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@xxxxxxxxxx>
---
fs/lockd/mon.c | 27 ++++++++-------------------
include/linux/lockd/lockd.h | 1 +
2 files changed, 9 insertions(+), 19 deletions(-)
diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
index 497dfea..a606fbb 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;
@@ -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);
}
/*
diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
index 54dbb45..d3c7247 100644
--- a/include/linux/lockd/lockd.h
+++ b/include/linux/lockd/lockd.h
@@ -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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