[2/3] plugin: Introduce the junction plug-in API

diff --git a/INSTALL b/INSTALL
index 186678d..a2ef958 100644
--- a/INSTALL
+++ b/INSTALL
@@ -121,9 +121,9 @@  FedFS file server
   o Install kernel with patches to do export cache upcalls when
     encountering a junction
 
-  o Install resolve-junction program
+  o Install junction resolution plug-in
 
-  o Install mountd with patches to resolve junctions
+  o Install mountd with patches to invoke the plug-in
 
   o Install the nfsref program
 
@@ -177,3 +177,22 @@  FedFS admin client
 In addition to these tasks, you should choose one of the FedFS-enabled
 file servers on which to host the domain root directory, and set up a
 DNS SRV record to allow FedFS file system clients to find it.
+
+
+Configuring the junction resolution plug-in
+
+By default, the junction resolution plug-in library is installed in
+/usr/local/lib.  Mountd's junction plug-in support searches the default
+library path for this plug-in, but mountd's library path does not
+normally contain /usr/local/lib.
+
+There are several options:
+
+  o Specify an LD_LIBRARY_PATH when starting mountd that includes
+    /usr/local/lib,
+
+  o Move the installed plug-in files to a directory that is included
+    in mountd's existing library path, or
+
+  o Use the --libdir= command line option on fedfs-utils's ./configure
+    to change the installed location of the plug-in library.
diff --git a/configure.ac b/configure.ac
index bbe3f19..c27ba78 100644
--- a/configure.ac
+++ b/configure.ac
@@ -173,5 +173,6 @@  AC_CONFIG_FILES([Makefile
                  src/nfsref/Makefile
                  src/nsdbc/Makefile
                  src/nsdbparams/Makefile
+                 src/plug-ins/Makefile
                  src/resolve-junction/Makefile])
 AC_OUTPUT
diff --git a/src/Makefile.am b/src/Makefile.am
index fcb84e6..777b618 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -26,7 +26,7 @@ 
 SUBDIRS			= include libxlog libadmin libnsdb libjunction \
 			  libparser libsi \
 			  fedfsc fedfsd mount nfsref nsdbc nsdbparams \
-			  resolve-junction
+			  plug-ins resolve-junction
 
 CLEANFILES		= cscope.in.out cscope.out cscope.po.out *~
 DISTCLEANFILES		= Makefile.in
diff --git a/src/include/Makefile.am b/src/include/Makefile.am
index 5f779b3..bda3d3c 100644
--- a/src/include/Makefile.am
+++ b/src/include/Makefile.am
@@ -23,6 +23,7 @@ 
 ##	http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
 ##
 
+include_HEADERS		= nfs-plugin.h
 noinst_HEADERS		= fedfs_admin.h fedfs.h getsrvinfo.h gpl-boiler.h \
 			  junction.h list.h nsdb.h parse_opt.h \
 			  token.h xlog.h
diff --git a/src/include/nfs-plugin.h b/src/include/nfs-plugin.h
new file mode 100644
index 0000000..60d2993
--- /dev/null
+++ b/src/include/nfs-plugin.h
@@ -0,0 +1,96 @@ 
+/*
+ * @file src/include/nfs-plugin.h
+ * @brief Definition of NFS junction plug-in API
+ */
+
+/*
+ * Copyright 2011 Oracle.  All rights reserved.
+ *
+ * This file is part of fedfs-utils.
+ *
+ * fedfs-utils is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2.0 as
+ * published by the Free Software Foundation.
+ *
+ * fedfs-utils is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License version 2.0 for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2.0 along with fedfs-utils.  If not, see:
+ *
+ *	http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
+ */
+
+/*
+ * The purpose of this API is to provide an opaque mechanism for
+ * the NFS mountd daemon to resolve NFS basic and FedFS junctions.
+ * This interface is therefore quite specific to NFS.
+ */
+
+#ifndef FEDFS_NFS_PLUGIN_H
+#define FEDFS_NFS_PLUGIN_H
+
+#include <stdint.h>
+
+__BEGIN_DECLS
+
+/**
+ * Current version of API
+ */
+#define JP_API_VERSION		(1)
+
+/**
+ * A set of NFS FS locations
+ */
+struct nfs_fsloc_set;
+typedef struct nfs_fsloc_set	 *nfs_fsloc_set_t;
+
+/**
+ * Junction operation status codes
+ */
+enum jp_status {
+	JP_OK			=  0,
+	JP_INVAL		= -1,
+	JP_ACCESS		= -2,
+	JP_EXIST		= -3,
+	JP_TYPE_NOT_SUPP	= -4,
+	JP_OP_NOT_SUPP		= -5,
+	JP_ISJUNCTION		= -6,
+	JP_NOTJUNCTION		= -7,
+	JP_NSDBLOCAL		= -8,
+	JP_NSDBREMOTE		= -9,
+	JP_MEMORY		= -10,
+	JP_SYSTEM		= -11,
+	JP_PARSE		= -1000,
+	JP_EMPTY		= -1001,
+};
+
+/**
+ * Vector of methods provided by a junction plug-in
+ */
+struct jp_ops {
+	unsigned int	  jp_api_version;
+
+	enum jp_status	  (*jp_init)(_Bool want_debugging);
+	void		  (*jp_done)(void);
+
+	const char *	  (*jp_error)(enum jp_status status);
+	void		  (*jp_put_locations)(nfs_fsloc_set_t locset);
+	enum jp_status	  (*jp_get_locations)(const char *junct_path,
+					nfs_fsloc_set_t *locset);
+	void		  (*jp_rewind_locations)(nfs_fsloc_set_t locset);
+	enum jp_status	  (*jp_get_next_location)(nfs_fsloc_set_t locset,
+					char **hostname, char **export_path,
+					int *ttl);
+};
+
+/**
+ * Load this symbol to get access to the junction API
+ */
+extern struct jp_ops	  nfs_junction_ops;
+
+__END_DECLS
+
+#endif	/* !FEDFS_NFS_PLUGIN_H */
diff --git a/src/plug-ins/Makefile.am b/src/plug-ins/Makefile.am
new file mode 100644
index 0000000..1427708
--- /dev/null
+++ b/src/plug-ins/Makefile.am
@@ -0,0 +1,41 @@ 
+##
+## @file src/plug-ins/Makefile.am
+## @brief Process this file with automake to produce src/plug-ins/Makefile.in
+##
+
+##
+## Copyright 2011 Oracle.  All rights reserved.
+##
+## This file is part of fedfs-utils.
+##
+## fedfs-utils is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License version 2.0 as
+## published by the Free Software Foundation.
+##
+## fedfs-utils is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License version 2.0 for more details.
+##
+## You should have received a copy of the GNU General Public License
+## version 2.0 along with fedfs-utils.  If not, see:
+##
+##	http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
+##
+
+lib_LTLIBRARIES		= libnfsjunct.la
+libnfsjunct_la_SOURCES	= nfs-plugin.c
+libnfsjunct_la_LIBADD	= $(LIBLDAP) $(LIBLBER) $(LIBXML2) \
+			  $(LIBSQLITE3) $(LIBIDN) $(LIBUUID) \
+			  $(top_builddir)/src/libnsdb/libnsdb.la \
+			  $(top_builddir)/src/libxlog/libxlog.la \
+			  $(top_builddir)/src/libjunction/libjunction.la
+
+CLEANFILES		= cscope.in.out cscope.out cscope.po.out *~
+DISTCLEANFILES		= Makefile.in
+
+AM_CFLAGS		= -ggdb -fstrict-aliasing -fPIC \
+			  -Wall -Wextra -pedantic -Wformat=2 \
+			  -Wstrict-aliasing=2 -Wp,-D_FORTIFY_SOURCE=2
+AM_CPPFLAGS		= -I. -I$(top_srcdir)/src/include \
+			  -I/usr/include/libxml2
diff --git a/src/plug-ins/nfs-plugin.c b/src/plug-ins/nfs-plugin.c
new file mode 100644
index 0000000..275caf1
--- /dev/null
+++ b/src/plug-ins/nfs-plugin.c
@@ -0,0 +1,567 @@ 
+/**
+ * @file src/plug-ins/nfs-plugin.c
+ * @brief DLL to resolve junction information
+ */
+
+/*
+ * Copyright 2011 Oracle.  All rights reserved.
+ *
+ * This file is part of fedfs-utils.
+ *
+ * fedfs-utils is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2.0 as
+ * published by the Free Software Foundation.
+ *
+ * fedfs-utils is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License version 2.0 for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2.0 along with fedfs-utils.  If not, see:
+ *
+ *	http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include <libxml/parser.h>
+
+#include "fedfs_admin.h"
+#include "nfs-plugin.h"
+#include "junction.h"
+
+struct nfs_fsloc_set {
+	struct nfs_fsloc	 *ns_current;
+	struct nfs_fsloc	 *ns_list;
+};
+
+static _Bool debug = false;
+
+/**
+ * Write a debugging message to stderr
+ *
+ * @param fmt NUL-terminated C string containing output format specification
+ *
+ * NB:	Caller may have already opened syslog for her own use.  We can't
+ *	hijack it here, so using xlog() is right out.  Thus output is
+ *	directed to stderr via fprintf(3).
+ */
+static void
+nfs_jp_debug(const char *fmt, ...)
+{
+	va_list args;
+
+	if (!debug)
+		return;
+
+	va_start(args, fmt);
+	vfprintf(stderr, fmt, args);
+	va_end(args);
+}
+
+/**
+ * Perform any plug-in startup processing
+ *
+ * @param want_debugging true if caller wants to enable debugging output
+ * @return a junction status code
+ */
+static enum jp_status
+nfs_jp_init(_Bool want_debugging)
+{
+	debug = want_debugging;
+	nfs_jp_debug("%s: Junction plug-in version " VERSION "\n", __func__);
+	xmlInitParser();
+	return JP_OK;
+}
+
+/**
+ * Perform any plug-in shutdown processing
+ *
+ * Nothing to be done for NFS junctions.
+ */
+static void
+nfs_jp_done(void)
+{
+	nfs_jp_debug("%s: Finishing\n", __func__);
+	xmlCleanupParser();
+	return;
+}
+
+/**
+ * Given an status code, return a pointer to a static error message
+ *
+ * @param status a junction plug-in status code
+ * @return a static NUL-terminated string
+ */
+static const char *
+nfs_jp_error(enum jp_status status)
+{
+	static char buf[128];
+
+	switch (status) {
+	case JP_OK:
+		return "Success";
+	case JP_INVAL:
+		return "Invalid parameter";
+	case JP_ACCESS:
+		return "Permission denied";
+	case JP_EXIST:
+		return "Object cannot be made into a junction";
+	case JP_TYPE_NOT_SUPP:
+		return "Junction type not supported";
+	case JP_OP_NOT_SUPP:
+		return "Junction method not supported";
+	case JP_ISJUNCTION:
+		return "Object is a junction";
+	case JP_NOTJUNCTION:
+		return "Object is not a junction";
+	case JP_NSDBLOCAL:
+		return "A local NSDB configuration error occurred";
+	case JP_NSDBREMOTE:
+		return "An error occurred on the NSDB";
+	case JP_MEMORY:
+		return "Memory allocation failure";
+	case JP_SYSTEM:
+		snprintf(buf, sizeof(buf), "System error (%d): %s",
+				status, strerror(errno));
+		return buf;
+	case JP_PARSE:
+		return "Failed to parse locations data";
+	case JP_EMPTY:
+		return "No more locations in location set";
+	}
+
+	snprintf(buf, sizeof(buf), "Unknown error (%d)", status);
+	return buf;
+}
+
+/**
+ * Release a set of NFS locations
+ *
+ * @param locset set of NFS locations to release
+ */
+static void
+nfs_jp_put_locations(nfs_fsloc_set_t locset)
+{
+	if (locset == NULL) {
+		nfs_jp_debug("%s: Invalid parameters\n", __func__);
+		return;
+	}
+
+	nfs_jp_debug("%s: Freeing location set %p, ns_list=%p\n",
+		__func__, locset, locset->ns_list);
+	nfs_free_locations(locset->ns_list);
+	free(locset);
+}
+
+/**
+ * Internal function to allocate a set of NFS locations
+ *
+ * @return dynamically allocated nfs_fsloc_set_t object
+ *
+ * If return value is non-NULL, caller must free it with
+ * nfs_jp_put_locations().
+ */
+__attribute_malloc__
+static nfs_fsloc_set_t
+nfs_jp_alloc_locations(void)
+{
+	return calloc(1, sizeof(struct nfs_fsloc_set));
+}
+
+/**
+ * Internal function to rewind a set of locations
+ *
+ * @param locset set of NFS locations to rewind
+ */
+static void
+nfs_jp_do_rewind_locations(nfs_fsloc_set_t locset)
+{
+	locset->ns_current = locset->ns_list;
+}
+
+/**
+ * Resolve NFS basic junction information into a set of NFS locations
+ *
+ * @param junct_path NUL-terminated C string containing POSIX path of junction
+ * @param locset OUT set of NFS locations
+ * @return a junction status code
+ *
+ * If this entry point returns JP_OK, the caller must free the returned
+ * set of locations by calling the jp_put_locations entry point.
+ */
+static enum jp_status
+nfs_jp_get_basic(const char *junct_path, nfs_fsloc_set_t *locset)
+{
+	nfs_fsloc_set_t new;
+	FedFsStatus retval;
+
+	new = nfs_jp_alloc_locations();
+	if (new == NULL) {
+		nfs_jp_debug("%s: No memory\n", __func__);
+		return JP_MEMORY;
+	}
+
+	retval = nfs_get_locations(junct_path, &new->ns_list);
+	if (retval != FEDFS_OK) {
+		nfs_jp_debug("%s: Failed to get locations: %s\n",
+			__func__, nsdb_display_fedfsstatus(retval));
+		nfs_jp_put_locations(new);
+		return JP_PARSE;
+	}
+
+	nfs_jp_debug("%s: Returning location set %p\n", __func__, new);
+	nfs_jp_do_rewind_locations(new);
+	*locset = new;
+	return JP_OK;
+}
+
+/**
+ * Convert one FedFS fileset location into one NFS location
+ *
+ * @param fsl a FedFS fileset location
+ * @param fsloc OUT an NFS location
+ * @return a junction status code
+ *
+ * If nfs_jp_convert_fedfs_fsl() returns JP_OK, the caller must free the
+ * returned location by calling nfs_free_location().
+ */
+static enum jp_status
+nfs_jp_convert_fedfs_fsl(struct fedfs_fsl *fsl, struct nfs_fsloc **fsloc)
+{
+	struct fedfs_nfs_fsl *nfs_fsl = &fsl->fl_u.fl_nfsfsl;
+	struct nfs_fsloc *new;
+
+	new = nfs_new_location();
+	if (new == NULL) {
+		nfs_jp_debug("%s: No memory\n", __func__);
+		return JP_MEMORY;
+	}
+
+	new->nfl_hostname = strdup(fsl->fl_fslhost);
+	new->nfl_rootpath = nfs_dup_string_array(nfs_fsl->fn_nfspath);
+	if (new->nfl_hostname == NULL || new->nfl_rootpath == NULL) {
+		nfs_free_location(new);
+		nfs_jp_debug("%s: No memory\n", __func__);
+		return JP_MEMORY;
+	}
+
+	new->nfl_hostport = fsl->fl_fslport;
+	new->nfl_ttl = fsl->fl_fslttl;
+
+	new->nfl_flags.nfl_varsub = nfs_fsl->fn_varsub;
+	new->nfl_currency = nfs_fsl->fn_currency;
+	new->nfl_validfor = nfs_fsl->fn_validfor;
+	new->nfl_genflags.nfl_writable = nfs_fsl->fn_gen_writable;
+	new->nfl_genflags.nfl_going = nfs_fsl->fn_gen_going;
+	new->nfl_genflags.nfl_split = nfs_fsl->fn_gen_split;
+	new->nfl_transflags.nfl_rdma = nfs_fsl->fn_trans_rdma;
+	new->nfl_info.nfl_simul = nfs_fsl->fn_class_simul;
+	new->nfl_info.nfl_handle = nfs_fsl->fn_class_handle;
+	new->nfl_info.nfl_fileid = nfs_fsl->fn_class_fileid;
+	new->nfl_info.nfl_writever = nfs_fsl->fn_class_writever;
+	new->nfl_info.nfl_change = nfs_fsl->fn_class_change;
+	new->nfl_info.nfl_readdir = nfs_fsl->fn_class_readdir;
+	new->nfl_info.nfl_readrank = nfs_fsl->fn_readrank;
+	new->nfl_info.nfl_writerank = nfs_fsl->fn_writerank;
+	new->nfl_info.nfl_readorder = nfs_fsl->fn_readorder;
+	new->nfl_info.nfl_writeorder = nfs_fsl->fn_writeorder;
+	new->nfl_majorver = nfs_fsl->fn_majorver;
+	new->nfl_minorver = nfs_fsl->fn_minorver;
+
+	*fsloc = new;
+	return JP_OK;
+}
+
+/**
+ * Convert FedFS fileset locations into a set of NFS locations
+ *
+ * @param fsls a list of FedFS fileset locations
+ * @param new empty set of NFS locations to fill in
+ * @return a junction status code
+ *
+ * If nfs_jp_convert_fedfs_fsls() returns JP_OK, the caller must free the returned
+ * set of locations by calling nfs_jp_put_locations().
+ */
+static enum jp_status
+nfs_jp_convert_fedfs_fsls(struct fedfs_fsl *fsls, nfs_fsloc_set_t new)
+{
+	struct fedfs_fsl *fsl;
+
+	if (fsls == NULL) {
+		nfs_jp_debug("%s: No locations\n", __func__);
+		return JP_EMPTY;
+	}
+
+	for (fsl = fsls; fsl != NULL; fsl = fsl->fl_next) {
+		struct nfs_fsloc *fsloc;
+		enum jp_status status;
+
+		status = nfs_jp_convert_fedfs_fsl(fsl, &fsloc);
+		if (status != JP_OK) {
+			nfs_jp_put_locations(new);
+			return status;
+		}
+
+		if (new->ns_list == NULL)
+			new->ns_list = fsloc;
+		else {
+			fsloc->nfl_next = new->ns_list;
+			new->ns_list = fsloc;
+		}
+	}
+
+	nfs_jp_do_rewind_locations(new);
+	return JP_OK;
+}
+
+/**
+ * Resolve a FedFS fileset name into a set of NFS locations
+ *
+ * @param fsn_uuid NUL-terminated C string containing FSN UUID to resolve
+ * @param host an initialized NSDB host object
+ * @param new empty set of NFS locations
+ * @return a junction status code
+ *
+ * If nfs_jp_resolve_fsn() returns JP_OK, the caller must free the returned
+ * set of locations by calling nfs_jp_put_locations().
+ */
+static enum jp_status
+nfs_jp_resolve_fsn(const char *fsn_uuid, nsdb_t host,
+		nfs_fsloc_set_t new)
+{
+	enum jp_status status = JP_NSDBREMOTE;
+	struct fedfs_fsl *fsls;
+	unsigned int ldap_err;
+	FedFsStatus retval;
+
+	if (nsdb_open_nsdb(host, NULL, NULL, &ldap_err) != FEDFS_OK)
+		return JP_NSDBLOCAL;
+
+	retval = nsdb_resolve_fsn_s(host, NULL, fsn_uuid, &fsls, &ldap_err);
+	switch (retval) {
+	case FEDFS_OK:
+		status = nfs_jp_convert_fedfs_fsls(fsls, new);
+		nfs_jp_debug("%s: Returning %p, ns_list=%p\n",
+			__func__, new, new->ns_list);
+		nsdb_free_fedfs_fsls(fsls);
+		break;
+	case FEDFS_ERR_NSDB_NOFSL:
+		nfs_jp_debug("%s: No FSL entries for FSN %s\n",
+			__func__, fsn_uuid);
+		break;
+	case FEDFS_ERR_NSDB_NOFSN:
+		nfs_jp_debug("%s: No FSN %s found\n",
+			__func__, fsn_uuid);
+		break;
+	case FEDFS_ERR_NSDB_LDAP_VAL:
+		nfs_jp_debug("%s: NSDB operation failed with %s\n",
+			__func__, ldap_err2string(ldap_err));
+		break;
+	default:
+		nfs_jp_debug("%s: Failed to resolve FSN %s: %s\n",
+			__func__, fsn_uuid, nsdb_display_fedfsstatus(status));
+	}
+
+	nsdb_close_nsdb(host);
+	return status;
+}
+
+/**
+ * Resolve FedFS junction information into a set of NFS locations
+ *
+ * @param junct_path NUL-terminated C string containing POSIX path of junction
+ * @param new empty set of NFS locations
+ * @return a junction status code
+ *
+ * If nfs_jp_resolve_fedfs_junction() returns JP_OK, the caller must free
+ * the returned set of locations by calling nfs_jp_put_locations().
+ */
+static enum jp_status
+nfs_jp_resolve_fedfs_junction(const char *junct_path, nfs_fsloc_set_t new)
+{
+	enum jp_status status;
+	FedFsStatus retval;
+	char *fsn_uuid;
+	nsdb_t host;
+
+	retval = fedfs_get_fsn(junct_path, &fsn_uuid, &host);
+	/* XXX: Needs expansion */
+	if (retval != FEDFS_OK) {
+		nfs_jp_debug("%s: Failed to get FSN: %s\n",
+			__func__, nsdb_display_fedfsstatus(retval));
+		return JP_NSDBREMOTE;
+	}
+
+	status = nfs_jp_resolve_fsn(fsn_uuid, host, new);
+
+	nsdb_free_nsdb(host);
+	free(fsn_uuid);
+	return status;
+}
+
+/**
+ * Resolve FedFS junction into a set of NFS locations
+ *
+ * @param junct_path NUL-terminated C string containing POSIX path of junction
+ * @param locset OUT set of NFS locations
+ * @return a junction status code
+ *
+ * If nfs_jp_get_fedfs() returns JP_OK, the caller must free the returned
+ * set of locations by calling nfs_jp_put_locations().
+ */
+static enum jp_status
+nfs_jp_get_fedfs(const char *junct_path, nfs_fsloc_set_t *locset)
+{
+	enum jp_status status;
+	nfs_fsloc_set_t new;
+
+	new = nfs_jp_alloc_locations();
+	if (new == NULL) {
+		nfs_jp_debug("%s: No memory\n", __func__);
+		return JP_MEMORY;
+	}
+
+	status = nfs_jp_resolve_fedfs_junction(junct_path, new);
+	if (status != JP_OK) {
+		nfs_jp_put_locations(new);
+		return status;
+	}
+
+	*locset = new;
+	nfs_jp_debug("%s: Returning location set %p\n", __func__, new);
+	return JP_OK;
+}
+
+/**
+ * Resolve junction information into a set of NFS locations
+ *
+ * @param junct_path NUL-terminated C string containing POSIX path of junction
+ * @param locset OUT set of NFS locations
+ * @return a junction status code
+ *
+ * If this entry point returns JP_OK, the caller must free the returned
+ * set of locations by calling the jp_put_locations entry point.
+ */
+static enum jp_status
+nfs_jp_get_locations(const char *junct_path, nfs_fsloc_set_t *locset)
+{
+	FedFsStatus retval;
+
+	if (junct_path == NULL || locset == NULL) {
+		nfs_jp_debug("%s: Invalid parameters\n", __func__);
+		return JP_INVAL;
+	}
+	nfs_jp_debug("%s: %s\n", __func__, junct_path);
+
+	retval = nfs_is_junction(junct_path);
+	if (retval == FEDFS_OK)
+		return nfs_jp_get_basic(junct_path, locset);
+	if (retval != FEDFS_ERR_NOTJUNCT)
+		return JP_NOTJUNCTION;
+	retval = fedfs_is_junction(junct_path);
+	if (retval == FEDFS_OK)
+		return nfs_jp_get_fedfs(junct_path, locset);
+
+	nfs_jp_debug("%s: Not a junction\n", __func__);
+	return JP_NOTJUNCTION;
+}
+
+/**
+ * Reset the current location to the first location in the list
+ *
+ * @param locset set of NFS locations
+ */
+static void
+nfs_jp_rewind_locations(nfs_fsloc_set_t locset)
+{
+	if (locset == NULL) {
+		nfs_jp_debug("%s: Invalid parameters\n", __func__);
+		return;
+	}
+
+	nfs_jp_debug("%s: Rewinding %p\n", __func__, locset);
+	nfs_jp_do_rewind_locations(locset);
+}
+
+/**
+ * Get the fileserver hostname and export path from the next location in the set
+ *
+ * @param locset set of NFS locations
+ * @param hostname OUT NUL-terminated C string containing hostname of fileserver
+ * @param export_path OUT NUL-terminated C string containing export path
+ * @param ttl OUT cache time-to-live, in seconds
+ * @return a junction status code
+ *
+ * If this entry point returns JP_OK, the caller must free the hostname
+ * and export_path strings with free(3).
+ */
+static enum jp_status
+nfs_jp_get_next_location(nfs_fsloc_set_t locset,
+		char **hostname, char **export_path, int *ttl)
+{
+	char *hostname_tmp, *export_path_tmp;
+	struct nfs_fsloc *fsloc;
+
+	if (locset == NULL || hostname == NULL ||
+	    export_path == NULL || ttl == NULL) {
+		nfs_jp_debug("%s: Invalid parameters\n", __func__);
+		return JP_INVAL;
+	}
+	nfs_jp_debug("%s: locset=%p, ns_current=%p, ns_list=%p\n",
+		__func__, locset, locset->ns_current, locset->ns_list);
+
+	if (locset->ns_current == NULL) {
+		nfs_jp_debug("%s: No locations\n", __func__);
+		return JP_EMPTY;
+	}
+	fsloc = locset->ns_current;
+
+	hostname_tmp = strdup(fsloc->nfl_hostname);
+	if (hostname_tmp == NULL) {
+		nfs_jp_debug("%s: No memory\n", __func__);
+		return JP_MEMORY;
+	}
+
+	if (nsdb_path_array_to_posix(fsloc->nfl_rootpath,
+					&export_path_tmp) != FEDFS_OK) {
+		free(hostname_tmp);
+		nfs_jp_debug("%s: Failed to parse\n", __func__);
+		return JP_PARSE;
+	}
+
+	nfs_jp_debug("%s: Success; hostname=%s path=%s\n",
+		__func__, hostname_tmp, export_path_tmp);
+	*hostname = hostname_tmp;
+	*export_path = export_path_tmp;
+	*ttl = fsloc->nfl_ttl;
+	locset->ns_current = locset->ns_current->nfl_next;
+	return JP_OK;
+}
+
+/**
+ * Vector of methods provided by this plug-in
+ */
+struct jp_ops nfs_junction_ops = {
+	.jp_api_version		= JP_API_VERSION,
+	.jp_init		= nfs_jp_init,
+	.jp_done		= nfs_jp_done,
+	.jp_error		= nfs_jp_error,
+	.jp_put_locations	= nfs_jp_put_locations,
+	.jp_get_locations	= nfs_jp_get_locations,
+	.jp_rewind_locations	= nfs_jp_rewind_locations,
+	.jp_get_next_location	= nfs_jp_get_next_location,
+};