[Samba] updates of repsFrom/repsTo attributes (was : Re: replPropertyMetaData & KCC issues after updating to Samba 4.5.0)

[garming at catalyst.net.nz]

> The link also references how a DC alerts other DC's that a ISTG has
> gone down in a site. This is the critical component I was worried
> about. Is this feature currently implemented in Samba? On a Microsoft
> DC you can alert how often you want to check for the ISTG in a
> registry setting. Do you have plans to add this as a option for the
> smb.conf?

That likely maps to some attributes in the directory which we probably 
partly respect. I think a bit more work is needed to allow the failover 
times to have better configuration.

> I will also point out Samba did correctly set the ISTG for my sites to
> DC1. The first DC I joined to that site. After deleting the NTDS
> connections, I see that my second DC in a site was chosen as the ISTG.
> This tells me some sort of check may be happening to switch the ISTG?
> 

The role can rotate from time to time for various reasons, so doesn't 
necessarily stay fixed.

> Based on all this it appears the new KCC does in fact work correctly
> with a few minor issues relating to the replications To and From.
> Thanks for the hard work.

It's still a work in progress and there are some failover modes which I 
would like to improve, but in a happy, relatively healthy network, 
replication traffic should be heavily decreased, CPU usage should be 
less of a problem and the DC should suffer fewer blockages. With this 
work, I look forward to seeing what Samba will be able to achieve in 
future.

Cheers,

Garming