38.0) Gecko/20100101 Thunderbird/38.7.2

Your "TCP packets larger than one Ethernet packet" translate to two Ethernet frames. Sometimes, in the capture file, you see that the first one is acknowledged and some time(out) after the second one is retransmitted. Assuming the echorequester is a PC and the echoresponder is an lwIP device, then the device is sometimes missing the second frame.
There are a lot of situations in which this could happen.
You could have the (in)famous buggy driver which does not poll the controller for all the frames and only gets the latest outstanding one
        You could have a buggy port that misses data
You could have a buggy application that misses data. Since it is echo, I assume you are using the one in the contrib tree that works OK. Your API is ?
I see in your opts file
/* FreeRTOS is used. */
#define NO_SYS                                                  0
You could not be honoring the single-threading requirements and calling lwIP low-level functions from multiple threads (like rxing frames on an interrupt and txing on the main thread), but since you are running just the echo application I bet this problem is not because of this common error.
I would suggest you change the subject to "buggy driver issue sometimes missing the second out of two consecutive frames"... ;^)

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