[cifs-protocol] cifs client timeouts and hard/soft mounts

[Jeff Layton]

On Sat, 4 Dec 2010 06:25:07 -0600
Shirish Pargaonkar <shirishpargaonkar at gmail.com> wrote:

> On Sat, Dec 4, 2010 at 5:44 AM, Jeff Layton <jlayton at samba.org> wrote:
> 
> > On Sat, 4 Dec 2010 09:13:21 +0100
> > Volker Lendecke <Volker.Lendecke at SerNet.DE> wrote:
> >
> > > On Fri, Dec 03, 2010 at 09:54:13PM -0600, Christopher R. Hertel wrote:
> > > > That may seem to be in the "who cares" category, since those old
> > transports
> > > > are essentially dead (much more dead than NBT, or even NBF).
> >  Unfortunately,
> > > > the code to handle the old transports is still there in Windows, so
> > there
> > > > are behaviors -- things like the timeouts you're talking about and the
> > weird
> > > > VC=0 shutdown behvior -- that exist because of these old disused
> > transports.
> > >
> > > VC=0, how does Windows treat this facing NAT (masquerading)
> > > networks? I've done tests in the past where Windows killed
> > > valid connections from behind a NAT box when a new client
> > > came in.
> > >
> > > Volker
> >
> > It seems like the best way to deal with this on the server side with
> > direct hosted TCP would be to treat VC=0 like any other VC number
> > (MS-CIFS says that this is allowed).
> >
> > Ideally any new connection event from a host however should make the
> > server check the validity of any other connection from the same host.
> > That way you could release resources held by dead connections in case
> > the new one is a reconnect and needs to reclaim state.
> >
> > The question is how to check that validity. Unfortunately, the best you
> > can probably do is rely on TCP keepalives.
> >
> > --
> > Jeff Layton <jlayton at samba.org>
> >  --
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> >
> 
> 
> Is SMB Echo command the only way to determine whether to reconnect or not?
> The assumption here is SMB server is unresponsive.
> There could be other circumstances on the server box (or even client box)
> that are
> slowing down the SMB server responses such as slow network, slow network
> stack,
> memory pressure etc.
> So server could be fine all along and yet client would ask for reconnection!

I think it's the best mechanism that the protocol has. If we aren't
going to use SMB echoes to detect an unresponsive server, then what
would you suggest? I don't think we can make calls wait indefinitely
for a response without a mechanism to determine when the server is gone
and attempt to reestablish the connection to it.

-- 
Jeff Layton <jlayton at samba.org>