Re: [RFC][PATCH 2/4] sunrpc: Use utsnamespaces

[Matt Helsley <matthltc@us.ibm.com>]

On Tue, 2009-01-06 at 15:20 -0500, J. Bruce Fields wrote:
> On Tue, Jan 06, 2009 at 02:02:29PM -0600, Serge E. Hallyn wrote:
> > Quoting Matt Helsley (matthltc@us.ibm.com):
> > > We can often specify the UTS namespace to use when starting an RPC client.
> > > However sometimes no UTS namespace is available (specifically during system
> > > shutdown as the last NFS mount in a container is unmounted) so fall
> > > back to the initial UTS namespace.
> > 
> > So what happens if we take this patch and do nothing else?
> > 
> > The only potential problem situation will be rpc requests
> > made on behalf of a container in which the last task has
> > exited, right?  So let's say a container did an nfs mount
> > and then exits, causing an nfs umount request.
> > 
> > That umount request will now be sent with the wrong nodename.
> > Does that actually cause problems, will the server use the
> > nodename to try and determine the client sending the request?
> 
> This is just the machine name in the auth_unix credential?  The linux
> server ignores that completely (for the purpose of auth_unix
> authenication, it identifies clients only by source ip address).  I
> suspect other servers also ignore it, but I don't know.
> 
> --b.

I was wondering about this because I kept coming back to the question of
how the server could trust the name the client supplies (seems it
can't). This is very useful information -- it certainly suggests that
this patch would be sufficient.

Thanks!

Cheers,
	-Matt Helsley

> > 
> > thanks,
> > -serge
> > 
> > > Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
> > > Cc: Cedric Le Goater <clg@fr.ibm.com>
> > > Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
> > > Cc: linux-nfs@vger.kernel.org
> > > Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
> > > Cc: Chuck Lever <chuck.lever@oracle.com>
> > > Cc: Eric W. Biederman <ebiederm@xmission.com>
> > > Cc: Linux Containers <containers@lists.osdl.org>
> > > 
> > > ---
> > >  net/sunrpc/clnt.c |    7 +++++--
> > >  1 file changed, 5 insertions(+), 2 deletions(-)
> > > 
> > > Index: linux-2.6.28/net/sunrpc/clnt.c
> > > ===================================================================
> > > --- linux-2.6.28.orig/net/sunrpc/clnt.c
> > > +++ linux-2.6.28/net/sunrpc/clnt.c
> > > @@ -128,6 +128,7 @@ static struct rpc_clnt * rpc_new_client(
> > >  	struct rpc_version	*version;
> > >  	struct rpc_clnt		*clnt = NULL;
> > >  	struct rpc_auth		*auth;
> > > +	struct new_utsname	*uts_ns = init_utsname();
> > >  	int err;
> > >  	size_t len;
> > > 
> > > @@ -213,10 +214,12 @@ static struct rpc_clnt * rpc_new_client(
> > >  	}
> > > 
> > >  	/* save the nodename */
> > > -	clnt->cl_nodelen = strlen(init_utsname()->nodename);
> > > +	if (current->nsproxy != NULL)
> > > +		uts_ns = utsname();
> > > +	clnt->cl_nodelen = strlen(uts_ns->nodename);
> > >  	if (clnt->cl_nodelen > UNX_MAXNODENAME)
> > >  		clnt->cl_nodelen = UNX_MAXNODENAME;
> > > -	memcpy(clnt->cl_nodename, init_utsname()->nodename, clnt->cl_nodelen);
> > > +	memcpy(clnt->cl_nodename, uts_ns->nodename, clnt->cl_nodelen);
> > >  	rpc_register_client(clnt);
> > >  	return clnt;
> > > 
> > > 
> > > -- 
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