Re: RFC: nlmclnt_grant() address check vs. callback address binding

[Frank van Maarseveen <frankvm@frankvm.com>]

On Mon, Jul 02, 2007 at 09:04:30PM -0400, Trond Myklebust wrote:
> On Mon, 2007-07-02 at 17:49 +0200, Frank van Maarseveen wrote:
> 
> > At first I thought fixing the server is the right thing to do because
> > the server behavior is arguably incorrect. Not easy but certainly doable
> > (I'd do it if it has a chance of being accepted). It might also help
> > NATting NFS traffic in some cases. However:
> > 
> > -	I'm not sure if an address check such as in nlmclnt_grant()
> > 	is actually buying us anything.
> 
> Exactly how else is the client going to figure out which lock this
> corresponds to?

The filehandle + pid/svid + lock start + lock end as it is doing right
now. Filehandles offer a pretty strong check already because they are
designed to handle inode reuse too.

The 32 bit pid/svid/lockowner number is conclusive.


> 
> > -	clients requiring a correct callback src address might not
> > 	work with other NFS server implementations and/or (future?)
> > 	concepts for clustering/load balancing.
> 
> NFSv3 development is dead. NLM locking development is doubly so...

Not everyone is using (or can use) NFSv4. This is not about developing
NFSv3 but about optimizing/fixing it in its current deployment.


> 
> > -	Multiple IP addresses may be a workaround for reserved port
> > 	shortage.
> 
> There is _NO_ way for the client to figure out what lock the granted
> request refers to if the server starts transmitting from random IP
> addresses.
>       * There is no universal namespace for filehandles that can be used
>         to identify which file the granted request is meant for
>       * The cookie is not guaranteed to be the same as that sent by the
>         client for the LOCK request
>       * There is nothing else in the nlm_lock that can be used to
>         identify which file we're talking about.

The svid/pid. See nlm_find_lockowner().

-- 
Frank

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