Fix mount helper

Several issues related to strange mount/umount behavior were reported
and this commit should address most of them.  The original idea was
to put in place a zfs mount helper (mount.zfs).  This helper is used
to enforce 'legacy' mount behavior, and perform any extra mount argument
processing (selinux, zfsutil, etc).  This helper wasn't ready for the
0.6.0-rc1 release but with this change it's functional but needs to
extensively tested.

This change addresses the following open issues.
Closes #101
Closes #107
Closes #113
Closes #115
Closes #119

1 files changed, 470 insertions, 0 deletions

diff --git a/cmd/mount_zfs/mount_zfs.c b/cmd/mount_zfs/mount_zfs.c
new file mode 100644
index 000000000..32f092199
--- /dev/null
+++ b/cmd/mount_zfs/mount_zfs.c
@@ -0,0 +1,470 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011 Lawrence Livermore National Security, LLC.
+ */
+
+#include <libintl.h>
+#include <unistd.h>
+#include <sys/file.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <libzfs.h>
+#ifdef HAVE_LIBSELINUX
+#include <selinux/selinux.h>
+#endif /* HAVE_LIBSELINUX */
+
+libzfs_handle_t *g_zfs;
+
+typedef struct option_map {
+	const char *name;
+	unsigned long mntmask;
+	unsigned long zfsmask;
+} option_map_t;
+
+static const option_map_t option_map[] = {
+	/* Canonicalized filesystem independent options from mount(8) */
+	{ MNTOPT_NOAUTO,	MS_COMMENT,	ZS_COMMENT	},
+	{ MNTOPT_DEFAULTS,	MS_COMMENT,	ZS_COMMENT	},
+	{ MNTOPT_NODEVICES,	MS_NODEV,	ZS_COMMENT	},
+	{ MNTOPT_DIRSYNC,	MS_DIRSYNC,	ZS_COMMENT	},
+	{ MNTOPT_NOEXEC,	MS_NOEXEC,	ZS_COMMENT	},
+	{ MNTOPT_GROUP,		MS_GROUP,	ZS_COMMENT	},
+	{ MNTOPT_NETDEV,	MS_COMMENT,	ZS_COMMENT	},
+	{ MNTOPT_NOFAIL,	MS_COMMENT,	ZS_COMMENT	},
+	{ MNTOPT_NOSUID,	MS_NOSUID,	ZS_COMMENT	},
+	{ MNTOPT_OWNER,		MS_OWNER,	ZS_COMMENT	},
+	{ MNTOPT_REMOUNT,	MS_REMOUNT,	ZS_COMMENT	},
+	{ MNTOPT_RO,		MS_RDONLY,	ZS_COMMENT	},
+	{ MNTOPT_RW,		MS_COMMENT,	ZS_COMMENT	},
+	{ MNTOPT_SYNC,		MS_SYNCHRONOUS,	ZS_COMMENT	},
+	{ MNTOPT_USER,		MS_USERS,	ZS_COMMENT	},
+	{ MNTOPT_USERS,		MS_USERS,	ZS_COMMENT	},
+#ifdef MS_NOATIME
+	{ MNTOPT_NOATIME,	MS_NOATIME,	ZS_COMMENT	},
+#endif
+#ifdef MS_NODIRATIME
+	{ MNTOPT_NODIRATIME,	MS_NODIRATIME,	ZS_COMMENT	},
+#endif
+#ifdef MS_RELATIME
+	{ MNTOPT_RELATIME,	MS_RELATIME,	ZS_COMMENT	},
+#endif
+#ifdef MS_STRICTATIME
+	{ MNTOPT_DFRATIME,	MS_STRICTATIME,	ZS_COMMENT	},
+#endif
+#ifdef HAVE_SELINUX
+	{ MNTOPT_CONTEXT,	MS_COMMENT,	ZS_NOCONTEXT	},
+	{ MNTOPT_NOCONTEXT,	MS_COMMENT,	ZS_NOCONTEXT	},
+	{ MNTOPT_FSCONTEXT,	MS_COMMENT,	ZS_NOCONTEXT	},
+	{ MNTOPT_DEFCONTEXT,	MS_COMMENT,	ZS_NOCONTEXT	},
+	{ MNTOPT_ROOTCONTEXT,	MS_COMMENT,	ZS_NOCONTEXT	},
+#endif
+#ifdef MS_I_VERSION
+	{ MNTOPT_IVERSION,	MS_I_VERSION,	ZS_COMMENT	},
+#endif
+#ifdef MS_MANDLOCK
+	{ MNTOPT_NBMAND,	MS_MANDLOCK,	ZS_COMMENT	},
+#endif
+	/* Valid options not found in mount(8) */
+	{ MNTOPT_BIND,		MS_BIND,	ZS_COMMENT	},
+#ifdef MS_REC
+	{ MNTOPT_RBIND,		MS_BIND|MS_REC,	ZS_COMMENT	},
+#endif
+	{ MNTOPT_COMMENT,	MS_COMMENT,	ZS_COMMENT	},
+#ifdef MS_NOSUB
+	{ MNTOPT_NOSUB,		MS_NOSUB,	ZS_COMMENT	},
+#endif
+#ifdef MS_SILENT
+	{ MNTOPT_QUIET,		MS_SILENT,	ZS_COMMENT	},
+#endif
+	/* Custom zfs options */
+	{ MNTOPT_NOXATTR,	MS_COMMENT,	ZS_COMMENT	},
+	{ MNTOPT_ZFSUTIL,	MS_COMMENT,	ZS_ZFSUTIL	},
+	{ NULL,			0,		0		} };
+
+/*
+ * Break the mount option in to a name/value pair.  The name is
+ * validated against the option map and mount flags set accordingly.
+ */
+static int
+parse_option(char *mntopt, unsigned long *mntflags,
+    unsigned long *zfsflags, int sloppy)
+{
+	const option_map_t *opt;
+	char *ptr, *name, *value = NULL;
+	int error = 0;
+
+	name = strdup(mntopt);
+	if (name == NULL)
+		return (ENOMEM);
+
+	for (ptr = name; ptr && *ptr; ptr++) {
+		if (*ptr == '=') {
+			*ptr = '\0';
+			value = ptr+1;
+			break;
+		}
+	}
+
+	for (opt = option_map; opt->name != NULL; opt++) {
+		if (strncmp(name, opt->name, strlen(name)) == 0) {
+			*mntflags |= opt->mntmask;
+			*zfsflags |= opt->zfsmask;
+
+			/* MS_USERS implies default user options */
+			if (opt->mntmask & (MS_USERS))
+				*mntflags |= (MS_NOEXEC|MS_NOSUID|MS_NODEV);
+
+			/* MS_OWNER|MS_GROUP imply default owner options */
+			if (opt->mntmask & (MS_OWNER | MS_GROUP))
+				*mntflags |= (MS_NOSUID|MS_NODEV);
+
+			error = 0;
+			goto out;
+		}
+	}
+
+	if (!sloppy)
+		error = ENOENT;
+out:
+	/* If required further process on the value may be done here */
+	free(name);
+	return (error);
+}
+
+/*
+ * Translate the mount option string in to MS_* mount flags for the
+ * kernel vfs.  When sloppy is non-zero unknown options will be ignored
+ * otherwise they are considered fatal are copied in to badopt.
+ */
+static int
+parse_options(char *mntopts, unsigned long *mntflags,
+    unsigned long *zfsflags, int sloppy, char *badopt)
+{
+	int error = 0, quote = 0, flag = 0;
+	char *ptr, *opt, *opts;
+
+	opts = strdup(mntopts);
+	if (opts == NULL)
+		return (ENOMEM);
+
+	*mntflags = 0;
+	opt = NULL;
+
+	/*
+	 * Scan through all mount options which must be comma delimited.
+	 * We must be careful to notice regions which are double quoted
+	 * and skip commas in these regions.  Each option is then checked
+	 * to determine if it is a known option.
+	 */
+	for (ptr = opts; ptr && !flag; ptr++) {
+		if (opt == NULL)
+			opt = ptr;
+
+		if (*ptr == '"')
+			quote = !quote;
+
+		if (quote)
+			continue;
+
+		if (*ptr == '\0')
+			flag = 1;
+
+		if ((*ptr == ',') || (*ptr == '\0')) {
+			*ptr = '\0';
+
+			error = parse_option(opt, mntflags, zfsflags, sloppy);
+			if (error) {
+				strcpy(badopt, opt);
+				goto out;
+			}
+
+			opt = NULL;
+		}
+	}
+
+out:
+	free(opts);
+	return (error);
+}
+
+/*
+ * If a file or directory in your current working directory is named
+ * 'dataset' then mount(8) will prepend your current working directory
+ * to dataset.  The is no way to prevent this behavior so we simply
+ * check for it and strip the prepended patch when it is added.
+ */
+static char *
+parse_dataset(char *dataset)
+{
+	char cwd[PATH_MAX];
+
+	(void) getcwd(cwd, PATH_MAX);
+	if (!strncmp(cwd, dataset, strlen(cwd)))
+		return (dataset + strlen(cwd) + 1);
+
+	return (dataset);
+}
+
+/*
+ * Update the mtab_* code to use the libmount library when it is commonly
+ * available otherwise fallback to legacy mode.  The mount(8) utility will
+ * manage the lock file for us to prevent racing updates to /etc/mtab.
+ */
+static int
+mtab_is_writeable(void)
+{
+	struct stat st;
+	int error, fd;
+
+	error = stat(MNTTAB, &st);
+	if (error || S_ISLNK(st.st_mode))
+		return (0);
+
+	fd = open(MNTTAB, O_RDWR | O_CREAT, 0644);
+	if (fd < 0)
+		return (0);
+
+	close(fd);
+	return (1);
+}
+
+static int
+mtab_update(char *dataset, char *mntpoint, char *type, char *mntopts)
+{
+	struct mntent mnt;
+	FILE *fp;
+	int error;
+
+	mnt.mnt_fsname = dataset;
+	mnt.mnt_dir = mntpoint;
+	mnt.mnt_type = type;
+	mnt.mnt_opts = mntopts ? mntopts : "";
+	mnt.mnt_freq = 0;
+	mnt.mnt_passno = 0;
+
+	fp = setmntent(MNTTAB, "a+");
+	if (!fp) {
+		(void) fprintf(stderr, gettext(
+		    "filesystem '%s' was mounted, but %s "
+		    "could not be opened due to error %d\n"),
+		    dataset, MNTTAB, errno);
+		return (MOUNT_FILEIO);
+	}
+
+	error = addmntent(fp, &mnt);
+	if (error) {
+		(void) fprintf(stderr, gettext(
+		    "filesystem '%s' was mounted, but %s "
+		    "could not be updated due to error %d\n"),
+		    dataset, MNTTAB, errno);
+		return (MOUNT_FILEIO);
+	}
+
+	(void) endmntent(fp);
+
+	return (MOUNT_SUCCESS);
+}
+
+int
+main(int argc, char **argv)
+{
+	zfs_handle_t *zhp;
+	char legacy[ZFS_MAXPROPLEN];
+	char mntopts[MNT_LINE_MAX] = { '\0' };
+	char badopt[MNT_LINE_MAX] = { '\0' };
+	char *dataset, *mntpoint;
+	unsigned long mntflags = 0, zfsflags = 0;
+	int sloppy = 0, fake = 0, verbose = 0, nomtab = 0, zfsutil = 0;
+	int error, c;
+
+	(void) setlocale(LC_ALL, "");
+	(void) textdomain(TEXT_DOMAIN);
+
+	opterr = 0;
+
+	/* check options */
+	while ((c = getopt(argc, argv, "sfnvo:h?")) != -1) {
+		switch (c) {
+		case 's':
+			sloppy = 1;
+			break;
+		case 'f':
+			fake = 1;
+			break;
+		case 'n':
+			nomtab = 1;
+			break;
+		case 'v':
+			verbose++;
+			break;
+		case 'o':
+			(void) strlcpy(mntopts, optarg, sizeof (mntopts));
+			break;
+		case 'h':
+		case '?':
+			(void) fprintf(stderr, gettext("Invalid option '%c'\n"),
+			    optopt);
+			(void) fprintf(stderr, gettext("Usage: mount.zfs "
+			    "[-sfnv] [-o options] <dataset> <mountpoint>\n"));
+			return (MOUNT_USAGE);
+		}
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	/* check that we only have two arguments */
+	if (argc != 2) {
+		if (argc == 0)
+			(void) fprintf(stderr, gettext("missing dataset "
+			    "argument\n"));
+		else if (argc == 1)
+			(void) fprintf(stderr,
+			    gettext("missing mountpoint argument\n"));
+		else
+			(void) fprintf(stderr, gettext("too many arguments\n"));
+		(void) fprintf(stderr, "usage: mount <dataset> <mountpoint>\n");
+		return (MOUNT_USAGE);
+	}
+
+	dataset = parse_dataset(argv[0]);
+	mntpoint = argv[1];
+
+	/* validate mount options and set mntflags */
+	error = parse_options(mntopts, &mntflags, &zfsflags, sloppy, badopt);
+	if (error) {
+		switch (error) {
+		case ENOMEM:
+			(void) fprintf(stderr, gettext("filesystem '%s' "
+			    "cannot be mounted due to a memory allocation "
+			    "failure\n"), dataset);
+			return (MOUNT_SYSERR);
+		case EINVAL:
+			(void) fprintf(stderr, gettext("filesystem '%s' "
+			    "cannot be mounted of due to the invalid option "
+			    "'%s'\n"), dataset, badopt);
+			(void) fprintf(stderr, gettext("Use the '-s' option "
+			    "to ignore the bad mount option.\n"));
+			return (MOUNT_USAGE);
+		default:
+			(void) fprintf(stderr, gettext("filesystem '%s' "
+			    "cannot be mounted due to internal error %d\n"),
+			    dataset, error);
+			return (MOUNT_SOFTWARE);
+		}
+	}
+
+#ifdef HAVE_LIBSELINUX
+	/*
+	 * Automatically add the default zfs context when selinux is enabled
+	 * and the caller has not specified their own context.  This must be
+	 * done until zfs is added to the default selinux policy configuration
+	 * as a known filesystem type which supports xattrs.
+	 */
+        if (is_selinux_enabled() && !(zfsflags & ZS_NOCONTEXT))
+                (void) strlcat(mntopts, ",context=\"system_u:"
+                    "object_r:file_t:s0\"", sizeof (mntopts));
+#endif /* HAVE_LIBSELINUX */
+
+
+	if (verbose)
+		(void) fprintf(stdout, gettext("mount.zfs:\n"
+		    "  dataset:    \"%s\"\n  mountpoint: \"%s\"\n"
+		    "  mountflags: 0x%lx\n  zfsflags:   0x%lx\n"
+		    "  mountopts:  \"%s\"\n\n"),
+		    dataset, mntpoint, mntflags, zfsflags, mntopts);
+
+	if (mntflags & MS_REMOUNT)
+		nomtab = 1;
+
+	if (zfsflags * ZS_ZFSUTIL)
+		zfsutil = 1;
+
+	if ((g_zfs = libzfs_init()) == NULL)
+		return (MOUNT_SYSERR);
+
+	/* try to open the dataset to access the mount point */
+	if ((zhp = zfs_open(g_zfs, dataset, ZFS_TYPE_FILESYSTEM)) == NULL) {
+		(void) fprintf(stderr, gettext("filesystem '%s' cannot be "
+		    "mounted, unable to open the dataset\n"), dataset);
+		libzfs_fini(g_zfs);
+		return (MOUNT_USAGE);
+	}
+
+	(void) zfs_prop_get(zhp, ZFS_PROP_MOUNTPOINT, legacy,
+	    sizeof (legacy), NULL, NULL, 0, B_FALSE);
+
+	zfs_close(zhp);
+	libzfs_fini(g_zfs);
+
+	/*
+	 * Legacy mount points may only be mounted using 'mount', never using
+	 * 'zfs mount'.  However, since 'zfs mount' actually invokes 'mount'
+	 * we differentiate the two cases using the 'zfsutil' mount option.
+	 * This mount option should only be supplied by the 'zfs mount' util.
+	 */
+	if (zfsutil && !strcmp(legacy, ZFS_MOUNTPOINT_LEGACY)) {
+		(void) fprintf(stderr, gettext(
+		    "filesystem '%s' cannot be mounted using 'zfs mount'.\n"
+		    "Use 'zfs set mountpoint=%s' or 'mount -t zfs %s %s'.\n"
+		    "See zfs(8) for more information.\n"),
+		   dataset, mntpoint, dataset, mntpoint);
+		return (MOUNT_USAGE);
+	}
+
+	if (!zfsutil && strcmp(legacy, ZFS_MOUNTPOINT_LEGACY)) {
+		(void) fprintf(stderr, gettext(
+		    "filesystem '%s' cannot be mounted using 'mount'.\n"
+		    "Use 'zfs set mountpoint=%s' or 'zfs mount %s'.\n"
+		    "See zfs(8) for more information.\n"),
+		    dataset, "legacy", dataset);
+		return (MOUNT_USAGE);
+	}
+
+	if (!fake) {
+		error = mount(dataset, mntpoint, MNTTYPE_ZFS,
+		    mntflags, mntopts);
+		if (error) {
+			switch (errno) {
+			case EBUSY:
+				(void) fprintf(stderr, gettext("filesystem "
+				    "'%s' is already mounted\n"), dataset);
+				return (MOUNT_SYSERR);
+			default:
+				(void) fprintf(stderr, gettext("filesystem "
+				    "'%s' can not be mounted due to error "
+				    "%d\n"), dataset, errno);
+				return (MOUNT_USAGE);
+			}
+		}
+	}
+
+	if (!nomtab && mtab_is_writeable()) {
+		error = mtab_update(dataset, mntpoint, MNTTYPE_ZFS, mntopts);
+		if (error)
+			return (error);
+	}
+
+	return (MOUNT_SUCCESS);
+}