Re: [ANNOUNCEMENT] TEST RELEASE: Cygwin 1.7.35-0.3

[Tom Honermann <thonermann at coverity dot com>]

On 02/20/2015 11:24 AM, Corinna Vinschen wrote:
> On Feb 20 11:07, Tom Honermann wrote:
> > On 02/20/2015 04:56 AM, Corinna Vinschen wrote:
> > > > Lastly, running cygserver to cache the LDAP data has another side-effect
> > > > when using VPN.  Since the cygserver is usually started before you've
> > > > dialed into the VPN, your username and some groups will get reported as
> > > > "DOM+User(12345)".  You have to restart cygserver after the VPN is up to
> > > > correct that.
> > >
> > > Yep.  We should contemplate to allow sending a signal to cygserver to
> > > invalidate its cache.
> >
> > Perhaps cygserver could subscribe to network event notifications and
> > automatically invalidate its cache?
> >
> > https://msdn.microsoft.com/en-us/library/windows/desktop/aa366334%28v=vs.85%29.aspx
>
> How do you know if and when an interface change requires a cache
> invalidation?

I doubt there is a perfect algorithm, but perhaps a heuristic would work 
fairly well.  For non-mobile systems, interface changes are presumably 
rather rare and invalidation on the addition of any new interface might 
be acceptable.  For mobile systems migrating between networks, the 
situation is tougher - invalidating the cache when not connected to a 
network from which it can be rebuilt would be frustrating.  An ugly 
solution would be to invalidate depending on whether a (set of) user 
specified address(es) has transitioned from non-reachable to reachable 
(perhaps cache addresses of previously known AD servers?).  A 
not-quite-as-ugly solution might be to invalidate based on specific 
networks (ie, a user specified wifi network name).  None of these sound 
great to me, but perhaps would work well enough in practice.

Tom.

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