Re: [nfsv4] NFS4 over VPN hangs when connecting > 2 clients

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Mar 19, 2012 at 03:00:57PM -0400, Chuck Lever wrote:
> 
> On Mar 19, 2012, at 2:54 PM, J. Bruce Fields wrote:
> 
> > On Mon, Mar 19, 2012 at 02:42:30PM -0400, Chuck Lever wrote:
> >> 
> >> On Mar 19, 2012, at 2:39 PM, J. Bruce Fields wrote:
> >> 
> >>> On Mon, Mar 19, 2012 at 02:29:46PM -0400, Chuck Lever wrote:
> >>>> 
> >>>> On Mar 19, 2012, at 2:27 PM, J. Bruce Fields wrote:
> >>>>> That's also not this case, sorry, this time with all the conditions:
> >>>>> 
> >>>>> 	- if the nfs_client_id4 is the same, and
> >>>>> 	- if the flavor is auth_sys, and
> >>>>> 	- if the client IP address is different,
> >>>>> 	- then return NFS4ERR_INUSE.
> >>>> 
> >>>> This still breaks for multi-homed servers and UCS clients.  The client IP address can be different depending on what server IP address the client is accessing, but all the other parameters are the same.
> >>> 
> >>> OK.  So probably there's nothing we can do to help here.
> >>> 
> >>> As a bandaid maybe a rate-limited log message ("clientid X now in use
> >>> from IP Y") might help debug these things....
> >> 
> >> Hm, OK.  That implies your server implementation assumes that a clientid4 maps to exactly one client IP address at a time.
> > 
> > OK, agreed.  So how about something like "state for client X previously
> > established from IP Y now cleared from IP Z"  ??
> > 
> > (Assuming it's only the I-just-rebooted setclientid case that's likely
> > to be the sign of a problem.)
> 
> We would see that only in the case where the boot verifier and the client IP change at the same time.  That can happen legitimately, too, if the client has a dynamically assigned IP address.  Maybe this event is only interesting if it happens more than once during the same second.

"Warning: IP addresses Y and Z currently appear to be in a bitter
struggle over client id X"....

That may be getting complicated enough to not be worth it except as a
part of some more general statistics.

--b.