Bug? UDP packet transmitted via sendto() intermitently not being transmitted to network

Estabrook, Edward Edward.Estabrook@Polycom.com
Wed Dec 22 05:55:00 GMT 2010

On Dec 10 14:37, Estabrook, Edward wrote:
>> Generally I am seeking information regarding:
>> 1) Where can I download and install an older version of Cygwin (say
>> 1.5 era) to test if the problem is newly introduced?
> Corinna wrote:
What for?  If it doesn't work on 1.5 you're exactly at the same spot as
>now.  If it works on 1.5, we know it works on 1.5 but we still don't
>know why it doesn't work on 1.7, which means, you're still exactly at
>the same spot as now.  So that's not really an option.  The best option
>is either to debug the (slim) layer in Cygwin which provides send/recv,
>or at least to send an as-simple-as-possible, self-sufficient testcase,
>preferredly in plain C, which allows to reproduce the problem.

Two reasons.  If it works on 1.5, I'll simply use it to perform my testing
and the time-pressure to solve the root cause is lessened.  
Whether it works or not, it'll tell me if the issue is a change between 
those versions or something older.  (Plus the build instructions and 
distributed executable are for SIPp are written with cygwin 1.5 in mind.

The setup-legacy installer for older versions of Windows is exactly what I
needed.  I tested this out and confirmed the issue exists in the old version as well.

>> 2) What tools are available to measure potential packet loss within
>> cygwin itself? (the Windows stack is not reporting dropped UDP
>> packets, and the packets are not even making it into a locally running
>> instance of wireshark).  Is there a way to dump / access / sniff the
>> inputs and outputs to the cygwin IP stack?  Traffic volume is low so
>> verbosity would not pose a problem.
> Corinna wrote:
>You can add debug output to Cygwin's send and receive functions and use

OK, thanks.  I see debug_printf() and syscall_printf() statements sprinkled around the source.  Where do these end up displayed / logged?  How are they enabled?  

> Corinna wrote:
>Apart from actual debugging it yourself, a testcase, as outlined above,
>might be helpful.  The details describe *what* happens, but unfortunately
>don't even allow to guess *why* it happens.

Understood.  I need to perform more investigation before I can guess why, either.

Best Regards,

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