Re: [lwip-users] ERR_MEM when sending large data, LWIP stats show no error

[Adrian Figueroa]

I find no errors or dropped packets in any of the lwIP stats categories. 

So, I tried reducing my application to sending the same data all the time. 
Every 15 packets precisely, there is a lost packet. This is after a payload of 
21900 bytes.

By the way, 21900 bytes equals exactly my MEM_SIZE (23360) minus one TCP_MSS 
(1460), so this may be a hint. My TCP_SND_QUEUELEN is 16.

Still, the mem stats show:

LwIP_stats.mem
        Err: 0
        Avail: 23360
        Used: 6288
        Max: 6356
        Illegal: 0

I am a little lost at this point. How could the memory be filled up? I get ACKs 
after each two packets.

Best regards,
Adrian

-----Ursprüngliche Nachricht-----
Von: lwip-users [mailto:address@hidden Im Auftrag von Sergio R. Caprile
Gesendet: Friday, September 1, 2017 5:46 PM
An: address@hidden
Betreff: Re: [lwip-users] ERR_MEM when sending large data, LWIP stats show no 
error

Ha, I love the word "severe" being used here...
I don't know, I've read some guys finding bugs on the Cube drivers, and seems 
to vary depending on which micro you are using. Search the list.
The fact is that your messages are getting lost and you need to find where...
I suggest running an echo with your current configuration. This way we can 
discard your application doing something nasty.
I'm not good at reading the stats, try enabling some TCP and netif stats to see 
if you find discards/drops/ or anything leading that way. I would blame the 
driver but I'm baffled by the correlation to TCP_SND_BUF being twice TCP_MSS. 
Perhaps Simon or one of the developers has an idea. I would check how TCP 
splits your data into wouldbe frames, maybe the way you partition gives the 
driver some fresh air not to drop frames... I don't know. Most of the times is 
a vendor fault so I'm biased here.

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