Re: [PATCH 03/14] NSM: Support IPv6 version of mon_name

[Chuck Lever <chuck.lever@xxxxxxxxxx>]

On Oct 29, 2008, at 4:00 PM, J. Bruce Fields wrote:

> On Fri, Oct 24, 2008 at 02:10:09PM -0400, Chuck Lever wrote:
> > When the "nsm_use_hostnames" sysctl is set to zero, the kernel's NSM
> > provides a presentation format IP address in the mon_name argument of
> > SM_MON upcalls.  This is part of the private interface between  
> > Linux's
> > rpc.statd and the kernel's lockd implementation.  Linux's rpc.statd
> > can then resolve this address with DNS as a sanity check.
>
> Have you checked how rpc.statd actually uses this field?

The main piece is here:

  utils/statd/monitor.c:sm_mon_1_svc()

This function receives the incoming SM_MON RPC and attempts to sanity  
check the contents of the mon_name argument by performing a DNS lookup.

It appears to use a second DNS lookup to normalize all incoming names  
so that subsequent hostname matches (ie when handling an SM_NOTIFY  
request) have a better change of succeeding.

> --b.
>
> > To support IPv6 addresses for the mon_name argument, just point the
> > XDR encoder to the nsm_handle's eye-catcher, which already contains a
> > presentation format address string.
> >
> > Finally, provide some debugging message clean up.
> >
> > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > ---
> >
> > fs/lockd/mon.c |   43 +++++++++++++++----------------------------
> > 1 files changed, 15 insertions(+), 28 deletions(-)
> >
> > diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
> > index a5c6ec4..1c058b1 100644
> > --- a/fs/lockd/mon.c
> > +++ b/fs/lockd/mon.c
> > @@ -18,8 +18,6 @@
> >
> > #define NLMDBG_FACILITY		NLMDBG_MONITOR
> >
> > -#define XDR_ADDRBUF_LEN		(20)
> > -
> > static struct rpc_clnt *	nsm_create(void);
> >
> > static struct rpc_program	nsm_program;
> > @@ -40,7 +38,14 @@ nsm_mon_unmon(struct nsm_handle *nsm, u32 proc,  
> > struct nsm_res *res)
> > {
> > 	struct rpc_clnt	*clnt;
> > 	int		status;
> > -	struct nsm_args	args;
> > +	struct nsm_args	args = {
> > +		.addr		= nsm_addr_in(nsm)->sin_addr.s_addr,
> > +		.prog		= NLM_PROGRAM,
> > +		.vers		= 3,
> > +		.proc		= NLMPROC_NSM_NOTIFY,
> > +		.mon_name	= nsm_use_hostnames ?
> > +					nsm->sm_name : nsm->sm_addrbuf,
> > +	};
> > 	struct rpc_message msg = {
> > 		.rpc_argp	= &args,
> > 		.rpc_resp	= res,
> > @@ -49,24 +54,21 @@ nsm_mon_unmon(struct nsm_handle *nsm, u32 proc,  
> > struct nsm_res *res)
> > 	clnt = nsm_create();
> > 	if (IS_ERR(clnt)) {
> > 		status = PTR_ERR(clnt);
> > +		dprintk("lockd: failed to create nsm transport, "
> > +				"status=%d\n", status);
> > 		goto out;
> > 	}
> >
> > -	memset(&args, 0, sizeof(args));
> > -	args.mon_name = nsm->sm_name;
> > -	args.addr = nsm_addr_in(nsm)->sin_addr.s_addr;
> > -	args.prog = NLM_PROGRAM;
> > -	args.vers = 3;
> > -	args.proc = NLMPROC_NSM_NOTIFY;
> > 	memset(res, 0, sizeof(*res));
> >
> > 	msg.rpc_proc = &clnt->cl_procinfo[proc];
> > 	status = rpc_call_sync(clnt, &msg, 0);
> > 	if (status < 0)
> > -		printk(KERN_DEBUG "nsm_mon_unmon: rpc failed, status=%d\n",
> > -			status);
> > -	else
> > +		dprintk("lockd: nsm rpc failed, status=%d\n", status);
> > +	else {
> > 		status = 0;
> > +		dprintk("lockd: monitoring '%s'\n", args.mon_name);
> > +	}
> > 	rpc_shutdown_client(clnt);
> >  out:
> > 	return status;
> > @@ -253,25 +255,10 @@ static __be32 *xdr_encode_nsm_string(__be32  
> > *p, char *string)
> >
> > /*
> >  * "mon_name" specifies the host to be monitored.
> > - *
> > - * Linux uses a text version of the IP address of the remote
> > - * host as the host identifier (the "mon_name" argument).
> > - *
> > - * Linux statd always looks up the canonical hostname first for
> > - * whatever remote hostname it receives, so this works alright.
> >  */
> > static __be32 *xdr_encode_mon_name(__be32 *p, struct nsm_args *argp)
> > {
> > -	char	buffer[XDR_ADDRBUF_LEN + 1];
> > -	char	*name = argp->mon_name;
> > -
> > -	if (!nsm_use_hostnames) {
> > -		snprintf(buffer, XDR_ADDRBUF_LEN,
> > -			 NIPQUAD_FMT, NIPQUAD(argp->addr));
> > -		name = buffer;
> > -	}
> > -
> > -	return xdr_encode_nsm_string(p, name);
> > +	return xdr_encode_nsm_string(p, argp->mon_name);
> > }
> >
> > /*
> >
> > --
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--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com



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