X-Git-Url: https://git.decadent.org.uk/gitweb/?p=nfs-utils.git;a=blobdiff_plain;f=utils%2Fmount%2Fstropts.c;h=50a1a2a06626a72ba2c09fe656df3331e66a85b1;hp=ec95b78619a2c7ab342bfcb20d0863252d4bd01f;hb=a88c279992f4b63e3dcaac9930e300fd4bb03dd7;hpb=bfa1df2e24b7f8c7fee299049a6ee36e1262dacd

diff --git a/utils/mount/stropts.c b/utils/mount/stropts.c
index ec95b78..50a1a2a 100644
--- a/utils/mount/stropts.c
+++ b/utils/mount/stropts.c
@@ -35,9 +35,11 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 
+#include "sockaddr.h"
 #include "xcommon.h"
 #include "mount.h"
 #include "nls.h"
+#include "nfsrpc.h"
 #include "mount_constants.h"
 #include "stropts.h"
 #include "error.h"
@@ -45,6 +47,11 @@
 #include "parse_opt.h"
 #include "version.h"
 #include "parse_dev.h"
+#include "conffile.h"
+
+#ifndef HAVE_DECL_AI_ADDRCONFIG
+#define AI_ADDRCONFIG	0
+#endif
 
 #ifndef NFS_PROGRAM
 #define NFS_PROGRAM	(100003)
@@ -80,15 +87,36 @@ struct nfsmount_info {
 				*node,		/* mounted-on dir */
 				*type;		/* "nfs" or "nfs4" */
 	char			*hostname;	/* server's hostname */
+	struct addrinfo		*address;	/* server's addresses */
 
 	struct mount_options	*options;	/* parsed mount options */
 	char			**extra_opts;	/* string for /etc/mtab */
 
+	unsigned long		version;	/* NFS version */
 	int			flags,		/* MS_ flags */
 				fake,		/* actually do the mount? */
 				child;		/* forked bg child? */
 };
 
+#ifdef MOUNT_CONFIG
+static void nfs_default_version(struct nfsmount_info *mi);
+
+static void nfs_default_version(struct nfsmount_info *mi)
+{
+	extern unsigned long config_default_vers;
+	/*
+	 * Use the default value set in the config file when
+	 * the version has not been explicitly set.
+	 */
+	if (mi->version == 0 && config_default_vers) {
+		if (config_default_vers < 4)
+			mi->version = config_default_vers;
+	}
+}
+#else
+inline void nfs_default_version(struct nfsmount_info *mi) {}
+#endif /* MOUNT_CONFIG */
+
 /*
  * Obtain a retry timeout value based on the value of the "retry=" option.
  *
@@ -130,12 +158,14 @@ static int nfs_append_generic_address_option(const struct sockaddr *sap,
 {
 	char address[NI_MAXHOST];
 	char new_option[512];
+	int len;
 
 	if (!nfs_present_sockaddr(sap, salen, address, sizeof(address)))
 		goto out_err;
 
-	if (snprintf(new_option, sizeof(new_option), "%s=%s",
-					keyword, address) >= sizeof(new_option))
+	len = snprintf(new_option, sizeof(new_option), "%s=%s",
+						keyword, address);
+	if (len < 0 || (size_t)len >= sizeof(new_option))
 		goto out_err;
 
 	if (po_append(options, new_option) != PO_SUCCEEDED)
@@ -179,9 +209,9 @@ static int nfs_append_clientaddr_option(const struct sockaddr *sap,
 					socklen_t salen,
 					struct mount_options *options)
 {
-	struct sockaddr_storage dummy;
-	struct sockaddr *my_addr = (struct sockaddr *)&dummy;
-	socklen_t my_len = sizeof(dummy);
+	union nfs_sockaddr address;
+	struct sockaddr *my_addr = &address.sa;
+	socklen_t my_len = sizeof(address);
 
 	if (po_contains(options, "clientaddr") == PO_FOUND)
 		return 1;
@@ -193,21 +223,33 @@ static int nfs_append_clientaddr_option(const struct sockaddr *sap,
 }
 
 /*
- * Resolve the 'mounthost=' hostname and append a new option using
- * the resulting address.
+ * Determine whether to append a 'mountaddr=' option.  The option is needed if:
+ *
+ *   1. "mounthost=" was specified, or
+ *   2. The address families for proto= and mountproto= are different.
  */
-static int nfs_fix_mounthost_option(struct mount_options *options)
+static int nfs_fix_mounthost_option(struct mount_options *options,
+		const char *nfs_hostname)
 {
-	struct sockaddr_storage dummy;
-	struct sockaddr *sap = (struct sockaddr *)&dummy;
-	socklen_t salen = sizeof(dummy);
+	union nfs_sockaddr address;
+	struct sockaddr *sap = &address.sa;
+	socklen_t salen = sizeof(address);
+	sa_family_t nfs_family, mnt_family;
 	char *mounthost;
 
+	if (!nfs_nfs_proto_family(options, &nfs_family))
+		return 0;
+	if (!nfs_mount_proto_family(options, &mnt_family))
+		return 0;
+
 	mounthost = po_get(options, "mounthost");
-	if (!mounthost)
-		return 1;
+	if (mounthost == NULL) {
+		if (nfs_family == mnt_family)
+			return 1;
+		mounthost = (char *)nfs_hostname;
+	}
 
-	if (!nfs_name_to_address(mounthost, sap, &salen)) {
+	if (!nfs_lookup(mounthost, mnt_family, sap, &salen)) {
 		nfs_error(_("%s: unable to determine mount server's address"),
 				progname);
 		return 0;
@@ -253,57 +295,85 @@ static int nfs_append_sloppy_option(struct mount_options *options)
 	return 1;
 }
 
+static int nfs_set_version(struct nfsmount_info *mi)
+{
+	if (!nfs_nfs_version(mi->options, &mi->version))
+		return 0;
+
+	if (strncmp(mi->type, "nfs4", 4) == 0)
+		mi->version = 4;
+
+	/*
+	 * Before 2.6.32, the kernel NFS client didn't
+	 * support "-t nfs vers=4" mounts, so NFS version
+	 * 4 cannot be included when autonegotiating
+	 * while running on those kernels.
+	 */
+	if (mi->version == 0 &&
+	    linux_version_code() <= MAKE_VERSION(2, 6, 31))
+		mi->version = 3;
+
+	/*
+	 * If we still don't know, check for version-specific
+	 * mount options.
+	 */
+	if (mi->version == 0) {
+		if (po_contains(mi->options, "mounthost") ||
+		    po_contains(mi->options, "mountaddr") ||
+		    po_contains(mi->options, "mountvers") ||
+		    po_contains(mi->options, "mountproto"))
+			mi->version = 3;
+	}
+
+	/*
+	 * If enabled, see if the default version was
+	 * set in the config file
+	 */
+	nfs_default_version(mi);
+	
+	return 1;
+}
+
 /*
- * Set up mandatory NFS mount options.
+ * Set up mandatory non-version specific NFS mount options.
  *
  * Returns 1 if successful; otherwise zero.
  */
 static int nfs_validate_options(struct nfsmount_info *mi)
 {
-	struct sockaddr_storage dummy;
-	struct sockaddr *sap = (struct sockaddr *)&dummy;
-	socklen_t salen = sizeof(dummy);
+	struct addrinfo hint = {
+		.ai_protocol	= (int)IPPROTO_UDP,
+		.ai_flags	= AI_ADDRCONFIG,
+	};
+	sa_family_t family;
+	int error;
 
 	if (!nfs_parse_devname(mi->spec, &mi->hostname, NULL))
 		return 0;
 
-	if (!nfs_name_to_address(mi->hostname, sap, &salen))
+	if (!nfs_nfs_proto_family(mi->options, &family))
 		return 0;
 
-	if (strncmp(mi->type, "nfs4", 4) == 0) {
-		if (!nfs_append_clientaddr_option(sap, salen, mi->options))
-			return 0;
-	} else {
-		if (!nfs_fix_mounthost_option(mi->options))
-			return 0;
-		if (!mi->fake && !nfs_verify_lock_option(mi->options))
-			return 0;
+	hint.ai_family = (int)family;
+	error = getaddrinfo(mi->hostname, NULL, &hint, &mi->address);
+	if (error != 0) {
+		nfs_error(_("%s: Failed to resolve server %s: %s"),
+			progname, mi->hostname, gai_strerror(error));
+		mi->address = NULL;
+		return 0;
 	}
 
+	if (!nfs_set_version(mi))
+		return 0;
+
 	if (!nfs_append_sloppy_option(mi->options))
 		return 0;
 
-	return nfs_append_addr_option(sap, salen, mi->options);
-}
+	if (!nfs_append_addr_option(mi->address->ai_addr,
+					mi->address->ai_addrlen, mi->options))
+		return 0;
 
-/*
- * Distinguish between permanent and temporary errors.
- *
- * Returns 0 if the passed-in error is temporary, thus the
- * mount system call should be retried; returns one if the
- * passed-in error is permanent, thus the mount system call
- * should not be retried.
- */
-static int nfs_is_permanent_error(int error)
-{
-	switch (error) {
-	case ESTALE:
-	case ETIMEDOUT:
-	case ECONNREFUSED:
-		return 0;	/* temporary */
-	default:
-		return 1;	/* permanent */
-	}
+	return 1;
 }
 
 /*
@@ -323,26 +393,27 @@ static int nfs_extract_server_addresses(struct mount_options *options,
 	option = po_get(options, "addr");
 	if (option == NULL)
 		return 0;
-	if (!nfs_string_to_sockaddr(option, strlen(option),
-						nfs_saddr, nfs_salen))
+	if (!nfs_string_to_sockaddr(option, nfs_saddr, nfs_salen))
 		return 0;
 
 	option = po_get(options, "mountaddr");
 	if (option == NULL) {
 		memcpy(mnt_saddr, nfs_saddr, *nfs_salen);
 		*mnt_salen = *nfs_salen;
-	} else if (!nfs_string_to_sockaddr(option, strlen(option),
-						mnt_saddr, mnt_salen))
+	} else if (!nfs_string_to_sockaddr(option, mnt_saddr, mnt_salen))
 		return 0;
 
 	return 1;
 }
 
 static int nfs_construct_new_options(struct mount_options *options,
+				     struct sockaddr *nfs_saddr,
 				     struct pmap *nfs_pmap,
+				     struct sockaddr *mnt_saddr,
 				     struct pmap *mnt_pmap)
 {
 	char new_option[64];
+	char *netid;
 
 	po_remove_all(options, "nfsprog");
 	po_remove_all(options, "mountprog");
@@ -359,20 +430,14 @@ static int nfs_construct_new_options(struct mount_options *options,
 	po_remove_all(options, "proto");
 	po_remove_all(options, "udp");
 	po_remove_all(options, "tcp");
-	switch (nfs_pmap->pm_prot) {
-	case IPPROTO_TCP:
-		snprintf(new_option, sizeof(new_option) - 1,
-			 "proto=tcp");
-		if (po_append(options, new_option) == PO_FAILED)
-			return 0;
-		break;
-	case IPPROTO_UDP:
-		snprintf(new_option, sizeof(new_option) - 1,
-			 "proto=udp");
-		if (po_append(options, new_option) == PO_FAILED)
-			return 0;
-		break;
-	}
+	netid = nfs_get_netid(nfs_saddr->sa_family, nfs_pmap->pm_prot);
+	if (netid == NULL)
+		return 0;
+	snprintf(new_option, sizeof(new_option) - 1,
+			 "proto=%s", netid);
+	free(netid);
+	if (po_append(options, new_option) == PO_FAILED)
+		return 0;
 
 	po_remove_all(options, "port");
 	if (nfs_pmap->pm_port != NFS_PORT) {
@@ -389,20 +454,14 @@ static int nfs_construct_new_options(struct mount_options *options,
 		return 0;
 
 	po_remove_all(options, "mountproto");
-	switch (mnt_pmap->pm_prot) {
-	case IPPROTO_TCP:
-		snprintf(new_option, sizeof(new_option) - 1,
-			 "mountproto=tcp");
-		if (po_append(options, new_option) == PO_FAILED)
-			return 0;
-		break;
-	case IPPROTO_UDP:
-		snprintf(new_option, sizeof(new_option) - 1,
-			 "mountproto=udp");
-		if (po_append(options, new_option) == PO_FAILED)
-			return 0;
-		break;
-	}
+	netid = nfs_get_netid(mnt_saddr->sa_family, mnt_pmap->pm_prot);
+	if (netid == NULL)
+		return 0;
+	snprintf(new_option, sizeof(new_option) - 1,
+			 "mountproto=%s", netid);
+	free(netid);
+	if (po_append(options, new_option) == PO_FAILED)
+		return 0;
 
 	po_remove_all(options, "mountport");
 	snprintf(new_option, sizeof(new_option) - 1,
@@ -420,76 +479,107 @@ static int nfs_construct_new_options(struct mount_options *options,
  *
  * To handle version and transport protocol fallback properly, we
  * need to parse some of the mount options in order to set up a
- * portmap probe.  Mount options that nfs_rewrite_mount_options()
+ * portmap probe.  Mount options that nfs_rewrite_pmap_mount_options()
  * doesn't recognize are left alone.
  *
- * Returns a new group of mount options if successful; otherwise
- * NULL is returned if some failure occurred.
+ * Returns TRUE if rewriting was successful; otherwise
+ * FALSE is returned if some failure occurred.
  */
-static struct mount_options *nfs_rewrite_mount_options(char *str)
+static int
+nfs_rewrite_pmap_mount_options(struct mount_options *options)
 {
-	struct mount_options *options;
-	struct sockaddr_storage nfs_address;
-	struct sockaddr *nfs_saddr = (struct sockaddr *)&nfs_address;
-	socklen_t nfs_salen;
+	union nfs_sockaddr nfs_address;
+	struct sockaddr *nfs_saddr = &nfs_address.sa;
+	socklen_t nfs_salen = sizeof(nfs_address);
 	struct pmap nfs_pmap;
-	struct sockaddr_storage mnt_address;
-	struct sockaddr *mnt_saddr = (struct sockaddr *)&mnt_address;
-	socklen_t mnt_salen;
+	union nfs_sockaddr mnt_address;
+	struct sockaddr *mnt_saddr = &mnt_address.sa;
+	socklen_t mnt_salen = sizeof(mnt_address);
+	unsigned long protocol;
 	struct pmap mnt_pmap;
 
-	options = po_split(str);
-	if (!options) {
-		errno = EFAULT;
-		return NULL;
+	/*
+	 * Version and transport negotiation is not required
+	 * and does not work for RDMA mounts.
+	 */
+	if (!nfs_nfs_protocol(options, &protocol)) {
+		errno = EINVAL;
+		return 0;
 	}
+	if (protocol == NFSPROTO_RDMA)
+		goto out;
 
+	/*
+	 * Extract just the options needed to contact server.
+	 * Bail now if any of these have bad values.
+	 */
 	if (!nfs_extract_server_addresses(options, nfs_saddr, &nfs_salen,
 						mnt_saddr, &mnt_salen)) {
 		errno = EINVAL;
-		goto err;
+		return 0;
+	}
+	if (!nfs_options2pmap(options, &nfs_pmap, &mnt_pmap)) {
+		errno = EINVAL;
+		return 0;
 	}
 
-	nfs_options2pmap(options, &nfs_pmap, &mnt_pmap);
-
-	/* The kernel NFS client doesn't support changing the RPC program
-	 * number for these services, so reset these fields before probing
-	 * the server's ports.  */
+	/*
+	 * The kernel NFS client doesn't support changing the RPC
+	 * program number for these services, so force the value of
+	 * these fields before probing the server's ports.
+	 */
 	nfs_pmap.pm_prog = NFS_PROGRAM;
 	mnt_pmap.pm_prog = MOUNTPROG;
 
+	/*
+	 * If the server's rpcbind service isn't available, we can't
+	 * negotiate.  Bail now if we can't contact it.
+	 */
 	if (!nfs_probe_bothports(mnt_saddr, mnt_salen, &mnt_pmap,
 				 nfs_saddr, nfs_salen, &nfs_pmap)) {
 		errno = ESPIPE;
-		goto err;
+		if (rpc_createerr.cf_stat == RPC_PROGNOTREGISTERED)
+			errno = EOPNOTSUPP;
+		else if (rpc_createerr.cf_error.re_errno != 0)
+			errno = rpc_createerr.cf_error.re_errno;
+		return 0;
 	}
 
-	if (!nfs_construct_new_options(options, &nfs_pmap, &mnt_pmap)) {
-		errno = EINVAL;
-		goto err;
+	if (!nfs_construct_new_options(options, nfs_saddr, &nfs_pmap,
+					mnt_saddr, &mnt_pmap)) {
+		if (rpc_createerr.cf_stat == RPC_UNKNOWNPROTO)
+			errno = EPROTONOSUPPORT;
+		else
+			errno = EINVAL;
+		return 0;
 	}
 
+out:
 	errno = 0;
-	return options;
-
-err:
-	po_destroy(options);
-	return NULL;
+	return 1;
 }
 
 /*
  * Do the mount(2) system call.
  *
- * Returns 1 if successful, otherwise zero.
+ * Returns TRUE if successful, otherwise FALSE.
  * "errno" is set to reflect the individual error.
  */
-static int nfs_sys_mount(const struct nfsmount_info *mi, const char *type,
-			 const char *options)
+static int nfs_sys_mount(struct nfsmount_info *mi, struct mount_options *opts)
 {
+	char *options = NULL;
 	int result;
 
-	result = mount(mi->spec, mi->node, type,
-				mi->flags & ~(MS_USER|MS_USERS), options);
+	if (po_join(opts, &options) == PO_FAILED) {
+		errno = EIO;
+		return 0;
+	}
+
+	if (mi->fake)
+		return 1;
+
+	result = mount(mi->spec, mi->node, mi->type,
+			mi->flags & ~(MS_USER|MS_USERS), options);
 	if (verbose && result) {
 		int save = errno;
 		nfs_error(_("%s: mount(2): %s"), progname, strerror(save));
@@ -498,128 +588,266 @@ static int nfs_sys_mount(const struct nfsmount_info *mi, const char *type,
 	return !result;
 }
 
-/*
- * Retry an NFS mount that failed because the requested service isn't
- * available on the server.
- *
- * Returns 1 if successful.  Otherwise, returns zero.
- * "errno" is set to reflect the individual error.
- *
- * Side effect: If the retry is successful, both 'options' and
- * 'extra_opts' are updated to reflect the mount options that worked.
- * If the retry fails, 'options' and 'extra_opts' are left unchanged.
- */
-static int nfs_retry_nfs23mount(struct nfsmount_info *mi)
+static int nfs_do_mount_v3v2(struct nfsmount_info *mi,
+		struct sockaddr *sap, socklen_t salen)
 {
-	struct mount_options *retry_options;
-	char *retry_str = NULL;
-	char **extra_opts = mi->extra_opts;
+	struct mount_options *options = po_dup(mi->options);
+	int result = 0;
 
-	retry_options = nfs_rewrite_mount_options(*extra_opts);
-	if (!retry_options)
-		return 0;
+	if (!options) {
+		errno = ENOMEM;
+		return result;
+	}
+	errno = 0;
+	if (!nfs_append_addr_option(sap, salen, options)) {
+		if (errno == 0)
+			errno = EINVAL;
+		goto out_fail;
+	}
 
-	if (po_join(retry_options, &retry_str) == PO_FAILED) {
-		po_destroy(retry_options);
-		errno = EIO;
-		return 0;
+	if (!nfs_fix_mounthost_option(options, mi->hostname)) {
+		if (errno == 0)
+			errno = EINVAL;
+		goto out_fail;
+	}
+	if (!mi->fake && !nfs_verify_lock_option(options)) {
+		if (errno == 0)
+			errno = EINVAL;
+		goto out_fail;
+	}
+
+	/*
+	 * Options we negotiate below may be stale by the time this
+	 * file system is unmounted.  In order to force umount.nfs
+	 * to renegotiate with the server, only write the user-
+	 * specified options, and not negotiated options, to /etc/mtab.
+	 */
+	if (po_join(options, mi->extra_opts) == PO_FAILED) {
+		errno = ENOMEM;
+		goto out_fail;
 	}
 
 	if (verbose)
-		printf(_("%s: text-based options (retry): '%s'\n"),
-			progname, retry_str);
+		printf(_("%s: trying text-based options '%s'\n"),
+			progname, *mi->extra_opts);
 
-	if (!nfs_sys_mount(mi, "nfs", retry_str)) {
-		po_destroy(retry_options);
-		free(retry_str);
-		return 0;
-	}
+	if (!nfs_rewrite_pmap_mount_options(options))
+		goto out_fail;
 
-	free(*extra_opts);
-	*extra_opts = retry_str;
-	po_replace(mi->options, retry_options);
-	return 1;
+	result = nfs_sys_mount(mi, options);
+
+out_fail:
+	po_destroy(options);
+	return result;
 }
 
 /*
- * Attempt an NFSv2/3 mount via a mount(2) system call.  If the kernel
- * claims the requested service isn't supported on the server, probe
- * the server to see what's supported, rewrite the mount options,
- * and retry the request.
+ * Attempt a "-t nfs vers=2" or "-t nfs vers=3" mount.
  *
- * Returns 1 if successful.  Otherwise, returns zero.
+ * Returns TRUE if successful, otherwise FALSE.
  * "errno" is set to reflect the individual error.
- *
- * Side effect: If the retry is successful, both 'options' and
- * 'extra_opts' are updated to reflect the mount options that worked.
- * If the retry fails, 'options' and 'extra_opts' are left unchanged.
  */
-static int nfs_try_nfs23mount(struct nfsmount_info *mi)
+static int nfs_try_mount_v3v2(struct nfsmount_info *mi)
 {
-	char **extra_opts = mi->extra_opts;
+	struct addrinfo *ai;
+	int ret;
+
+	for (ai = mi->address; ai != NULL; ai = ai->ai_next) {
+		ret = nfs_do_mount_v3v2(mi, ai->ai_addr, ai->ai_addrlen);
+		if (ret != 0)
+			return ret;
+
+		switch (errno) {
+		case ECONNREFUSED:
+		case EOPNOTSUPP:
+		case EHOSTUNREACH:
+			continue;
+		default:
+			break;
+		}
+	}
+	return ret;
+}
 
-	if (po_join(mi->options, extra_opts) == PO_FAILED) {
-		errno = EIO;
-		return 0;
+static int nfs_do_mount_v4(struct nfsmount_info *mi,
+		struct sockaddr *sap, socklen_t salen)
+{
+	struct mount_options *options = po_dup(mi->options);
+	int result = 0;
+
+	if (!options) {
+		errno = ENOMEM;
+		return result;
 	}
 
-	if (verbose)
-		printf(_("%s: text-based options: '%s'\n"),
-			progname, *extra_opts);
+	if (mi->version == 0) {
+		if (po_contains(options, "mounthost") ||
+			po_contains(options, "mountaddr") ||
+			po_contains(options, "mountvers") ||
+			po_contains(options, "mountproto")) {
+		/*
+		 * Since these mountd options are set assume version 3
+		 * is wanted so error out with EPROTONOSUPPORT so the
+		 * protocol negation starts with v3.
+		 */
+			errno = EPROTONOSUPPORT;
+			goto out_fail;
+		}
+		if (po_append(options, "vers=4") == PO_FAILED) {
+			errno = EINVAL;
+			goto out_fail;
+		}
+	}
 
-	if (mi->fake)
-		return 1;
+	if (!nfs_append_addr_option(sap, salen, options)) {
+		errno = EINVAL;
+		goto out_fail;
+	}
 
-	if (nfs_sys_mount(mi, "nfs", *extra_opts))
-		return 1;
+	if (!nfs_append_clientaddr_option(sap, salen, options)) {
+		errno = EINVAL;
+		goto out_fail;
+	}
 
 	/*
-	 * The kernel returns EOPNOTSUPP if the RPC bind failed,
-	 * and EPROTONOSUPPORT if the version isn't supported.
+	 * Update option string to be recorded in /etc/mtab.
 	 */
-	if (errno != EOPNOTSUPP && errno != EPROTONOSUPPORT)
-		return 0;
+	if (po_join(options, mi->extra_opts) == PO_FAILED) {
+		errno = ENOMEM;
+		goto out_fail;
+	}
 
-	return nfs_retry_nfs23mount(mi);
+	if (verbose)
+		printf(_("%s: trying text-based options '%s'\n"),
+			progname, *mi->extra_opts);
+
+	result = nfs_sys_mount(mi, options);
+
+out_fail:
+	po_destroy(options);
+	return result;
 }
 
 /*
- * Attempt an NFS v4 mount via a mount(2) system call.
+ * Attempt a "-t nfs -o vers=4" or "-t nfs4" mount.
  *
- * Returns 1 if successful.  Otherwise, returns zero.
+ * Returns TRUE if successful, otherwise FALSE.
  * "errno" is set to reflect the individual error.
  */
-static int nfs_try_nfs4mount(struct nfsmount_info *mi)
+static int nfs_try_mount_v4(struct nfsmount_info *mi)
 {
-	char **extra_opts = mi->extra_opts;
-
-	if (po_join(mi->options, extra_opts) == PO_FAILED) {
-		errno = EIO;
-		return 0;
+	struct addrinfo *ai;
+	int ret;
+
+	for (ai = mi->address; ai != NULL; ai = ai->ai_next) {
+		ret = nfs_do_mount_v4(mi, ai->ai_addr, ai->ai_addrlen);
+		if (ret != 0)
+			return ret;
+
+		switch (errno) {
+		case ECONNREFUSED:
+		case EHOSTUNREACH:
+			continue;
+		default:
+			break;
+		}
 	}
+	return ret;
+}
 
-	if (verbose)
-		printf(_("%s: text-based options: '%s'\n"),
-			progname, *extra_opts);
+/*
+ * Handle NFS version and transport protocol
+ * autonegotiation.
+ *
+ * When no version or protocol is specified on the
+ * command line, mount.nfs negotiates with the server
+ * to determine appropriate settings for the new
+ * mount point.
+ *
+ * Returns TRUE if successful, otherwise FALSE.
+ * "errno" is set to reflect the individual error.
+ */
+static int nfs_autonegotiate(struct nfsmount_info *mi)
+{
+	int result;
 
-	if (mi->fake)
-		return 1;
+	result = nfs_try_mount_v4(mi);
+	if (result)
+		return result;
+		
+	switch (errno) {
+	case EPROTONOSUPPORT:
+		/* A clear indication that the server or our
+		 * client does not support NFS version 4. */
+		goto fall_back;
+	case ENOENT:
+		/* Legacy Linux servers don't export an NFS
+		 * version 4 pseudoroot. */
+		goto fall_back;
+	case EPERM:
+		/* Linux servers prior to 2.6.25 may return
+		 * EPERM when NFS version 4 is not supported. */
+		goto fall_back;
+	default:
+		return result;
+	}
 
-	return nfs_sys_mount(mi, "nfs4", *extra_opts);
+fall_back:
+	return nfs_try_mount_v3v2(mi);
 }
 
 /*
- * Perform either an NFSv2/3 mount, or an NFSv4 mount system call.
+ * This is a single pass through the fg/bg loop.
  *
- * Returns 1 if successful.  Otherwise, returns zero.
+ * Returns TRUE if successful, otherwise FALSE.
  * "errno" is set to reflect the individual error.
  */
 static int nfs_try_mount(struct nfsmount_info *mi)
 {
-	if (strncmp(mi->type, "nfs4", 4) == 0)
-		return nfs_try_nfs4mount(mi);
-	else
-		return nfs_try_nfs23mount(mi);
+	int result = 0;
+
+	switch (mi->version) {
+	case 0:
+		result = nfs_autonegotiate(mi);
+		break;
+	case 2:
+	case 3:
+		result = nfs_try_mount_v3v2(mi);
+		break;
+	case 4:
+		result = nfs_try_mount_v4(mi);
+		break;
+	default:
+		errno = EIO;
+	}
+
+	return result;
+}
+
+/*
+ * Distinguish between permanent and temporary errors.
+ *
+ * Basically, we retry if communication with the server has
+ * failed so far, but fail immediately if there is a local
+ * error (like a bad mount option).
+ *
+ * ESTALE is also a temporary error because some servers
+ * return ESTALE when a share is temporarily offline.
+ *
+ * Returns 1 if we should fail immediately, or 0 if we
+ * should retry.
+ */
+static int nfs_is_permanent_error(int error)
+{
+	switch (error) {
+	case ESTALE:
+	case ETIMEDOUT:
+	case ECONNREFUSED:
+	case EHOSTUNREACH:
+		return 0;	/* temporary */
+	default:
+		return 1;	/* permanent */
+	}
 }
 
 /*
@@ -738,6 +966,26 @@ static int nfsmount_bg(struct nfsmount_info *mi)
 		return nfsmount_child(mi);
 }
 
+/*
+ * Usually all that is needed for an NFS remount is to change
+ * generic mount options like "sync" or "ro".  These generic
+ * options are controlled by mi->flags, not by text-based
+ * options, and no contact with the server is needed.
+ *
+ * Take care with the /etc/mtab entry for this mount; just
+ * calling update_mtab() will change an "-t nfs -o vers=4"
+ * mount to an "-t nfs -o remount" mount, and that will
+ * confuse umount.nfs.
+ *
+ * Returns a valid mount command exit code.
+ */
+static int nfs_remount(struct nfsmount_info *mi)
+{
+	if (nfs_sys_mount(mi, mi->options))
+		return EX_SUCCESS;
+	return EX_FAIL;
+}
+
 /*
  * Process mount options and try a mount system call.
  *
@@ -754,6 +1002,12 @@ static int nfsmount_start(struct nfsmount_info *mi)
 	if (!nfs_validate_options(mi))
 		return EX_FAIL;
 
+	/*
+	 * Avoid retry and negotiation logic when remounting
+	 */
+	if (mi->flags & MS_REMOUNT)
+		return nfs_remount(mi);
+
 	if (po_rightmost(mi->options, nfs_background_opttbl) == 0)
 		return nfsmount_bg(mi);
 	else
@@ -770,6 +1024,8 @@ static int nfsmount_start(struct nfsmount_info *mi)
  *		(input and output argument)
  * @fake: flag indicating whether to carry out the whole operation
  * @child: one if this is a mount daemon (bg)
+ *
+ * Returns a valid mount command exit code.
  */
 int nfsmount_string(const char *spec, const char *node, const char *type,
 		    int flags, char **extra_opts, int fake, int child)
@@ -777,6 +1033,7 @@ int nfsmount_string(const char *spec, const char *node, const char *type,
 	struct nfsmount_info mi = {
 		.spec		= spec,
 		.node		= node,
+		.address	= NULL,
 		.type		= type,
 		.extra_opts	= extra_opts,
 		.flags		= flags,
@@ -792,6 +1049,7 @@ int nfsmount_string(const char *spec, const char *node, const char *type,
 	} else
 		nfs_error(_("%s: internal option parsing error"), progname);
 
+	freeaddrinfo(mi.address);
 	free(mi.hostname);
 	return retval;
 }