/* vi: set sw=4 ts=4: */
/*
 * Mini mount implementation for busybox
 *
 * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
 * Copyright (C) 2005-2006 by Rob Landley <rob@landley.net>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
// Design notes: There is no spec for mount.  Remind me to write one.
//
// mount_main() calls singlemount() which calls mount_it_now().
//
// mount_main() can loop through /etc/fstab for mount -a
// singlemount() can loop through /etc/filesystems for fstype detection.
// mount_it_now() does the actual mount.
//

//config:config MOUNT
//config:       bool "mount (23 kb)"
//config:       default y
//config:       select PLATFORM_LINUX
//config:       help
//config:       All files and filesystems in Unix are arranged into one big directory
//config:       tree. The 'mount' utility is used to graft a filesystem onto a
//config:       particular part of the tree. A filesystem can either live on a block
//config:       device, or it can be accessible over the network, as is the case with
//config:       NFS filesystems.
//config:
//config:config FEATURE_MOUNT_FAKE
//config:       bool "Support -f (fake mount)"
//config:       default y
//config:       depends on MOUNT
//config:       help
//config:       Enable support for faking a file system mount.
//config:
//config:config FEATURE_MOUNT_VERBOSE
//config:       bool "Support -v (verbose)"
//config:       default y
//config:       depends on MOUNT
//config:       help
//config:       Enable multi-level -v[vv...] verbose messages. Useful if you
//config:       debug mount problems and want to see what is exactly passed
//config:       to the kernel.
//config:
//config:config FEATURE_MOUNT_HELPERS
//config:       bool "Support mount helpers"
//config:       default n
//config:       depends on MOUNT
//config:       help
//config:       Enable mounting of virtual file systems via external helpers.
//config:       E.g. "mount obexfs#-b00.11.22.33.44.55 /mnt" will in effect call
//config:       "obexfs -b00.11.22.33.44.55 /mnt"
//config:       Also "mount -t sometype [-o opts] fs /mnt" will try
//config:       "sometype [-o opts] fs /mnt" if simple mount syscall fails.
//config:       The idea is to use such virtual filesystems in /etc/fstab.
//config:
//config:config FEATURE_MOUNT_LABEL
//config:       bool "Support specifying devices by label or UUID"
//config:       default y
//config:       depends on MOUNT
//config:       select VOLUMEID
//config:       help
//config:       This allows for specifying a device by label or uuid, rather than by
//config:       name. This feature utilizes the same functionality as blkid/findfs.
//config:
//config:config FEATURE_MOUNT_NFS
//config:       bool "Support mounting NFS file systems on Linux < 2.6.23"
//config:       default n
//config:       depends on MOUNT
//config:       select FEATURE_SYSLOG
//config:       help
//config:       Enable mounting of NFS file systems on Linux kernels prior
//config:       to version 2.6.23. Note that in this case mounting of NFS
//config:       over IPv6 will not be possible.
//config:
//config:       Note that this option links in RPC support from libc,
//config:       which is rather large (~10 kbytes on uclibc).
//config:
//config:config FEATURE_MOUNT_CIFS
//config:       bool "Support mounting CIFS/SMB file systems"
//config:       default y
//config:       depends on MOUNT
//config:       help
//config:       Enable support for samba mounts.
//config:
//config:config FEATURE_MOUNT_FLAGS
//config:       depends on MOUNT
//config:       bool "Support lots of -o flags"
//config:       default y
//config:       help
//config:       Without this, mount only supports ro/rw/remount. With this, it
//config:       supports nosuid, suid, dev, nodev, exec, noexec, sync, async, atime,
//config:       noatime, diratime, nodiratime, loud, bind, move, shared, slave,
//config:       private, unbindable, rshared, rslave, rprivate, and runbindable.
//config:
//config:config FEATURE_MOUNT_FSTAB
//config:       depends on MOUNT
//config:       bool "Support /etc/fstab and -a (mount all)"
//config:       default y
//config:       help
//config:       Support mount all and looking for files in /etc/fstab.
//config:
//config:config FEATURE_MOUNT_OTHERTAB
//config:       depends on FEATURE_MOUNT_FSTAB
//config:       bool "Support -T <alt_fstab>"
//config:       default y
//config:       help
//config:       Support mount -T (specifying an alternate fstab)

/* On full-blown systems, requires suid for user mounts.
 * But it's not unthinkable to have it available in non-suid flavor on some systems,
 * for viewing mount table.
 * Therefore we use BB_SUID_MAYBE instead of BB_SUID_REQUIRE: */
//applet:IF_MOUNT(APPLET(mount, BB_DIR_BIN, IF_DESKTOP(BB_SUID_MAYBE) IF_NOT_DESKTOP(BB_SUID_DROP)))

//kbuild:lib-$(CONFIG_MOUNT) += mount.o

//usage:#define mount_trivial_usage
//usage:       "[OPTIONS] [-o OPT] DEVICE NODE"
//usage:#define mount_full_usage "\n\n"
//usage:       "Mount a filesystem. Filesystem autodetection requires /proc.\n"
//usage:     "\n        -a              Mount all filesystems in fstab"
//usage:        IF_FEATURE_MOUNT_FAKE(
//usage:        IF_FEATURE_MTAB_SUPPORT(
//usage:     "\n        -f              Update /etc/mtab, but don't mount"
//usage:        )
//usage:        IF_NOT_FEATURE_MTAB_SUPPORT(
//usage:     "\n        -f              Dry run"
//usage:        )
//usage:        )
//usage:        IF_FEATURE_MOUNT_HELPERS(
//usage:     "\n        -i              Don't run mount helper"
//usage:        )
//usage:        IF_FEATURE_MTAB_SUPPORT(
//usage:     "\n        -n              Don't update /etc/mtab"
//usage:        )
//usage:        IF_FEATURE_MOUNT_VERBOSE(
//usage:     "\n        -v              Verbose"
//usage:        )
////usage:   "\n        -s              Sloppy (ignored)"
//usage:     "\n        -r              Read-only mount"
////usage:     "\n      -w              Read-write mount (default)"
//usage:     "\n        -t FSTYPE[,...] Filesystem type(s)"
//usage:        IF_FEATURE_MOUNT_OTHERTAB(
//usage:     "\n        -T FILE         Read FILE instead of /etc/fstab"
//usage:        )
//usage:     "\n        -O OPT          Mount only filesystems with option OPT (-a only)"
//usage:     "\n-o OPT:"
//usage:        IF_FEATURE_MOUNT_LOOP(
//usage:     "\n        loop            Ignored (loop devices are autodetected)"
//usage:        )
//usage:        IF_FEATURE_MOUNT_FLAGS(
//usage:     "\n        [a]sync         Writes are [a]synchronous"
//usage:     "\n        [no]atime       Disable/enable updates to inode access times"
//usage:     "\n        [no]diratime    Disable/enable atime updates to directories"
//usage:     "\n        [no]relatime    Disable/enable atime updates relative to modification time"
//usage:     "\n        [no]dev         (Dis)allow use of special device files"
//usage:     "\n        [no]exec        (Dis)allow use of executable files"
//usage:     "\n        [no]suid        (Dis)allow set-user-id-root programs"
//usage:     "\n        [r]shared       Convert [recursively] to a shared subtree"
//usage:     "\n        [r]slave        Convert [recursively] to a slave subtree"
//usage:     "\n        [r]private      Convert [recursively] to a private subtree"
//usage:     "\n        [un]bindable    Make mount point [un]able to be bind mounted"
//usage:     "\n        [r]bind         Bind a file or directory [recursively] to another location"
//usage:     "\n        move            Relocate an existing mount point"
//usage:        )
//usage:     "\n        remount         Remount a mounted filesystem, changing flags"
//usage:     "\n        ro              Same as -r"
//usage:     "\n"
//usage:     "\nThere are filesystem-specific -o flags."
//usage:
//usage:#define mount_example_usage
//usage:       "$ mount\n"
//usage:       "/dev/hda3 on / type minix (rw)\n"
//usage:       "proc on /proc type proc (rw)\n"
//usage:       "devpts on /dev/pts type devpts (rw)\n"
//usage:       "$ mount /dev/fd0 /mnt -t msdos -o ro\n"
//usage:       "$ mount /tmp/diskimage /opt -t ext2 -o loop\n"
//usage:       "$ mount cd_image.iso mydir\n"
//usage:#define mount_notes_usage
//usage:       "Returns 0 for success, number of failed mounts for -a, or errno for one mount."

#include <mntent.h>
#include <syslog.h>
#include <sys/mount.h>
// Grab more as needed from util-linux's mount/mount_constants.h
#ifndef MS_DIRSYNC
# define MS_DIRSYNC     (1 << 7) // Directory modifications are synchronous
#endif
#ifndef MS_UNION
# define MS_UNION       (1 << 8)
#endif
#ifndef MS_BIND
# define MS_BIND        (1 << 12)
#endif
#ifndef MS_MOVE
# define MS_MOVE        (1 << 13)
#endif
#ifndef MS_RECURSIVE
# define MS_RECURSIVE   (1 << 14)
#endif
#ifndef MS_SILENT
# define MS_SILENT      (1 << 15)
#endif
// The shared subtree stuff, which went in around 2.6.15
#ifndef MS_UNBINDABLE
# define MS_UNBINDABLE  (1 << 17)
#endif
#ifndef MS_PRIVATE
# define MS_PRIVATE     (1 << 18)
#endif
#ifndef MS_SLAVE
# define MS_SLAVE       (1 << 19)
#endif
#ifndef MS_SHARED
# define MS_SHARED      (1 << 20)
#endif
#ifndef MS_RELATIME
# define MS_RELATIME    (1 << 21)
#endif
#ifndef MS_STRICTATIME
# define MS_STRICTATIME (1 << 24)
#endif

/* Any ~MS_FOO value has this bit set: */
#define BB_MS_INVERTED_VALUE (1u << 31)

#include "libbb.h"
#include "common_bufsiz.h"
#if ENABLE_FEATURE_MOUNT_LABEL
# include "volume_id.h"
#else
# define resolve_mount_spec(fsname) ((void)0)
#endif

// Needed for nfs support only
#include <sys/utsname.h>
#undef TRUE
#undef FALSE
#if ENABLE_FEATURE_MOUNT_NFS
/* This is just a warning of a common mistake.  Possibly this should be a
 * uclibc faq entry rather than in busybox... */
# if defined(__UCLIBC__) && ! defined(__UCLIBC_HAS_RPC__)
#  warning "You probably need to build uClibc with UCLIBC_HAS_RPC for NFS support"
   /* not #error, since user may be using e.g. libtirpc instead.
    * This might work:
    * CONFIG_EXTRA_CFLAGS="-I/usr/include/tirpc"
    * CONFIG_EXTRA_LDLIBS="tirpc"
    */
# endif
# include <rpc/rpc.h>
# include <rpc/pmap_prot.h>
# include <rpc/pmap_clnt.h>
#endif


#if defined(__dietlibc__)
// 16.12.2006, Sampo Kellomaki (sampo@iki.fi)
// dietlibc-0.30 does not have implementation of getmntent_r()
static struct mntent *getmntent_r(FILE* stream, struct mntent* result,
                char* buffer UNUSED_PARAM, int bufsize UNUSED_PARAM)
{
        struct mntent* ment = getmntent(stream);
        return memcpy(result, ment, sizeof(*ment));
}
#endif


// Not real flags, but we want to be able to check for this.
enum {
        MOUNT_USERS  = (1 << 27) * ENABLE_DESKTOP,
        MOUNT_NOFAIL = (1 << 28) * ENABLE_DESKTOP,
        MOUNT_NOAUTO = (1 << 29),
        MOUNT_SWAP   = (1 << 30),
        MOUNT_FAKEFLAGS = MOUNT_USERS | MOUNT_NOFAIL | MOUNT_NOAUTO | MOUNT_SWAP
};


#define OPTION_STR "o:*t:rwanfvsiO:" IF_FEATURE_MOUNT_OTHERTAB("T:")
enum {
        OPT_o = (1 << 0),
        OPT_t = (1 << 1),
        OPT_r = (1 << 2),
        OPT_w = (1 << 3),
        OPT_a = (1 << 4),
        OPT_n = (1 << 5),
        OPT_f = (1 << 6),
        OPT_v = (1 << 7),
        OPT_s = (1 << 8),
        OPT_i = (1 << 9),
        OPT_O = (1 << 10),
        OPT_T = (1 << 11),
};

#if ENABLE_FEATURE_MTAB_SUPPORT
#define USE_MTAB (!(option_mask32 & OPT_n))
#else
#define USE_MTAB 0
#endif

#if ENABLE_FEATURE_MOUNT_FAKE
#define FAKE_IT (option_mask32 & OPT_f)
#else
#define FAKE_IT 0
#endif

#if ENABLE_FEATURE_MOUNT_HELPERS
#define HELPERS_ALLOWED (!(option_mask32 & OPT_i))
#else
#define HELPERS_ALLOWED 0
#endif


// TODO: more "user" flag compatibility.
// "user" option (from mount manpage):
// Only the user that mounted a filesystem can unmount it again.
// If any user should be able to unmount, then use users instead of user
// in the fstab line.  The owner option is similar to the user option,
// with the restriction that the user must be the owner of the special file.
// This may be useful e.g. for /dev/fd if a login script makes
// the console user owner of this device.

// Standard mount options (from -o options or --options),
// with corresponding flags
static const int32_t mount_options[] = {
        // MS_FLAGS set a bit.  ~MS_FLAGS disable that bit.  0 flags are NOPs.

        IF_FEATURE_MOUNT_LOOP(
                /* "loop" */ 0,
        )

        IF_FEATURE_MOUNT_FSTAB(
                /* "defaults" */ 0,
                /* "quiet" 0 - do not filter out, vfat wants to see it */
                /* "noauto" */ MOUNT_NOAUTO,
                /* "sw"     */ MOUNT_SWAP,
                /* "swap"   */ MOUNT_SWAP,
                IF_DESKTOP(/* "user"  */ MOUNT_USERS,)
                IF_DESKTOP(/* "users" */ MOUNT_USERS,)
                IF_DESKTOP(/* "nofail" */ MOUNT_NOFAIL,)
                /* "_netdev" */ 0,
                IF_DESKTOP(/* "comment=" */ 0,) /* systemd uses this in fstab */
        )

        IF_FEATURE_MOUNT_FLAGS(
                // vfs flags
                /* "nosuid"      */ MS_NOSUID,
                /* "suid"        */ ~MS_NOSUID,
                /* "dev"         */ ~MS_NODEV,
                /* "nodev"       */ MS_NODEV,
                /* "exec"        */ ~MS_NOEXEC,
                /* "noexec"      */ MS_NOEXEC,
                /* "sync"        */ MS_SYNCHRONOUS,
                /* "dirsync"     */ MS_DIRSYNC,
                /* "async"       */ ~MS_SYNCHRONOUS,
                /* "atime"       */ ~MS_NOATIME,
                /* "noatime"     */ MS_NOATIME,
                /* "diratime"    */ ~MS_NODIRATIME,
                /* "nodiratime"  */ MS_NODIRATIME,
                /* "mand"        */ MS_MANDLOCK,
                /* "nomand"      */ ~MS_MANDLOCK,
                /* "relatime"    */ MS_RELATIME,
                /* "norelatime"  */ ~MS_RELATIME,
                /* "strictatime" */ MS_STRICTATIME,
                /* "loud"        */ ~MS_SILENT,
                /* "rbind"       */ MS_BIND|MS_RECURSIVE,

                // action flags
                /* "union"       */ MS_UNION,
                /* "bind"        */ MS_BIND,
                /* "move"        */ MS_MOVE,
                /* "shared"      */ MS_SHARED,
                /* "slave"       */ MS_SLAVE,
                /* "private"     */ MS_PRIVATE,
                /* "unbindable"  */ MS_UNBINDABLE,
                /* "rshared"     */ MS_SHARED|MS_RECURSIVE,
                /* "rslave"      */ MS_SLAVE|MS_RECURSIVE,
                /* "rprivate"    */ MS_PRIVATE|MS_RECURSIVE,
                /* "runbindable" */ MS_UNBINDABLE|MS_RECURSIVE,
        )

        // Always understood.
        /* "ro"      */ MS_RDONLY,  // vfs flag
        /* "rw"      */ ~MS_RDONLY, // vfs flag
        /* "remount" */ MS_REMOUNT  // action flag
};

static const char mount_option_str[] ALIGN1 =
        IF_FEATURE_MOUNT_LOOP(
                "loop\0"
        )
        IF_FEATURE_MOUNT_FSTAB(
                "defaults\0"
                // "quiet\0" - do not filter out, vfat wants to see it
                "noauto\0"
                "sw\0"
                "swap\0"
                IF_DESKTOP("user\0")
                IF_DESKTOP("users\0")
                IF_DESKTOP("nofail\0")
                "_netdev\0"
                IF_DESKTOP("comment=\0") /* systemd uses this in fstab */
        )
        IF_FEATURE_MOUNT_FLAGS(
                // vfs flags
                "nosuid\0"
                "suid\0"
                "dev\0"
                "nodev\0"
                "exec\0"
                "noexec\0"
                "sync\0"
                "dirsync\0"
                "async\0"
                "atime\0"
                "noatime\0"
                "diratime\0"
                "nodiratime\0"
                "mand\0"
                "nomand\0"
                "relatime\0"
                "norelatime\0"
                "strictatime\0"
                "loud\0"
                "rbind\0"

                // action flags
                "union\0"
                "bind\0"
                "move\0"
                "make-shared\0"
                "make-slave\0"
                "make-private\0"
                "make-unbindable\0"
                "make-rshared\0"
                "make-rslave\0"
                "make-rprivate\0"
                "make-runbindable\0"
        )

        // Always understood.
        "ro\0"        // vfs flag
        "rw\0"        // vfs flag
        "remount\0"   // action flag
;


struct globals {
#if ENABLE_FEATURE_MOUNT_NFS
        smalluint nfs_mount_version;
#endif
#if ENABLE_FEATURE_MOUNT_VERBOSE
        unsigned verbose;
#endif
        llist_t *fslist;
        char getmntent_buf[1];
} FIX_ALIASING;
enum { GETMNTENT_BUFSIZE = COMMON_BUFSIZE - offsetof(struct globals, getmntent_buf) };
#define G (*(struct globals*)bb_common_bufsiz1)
#define nfs_mount_version (G.nfs_mount_version)
#if ENABLE_FEATURE_MOUNT_VERBOSE
#define verbose           (G.verbose          )
#else
#define verbose           0
#endif
#define fslist            (G.fslist           )
#define getmntent_buf     (G.getmntent_buf    )
#define INIT_G() do { setup_common_bufsiz(); } while (0)

#if ENABLE_FEATURE_MTAB_SUPPORT
/*
 * update_mtab_entry_on_move() is used to update entry in case of mount --move.
 * we are looking for existing entries mnt_dir which is equal to mnt_fsname of
 * input mntent and replace it by new one.
 */
static void FAST_FUNC update_mtab_entry_on_move(const struct mntent *mp)
{
        struct mntent *entries, *m;
        int i, count;
        FILE *mountTable;

        mountTable = setmntent(bb_path_mtab_file, "r");
        if (!mountTable) {
                bb_perror_msg(bb_path_mtab_file);
                return;
        }

        entries = NULL;
        count = 0;
        while ((m = getmntent(mountTable)) != NULL) {
                entries = xrealloc_vector(entries, 3, count);
                entries[count].mnt_fsname = xstrdup(m->mnt_fsname);
                entries[count].mnt_dir = xstrdup(m->mnt_dir);
                entries[count].mnt_type = xstrdup(m->mnt_type);
                entries[count].mnt_opts = xstrdup(m->mnt_opts);
                entries[count].mnt_freq = m->mnt_freq;
                entries[count].mnt_passno = m->mnt_passno;
                count++;
        }
        endmntent(mountTable);

        mountTable = setmntent(bb_path_mtab_file, "w");
        if (mountTable) {
                for (i = 0; i < count; i++) {
                        if (strcmp(entries[i].mnt_dir, mp->mnt_fsname) != 0)
                                addmntent(mountTable, &entries[i]);
                        else
                                addmntent(mountTable, mp);
                }
                endmntent(mountTable);
        } else if (errno != EROFS)
                bb_perror_msg(bb_path_mtab_file);

        if (ENABLE_FEATURE_CLEAN_UP) {
                for (i = 0; i < count; i++) {
                        free(entries[i].mnt_fsname);
                        free(entries[i].mnt_dir);
                        free(entries[i].mnt_type);
                        free(entries[i].mnt_opts);
                }
                free(entries);
        }
}
#endif

#if ENABLE_FEATURE_MOUNT_VERBOSE
static int verbose_mount(const char *source, const char *target,
                const char *filesystemtype,
                unsigned long mountflags, const void *data)
{
        int rc;

        errno = 0;
        rc = mount(source, target, filesystemtype, mountflags, data);
        if (verbose >= 2)
                bb_perror_msg("mount('%s','%s','%s',0x%08lx,'%s'):%d",
                        source, target, filesystemtype,
                        mountflags, (char*)data, rc);
        return rc;
}
#else
#define verbose_mount(...) mount(__VA_ARGS__)
#endif

// Append mount options to string
static void append_mount_options(char **oldopts, const char *newopts)
{
        if (*oldopts && **oldopts) {
                // Do not insert options which are already there
                while (newopts[0]) {
                        char *p;
                        int len = strlen(newopts);
                        p = strchr(newopts, ',');
                        if (p) len = p - newopts;
                        p = *oldopts;
                        while (1) {
                                if (!strncmp(p, newopts, len)
                                 && (p[len] == ',' || p[len] == '\0'))
                                        goto skip;
                                p = strchr(p,',');
                                if (!p) break;
                                p++;
                        }
                        p = xasprintf("%s,%.*s", *oldopts, len, newopts);
                        free(*oldopts);
                        *oldopts = p;
 skip:
                        newopts += len;
                        while (newopts[0] == ',') newopts++;
                }
        } else {
                if (ENABLE_FEATURE_CLEAN_UP) free(*oldopts);
                *oldopts = xstrdup(newopts);
        }
}

// Use the mount_options list to parse options into flags.
// Also update list of unrecognized options if unrecognized != NULL
static unsigned long parse_mount_options(char *options, char **unrecognized)
{
        unsigned long flags = MS_SILENT;

        // Loop through options
        for (;;) {
                unsigned i;
                char *comma = strchr(options, ',');
                const char *option_str = mount_option_str;

                if (comma) *comma = '\0';

// FIXME: use hasmntopt()
                // Find this option in mount_options
                for (i = 0; i < ARRAY_SIZE(mount_options); i++) {
                        unsigned opt_len = strlen(option_str);

                        if (strncasecmp(option_str, options, opt_len) == 0
                         && (options[opt_len] == '\0'
                            /* or is it "comment=" thingy in fstab? */
                            IF_FEATURE_MOUNT_FSTAB(IF_DESKTOP( || option_str[opt_len-1] == '=' ))
                            )
                        ) {
                                unsigned long fl = mount_options[i];
                                if (fl & BB_MS_INVERTED_VALUE)
                                        flags &= fl;
                                else
                                        flags |= fl;
                                goto found;
                        }
                        option_str += opt_len + 1;
                }
                // We did not recognize this option.
                // If "unrecognized" is not NULL, append option there.
                // Note that we should not append *empty* option -
                // in this case we want to pass NULL, not "", to "data"
                // parameter of mount(2) syscall.
                // This is crucial for filesystems that don't accept
                // any arbitrary mount options, like cgroup fs:
                // "mount -t cgroup none /mnt"
                if (options[0] && unrecognized) {
                        // Add it to strflags, to pass on to kernel
                        char *p = *unrecognized;
                        unsigned len = p ? strlen(p) : 0;
                        *unrecognized = p = xrealloc(p, len + strlen(options) + 2);

                        // Comma separated if it's not the first one
                        if (len) p[len++] = ',';
                        strcpy(p + len, options);
                }
 found:
                if (!comma)
                        break;
                // Advance to next option
                *comma = ',';
                options = ++comma;
        }

        return flags;
}

// Return a list of all block device backed filesystems
static llist_t *get_block_backed_filesystems(void)
{
        static const char filesystems[2][sizeof("/proc/filesystems")] = {
                "/etc/filesystems",
                "/proc/filesystems",
        };
        char *fs, *buf;
        llist_t *list = NULL;
        int i;
        FILE *f;

        for (i = 0; i < 2; i++) {
                f = fopen_for_read(filesystems[i]);
                if (!f) continue;

                while ((buf = xmalloc_fgetline(f)) != NULL) {
                        if (is_prefixed_with(buf, "nodev") && isspace(buf[5]))
                                goto next;
                        fs = skip_whitespace(buf);
                        if (*fs == '#' || *fs == '*' || !*fs)
                                goto next;

                        llist_add_to_end(&list, xstrdup(fs));
 next:
                        free(buf);
                }
                if (ENABLE_FEATURE_CLEAN_UP) fclose(f);
        }

        return list;
}

#if ENABLE_FEATURE_CLEAN_UP
static void delete_block_backed_filesystems(void)
{
        llist_free(fslist, free);
}
#else
void delete_block_backed_filesystems(void);
#endif

// Perform actual mount of specific filesystem at specific location.
// NB: mp->xxx fields may be trashed on exit
static int mount_it_now(struct mntent *mp, unsigned long vfsflags, char *filteropts)
{
        int rc = 0;

        vfsflags &= ~(unsigned long)MOUNT_FAKEFLAGS;

        if (FAKE_IT) {
                if (verbose >= 2)
                        bb_error_msg("would do mount('%s','%s','%s',0x%08lx,'%s')",
                                mp->mnt_fsname, mp->mnt_dir, mp->mnt_type,
                                vfsflags, filteropts);
                goto mtab;
        }

        // Mount, with fallback to read-only if necessary.
        for (;;) {
                errno = 0;
                rc = verbose_mount(mp->mnt_fsname, mp->mnt_dir, mp->mnt_type,
                                vfsflags, filteropts);

                // If mount failed, try
                // helper program mount.<mnt_type>
                if (HELPERS_ALLOWED && rc && mp->mnt_type) {
                        char *args[8];
                        int errno_save = errno;
                        args[0] = xasprintf("mount.%s", mp->mnt_type);
                        rc = 1;
                        if (FAKE_IT)
                                args[rc++] = (char *)"-f";
                        if (ENABLE_FEATURE_MTAB_SUPPORT && !USE_MTAB)
                                args[rc++] = (char *)"-n";
                        args[rc++] = mp->mnt_fsname;
                        args[rc++] = mp->mnt_dir;
                        if (filteropts) {
                                args[rc++] = (char *)"-o";
                                args[rc++] = filteropts;
                        }
                        args[rc] = NULL;
                        rc = spawn_and_wait(args);
                        free(args[0]);
                        if (!rc)
                                break;
                        errno = errno_save;
                }

                if (!rc || (vfsflags & MS_RDONLY) || (errno != EACCES && errno != EROFS))
                        break;
                if (!(vfsflags & MS_SILENT))
                        bb_error_msg("%s is write-protected, mounting read-only",
                                                mp->mnt_fsname);
                vfsflags |= MS_RDONLY;
        }

        // Abort entirely if permission denied.

        if (rc && errno == EPERM)
                bb_error_msg_and_die(bb_msg_perm_denied_are_you_root);

        // If the mount was successful, and we're maintaining an old-style
        // mtab file by hand, add the new entry to it now.
 mtab:
        if (USE_MTAB && !rc && !(vfsflags & MS_REMOUNT)) {
                char *fsname;
                FILE *mountTable = setmntent(bb_path_mtab_file, "a+");
                const char *option_str = mount_option_str;
                int i;

                if (!mountTable) {
                        bb_perror_msg(bb_path_mtab_file);
                        goto ret;
                }

                // Add vfs string flags
                for (i = 0; mount_options[i] != MS_REMOUNT; i++) {
                        if (mount_options[i] > 0 && (mount_options[i] & vfsflags))
                                append_mount_options(&(mp->mnt_opts), option_str);
                        option_str += strlen(option_str) + 1;
                }

                // Remove trailing / (if any) from directory we mounted on
                i = strlen(mp->mnt_dir) - 1;
                while (i > 0 && mp->mnt_dir[i] == '/')
                        mp->mnt_dir[i--] = '\0';

                // Convert to canonical pathnames as needed
                mp->mnt_dir = bb_simplify_path(mp->mnt_dir);
                fsname = NULL;
                if (!mp->mnt_type || !*mp->mnt_type) { // bind mount
                        mp->mnt_fsname = fsname = bb_simplify_path(mp->mnt_fsname);
                        mp->mnt_type = (char*)"bind";
                }
                mp->mnt_freq = mp->mnt_passno = 0;

                // Write and close
#if ENABLE_FEATURE_MTAB_SUPPORT
                if (vfsflags & MS_MOVE)
                        update_mtab_entry_on_move(mp);
                else
#endif
                        addmntent(mountTable, mp);
                endmntent(mountTable);

                if (ENABLE_FEATURE_CLEAN_UP) {
                        free(mp->mnt_dir);
                        free(fsname);
                }
        }
 ret:
        return rc;
}

#if ENABLE_FEATURE_MOUNT_NFS

/*
 * Linux NFS mount
 * Copyright (C) 1993 Rick Sladkey <jrs@world.std.com>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 *
 * Wed Feb  8 12:51:48 1995, biro@yggdrasil.com (Ross Biro): allow all port
 * numbers to be specified on the command line.
 *
 * Fri, 8 Mar 1996 18:01:39, Swen Thuemmler <swen@uni-paderborn.de>:
 * Omit the call to connect() for Linux version 1.3.11 or later.
 *
 * Wed Oct  1 23:55:28 1997: Dick Streefland <dick_streefland@tasking.com>
 * Implemented the "bg", "fg" and "retry" mount options for NFS.
 *
 * 1999-02-22 Arkadiusz Mickiewicz <misiek@misiek.eu.org>
 * - added Native Language Support
 *
 * Modified by Olaf Kirch and Trond Myklebust for new NFS code,
 * plus NFSv3 stuff.
 */

#define MOUNTPORT 635
#define MNTPATHLEN 1024
#define MNTNAMLEN 255
#define FHSIZE 32
#define FHSIZE3 64

typedef char fhandle[FHSIZE];

typedef struct {
        unsigned int fhandle3_len;
        char *fhandle3_val;
} fhandle3;

enum mountstat3 {
        MNT_OK = 0,
        MNT3ERR_PERM = 1,
        MNT3ERR_NOENT = 2,
        MNT3ERR_IO = 5,
        MNT3ERR_ACCES = 13,
        MNT3ERR_NOTDIR = 20,
        MNT3ERR_INVAL = 22,
        MNT3ERR_NAMETOOLONG = 63,
        MNT3ERR_NOTSUPP = 10004,
        MNT3ERR_SERVERFAULT = 10006,
};
typedef enum mountstat3 mountstat3;

struct fhstatus {
        unsigned int fhs_status;
        union {
                fhandle fhs_fhandle;
        } fhstatus_u;
};
typedef struct fhstatus fhstatus;

struct mountres3_ok {
        fhandle3 fhandle;
        struct {
                unsigned int auth_flavours_len;
                char *auth_flavours_val;
        } auth_flavours;
};
typedef struct mountres3_ok mountres3_ok;

struct mountres3 {
        mountstat3 fhs_status;
        union {
                mountres3_ok mountinfo;
        } mountres3_u;
};
typedef struct mountres3 mountres3;

typedef char *dirpath;

typedef char *name;

typedef struct mountbody *mountlist;

struct mountbody {
        name ml_hostname;
        dirpath ml_directory;
        mountlist ml_next;
};
typedef struct mountbody mountbody;

typedef struct groupnode *groups;

struct groupnode {
        name gr_name;
        groups gr_next;
};
typedef struct groupnode groupnode;

typedef struct exportnode *exports;

struct exportnode {
        dirpath ex_dir;
        groups ex_groups;
        exports ex_next;
};
typedef struct exportnode exportnode;

struct ppathcnf {
        int pc_link_max;
        short pc_max_canon;
        short pc_max_input;
        short pc_name_max;
        short pc_path_max;
        short pc_pipe_buf;
        uint8_t pc_vdisable;
        char pc_xxx;
        short pc_mask[2];
};
typedef struct ppathcnf ppathcnf;

#define MOUNTPROG 100005
#define MOUNTVERS 1

#define MOUNTPROC_NULL 0
#define MOUNTPROC_MNT 1
#define MOUNTPROC_DUMP 2
#define MOUNTPROC_UMNT 3
#define MOUNTPROC_UMNTALL 4
#define MOUNTPROC_EXPORT 5
#define MOUNTPROC_EXPORTALL 6

#define MOUNTVERS_POSIX 2

#define MOUNTPROC_PATHCONF 7

#define MOUNT_V3 3

#define MOUNTPROC3_NULL 0
#define MOUNTPROC3_MNT 1
#define MOUNTPROC3_DUMP 2
#define MOUNTPROC3_UMNT 3
#define MOUNTPROC3_UMNTALL 4
#define MOUNTPROC3_EXPORT 5

enum {
#ifndef NFS_FHSIZE
        NFS_FHSIZE = 32,
#endif
#ifndef NFS_PORT
        NFS_PORT = 2049
#endif
};

/*
 * We want to be able to compile mount on old kernels in such a way
 * that the binary will work well on more recent kernels.
 * Thus, if necessary we teach nfsmount.c the structure of new fields
 * that will come later.
 *
 * Moreover, the new kernel includes conflict with glibc includes
 * so it is easiest to ignore the kernel altogether (at compile time).
 */

struct nfs2_fh {
        char            data[32];
};
struct nfs3_fh {
        unsigned short  size;
        unsigned char   data[64];
};

struct nfs_mount_data {
        int             version;        /* 1 */
        int             fd;             /* 1 */
        struct nfs2_fh  old_root;       /* 1 */
        int             flags;          /* 1 */
        int             rsize;          /* 1 */
        int             wsize;          /* 1 */
        int             timeo;          /* 1 */
        int             retrans;        /* 1 */
        int             acregmin;       /* 1 */
        int             acregmax;       /* 1 */
        int             acdirmin;       /* 1 */
        int             acdirmax;       /* 1 */
        struct sockaddr_in addr;        /* 1 */
        char            hostname[256];  /* 1 */
        int             namlen;         /* 2 */
        unsigned int    bsize;          /* 3 */
        struct nfs3_fh  root;           /* 4 */
};

/* bits in the flags field */
enum {
        NFS_MOUNT_SOFT = 0x0001,        /* 1 */
        NFS_MOUNT_INTR = 0x0002,        /* 1 */
        NFS_MOUNT_SECURE = 0x0004,      /* 1 */
        NFS_MOUNT_POSIX = 0x0008,       /* 1 */
        NFS_MOUNT_NOCTO = 0x0010,       /* 1 */
        NFS_MOUNT_NOAC = 0x0020,        /* 1 */
        NFS_MOUNT_TCP = 0x0040,         /* 2 */
        NFS_MOUNT_VER3 = 0x0080,        /* 3 */
        NFS_MOUNT_KERBEROS = 0x0100,    /* 3 */
        NFS_MOUNT_NONLM = 0x0200,       /* 3 */
        NFS_MOUNT_NOACL = 0x0800,       /* 4 */
        NFS_MOUNT_NORDIRPLUS = 0x4000

};


/*
 * We need to translate between nfs status return values and
 * the local errno values which may not be the same.
 *
 * Andreas Schwab <schwab@LS5.informatik.uni-dortmund.de>: change errno:
 * "after #include <errno.h> the symbol errno is reserved for any use,
 *  it cannot even be used as a struct tag or field name".
 */
#ifndef EDQUOT
# define EDQUOT ENOSPC
#endif
/* Convert each NFSERR_BLAH into EBLAH */
static const uint8_t nfs_err_stat[] ALIGN1 = {
         1,  2,  5,  6, 13, 17,
        19, 20, 21, 22, 27, 28,
        30, 63, 66, 69, 70, 71
};
#if ( \
        EPERM | ENOENT      | EIO      | ENXIO | EACCES| EEXIST | \
        ENODEV| ENOTDIR     | EISDIR   | EINVAL| EFBIG | ENOSPC | \
        EROFS | ENAMETOOLONG| ENOTEMPTY| EDQUOT| ESTALE| EREMOTE) < 256
typedef uint8_t nfs_err_type;
#else
typedef uint16_t nfs_err_type;
#endif
static const nfs_err_type nfs_err_errnum[] ALIGN2 = {
        EPERM , ENOENT      , EIO      , ENXIO , EACCES, EEXIST,
        ENODEV, ENOTDIR     , EISDIR   , EINVAL, EFBIG , ENOSPC,
        EROFS , ENAMETOOLONG, ENOTEMPTY, EDQUOT, ESTALE, EREMOTE
};
static char *nfs_strerror(int status)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(nfs_err_stat); i++) {
                if (nfs_err_stat[i] == status)
                        return strerror(nfs_err_errnum[i]);
        }
        return xasprintf("unknown nfs status return value: %d", status);
}

static bool_t xdr_fhandle(XDR *xdrs, fhandle objp)
{
        return xdr_opaque(xdrs, objp, FHSIZE);
}

static bool_t xdr_fhstatus(XDR *xdrs, fhstatus *objp)
{
        if (!xdr_u_int(xdrs, &objp->fhs_status))
                return FALSE;
        if (objp->fhs_status == 0)
                return xdr_fhandle(xdrs, objp->fhstatus_u.fhs_fhandle);
        return TRUE;
}

static bool_t xdr_dirpath(XDR *xdrs, dirpath *objp)
{
        return xdr_string(xdrs, objp, MNTPATHLEN);
}

static bool_t xdr_fhandle3(XDR *xdrs, fhandle3 *objp)
{
        return xdr_bytes(xdrs, (char **)&objp->fhandle3_val,
                        (unsigned int *) &objp->fhandle3_len,
                        FHSIZE3);
}

static bool_t xdr_mountres3_ok(XDR *xdrs, mountres3_ok *objp)
{
        if (!xdr_fhandle3(xdrs, &objp->fhandle))
                return FALSE;
        return xdr_array(xdrs, &(objp->auth_flavours.auth_flavours_val),
                        &(objp->auth_flavours.auth_flavours_len),
                        ~0,
                        sizeof(int),
                        (xdrproc_t) xdr_int);
}

static bool_t xdr_mountstat3(XDR *xdrs, mountstat3 *objp)
{
        return xdr_enum(xdrs, (enum_t *) objp);
}

static bool_t xdr_mountres3(XDR *xdrs, mountres3 *objp)
{
        if (!xdr_mountstat3(xdrs, &objp->fhs_status))
                return FALSE;
        if (objp->fhs_status == MNT_OK)
                return xdr_mountres3_ok(xdrs, &objp->mountres3_u.mountinfo);
        return TRUE;
}

#define MAX_NFSPROT ((nfs_mount_version >= 4) ? 3 : 2)

/*
 * Unfortunately, the kernel prints annoying console messages
 * in case of an unexpected nfs mount version (instead of
 * just returning some error).  Therefore we'll have to try
 * and figure out what version the kernel expects.
 *
 * Variables:
 *      KERNEL_NFS_MOUNT_VERSION: kernel sources at compile time
 *      NFS_MOUNT_VERSION: these nfsmount sources at compile time
 *      nfs_mount_version: version this source and running kernel can handle
 */
static void
find_kernel_nfs_mount_version(void)
{
        int kernel_version;

        if (nfs_mount_version)
                return;

        nfs_mount_version = 4; /* default */

        kernel_version = get_linux_version_code();
        if (kernel_version) {
                if (kernel_version < KERNEL_VERSION(2,2,18))
                        nfs_mount_version = 3;
                /* else v4 since 2.3.99pre4 */
        }
}

static void
get_mountport(struct pmap *pm_mnt,
        struct sockaddr_in *server_addr,
        long unsigned prog,
        long unsigned version,
        long unsigned proto,
        long unsigned port)
{
        struct pmaplist *pmap;

        server_addr->sin_port = PMAPPORT;
/* glibc 2.4 (still) has pmap_getmaps(struct sockaddr_in *).
 * I understand it like "IPv6 for this is not 100% ready" */
        pmap = pmap_getmaps(server_addr);

        if (version > MAX_NFSPROT)
                version = MAX_NFSPROT;
        if (!prog)
                prog = MOUNTPROG;
        pm_mnt->pm_prog = prog;
        pm_mnt->pm_vers = version;
        pm_mnt->pm_prot = proto;
        pm_mnt->pm_port = port;

        while (pmap) {
                if (pmap->pml_map.pm_prog != prog)
                        goto next;
                if (!version && pm_mnt->pm_vers > pmap->pml_map.pm_vers)
                        goto next;
                if (version > 2 && pmap->pml_map.pm_vers != version)
                        goto next;
                if (version && version <= 2 && pmap->pml_map.pm_vers > 2)
                        goto next;
                if (pmap->pml_map.pm_vers > MAX_NFSPROT
                 || (proto && pm_mnt->pm_prot && pmap->pml_map.pm_prot != proto)
                 || (port && pmap->pml_map.pm_port != port)
                ) {
                        goto next;
                }
                memcpy(pm_mnt, &pmap->pml_map, sizeof(*pm_mnt));
 next:
                pmap = pmap->pml_next;
        }
        if (!pm_mnt->pm_vers)
                pm_mnt->pm_vers = MOUNTVERS;
        if (!pm_mnt->pm_port)
                pm_mnt->pm_port = MOUNTPORT;
        if (!pm_mnt->pm_prot)
                pm_mnt->pm_prot = IPPROTO_TCP;
}

#if BB_MMU
static int daemonize(void)
{
        int pid = fork();
        if (pid < 0) /* error */
                return -errno;
        if (pid > 0) /* parent */
                return 0;
        /* child */
        close(0);
        xopen(bb_dev_null, O_RDWR);
        xdup2(0, 1);
        xdup2(0, 2);
        setsid();
        openlog(applet_name, LOG_PID, LOG_DAEMON);
        logmode = LOGMODE_SYSLOG;
        return 1;
}
#else
static inline int daemonize(void)
{
        return -ENOSYS;
}
#endif

/* TODO */
static inline int we_saw_this_host_before(const char *hostname UNUSED_PARAM)
{
        return 0;
}

/* RPC strerror analogs are terminally idiotic:
 * *mandatory* prefix and \n at end.
 * This hopefully helps. Usage:
 * error_msg_rpc(clnt_*error*(" ")) */
static void error_msg_rpc(const char *msg)
{
        int len;
        while (msg[0] == ' ' || msg[0] == ':') msg++;
        len = strlen(msg);
        while (len && msg[len-1] == '\n') len--;
        bb_error_msg("%.*s", len, msg);
}

/* NB: mp->xxx fields may be trashed on exit */
static NOINLINE int nfsmount(struct mntent *mp, unsigned long vfsflags, char *filteropts)
{
        CLIENT *mclient;
        char *hostname;
        char *pathname;
        char *mounthost;
        /* prior to 2.6.23, kernel took NFS options in a form of this struct
         * only. 2.6.23+ looks at data->version, and if it's not 1..6,
         * then data pointer is interpreted as a string. */
        struct nfs_mount_data data;
        char *opt;
        struct hostent *hp;
        struct sockaddr_in server_addr;
        struct sockaddr_in mount_server_addr;
        int msock, fsock;
        union {
                struct fhstatus nfsv2;
                struct mountres3 nfsv3;
        } status;
        int daemonized;
        char *s;
        int port;
        int mountport;
        int proto;
#if BB_MMU
        smallint bg = 0;
#else
        enum { bg = 0 };
#endif
        int retry;
        int mountprog;
        int mountvers;
        int nfsprog;
        int nfsvers;
        int retval;
        /* these all are one-bit really. gcc 4.3.1 likes this combination: */
        smallint tcp;
        smallint soft;
        int intr;
        int posix;
        int nocto;
        int noac;
        int nordirplus;
        int nolock;
        int noacl;

        find_kernel_nfs_mount_version();

        daemonized = 0;
        mounthost = NULL;
        retval = ETIMEDOUT;
        msock = fsock = -1;
        mclient = NULL;

        /* NB: hostname, mounthost, filteropts must be free()d prior to return */

        filteropts = xstrdup(filteropts); /* going to trash it later... */

        hostname = xstrdup(mp->mnt_fsname);
        /* mount_main() guarantees that ':' is there */
        s = strchr(hostname, ':');
        pathname = s + 1;
        *s = '\0';
        /* Ignore all but first hostname in replicated mounts
         * until they can be fully supported. (mack@sgi.com) */
        s = strchr(hostname, ',');
        if (s) {
                *s = '\0';
                bb_error_msg("warning: multiple hostnames not supported");
        }

        server_addr.sin_family = AF_INET;
        if (!inet_aton(hostname, &server_addr.sin_addr)) {
                hp = gethostbyname(hostname);
                if (hp == NULL) {
                        bb_herror_msg("%s", hostname);
                        goto fail;
                }
                if (hp->h_length != (int)sizeof(struct in_addr)) {
                        bb_error_msg_and_die("only IPv4 is supported");
                }
                memcpy(&server_addr.sin_addr, hp->h_addr_list[0], sizeof(struct in_addr));
        }

        memcpy(&mount_server_addr, &server_addr, sizeof(mount_server_addr));

        /* add IP address to mtab options for use when unmounting */

        if (!mp->mnt_opts) { /* TODO: actually mp->mnt_opts is never NULL */
                mp->mnt_opts = xasprintf("addr=%s", inet_ntoa(server_addr.sin_addr));
        } else {
                char *tmp = xasprintf("%s%saddr=%s", mp->mnt_opts,
                                        mp->mnt_opts[0] ? "," : "",
                                        inet_ntoa(server_addr.sin_addr));
                free(mp->mnt_opts);
                mp->mnt_opts = tmp;
        }

        /* Set default options.
         * rsize/wsize (and bsize, for ver >= 3) are left 0 in order to
         * let the kernel decide.
         * timeo is filled in after we know whether it'll be TCP or UDP. */
        memset(&data, 0, sizeof(data));
        data.retrans  = 3;
        data.acregmin = 3;
        data.acregmax = 60;
        data.acdirmin = 30;
        data.acdirmax = 60;
        data.namlen   = NAME_MAX;

        soft = 0;
        intr = 0;
        posix = 0;
        nocto = 0;
        nolock = 0;
        noac = 0;
        nordirplus = 0;
        noacl = 0;
        retry = 10000;          /* 10000 minutes ~ 1 week */
        tcp = 1;                        /* nfs-utils uses tcp per default */

        mountprog = MOUNTPROG;
        mountvers = 0;
        port = 0;
        mountport = 0;
        nfsprog = 100003;
        nfsvers = 0;

        /* parse options */
        if (filteropts) for (opt = strtok(filteropts, ","); opt; opt = strtok(NULL, ",")) {
                char *opteq = strchr(opt, '=');
                if (opteq) {
                        int val, idx;
                        static const char options[] ALIGN1 =
                                /* 0 */ "rsize\0"
                                /* 1 */ "wsize\0"
                                /* 2 */ "timeo\0"
                                /* 3 */ "retrans\0"
                                /* 4 */ "acregmin\0"
                                /* 5 */ "acregmax\0"
                                /* 6 */ "acdirmin\0"
                                /* 7 */ "acdirmax\0"
                                /* 8 */ "actimeo\0"
                                /* 9 */ "retry\0"
                                /* 10 */ "port\0"
                                /* 11 */ "mountport\0"
                                /* 12 */ "mounthost\0"
                                /* 13 */ "mountprog\0"
                                /* 14 */ "mountvers\0"
                                /* 15 */ "nfsprog\0"
                                /* 16 */ "nfsvers\0"
                                /* 17 */ "vers\0"
                                /* 18 */ "proto\0"
                                /* 19 */ "namlen\0"
                                /* 20 */ "addr\0";

                        *opteq++ = '\0';
                        idx = index_in_strings(options, opt);
                        switch (idx) {
                        case 12: // "mounthost"
                                mounthost = xstrndup(opteq,
                                                strcspn(opteq, " \t\n\r,"));
                                continue;
                        case 18: // "proto"
                                if (is_prefixed_with(opteq, "tcp"))
                                        tcp = 1;
                                else if (is_prefixed_with(opteq, "udp"))
                                        tcp = 0;
                                else
                                        bb_error_msg("warning: unrecognized proto= option");
                                continue;
                        case 20: // "addr" - ignore
                                continue;
                        case -1: // unknown
                                if (vfsflags & MS_REMOUNT)
                                        continue;
                        }

                        val = xatoi_positive(opteq);
                        switch (idx) {
                        case 0: // "rsize"
                                data.rsize = val;
                                continue;
                        case 1: // "wsize"
                                data.wsize = val;
                                continue;
                        case 2: // "timeo"
                                data.timeo = val;
                                continue;
                        case 3: // "retrans"
                                data.retrans = val;
                                continue;
                        case 4: // "acregmin"
                                data.acregmin = val;
                                continue;
                        case 5: // "acregmax"
                                data.acregmax = val;
                                continue;
                        case 6: // "acdirmin"
                                data.acdirmin = val;
                                continue;
                        case 7: // "acdirmax"
                                data.acdirmax = val;
                                continue;
                        case 8: // "actimeo"
                                data.acregmin = val;
                                data.acregmax = val;
                                data.acdirmin = val;
                                data.acdirmax = val;
                                continue;
                        case 9: // "retry"
                                retry = val;
                                continue;
                        case 10: // "port"
                                port = val;
                                continue;
                        case 11: // "mountport"
                                mountport = val;
                                continue;
                        case 13: // "mountprog"
                                mountprog = val;
                                continue;
                        case 14: // "mountvers"
                                mountvers = val;
                                continue;
                        case 15: // "nfsprog"
                                nfsprog = val;
                                continue;
                        case 16: // "nfsvers"
                        case 17: // "vers"
                                nfsvers = val;
                                continue;
                        case 19: // "namlen"
                                //if (nfs_mount_version >= 2)
                                        data.namlen = val;
                                //else
                                //      bb_error_msg("warning: option namlen is not supported\n");
                                continue;
                        default:
                                bb_error_msg("unknown nfs mount parameter: %s=%d", opt, val);
                                goto fail;
                        }
                }
                else { /* not of the form opt=val */
                        static const char options[] ALIGN1 =
                                "bg\0"
                                "fg\0"
                                "soft\0"
                                "hard\0"
                                "intr\0"
                                "posix\0"
                                "cto\0"
                                "ac\0"
                                "tcp\0"
                                "udp\0"
                                "lock\0"
                                "rdirplus\0"
                                "acl\0";
                        int val = 1;
                        if (is_prefixed_with(opt, "no")) {
                                val = 0;
                                opt += 2;
                        }
                        switch (index_in_strings(options, opt)) {
                        case 0: // "bg"
#if BB_MMU
                                bg = val;
#endif
                                break;
                        case 1: // "fg"
#if BB_MMU
                                bg = !val;
#endif
                                break;
                        case 2: // "soft"
                                soft = val;
                                break;
                        case 3: // "hard"
                                soft = !val;
                                break;
                        case 4: // "intr"
                                intr = val;
                                break;
                        case 5: // "posix"
                                posix = val;
                                break;
                        case 6: // "cto"
                                nocto = !val;
                                break;
                        case 7: // "ac"
                                noac = !val;
                                break;
                        case 8: // "tcp"
                                tcp = val;
                                break;
                        case 9: // "udp"
                                tcp = !val;
                                break;
                        case 10: // "lock"
                                if (nfs_mount_version >= 3)
                                        nolock = !val;
                                else
                                        bb_error_msg("warning: option nolock is not supported");
                                break;
                        case 11: //rdirplus
                                nordirplus = !val;
                                break;
                        case 12: // acl
                                noacl = !val;
                                break;
                        default:
                                bb_error_msg("unknown nfs mount option: %s%s", val ? "" : "no", opt);
                                goto fail;
                        }
                }
        }
        proto = (tcp) ? IPPROTO_TCP : IPPROTO_UDP;

        data.flags = (soft ? NFS_MOUNT_SOFT : 0)
                | (intr ? NFS_MOUNT_INTR : 0)
                | (posix ? NFS_MOUNT_POSIX : 0)
                | (nocto ? NFS_MOUNT_NOCTO : 0)
                | (noac ? NFS_MOUNT_NOAC : 0)
                | (nordirplus ? NFS_MOUNT_NORDIRPLUS : 0)
                | (noacl ? NFS_MOUNT_NOACL : 0);
        if (nfs_mount_version >= 2)
                data.flags |= (tcp ? NFS_MOUNT_TCP : 0);
        if (nfs_mount_version >= 3)
                data.flags |= (nolock ? NFS_MOUNT_NONLM : 0);
        if (nfsvers > MAX_NFSPROT || mountvers > MAX_NFSPROT) {
                bb_error_msg("NFSv%d not supported", nfsvers);
                goto fail;
        }
        if (nfsvers && !mountvers)
                mountvers = (nfsvers < 3) ? 1 : nfsvers;
        if (nfsvers && nfsvers < mountvers) {
                mountvers = nfsvers;
        }

        /* Adjust options if none specified */
        if (!data.timeo)
                data.timeo = tcp ? 70 : 7;

        data.version = nfs_mount_version;

        if (vfsflags & MS_REMOUNT)
                goto do_mount;

        /*
         * If the previous mount operation on the same host was
         * backgrounded, and the "bg" for this mount is also set,
         * give up immediately, to avoid the initial timeout.
         */
        if (bg && we_saw_this_host_before(hostname)) {
                daemonized = daemonize();
                if (daemonized <= 0) { /* parent or error */
                        retval = -daemonized;
                        goto ret;
                }
        }

        /* Create mount daemon client */
        /* See if the nfs host = mount host. */
        if (mounthost) {
                if (mounthost[0] >= '0' && mounthost[0] <= '9') {
                        mount_server_addr.sin_family = AF_INET;
                        mount_server_addr.sin_addr.s_addr = inet_addr(hostname);
                } else {
                        hp = gethostbyname(mounthost);
                        if (hp == NULL) {
                                bb_herror_msg("%s", mounthost);
                                goto fail;
                        }
                        if (hp->h_length != (int)sizeof(struct in_addr)) {
                                bb_error_msg_and_die("only IPv4 is supported");
                        }
                        mount_server_addr.sin_family = AF_INET;
                        memcpy(&mount_server_addr.sin_addr, hp->h_addr_list[0], sizeof(struct in_addr));
                }
        }

        /*
         * The following loop implements the mount retries. When the mount
         * times out, and the "bg" option is set, we background ourself
         * and continue trying.
         *
         * The case where the mount point is not present and the "bg"
         * option is set, is treated as a timeout. This is done to
         * support nested mounts.
         *
         * The "retry" count specified by the user is the number of
         * minutes to retry before giving up.
         */
        {
                struct timeval total_timeout;
                struct timeval retry_timeout;
                struct pmap pm_mnt;
                time_t t;
                time_t prevt;
                time_t timeout;

                retry_timeout.tv_sec = 3;
                retry_timeout.tv_usec = 0;
                total_timeout.tv_sec = 20;
                total_timeout.tv_usec = 0;
/* FIXME: use monotonic()? */
                timeout = time(NULL) + 60 * retry;
                prevt = 0;
                t = 30;
 retry:
                /* Be careful not to use too many CPU cycles */
                if (t - prevt < 30)
                        sleep(30);

                get_mountport(&pm_mnt, &mount_server_addr,
                                mountprog,
                                mountvers,
                                proto,
                                mountport);
                nfsvers = (pm_mnt.pm_vers < 2) ? 2 : pm_mnt.pm_vers;

                /* contact the mount daemon via TCP */
                mount_server_addr.sin_port = htons(pm_mnt.pm_port);
                msock = RPC_ANYSOCK;

                switch (pm_mnt.pm_prot) {
                case IPPROTO_UDP:
                        mclient = clntudp_create(&mount_server_addr,
                                                pm_mnt.pm_prog,
                                                pm_mnt.pm_vers,
                                                retry_timeout,
                                                &msock);
                        if (mclient)
                                break;
                        mount_server_addr.sin_port = htons(pm_mnt.pm_port);
                        msock = RPC_ANYSOCK;
                case IPPROTO_TCP:
                        mclient = clnttcp_create(&mount_server_addr,
                                                pm_mnt.pm_prog,
                                                pm_mnt.pm_vers,
                                                &msock, 0, 0);
                        break;
                default:
                        mclient = NULL;
                }
                if (!mclient) {
                        if (!daemonized && prevt == 0)
                                error_msg_rpc(clnt_spcreateerror(" "));
                } else {
                        enum clnt_stat clnt_stat;

                        /* Try to mount hostname:pathname */
                        mclient->cl_auth = authunix_create_default();

                        /* Make pointers in xdr_mountres3 NULL so
                         * that xdr_array allocates memory for us
                         */
                        memset(&status, 0, sizeof(status));

                        if (pm_mnt.pm_vers == 3)
                                clnt_stat = clnt_call(mclient, MOUNTPROC3_MNT,
                                                (xdrproc_t) xdr_dirpath,
                                                (caddr_t) &pathname,
                                                (xdrproc_t) xdr_mountres3,
                                                (caddr_t) &status,
                                                total_timeout);
                        else
                                clnt_stat = clnt_call(mclient, MOUNTPROC_MNT,
                                                (xdrproc_t) xdr_dirpath,
                                                (caddr_t) &pathname,
                                                (xdrproc_t) xdr_fhstatus,
                                                (caddr_t) &status,
                                                total_timeout);

                        if (clnt_stat == RPC_SUCCESS)
                                goto prepare_kernel_data; /* we're done */
                        if (errno != ECONNREFUSED) {
                                error_msg_rpc(clnt_sperror(mclient, " "));
                                goto fail;      /* don't retry */
                        }
                        /* Connection refused */
                        if (!daemonized && prevt == 0) /* print just once */
                                error_msg_rpc(clnt_sperror(mclient, " "));
                        auth_destroy(mclient->cl_auth);
                        clnt_destroy(mclient);
                        mclient = NULL;
                        close(msock);
                        msock = -1;
                }

                /* Timeout. We are going to retry... maybe */
                if (!bg)
                        goto fail;
                if (!daemonized) {
                        daemonized = daemonize();
                        if (daemonized <= 0) { /* parent or error */
                                retval = -daemonized;
                                goto ret;
                        }
                }
                prevt = t;
                t = time(NULL);
                if (t >= timeout)
                        /* TODO error message */
                        goto fail;

                goto retry;
        }

 prepare_kernel_data:

        if (nfsvers == 2) {
                if (status.nfsv2.fhs_status != 0) {
                        bb_error_msg("%s:%s failed, reason given by server: %s",
                                hostname, pathname,
                                nfs_strerror(status.nfsv2.fhs_status));
                        goto fail;
                }
                memcpy(data.root.data,
                                (char *) status.nfsv2.fhstatus_u.fhs_fhandle,
                                NFS_FHSIZE);
                data.root.size = NFS_FHSIZE;
                memcpy(data.old_root.data,
                                (char *) status.nfsv2.fhstatus_u.fhs_fhandle,
                                NFS_FHSIZE);
        } else {
                fhandle3 *my_fhandle;
                if (status.nfsv3.fhs_status != 0) {
                        bb_error_msg("%s:%s failed, reason given by server: %s",
                                hostname, pathname,
                                nfs_strerror(status.nfsv3.fhs_status));
                        goto fail;
                }
                my_fhandle = &status.nfsv3.mountres3_u.mountinfo.fhandle;
                memset(data.old_root.data, 0, NFS_FHSIZE);
                memset(&data.root, 0, sizeof(data.root));
                data.root.size = my_fhandle->fhandle3_len;
                memcpy(data.root.data,
                                (char *) my_fhandle->fhandle3_val,
                                my_fhandle->fhandle3_len);

                data.flags |= NFS_MOUNT_VER3;
        }

        /* Create nfs socket for kernel */
        if (tcp) {
                if (nfs_mount_version < 3) {
                        bb_error_msg("NFS over TCP is not supported");
                        goto fail;
                }
                fsock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
        } else
                fsock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
        if (fsock < 0) {
                bb_perror_msg("nfs socket");
                goto fail;
        }
        if (bindresvport(fsock, 0) < 0) {
                bb_perror_msg("nfs bindresvport");
                goto fail;
        }
        if (port == 0) {
                server_addr.sin_port = PMAPPORT;
                port = pmap_getport(&server_addr, nfsprog, nfsvers,
                                        tcp ? IPPROTO_TCP : IPPROTO_UDP);
                if (port == 0)
                        port = NFS_PORT;
        }
        server_addr.sin_port = htons(port);

        /* Prepare data structure for kernel */
        data.fd = fsock;
        memcpy((char *) &data.addr, (char *) &server_addr, sizeof(data.addr));
        strncpy(data.hostname, hostname, sizeof(data.hostname));

        /* Clean up */
        auth_destroy(mclient->cl_auth);
        clnt_destroy(mclient);
        close(msock);
        msock = -1;

        if (bg) {
                /* We must wait until mount directory is available */
                struct stat statbuf;
                int delay = 1;
                while (stat(mp->mnt_dir, &statbuf) == -1) {
                        if (!daemonized) {
                                daemonized = daemonize();
                                if (daemonized <= 0) { /* parent or error */
/* FIXME: parent doesn't close fsock - ??! */
                                        retval = -daemonized;
                                        goto ret;
                                }
                        }
                        sleep(delay);   /* 1, 2, 4, 8, 16, 30, ... */
                        delay *= 2;
                        if (delay > 30)
                                delay = 30;
                }
        }

        /* Perform actual mount */
 do_mount:
        retval = mount_it_now(mp, vfsflags, (char*)&data);
        goto ret;

        /* Abort */
 fail:
        if (msock >= 0) {
                if (mclient) {
                        auth_destroy(mclient->cl_auth);
                        clnt_destroy(mclient);
                }
                close(msock);
        }
        if (fsock >= 0)
                close(fsock);

 ret:
        free(hostname);
        free(mounthost);
        free(filteropts);
        return retval;
}

#else // !ENABLE_FEATURE_MOUNT_NFS

/* Linux 2.6.23+ supports nfs mounts with options passed as a string.
 * For older kernels, you must build busybox with ENABLE_FEATURE_MOUNT_NFS.
 * (However, note that then you lose any chances that NFS over IPv6 would work).
 */
static int nfsmount(struct mntent *mp, unsigned long vfsflags, char *filteropts)
{
        len_and_sockaddr *lsa;
        char *opts;
        char *end;
        char *dotted;
        int ret;

# if ENABLE_FEATURE_IPV6
        end = strchr(mp->mnt_fsname, ']');
        if (end && end[1] == ':')
                end++;
        else
# endif
                /* mount_main() guarantees that ':' is there */
                end = strchr(mp->mnt_fsname, ':');

        *end = '\0';
        lsa = xhost2sockaddr(mp->mnt_fsname, /*port:*/ 0);
        *end = ':';
        dotted = xmalloc_sockaddr2dotted_noport(&lsa->u.sa);
        if (ENABLE_FEATURE_CLEAN_UP) free(lsa);
        opts = xasprintf("%s%saddr=%s",
                filteropts ? filteropts : "",
                filteropts ? "," : "",
                dotted
        );
        if (ENABLE_FEATURE_CLEAN_UP) free(dotted);
        ret = mount_it_now(mp, vfsflags, opts);
        if (ENABLE_FEATURE_CLEAN_UP) free(opts);

        return ret;
}

#endif // !ENABLE_FEATURE_MOUNT_NFS

// Mount one directory.  Handles CIFS, NFS, loopback, autobind, and filesystem
// type detection.  Returns 0 for success, nonzero for failure.
// NB: mp->xxx fields may be trashed on exit
static int singlemount(struct mntent *mp, int ignore_busy)
{
        int loopfd = -1;
        int rc = -1;
        unsigned long vfsflags;
        char *loopFile = NULL, *filteropts = NULL;
        llist_t *fl = NULL;
        struct stat st;

        errno = 0;

        vfsflags = parse_mount_options(mp->mnt_opts, &filteropts);

        // Treat fstype "auto" as unspecified
        if (mp->mnt_type && strcmp(mp->mnt_type, "auto") == 0)
                mp->mnt_type = NULL;

        // Might this be a virtual filesystem?
        if (ENABLE_FEATURE_MOUNT_HELPERS && strchr(mp->mnt_fsname, '#')) {
                char *args[35];
                char *s;
                int n;
                // fsname: "cmd#arg1#arg2..."
                // WARNING: allows execution of arbitrary commands!
                // Try "mount 'sh#-c#sh' bogus_dir".
                // It is safe ONLY because non-root
                // cannot use two-argument mount command
                // and using one-argument "mount 'sh#-c#sh'" doesn't work:
                // "mount: can't find sh#-c#sh in /etc/fstab"
                // (if /etc/fstab has it, it's ok: root sets up /etc/fstab).

                s = mp->mnt_fsname;
                n = 0;
                args[n++] = s;
                while (*s && n < 35 - 2) {
                        if (*s++ == '#' && *s != '#') {
                                s[-1] = '\0';
                                args[n++] = s;
                        }
                }
                args[n++] = mp->mnt_dir;
                args[n] = NULL;
                rc = spawn_and_wait(args);
                goto report_error;
        }

        // Might this be an CIFS filesystem?
        if (ENABLE_FEATURE_MOUNT_CIFS
         && (!mp->mnt_type || strcmp(mp->mnt_type, "cifs") == 0)
         && (mp->mnt_fsname[0] == '/' || mp->mnt_fsname[0] == '\\')
         && mp->mnt_fsname[0] == mp->mnt_fsname[1]
        ) {
                int len;
                char c;
                char *hostname, *share;
                len_and_sockaddr *lsa;

                // Parse mp->mnt_fsname of the form "//hostname/share[/dir1/dir2]"

                hostname = mp->mnt_fsname + 2;
                len = strcspn(hostname, "/\\");
                share = hostname + len + 1;
                if (len == 0          // 3rd char is a [back]slash (IOW: empty hostname)
                 || share[-1] == '\0' // no [back]slash after hostname
                 || share[0] == '\0'  // empty share name
                ) {
                        goto report_error;
                }
                c = share[-1];
                share[-1] = '\0';
                len = strcspn(share, "/\\");

                // "unc=\\hostname\share" option is mandatory
                // after CIFS option parsing was rewritten in Linux 3.4.
                // Must use backslashes.
                // If /dir1/dir2 is present, also add "prefixpath=dir1/dir2"
                {
                        char *unc = xasprintf(
                                share[len] != '\0'  /* "/dir1/dir2" exists? */
                                        ? "unc=\\\\%s\\%.*s,prefixpath=%s"
                                        : "unc=\\\\%s\\%.*s",
                                hostname,
                                len, share,
                                share + len + 1  /* "dir1/dir2" */
                        );
                        parse_mount_options(unc, &filteropts);
                        if (ENABLE_FEATURE_CLEAN_UP) free(unc);
                }

                lsa = host2sockaddr(hostname, 0);
                share[-1] = c;
                if (!lsa)
                        goto report_error;

                // If there is no "ip=..." option yet
                if (!is_prefixed_with(filteropts, ",ip="+1)
                 && !strstr(filteropts, ",ip=")
                ) {
                        char *dotted, *ip;
                        // Insert "ip=..." option into options
                        dotted = xmalloc_sockaddr2dotted_noport(&lsa->u.sa);
                        if (ENABLE_FEATURE_CLEAN_UP) free(lsa);
                        ip = xasprintf("ip=%s", dotted);
                        if (ENABLE_FEATURE_CLEAN_UP) free(dotted);
// Note: IPv6 scoped addresses ("host%iface", see RFC 4007) should be
// handled by libc in getnameinfo() (inside xmalloc_sockaddr2dotted_noport()).
// Currently, glibc does not support that (has no NI_NUMERICSCOPE),
// musl apparently does. This results in "ip=numericIPv6%iface_name"

// (instead of _numeric_ iface_id) with glibc.
// This probably should be fixed in glibc, not here.
// The workaround is to manually specify correct "ip=ADDR%n" option.
                        parse_mount_options(ip, &filteropts);
                        if (ENABLE_FEATURE_CLEAN_UP) free(ip);
                }

                mp->mnt_type = (char*)"cifs";
                rc = mount_it_now(mp, vfsflags, filteropts);

                goto report_error;
        }

        // Might this be an NFS filesystem?
        if ((!mp->mnt_type || is_prefixed_with(mp->mnt_type, "nfs"))
         && strchr(mp->mnt_fsname, ':') != NULL
        ) {
                if (!mp->mnt_type)
                        mp->mnt_type = (char*)"nfs";
                rc = nfsmount(mp, vfsflags, filteropts);
                goto report_error;
        }

        // Look at the file.  (Not found isn't a failure for remount, or for
        // a synthetic filesystem like proc or sysfs.)
        // (We use stat, not lstat, in order to allow
        // mount symlink_to_file_or_blkdev dir)
        if (!stat(mp->mnt_fsname, &st)
         && !(vfsflags & (MS_REMOUNT | MS_BIND | MS_MOVE))
        ) {
                // Do we need to allocate a loopback device for it?
                if (ENABLE_FEATURE_MOUNT_LOOP && S_ISREG(st.st_mode)) {
                        loopFile = bb_simplify_path(mp->mnt_fsname);
                        mp->mnt_fsname = NULL; // will receive malloced loop dev name

                        // mount always creates AUTOCLEARed loopdevs, so that umounting
                        // drops them without any code in the userspace.
                        // This happens since circa linux-2.6.25:
                        // commit 96c5865559cee0f9cbc5173f3c949f6ce3525581
                        // Date:    Wed Feb 6 01:36:27 2008 -0800
                        // Subject: Allow auto-destruction of loop devices
                        loopfd = set_loop(&mp->mnt_fsname,
                                        loopFile,
                                        0,
                                        ((vfsflags & MS_RDONLY) ? BB_LO_FLAGS_READ_ONLY : 0)
                                                | BB_LO_FLAGS_AUTOCLEAR
                        );
                        if (loopfd < 0) {
                                if (errno == EPERM || errno == EACCES)
                                        bb_error_msg(bb_msg_perm_denied_are_you_root);
                                else
                                        bb_perror_msg("can't setup loop device");
                                return errno;
                        }

                // Autodetect bind mounts
                } else if (S_ISDIR(st.st_mode) && !mp->mnt_type)
                        vfsflags |= MS_BIND;
        }

        // If we know the fstype (or don't need to), jump straight
        // to the actual mount.
        if (mp->mnt_type || (vfsflags & (MS_REMOUNT | MS_BIND | MS_MOVE))) {
                char *next;
                for (;;) {
                        next = mp->mnt_type ? strchr(mp->mnt_type, ',') : NULL;
                        if (next)
                                *next = '\0';
                        rc = mount_it_now(mp, vfsflags, filteropts);
                        if (rc == 0 || !next)
                                break;
                        mp->mnt_type = next + 1;
                }
        } else {
                // Loop through filesystem types until mount succeeds
                // or we run out

                // Initialize list of block backed filesystems.
                // This has to be done here so that during "mount -a",
                // mounts after /proc shows up can autodetect.
                if (!fslist) {
                        fslist = get_block_backed_filesystems();
                        if (ENABLE_FEATURE_CLEAN_UP && fslist)
                                atexit(delete_block_backed_filesystems);
                }

                for (fl = fslist; fl; fl = fl->link) {
                        mp->mnt_type = fl->data;
                        rc = mount_it_now(mp, vfsflags, filteropts);
                        if (rc == 0)
                                break;
                }
        }

        // If mount failed, clean up loop file (if any).
        // (Newer kernels which support LO_FLAGS_AUTOCLEAR should not need this,
        // merely "close(loopfd)" should do it?)
        if (ENABLE_FEATURE_MOUNT_LOOP && rc && loopFile) {
                del_loop(mp->mnt_fsname);
                if (ENABLE_FEATURE_CLEAN_UP) {
                        free(loopFile);
                        /* No, "rc != 0" needs it: free(mp->mnt_fsname); */
                }
        }

 report_error:
        if (ENABLE_FEATURE_CLEAN_UP)
                free(filteropts);

        if (loopfd >= 0)
                close(loopfd);

        if (errno == EBUSY && ignore_busy)
                return 0;
        if (errno == ENOENT && (vfsflags & MOUNT_NOFAIL))
                return 0;
        if (rc != 0)
                bb_perror_msg("mounting %s on %s failed", mp->mnt_fsname, mp->mnt_dir);
        return rc;
}

// -O support
//    -O interprets a list of filter options which select whether a mount
// point will be mounted: only mounts with options matching *all* filtering
// options will be selected.
//    By default each -O filter option must be present in the list of mount
// options, but if it is prefixed by "no" then it must be absent.
// For example,
//  -O a,nob,c  matches  -o a,c  but fails to match  -o a,b,c
//              (and also fails to match  -o a  because  -o c  is absent).
//
// It is different from -t in that each option is matched exactly; a leading
// "no" at the beginning of one option does not negate the rest.
static int match_opt(const char *fs_opt_in, const char *O_opt)
{
        if (!O_opt)
                return 1;

        while (*O_opt) {
                const char *fs_opt = fs_opt_in;
                int O_len;
                int match;

                // If option begins with "no" then treat as an inverted match:
                // matching is a failure
                match = 0;
                if (O_opt[0] == 'n' && O_opt[1] == 'o') {
                        match = 1;
                        O_opt += 2;
                }
                // Isolate the current O option
                O_len = strchrnul(O_opt, ',') - O_opt;
                // Check for a match against existing options
                while (1) {
                        if (strncmp(fs_opt, O_opt, O_len) == 0
                         && (fs_opt[O_len] == '\0' || fs_opt[O_len] == ',')
                        ) {
                                if (match)
                                        return 0;  // "no" prefix, but option found
                                match = 1;  // current O option found, go check next one
                                break;
                        }
                        fs_opt = strchr(fs_opt, ',');
                        if (!fs_opt)
                                break;
                        fs_opt++;
                }
                if (match == 0)
                        return 0;     // match wanted but not found
                if (O_opt[O_len] == '\0') // end?
                        break;
                // Step to the next O option
                O_opt += O_len + 1;
        }
        // If we get here then everything matched
        return 1;
}

// Parse options, if necessary parse fstab/mtab, and call singlemount for
// each directory to be mounted.
int mount_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mount_main(int argc UNUSED_PARAM, char **argv)
{
        char *cmdopts = xzalloc(1);
        char *fstype = NULL;
        char *O_optmatch = NULL;
        char *storage_path;
        llist_t *lst_o = NULL;
        const char *fstabname = "/etc/fstab";
        FILE *fstab;
        int i, j;
        int rc = EXIT_SUCCESS;
        unsigned long cmdopt_flags;
        unsigned opt;
        struct mntent mtpair[2], *mtcur = mtpair;
        IF_NOT_DESKTOP(const int nonroot = 0;)

        IF_DESKTOP(int nonroot = ) sanitize_env_if_suid();

        INIT_G();

        // Parse long options, like --bind and --move.  Note that -o option
        // and --option are synonymous.  Yes, this means --remount,rw works.
        for (i = j = 1; argv[i]; i++) {
                if (argv[i][0] == '-' && argv[i][1] == '-')
                        append_mount_options(&cmdopts, argv[i] + 2);
                else
                        argv[j++] = argv[i];
        }
        argv[j] = NULL;

        // Parse remaining options
        // Max 2 params; -o is a list, -v is a counter
        opt = getopt32(argv, "^"
                OPTION_STR
                "\0" "?2"IF_FEATURE_MOUNT_VERBOSE("vv"),
                &lst_o, &fstype, &O_optmatch
                IF_FEATURE_MOUNT_OTHERTAB(, &fstabname)
                IF_FEATURE_MOUNT_VERBOSE(, &verbose)
        );

        while (lst_o) append_mount_options(&cmdopts, llist_pop(&lst_o)); // -o
        if (opt & OPT_r) append_mount_options(&cmdopts, "ro"); // -r
        if (opt & OPT_w) append_mount_options(&cmdopts, "rw"); // -w
        argv += optind;

        // If we have no arguments, show currently mounted filesystems
        if (!argv[0]) {
                if (!(opt & OPT_a)) {
                        FILE *mountTable = setmntent(bb_path_mtab_file, "r");

                        if (!mountTable)
                                bb_error_msg_and_die("no %s", bb_path_mtab_file);

                        while (getmntent_r(mountTable, &mtpair[0], getmntent_buf,
                                                                GETMNTENT_BUFSIZE))
                        {
                                // Don't show rootfs. FIXME: why??
                                // util-linux 2.12a happily shows rootfs...
                                //if (strcmp(mtpair->mnt_fsname, "rootfs") == 0) continue;

                                if (!fstype || strcmp(mtpair->mnt_type, fstype) == 0)
                                        printf("%s on %s type %s (%s)\n", mtpair->mnt_fsname,
                                                        mtpair->mnt_dir, mtpair->mnt_type,
                                                        mtpair->mnt_opts);
                        }
                        if (ENABLE_FEATURE_CLEAN_UP)
                                endmntent(mountTable);
                        return EXIT_SUCCESS;
                }
                storage_path = NULL;
        } else {
                // When we have two arguments, the second is the directory and we can
                // skip looking at fstab entirely.  We can always abspath() the directory
                // argument when we get it.
                if (argv[1]) {
                        if (nonroot)
                                bb_error_msg_and_die(bb_msg_you_must_be_root);
                        mtpair->mnt_fsname = argv[0];
                        mtpair->mnt_dir = argv[1];
                        mtpair->mnt_type = fstype;
                        mtpair->mnt_opts = cmdopts;
                        resolve_mount_spec(&mtpair->mnt_fsname);
                        rc = singlemount(mtpair, /*ignore_busy:*/ 0);
                        return rc;
                }
                storage_path = bb_simplify_path(argv[0]); // malloced
        }

        // Past this point, we are handling either "mount -a [opts]"
        // or "mount [opts] single_param"

        cmdopt_flags = parse_mount_options(cmdopts, NULL);
        if (nonroot && (cmdopt_flags & ~MS_SILENT)) // Non-root users cannot specify flags
                bb_error_msg_and_die(bb_msg_you_must_be_root);

        // If we have a shared subtree flag, don't worry about fstab or mtab.
        if (ENABLE_FEATURE_MOUNT_FLAGS
         && (cmdopt_flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
        ) {
                // verbose_mount(source, target, type, flags, data)
                rc = verbose_mount("", argv[0], "", cmdopt_flags, "");
                if (rc)
                        bb_simple_perror_msg_and_die(argv[0]);
                return rc;
        }

        // A malicious user could overmount /usr without this.
        if (ENABLE_FEATURE_MOUNT_OTHERTAB && nonroot)
                fstabname = "/etc/fstab";
        // Open either fstab or mtab
        if (cmdopt_flags & MS_REMOUNT) {
                // WARNING. I am not sure this matches util-linux's
                // behavior. It's possible util-linux does not
                // take -o opts from mtab (takes only mount source).
                fstabname = bb_path_mtab_file;
        }
        fstab = setmntent(fstabname, "r");
        if (!fstab)
                bb_perror_msg_and_die("can't read '%s'", fstabname);

        // Loop through entries until we find what we're looking for
        memset(mtpair, 0, sizeof(mtpair));
        for (;;) {
                struct mntent *mtother = (mtcur==mtpair ? mtpair+1 : mtpair);

                // Get next fstab entry
                if (!getmntent_r(fstab, mtcur, getmntent_buf
                                        + (mtcur==mtpair ? GETMNTENT_BUFSIZE/2 : 0),
                                GETMNTENT_BUFSIZE/2)
                ) { // End of fstab/mtab is reached
                        mtcur = mtother; // the thing we found last time
                        break;
                }

                // If we're trying to mount something specific and this isn't it,
                // skip it.  Note we must match the exact text in fstab (ala
                // "proc") or a full path from root
                if (argv[0]) {

                        // Is this what we're looking for?
                        if (strcmp(argv[0], mtcur->mnt_fsname) != 0
                         && strcmp(storage_path, mtcur->mnt_fsname) != 0
                         && strcmp(argv[0], mtcur->mnt_dir) != 0
                         && strcmp(storage_path, mtcur->mnt_dir) != 0
                        ) {
                                continue; // no
                        }

                        // Remember this entry.  Something later may have
                        // overmounted it, and we want the _last_ match.
                        mtcur = mtother;

                // If we're mounting all
                } else {
                        struct mntent *mp;
                        // No, mount -a won't mount anything,
                        // even user mounts, for mere humans
                        if (nonroot)
                                bb_error_msg_and_die(bb_msg_you_must_be_root);

                        // Does type match? (NULL matches always)
                        if (!fstype_matches(mtcur->mnt_type, fstype))
                                continue;

                        // Skip noauto and swap anyway
                        if ((parse_mount_options(mtcur->mnt_opts, NULL) & (MOUNT_NOAUTO | MOUNT_SWAP))
                        // swap is bogus "fstype", parse_mount_options can't check fstypes
                         || strcasecmp(mtcur->mnt_type, "swap") == 0
                        ) {
                                continue;
                        }

                        // Does (at least one) option match?
                        // (NULL matches always)
                        if (!match_opt(mtcur->mnt_opts, O_optmatch))
                                continue;

                        resolve_mount_spec(&mtcur->mnt_fsname);

                        // NFS mounts want this to be xrealloc-able
                        mtcur->mnt_opts = xstrdup(mtcur->mnt_opts);

                        // If nothing is mounted on this directory...
                        // (otherwise repeated "mount -a" mounts everything again)
                        mp = find_mount_point(mtcur->mnt_dir, /*subdir_too:*/ 0);
                        // We do not check fsname match of found mount point -
                        // "/" may have fsname of "/dev/root" while fstab
                        // says "/dev/something_else".
                        if (mp) {
                                if (verbose) {
                                        bb_error_msg("according to %s, "
                                                "%s is already mounted on %s",
                                                bb_path_mtab_file,
                                                mp->mnt_fsname, mp->mnt_dir);
                                }
                        } else {
                                // ...mount this thing
                                if (singlemount(mtcur, /*ignore_busy:*/ 1)) {
                                        // Count number of failed mounts
                                        rc++;
                                }
                        }
                        free(mtcur->mnt_opts);
                }
        }

        // End of fstab/mtab is reached.
        // Were we looking for something specific?
        if (argv[0]) { // yes
                unsigned long l;

                // If we didn't find anything, complain
                if (!mtcur->mnt_fsname)
                        bb_error_msg_and_die("can't find %s in %s",
                                argv[0], fstabname);

                // What happens when we try to "mount swap_partition"?
                // (fstab containts "swap_partition swap swap defaults 0 0")
                // util-linux-ng 2.13.1 does this:
                // stat("/sbin/mount.swap", 0x7fff62a3a350) = -1 ENOENT (No such file or directory)
                // mount("swap_partition", "swap", "swap", MS_MGC_VAL, NULL) = -1 ENOENT (No such file or directory)
                // lstat("swap", 0x7fff62a3a640)           = -1 ENOENT (No such file or directory)
                // write(2, "mount: mount point swap does not exist\n", 39) = 39
                // exit_group(32)                          = ?
#if 0
                // In case we want to simply skip swap partitions:
                l = parse_mount_options(mtcur->mnt_opts, NULL);
                if ((l & MOUNT_SWAP)
                // swap is bogus "fstype", parse_mount_options can't check fstypes
                 || strcasecmp(mtcur->mnt_type, "swap") == 0
                ) {
                        goto ret;
                }
#endif
                if (nonroot) {
                        // fstab must have "users" or "user"
                        l = parse_mount_options(mtcur->mnt_opts, NULL);
                        if (!(l & MOUNT_USERS))
                                bb_error_msg_and_die(bb_msg_you_must_be_root);
                }

                //util-linux-2.12 does not do this check.
                //// If nothing is mounted on this directory...
                //// (otherwise repeated "mount FOO" mounts FOO again)
                //mp = find_mount_point(mtcur->mnt_dir, /*subdir_too:*/ 0);
                //if (mp) {
                //      bb_error_msg("according to %s, "
                //              "%s is already mounted on %s",
                //              bb_path_mtab_file,
                //              mp->mnt_fsname, mp->mnt_dir);
                //} else {
                        // ...mount the last thing we found
                        mtcur->mnt_opts = xstrdup(mtcur->mnt_opts);
                        append_mount_options(&(mtcur->mnt_opts), cmdopts);
                        resolve_mount_spec(&mtpair->mnt_fsname);
                        rc = singlemount(mtcur, /*ignore_busy:*/ 0);
                        if (ENABLE_FEATURE_CLEAN_UP)
                                free(mtcur->mnt_opts);
                //}
        }

 //ret:
        if (ENABLE_FEATURE_CLEAN_UP)
                endmntent(fstab);
        if (ENABLE_FEATURE_CLEAN_UP) {
                free(storage_path);
                free(cmdopts);
        }

//TODO: exitcode should be ORed mask of (from "man mount"):
// 0 success
// 1 incorrect invocation or permissions
// 2 system error (out of memory, cannot fork, no more loop devices)
// 4 internal mount bug or missing nfs support in mount
// 8 user interrupt
//16 problems writing or locking /etc/mtab
//32 mount failure
//64 some mount succeeded
        return rc;
}