Re: [lwip-users] lwIP UDP echo server fails to send message lengths of 4385 & 4386

[Dan Nygren]

Sylvain wrote > ... Anyway, basic rule about using fragmented IP packets: avoid (to not say
don't).

Thank you for the advice Sylvain. My design is keeping its packets under the Ethernet 1500 octet MTU. I had made a diagnostic command to have my design send back arbitrarily sized messages to prove everything was working correctly when I ran into the 4385/4386 message size problem.

  Dan

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On Fri, Feb 3, 2023 at 1:24 PM Dan Nygren <dan.nygren@gmail.com> wrote:

Peter wrote:

> 4385/4386 could be 3x MTU ? ...

Peter, thanks for responding!

Yes, it seems like I've hit some corner case.

Is this the right place to notify the lwIP maintainers of problems? This is not a current problem for me as my messages are under the MTU size. I just hit this while developing some diagnostics for my board and I wanted to let others know about it.

            Dan

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On Wed, Feb 1, 2023 at 2:10 PM Dan Nygren <dan.nygren@gmail.com> wrote:

Hello fellow lwIP users. Can anyone point me in the right direction on how to resolve or report to the right folks the below issue?

I'm seeing rather bizarre behavior in that messages of length 4385 and 4386 I send to a lwIP based UDP echo server are not received back. udp_sendto() appears to be getting called and completing successfully. Wireshark indicates there are "bogus, payload length" errors with these lengths.

I have a detailed write up showing the behavior here:

https://github.com/Xilinx/embeddedsw/issues/212

I can copy the info above into an email for this mailing list if you prefer.

Let me know your suggestions on how to proceed. ...   Dan Nygren

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