Commit 29ed1407 authored Dec 04, 2008 by Chuck Lever Committed by J. Bruce Fields Jan 06, 2009

NSM: Support IPv6 version of mon_name



The "mon_name" argument of the NSMPROC_MON and NSMPROC_UNMON upcalls
is a string that contains the hostname or IP address of the remote peer
to be notified when this host has rebooted.  The sm-notify command uses
this identifier to contact the peer when we reboot, so it must be
either a well-qualified DNS hostname or a presentation format IP
address string.

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.
Otherwise, the "caller_name" argument from NLM requests is used,
which is usually just the DNS hostname of the peer.

To support IPv6 addresses for the mon_name argument, we use the
nsm_handle's address eye-catcher, which already contains an appropriate
presentation format address string.  Using the eye-catcher string
obviates the need to use a large buffer on the stack to form the
presentation address string for the upcall.

This patch also addresses a subtle bug.

An NSMPROC_MON request and the subsequent NSMPROC_UNMON request for the
same peer are required to use the same value for the "mon_name"
argument.  Otherwise, rpc.statd's NSMPROC_UNMON processing cannot
locate the database entry for that peer and remove it.

If the setting of nsm_use_hostnames is changed between the time the
kernel sends an NSMPROC_MON request and the time it sends the
NSMPROC_UNMON request for the same peer, the "mon_name" argument for
these two requests may not be the same.  This is because the value of
"mon_name" is currently chosen at the moment the call is made based on
the setting of nsm_use_hostnames

To ensure both requests pass identical contents in the "mon_name"
argument, we now select which string to use for the argument in the
nsm_monitor() function.  A pointer to this string is saved in the
nsm_handle so it can be used for a subsequent NSMPROC_UNMON upcall.

NB: There are other potential problems, such as how nlm_host_rebooted()
might behave if nsm_use_hostnames were changed while hosts are still
being monitored.  This patch does not attempt to address those
problems.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

parent f47534f7

fs/lockd/mon.c

+8 −19

Original line number	Diff line number	Diff line
		@@ -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;
		@@ -42,7 +40,7 @@ nsm_mon_unmon(struct nsm_handle nsm, u32 proc, struct nsm_res res)
		.prog = NLM_PROGRAM,
		.vers = 3,
		.proc = NLMPROC_NSM_NOTIFY,
		.mon_name = nsm->sm_name,
		.mon_name = nsm->sm_mon_name,
		};
		struct rpc_message msg = {
		.rpc_argp = &args,
		@@ -87,6 +85,12 @@ nsm_monitor(struct nlm_host *host)
		if (nsm->sm_monitored)
		return 0;

		/*
		* Choose whether to record the caller_name or IP address of
		* this peer in the local rpc.statd's database.
		*/
		nsm->sm_mon_name = nsm_use_hostnames ? nsm->sm_name : nsm->sm_addrbuf;

		status = nsm_mon_unmon(nsm, SM_MON, &res);

		if (status < 0 \|\| res.status != 0)
		@@ -167,25 +171,10 @@ 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,
		"%pI4", &argp->addr);
		name = buffer;
		}

		return xdr_encode_nsm_string(p, name);
		return xdr_encode_nsm_string(p, argp->mon_name);
		}

		/*

include/linux/lockd/lockd.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -79,6 +79,7 @@ struct nlm_host {
		struct nsm_handle {
		struct list_head sm_link;
		atomic_t sm_count;
		char *sm_mon_name;
		char *sm_name;
		struct sockaddr_storage sm_addr;
		size_t sm_addrlen;

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