All things related to multicast

[Frank Fulchiero <>]

Also, didn't someone fix this miniSAPserver bug, and make the patch,  
or newer version, available?
Sorry, I forgot...

Thanks,
Frank


On Sep 3, 2008, at 7:24 AM, Bruce Rodger wrote:

> On Thu, 26 Jun 2008, 
>
>  wrote:
>
> > miniSAPserver in its current (buggy) form has been around
> > for ages....and yet thee storms have only just started to
> > occur.  is it, perhaps, that some 'config example' which
> > is out there i the one causing this issue
>
> I've just managed to unintentionally reproduce the problem.  
> Fortunately, it
> was noticed quickly, and hopefully was only local :)
>
> miniSAPserver version 0.3.4
> on Ubuntu 7.10
>
> The default config contains:
>
> # Number of seconds between announces. 5 is default. Internet  
> announces better use 30.
> sap_delay=5
>
> If you use this default, all is OK. If you add the "-s" flag to the
> command, it prints a "." every time it sends out a sap. And as
> expected, we get a "." appearing every 5 seconds.
>
> However, if we make the suggested change and increase the value of
> sap_delay to 30 (in fact to any value greater than 15!) we get our
> SAP storm - thousands of SAPs (and thousands of dots on the screen)
> appearing per second.
>
> The problem appears to be an integer overflow in sapserver.cpp
>
>        unsigned n = config.Programs.size() ?: 1;
>         div_t d = div ((1000000000 / n) * config.GetDelay(),  
> 1000000000);
>         struct timespec delay;
>         delay.tv_sec = d.quot;
>         delay.tv_nsec = d.rem;
> (snip)
>         while(!should_exit)
>         {
>             for( unsigned int i = 0; i< announces.size() ; i ++ )
>             {
> (snip - send the SAP here)
>                 nanosleep( &delay, NULL );
>             }
>         }
>
> So it appears that when config.GetDelay is >15,  
> 1000000000*config.GetDelay
> overflows, the arguments to nanosleep are negative.... it doesn't
> sleep.... we get a storm.
>
> A quick workaround is to remove the "div" line, and just have
>         delay.tv_sec = config.GetDelay();
>         delay.tv_nsec = 0;
>
> I will leave development of a "proper" solution to someone else.  
> But I will log it on the videolan forum...
>
> Bruce.
> --
> Bruce Rodger                      
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