--- nfs-utils-1.0.9/utils/mountd/auth.c.~1~
+++ nfs-utils-1.0.9/utils/mountd/auth.c
@@ -76,21 +76,16 @@ auth_authenticate_internal(char *what, s
 	if (new_cache) {
 		int i;
 		/* return static nfs_export with details filled in */
-		if (my_client.m_naddr != 1 ||
-		    my_client.m_addrlist[0].s_addr != caller->sin_addr.s_addr) {
-			/* different client to last time, so do a lookup */
-			char *n;
-			my_client.m_naddr = 0;
-			my_client.m_addrlist[0] = caller->sin_addr;
-			n = client_compose(caller->sin_addr);
-			*error = unknown_host;
-			if (!n)
-				return NULL;
-			strcpy(my_client.m_hostname, *n?n:"DEFAULT");
-			free(n);
-			my_client.m_naddr = 1;
-		}
-
+		char *n;
+		my_client.m_naddr = 0;
+		my_client.m_addrlist[0] = caller->sin_addr;
+		n = client_compose(caller->sin_addr);
+		*error = unknown_host;
+		if (!n)
+			return NULL;
+		strcpy(my_client.m_hostname, *n?n:"DEFAULT");
+		free(n);
+		my_client.m_naddr = 1;
 		my_exp.m_client = &my_client;
 
 		exp = NULL;
--- nfs-utils-1.0.9/utils/mountd/cache.c.~1~
+++ nfs-utils-1.0.9/utils/mountd/cache.c
@@ -83,9 +83,6 @@ void auth_unix_ip(FILE *f)
 		qword_print(f, *client?client:"DEFAULT");
 	qword_eol(f);
 
-	if (client && strcmp(ipaddr, client))
-		mountlist_add(ipaddr, *client?client:"DEFAULT");
-
 	if (client) free(client);
 	
 }
@@ -295,7 +292,6 @@ void nfsd_export(FILE *f)
 		qword_printint(f, found->m_export.e_anonuid);
 		qword_printint(f, found->m_export.e_anongid);
 		qword_printint(f, found->m_export.e_fsid);
-		mountlist_add(dom, path);
 	}
 	qword_eol(f);
  out:
@@ -373,8 +369,6 @@ void cache_export_ent(char *domain, stru
 	qword_eol(f);
 
 	fclose(f);
-
-	mountlist_add(domain, exp->e_path);
 }
 
 void cache_export(nfs_export *exp)
@@ -393,9 +387,6 @@ void cache_export(nfs_export *exp)
 	
 	fclose(f);
 
-	if (strcmp(inet_ntoa(exp->m_client->m_addrlist[0]), exp->m_client->m_hostname))
-		mountlist_add(inet_ntoa(exp->m_client->m_addrlist[0]), exp->m_client->m_hostname);
-
 	cache_export_ent(exp->m_client->m_hostname, &exp->m_export);
 }
 
--- nfs-utils-1.0.9/utils/mountd/mountd.c.~1~
+++ nfs-utils-1.0.9/utils/mountd/mountd.c
@@ -37,6 +37,7 @@ static void		usage(const char *, int exi
 static exports		get_exportlist(void);
 static struct nfs_fh_len *get_rootfh(struct svc_req *, dirpath *, mountstat3 *, int v3);
 
+int reverse_resolve = 0;
 int new_cache = 0;
 
 /* PRC: a high-availability callout program can be specified with -H
@@ -66,6 +67,7 @@ static struct option longopts[] =
 	{ "ha-callout", 1, 0, 'H' },
 	{ "state-directory-path", 1, 0, 's' },
 	{ "num-threads", 1, 0, 't' },
+	{ "reverse-lookup", 0, 0, 'r' },
 	{ NULL, 0, 0, 0 }
 };
 
@@ -225,14 +227,11 @@ mount_umnt_1_svc(struct svc_req *rqstp, 
 	if (!(exp = auth_authenticate("unmount", sin, p))) {
 		return 1;
 	}
-	if (new_cache) {
-		if (strcmp(inet_ntoa(exp->m_client->m_addrlist[0]), exp->m_client->m_hostname))
-			mountlist_del(inet_ntoa(exp->m_client->m_addrlist[0]), exp->m_client->m_hostname);
-		mountlist_del(exp->m_client->m_hostname, p);
-	} else {
-		mountlist_del(exp->m_client->m_hostname, p);
+
+	if (!new_cache)
 		export_reset (exp);
-	}
+
+	mountlist_del(inet_ntoa(sin->sin_addr), p);
 	return 1;
 }
 
@@ -421,8 +420,10 @@ get_rootfh(struct svc_req *rqstp, dirpat
 		fh = cache_get_filehandle(exp, v3?64:32, p);
 		if (fh == NULL) 
 			*error = NFSERR_ACCES;
-		else
+		else {
 			*error = NFS_OK;
+			mountlist_add(inet_ntoa(sin->sin_addr), p);
+		}
 		return fh;
 	} else {
 		struct nfs_fh_len  *fh;
@@ -443,7 +444,7 @@ get_rootfh(struct svc_req *rqstp, dirpat
 						stb.st_dev, stb.st_ino);
 		}
 		if (fh != NULL) {
-			mountlist_add(exp->m_client->m_hostname, p);
+			mountlist_add(inet_ntoa(sin->sin_addr), p);
 			*error = NFS_OK;
 			export_reset (exp);
 			return fh;
@@ -558,7 +559,7 @@ main(int argc, char **argv)
 
 	/* Parse the command line options and arguments. */
 	opterr = 0;
-	while ((c = getopt_long(argc, argv, "o:n:Fd:f:p:P:hH:N:V:vs:t:", longopts, NULL)) != EOF)
+	while ((c = getopt_long(argc, argv, "o:n:Fd:f:p:P:hH:N:V:vrs:t:", longopts, NULL)) != EOF)
 		switch (c) {
 		case 'o':
 			descriptors = atoi(optarg);
@@ -598,6 +599,9 @@ main(int argc, char **argv)
 		case 'n':
 			_rpcfdtype = SOCK_DGRAM;
 			break;
+		case 'r':
+			reverse_resolve = 1;
+			break;
 		case 's':
 			if ((state_dir = xstrdup(optarg)) == NULL) {
 				fprintf(stderr, "%s: xstrdup(%s) failed!\n",
--- nfs-utils-1.0.9/utils/mountd/rmtab.c.~1~
+++ nfs-utils-1.0.9/utils/mountd/rmtab.c
@@ -25,6 +25,8 @@
 
 #include <limits.h> /* PATH_MAX */
 
+extern int reverse_resolve;
+
 /* If new path is a link do not destroy it but place the
  * file where the link points.
  */
@@ -185,6 +187,8 @@ mountlist_list(void)
 	struct rmtabent		*rep;
 	struct stat		stb;
 	int			lockid;
+	struct in_addr		addr;
+	struct hostent		*he;
 
 	if ((lockid = xflock(_PATH_RMTAB, "r")) < 0)
 		return NULL;
@@ -204,7 +208,14 @@ mountlist_list(void)
 		setrmtabent("r");
 		while ((rep = getrmtabent(1, NULL)) != NULL) {
 			m = (mountlist) xmalloc(sizeof(*m));
-			m->ml_hostname = xstrdup(rep->r_client);
+
+			if (reverse_resolve &&
+			   inet_aton((const char *) rep->r_client, &addr) &&
+			   (he = gethostbyaddr(&addr, sizeof(addr), AF_INET)))
+				m->ml_hostname = xstrdup(he->h_name);
+			else
+				m->ml_hostname = xstrdup(rep->r_client);
+
 			m->ml_directory = xstrdup(rep->r_path);
 			m->ml_next = mlist;
 			mlist = m;
--- nfs-utils-1.0.9/utils/mountd/mountd.man.~1~
+++ nfs-utils-1.0.9/utils/mountd/mountd.man
@@ -125,6 +125,13 @@ If this option is not specified the defa
 .BR /var/lib/nfs
 is used.
 .TP
+.BI "\-r," "" " \-\-reverse\-lookup"
+mountd tracks IP addresses in the rmtab, and when a DUMP request is made (by
+someone running showmount -a, for instance), it returns IP addresses instead
+of hostnames by default. This option causes mountd to do a reverse
+lookup on each IP address and return that hostname instead. Enabling this can
+have a substantial negative effect on performance in some situations.
+.TP
 .BR "\-t N" " or " "\-\-num\-threads=N"
 This option specifies the number of worker threads that rpc.mountd
 spawns.  The default is 1 thread, which is probably enough.  More
--- nfs-utils-1.0.9/utils/showmount/showmount.man.~1~
+++ nfs-utils-1.0.9/utils/showmount/showmount.man
@@ -25,8 +25,10 @@ appear as though it were processed throu
 .SH OPTIONS
 .TP
 .BR \-a " or " \-\-all
-List both the client hostname and mounted directory in
-host:dir format.
+List both the client hostname or IP address and mounted directory in
+host:dir format. This info should not be considered reliable. See the notes
+on rmtab in 
+.BR rpc.mountd (8).
 .TP
 .BR \-d " or " \-\-directories
 List only the directories mounted by some client.