From: "Mohit Katiyar" <katiyar.mohit@gmail.com>
Subject: Re: NFS inconsistent behaviour
Date: Thu, 19 Oct 2006 10:53:42 +0900
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Cc: Linux NFS mailing list <nfs@lists.sourceforge.net>,
	linux-kernel@vger.kernel.org,
	Frank van Maarseveen <frankvm@frankvm.com>
To: "Trond Myklebust" <trond.myklebust@fys.uio.no>
In-Reply-To: <1161194229.6095.81.camel@lade.trondhjem.org>
Sender: nfs-bounces@lists.sourceforge.net
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Yes, I do not want to mount unmount infinitely but was just checking
out of curiosity but mounting/unmounting infinitely works comepletely
fine on SLES 9 which uses 2.6.5 kernel. I was just wondering what has
been changed that it does not work now?

On 10/19/06, Trond Myklebust <trond.myklebust@fys.uio.no> wrote:
> On Wed, 2006-10-18 at 08:39 +0200, Frank van Maarseveen wrote:
> > On Wed, Oct 18, 2006 at 10:22:44AM +0900, Mohit Katiyar wrote:
> > > I checked it today and when i issued the netstat -t ,I could see a lot
> > > of tcp connections in TIME_WAIT state.
> > > Is this a normal behaviour?
> >
> > yes... but see below
> >
> > > So we cannot mount and umount infinitely
> > > with tcp option? Why there are so many connections in waiting state?
> >
> > I think it's called the 2MSL wait: there may be TCP segments on the
> > wire which (in theory) could disrupt new connections which reuse local
> > and remote port so the ports stay in use for a few minutes. This is
> > standard TCP behavior but only occurs when connections are improperly
> > shutdown. Apparently this happens when umounting a tcp NFS mount but
> > also for a lot of other tcp based RPC (showmount, rpcinfo).  I'm not
> > sure who's to blame but it might be the rpc functions inside glibc.
> >
> > I'd switch to NFS over udp if this is problem.
>
> Just out of interest. Why does anyone actually _want_ to keep
> mount/umounting to the point where they run out of ports? That is going
> to kill performance in all sorts of unhealthy ways, not least by
> completely screwing over any caching.
>
> Note also that you _can_ change the range of ports used by the NFS
> client itself at least. Just edit /proc/sys/sunrpc/{min,max}_resvport.
> On the server side, you can use the 'insecure' option in order to allow
> mounts that originate from non-privileged ports (i.e. port > 1024).
> If you are using strong authentication (for instance RPCSEC_GSS/krb5)
> then that actually makes a lot of sense, since the only reason for the
> privileged port requirement was to disallow unprivileged NFS clients.
>
> Cheers,
>  Trond
>
>

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