shared: fix double free in link

[thirdparty/systemd.git] / src / shared / install.c

/***
  This file is part of systemd.

  Copyright 2011 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty <of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <fnmatch.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

#include "alloc-util.h"
#include "conf-files.h"
#include "conf-parser.h"
#include "dirent-util.h"
#include "extract-word.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "hashmap.h"
#include "install-printf.h"
#include "install.h"
#include "locale-util.h"
#include "log.h"
#include "macro.h"
#include "mkdir.h"
#include "path-lookup.h"
#include "path-util.h"
#include "rm-rf.h"
#include "set.h"
#include "special.h"
#include "stat-util.h"
#include "string-table.h"
#include "string-util.h"
#include "strv.h"
#include "unit-name.h"

#define UNIT_FILE_FOLLOW_SYMLINK_MAX 64

typedef enum SearchFlags {
        SEARCH_LOAD = 1,
        SEARCH_FOLLOW_CONFIG_SYMLINKS = 2,
} SearchFlags;

typedef struct {
        OrderedHashmap *will_process;
        OrderedHashmap *have_processed;
} InstallContext;

typedef enum {
        PRESET_UNKNOWN,
        PRESET_ENABLE,
        PRESET_DISABLE,
} PresetAction;

typedef struct {
        char *pattern;
        PresetAction action;
} PresetRule;

typedef struct {
        PresetRule *rules;
        size_t n_rules;
} Presets;

static inline void presets_freep(Presets *p) {
        size_t i;

        if (!p)
                return;

        for (i = 0; i < p->n_rules; i++)
                free(p->rules[i].pattern);

        free(p->rules);
        p->n_rules = 0;
}

static int unit_file_lookup_state(UnitFileScope scope, const LookupPaths *paths, const char *name, UnitFileState *ret);

bool unit_type_may_alias(UnitType type) {
        return IN_SET(type,
                      UNIT_SERVICE,
                      UNIT_SOCKET,
                      UNIT_TARGET,
                      UNIT_DEVICE,
                      UNIT_TIMER,
                      UNIT_PATH);
}

bool unit_type_may_template(UnitType type) {
        return IN_SET(type,
                      UNIT_SERVICE,
                      UNIT_SOCKET,
                      UNIT_TARGET,
                      UNIT_TIMER,
                      UNIT_PATH);
}

static const char *unit_file_type_table[_UNIT_FILE_TYPE_MAX] = {
        [UNIT_FILE_TYPE_REGULAR] = "regular",
        [UNIT_FILE_TYPE_SYMLINK] = "symlink",
        [UNIT_FILE_TYPE_MASKED] = "masked",
};

DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(unit_file_type, UnitFileType);

static int in_search_path(const LookupPaths *p, const char *path) {
        _cleanup_free_ char *parent = NULL;
        char **i;

        assert(path);

        parent = dirname_malloc(path);
        if (!parent)
                return -ENOMEM;

        STRV_FOREACH(i, p->search_path)
                if (path_equal(parent, *i))
                        return true;

        return false;
}

static const char* skip_root(const LookupPaths *p, const char *path) {
        char *e;

        assert(p);
        assert(path);

        if (!p->root_dir)
                return path;

        e = path_startswith(path, p->root_dir);
        if (!e)
                return NULL;

        /* Make sure the returned path starts with a slash */
        if (e[0] != '/') {
                if (e == path || e[-1] != '/')
                        return NULL;

                e--;
        }

        return e;
}

static int path_is_generator(const LookupPaths *p, const char *path) {
        _cleanup_free_ char *parent = NULL;

        assert(p);
        assert(path);

        parent = dirname_malloc(path);
        if (!parent)
                return -ENOMEM;

        return path_equal_ptr(parent, p->generator) ||
               path_equal_ptr(parent, p->generator_early) ||
               path_equal_ptr(parent, p->generator_late);
}

static int path_is_transient(const LookupPaths *p, const char *path) {
        _cleanup_free_ char *parent = NULL;

        assert(p);
        assert(path);

        parent = dirname_malloc(path);
        if (!parent)
                return -ENOMEM;

        return path_equal_ptr(parent, p->transient);
}

static int path_is_control(const LookupPaths *p, const char *path) {
        _cleanup_free_ char *parent = NULL;

        assert(p);
        assert(path);

        parent = dirname_malloc(path);
        if (!parent)
                return -ENOMEM;

        return path_equal_ptr(parent, p->persistent_control) ||
               path_equal_ptr(parent, p->runtime_control);
}

static int path_is_config(const LookupPaths *p, const char *path) {
        _cleanup_free_ char *parent = NULL;

        assert(p);
        assert(path);

        /* Note that we do *not* have generic checks for /etc or /run in place, since with
         * them we couldn't discern configuration from transient or generated units */

        parent = dirname_malloc(path);
        if (!parent)
                return -ENOMEM;

        return path_equal_ptr(parent, p->persistent_config) ||
               path_equal_ptr(parent, p->runtime_config);
}

static int path_is_runtime(const LookupPaths *p, const char *path) {
        _cleanup_free_ char *parent = NULL;
        const char *rpath;

        assert(p);
        assert(path);

        /* Everything in /run is considered runtime. On top of that we also add
         * explicit checks for the various runtime directories, as safety net. */

        rpath = skip_root(p, path);
        if (rpath && path_startswith(rpath, "/run"))
                return true;

        parent = dirname_malloc(path);
        if (!parent)
                return -ENOMEM;

        return path_equal_ptr(parent, p->runtime_config) ||
               path_equal_ptr(parent, p->generator) ||
               path_equal_ptr(parent, p->generator_early) ||
               path_equal_ptr(parent, p->generator_late) ||
               path_equal_ptr(parent, p->transient) ||
               path_equal_ptr(parent, p->runtime_control);
}

static int path_is_vendor(const LookupPaths *p, const char *path) {
        const char *rpath;

        assert(p);
        assert(path);

        rpath = skip_root(p, path);
        if (!rpath)
                return 0;

        if (path_startswith(rpath, "/usr"))
                return true;

#ifdef HAVE_SPLIT_USR
        if (path_startswith(rpath, "/lib"))
                return true;
#endif

        return path_equal(rpath, SYSTEM_DATA_UNIT_PATH);
}

int unit_file_changes_add(
                UnitFileChange **changes,
                unsigned *n_changes,
                UnitFileChangeType type,
                const char *path,
                const char *source) {

        _cleanup_free_ char *p = NULL, *s = NULL;
        UnitFileChange *c;

        assert(path);
        assert(!changes == !n_changes);

        if (!changes)
                return 0;

        c = realloc(*changes, (*n_changes + 1) * sizeof(UnitFileChange));
        if (!c)
                return -ENOMEM;
        *changes = c;

        p = strdup(path);
        if (source)
                s = strdup(source);

        if (!p || (source && !s))
                return -ENOMEM;

        path_kill_slashes(p);
        if (s)
                path_kill_slashes(s);

        c[*n_changes] = (UnitFileChange) { type, p, s };
        p = s = NULL;
        (*n_changes) ++;
        return 0;
}

void unit_file_changes_free(UnitFileChange *changes, unsigned n_changes) {
        unsigned i;

        assert(changes || n_changes == 0);

        for (i = 0; i < n_changes; i++) {
                free(changes[i].path);
                free(changes[i].source);
        }

        free(changes);
}

void unit_file_dump_changes(int r, const char *verb, const UnitFileChange *changes, unsigned n_changes, bool quiet) {
        unsigned i;
        bool logged = false;

        assert(changes || n_changes == 0);
        /* If verb is not specified, errors are not allowed! */
        assert(verb || r >= 0);

        for (i = 0; i < n_changes; i++) {
                assert(verb || changes[i].type >= 0);

                switch(changes[i].type) {
                case UNIT_FILE_SYMLINK:
                        if (!quiet)
                                log_info("Created symlink %s %s %s.",
                                         changes[i].path,
                                         special_glyph(ARROW),
                                         changes[i].source);
                        break;
                case UNIT_FILE_UNLINK:
                        if (!quiet)
                                log_info("Removed %s.", changes[i].path);
                        break;
                case UNIT_FILE_IS_MASKED:
                        if (!quiet)
                                log_info("Unit %s is masked, ignoring.", changes[i].path);
                        break;
                case UNIT_FILE_IS_DANGLING:
                        if (!quiet)
                                log_info("Unit %s is an alias to a unit that is not present, ignoring.",
                                         changes[i].path);
                        break;
                case -EEXIST:
                        if (changes[i].source)
                                log_error_errno(changes[i].type,
                                                "Failed to %s unit, file %s already exists and is a symlink to %s.",
                                                verb, changes[i].path, changes[i].source);
                        else
                                log_error_errno(changes[i].type,
                                                "Failed to %s unit, file %s already exists.",
                                                verb, changes[i].path);
                        logged = true;
                        break;
                case -ERFKILL:
                        log_error_errno(changes[i].type, "Failed to %s unit, unit %s is masked.",
                                        verb, changes[i].path);
                        logged = true;
                        break;
                case -EADDRNOTAVAIL:
                        log_error_errno(changes[i].type, "Failed to %s unit, unit %s is transient or generated.",
                                        verb, changes[i].path);
                        logged = true;
                        break;
                case -ELOOP:
                        log_error_errno(changes[i].type, "Failed to %s unit, refusing to operate on linked unit file %s",
                                        verb, changes[i].path);
                        logged = true;
                        break;
                default:
                        assert(changes[i].type < 0);
                        log_error_errno(changes[i].type, "Failed to %s unit, file %s: %m.",
                                        verb, changes[i].path);
                        logged = true;
                }
        }

        if (r < 0 && !logged)
                log_error_errno(r, "Failed to %s: %m.", verb);
}

/**
 * Checks if two paths or symlinks from wd are the same, when root is the root of the filesystem.
 * wc should be the full path in the host file system.
 */
static bool chroot_symlinks_same(const char *root, const char *wd, const char *a, const char *b) {
        assert(path_is_absolute(wd));

        /* This will give incorrect results if the paths are relative and go outside
         * of the chroot. False negatives are possible. */

        if (!root)
                root = "/";

        a = strjoina(path_is_absolute(a) ? root : wd, "/", a);
        b = strjoina(path_is_absolute(b) ? root : wd, "/", b);
        return path_equal_or_files_same(a, b);
}

static int create_symlink(
                const LookupPaths *paths,
                const char *old_path,
                const char *new_path,
                bool force,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_free_ char *dest = NULL, *dirname = NULL;
        const char *rp;
        int r;

        assert(old_path);
        assert(new_path);

        rp = skip_root(paths, old_path);
        if (rp)
                old_path = rp;

        /* Actually create a symlink, and remember that we did. Is
         * smart enough to check if there's already a valid symlink in
         * place.
         *
         * Returns 1 if a symlink was created or already exists and points to
         * the right place, or negative on error.
         */

        mkdir_parents_label(new_path, 0755);

        if (symlink(old_path, new_path) >= 0) {
                unit_file_changes_add(changes, n_changes, UNIT_FILE_SYMLINK, new_path, old_path);
                return 1;
        }

        if (errno != EEXIST) {
                unit_file_changes_add(changes, n_changes, -errno, new_path, NULL);
                return -errno;
        }

        r = readlink_malloc(new_path, &dest);
        if (r < 0) {
                /* translate EINVAL (non-symlink exists) to EEXIST */
                if (r == -EINVAL)
                        r = -EEXIST;

                unit_file_changes_add(changes, n_changes, r, new_path, NULL);
                return r;
        }

        dirname = dirname_malloc(new_path);
        if (!dirname)
                return -ENOMEM;

        if (chroot_symlinks_same(paths->root_dir, dirname, dest, old_path))
                return 1;

        if (!force) {
                unit_file_changes_add(changes, n_changes, -EEXIST, new_path, dest);
                return -EEXIST;
        }

        r = symlink_atomic(old_path, new_path);
        if (r < 0) {
                unit_file_changes_add(changes, n_changes, r, new_path, NULL);
                return r;
        }

        unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, new_path, NULL);
        unit_file_changes_add(changes, n_changes, UNIT_FILE_SYMLINK, new_path, old_path);

        return 1;
}

static int mark_symlink_for_removal(
                Set **remove_symlinks_to,
                const char *p) {

        char *n;
        int r;

        assert(p);

        r = set_ensure_allocated(remove_symlinks_to, &string_hash_ops);
        if (r < 0)
                return r;

        n = strdup(p);
        if (!n)
                return -ENOMEM;

        path_kill_slashes(n);

        r = set_consume(*remove_symlinks_to, n);
        if (r == -EEXIST)
                return 0;
        if (r < 0)
                return r;

        return 1;
}

static int remove_marked_symlinks_fd(
                Set *remove_symlinks_to,
                int fd,
                const char *path,
                const char *config_path,
                const LookupPaths *lp,
                bool dry_run,
                bool *restart,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_closedir_ DIR *d = NULL;
        struct dirent *de;
        int r = 0;

        assert(remove_symlinks_to);
        assert(fd >= 0);
        assert(path);
        assert(config_path);
        assert(lp);
        assert(restart);

        d = fdopendir(fd);
        if (!d) {
                safe_close(fd);
                return -errno;
        }

        rewinddir(d);

        FOREACH_DIRENT(de, d, return -errno) {

                dirent_ensure_type(d, de);

                if (de->d_type == DT_DIR) {
                        _cleanup_free_ char *p = NULL;
                        int nfd, q;

                        nfd = openat(fd, de->d_name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
                        if (nfd < 0) {
                                if (errno == ENOENT)
                                        continue;

                                if (r == 0)
                                        r = -errno;
                                continue;
                        }

                        p = path_make_absolute(de->d_name, path);
                        if (!p) {
                                safe_close(nfd);
                                return -ENOMEM;
                        }

                        /* This will close nfd, regardless whether it succeeds or not */
                        q = remove_marked_symlinks_fd(remove_symlinks_to, nfd, p, config_path, lp, dry_run, restart, changes, n_changes);
                        if (q < 0 && r == 0)
                                r = q;

                } else if (de->d_type == DT_LNK) {
                        _cleanup_free_ char *p = NULL, *dest = NULL;
                        const char *rp;
                        bool found;
                        int q;

                        if (!unit_name_is_valid(de->d_name, UNIT_NAME_ANY))
                                continue;

                        p = path_make_absolute(de->d_name, path);
                        if (!p)
                                return -ENOMEM;
                        path_kill_slashes(p);

                        q = readlink_malloc(p, &dest);
                        if (q == -ENOENT)
                                continue;
                        if (q < 0) {
                                if (r == 0)
                                        r = q;
                                continue;
                        }

                        /* We remove all links pointing to a file or path that is marked, as well as all files sharing
                         * the same name as a file that is marked. */

                        found = set_contains(remove_symlinks_to, dest) ||
                                set_contains(remove_symlinks_to, basename(dest)) ||
                                set_contains(remove_symlinks_to, de->d_name);

                        if (!found)
                                continue;

                        if (!dry_run) {
                                if (unlinkat(fd, de->d_name, 0) < 0 && errno != ENOENT) {
                                        if (r == 0)
                                                r = -errno;
                                        unit_file_changes_add(changes, n_changes, -errno, p, NULL);
                                        continue;
                                }

                                (void) rmdir_parents(p, config_path);
                        }

                        unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, p, NULL);

                        /* Now, remember the full path (but with the root prefix removed) of
                         * the symlink we just removed, and remove any symlinks to it, too. */

                        rp = skip_root(lp, p);
                        q = mark_symlink_for_removal(&remove_symlinks_to, rp ?: p);
                        if (q < 0)
                                return q;
                        if (q > 0 && !dry_run)
                                *restart = true;
                }
        }

        return r;
}

static int remove_marked_symlinks(
                Set *remove_symlinks_to,
                const char *config_path,
                const LookupPaths *lp,
                bool dry_run,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_close_ int fd = -1;
        bool restart;
        int r = 0;

        assert(config_path);
        assert(lp);

        if (set_size(remove_symlinks_to) <= 0)
                return 0;

        fd = open(config_path, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC);
        if (fd < 0)
                return errno == ENOENT ? 0 : -errno;

        do {
                int q, cfd;
                restart = false;

                cfd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
                if (cfd < 0)
                        return -errno;

                /* This takes possession of cfd and closes it */
                q = remove_marked_symlinks_fd(remove_symlinks_to, cfd, config_path, config_path, lp, dry_run, &restart, changes, n_changes);
                if (r == 0)
                        r = q;
        } while (restart);

        return r;
}

static int find_symlinks_fd(
                const char *root_dir,
                const char *name,
                int fd,
                const char *path,
                const char *config_path,
                const LookupPaths *lp,
                bool *same_name_link) {

        _cleanup_closedir_ DIR *d = NULL;
        struct dirent *de;
        int r = 0;

        assert(name);
        assert(fd >= 0);
        assert(path);
        assert(config_path);
        assert(lp);
        assert(same_name_link);

        d = fdopendir(fd);
        if (!d) {
                safe_close(fd);
                return -errno;
        }

        FOREACH_DIRENT(de, d, return -errno) {

                dirent_ensure_type(d, de);

                if (de->d_type == DT_DIR) {
                        _cleanup_free_ char *p = NULL;
                        int nfd, q;

                        nfd = openat(fd, de->d_name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
                        if (nfd < 0) {
                                if (errno == ENOENT)
                                        continue;

                                if (r == 0)
                                        r = -errno;
                                continue;
                        }

                        p = path_make_absolute(de->d_name, path);
                        if (!p) {
                                safe_close(nfd);
                                return -ENOMEM;
                        }

                        /* This will close nfd, regardless whether it succeeds or not */
                        q = find_symlinks_fd(root_dir, name, nfd, p, config_path, lp, same_name_link);
                        if (q > 0)
                                return 1;
                        if (r == 0)
                                r = q;

                } else if (de->d_type == DT_LNK) {
                        _cleanup_free_ char *p = NULL, *dest = NULL;
                        bool found_path, found_dest, b = false;
                        int q;

                        /* Acquire symlink name */
                        p = path_make_absolute(de->d_name, path);
                        if (!p)
                                return -ENOMEM;

                        /* Acquire symlink destination */
                        q = readlink_malloc(p, &dest);
                        if (q == -ENOENT)
                                continue;
                        if (q < 0) {
                                if (r == 0)
                                        r = q;
                                continue;
                        }

                        /* Make absolute */
                        if (!path_is_absolute(dest)) {
                                char *x;

                                x = prefix_root(root_dir, dest);
                                if (!x)
                                        return -ENOMEM;

                                free(dest);
                                dest = x;
                        }

                        /* Check if the symlink itself matches what we
                         * are looking for */
                        if (path_is_absolute(name))
                                found_path = path_equal(p, name);
                        else
                                found_path = streq(de->d_name, name);

                        /* Check if what the symlink points to
                         * matches what we are looking for */
                        if (path_is_absolute(name))
                                found_dest = path_equal(dest, name);
                        else
                                found_dest = streq(basename(dest), name);

                        if (found_path && found_dest) {
                                _cleanup_free_ char *t = NULL;

                                /* Filter out same name links in the main
                                 * config path */
                                t = path_make_absolute(name, config_path);
                                if (!t)
                                        return -ENOMEM;

                                b = path_equal(t, p);
                        }

                        if (b)
                                *same_name_link = true;
                        else if (found_path || found_dest)
                                return 1;
                }
        }

        return r;
}

static int find_symlinks(
                const char *root_dir,
                const char *name,
                const char *config_path,
                const LookupPaths *lp,
                bool *same_name_link) {

        int fd;

        assert(name);
        assert(config_path);
        assert(same_name_link);

        fd = open(config_path, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC);
        if (fd < 0) {
                if (IN_SET(errno, ENOENT, ENOTDIR, EACCES))
                        return 0;
                return -errno;
        }

        /* This takes possession of fd and closes it */
        return find_symlinks_fd(root_dir, name, fd, config_path, config_path, lp, same_name_link);
}

static int find_symlinks_in_scope(
                UnitFileScope scope,
                const LookupPaths *paths,
                const char *name,
                UnitFileState *state) {

        bool same_name_link_runtime = false, same_name_link = false;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);
        assert(paths);
        assert(name);

        /* First look in the persistent config path */
        r = find_symlinks(paths->root_dir, name, paths->persistent_config, paths, &same_name_link);
        if (r < 0)
                return r;
        if (r > 0) {
                *state = UNIT_FILE_ENABLED;
                return r;
        }

        /* Then look in runtime config path */
        r = find_symlinks(paths->root_dir, name, paths->runtime_config, paths, &same_name_link_runtime);
        if (r < 0)
                return r;
        if (r > 0) {
                *state = UNIT_FILE_ENABLED_RUNTIME;
                return r;
        }

        /* Hmm, we didn't find it, but maybe we found the same name
         * link? */
        if (same_name_link) {
                *state = UNIT_FILE_LINKED;
                return 1;
        }
        if (same_name_link_runtime) {
                *state = UNIT_FILE_LINKED_RUNTIME;
                return 1;
        }

        return 0;
}

static void install_info_free(UnitFileInstallInfo *i) {

        if (!i)
                return;

        free(i->name);
        free(i->path);
        strv_free(i->aliases);
        strv_free(i->wanted_by);
        strv_free(i->required_by);
        strv_free(i->also);
        free(i->default_instance);
        free(i->symlink_target);
        free(i);
}

static OrderedHashmap* install_info_hashmap_free(OrderedHashmap *m) {
        UnitFileInstallInfo *i;

        if (!m)
                return NULL;

        while ((i = ordered_hashmap_steal_first(m)))
                install_info_free(i);

        return ordered_hashmap_free(m);
}

static void install_context_done(InstallContext *c) {
        assert(c);

        c->will_process = install_info_hashmap_free(c->will_process);
        c->have_processed = install_info_hashmap_free(c->have_processed);
}

static UnitFileInstallInfo *install_info_find(InstallContext *c, const char *name) {
        UnitFileInstallInfo *i;

        i = ordered_hashmap_get(c->have_processed, name);
        if (i)
                return i;

        return ordered_hashmap_get(c->will_process, name);
}

static int install_info_may_process(
                UnitFileInstallInfo *i,
                const LookupPaths *paths,
                UnitFileChange **changes,
                unsigned *n_changes) {
        assert(i);
        assert(paths);

        /* Checks whether the loaded unit file is one we should process, or is masked,
         * transient or generated and thus not subject to enable/disable operations. */

        if (i->type == UNIT_FILE_TYPE_MASKED) {
                unit_file_changes_add(changes, n_changes, -ERFKILL, i->path, NULL);
                return -ERFKILL;
        }
        if (path_is_generator(paths, i->path) ||
            path_is_transient(paths, i->path)) {
                unit_file_changes_add(changes, n_changes, -EADDRNOTAVAIL, i->path, NULL);
                return -EADDRNOTAVAIL;
        }

        return 0;
}

/**
 * Adds a new UnitFileInstallInfo entry under name in the InstallContext.will_process
 * hashmap, or retrieves the existing one if already present.
 *
 * Returns negative on error, 0 if the unit was already known, 1 otherwise.
 */
static int install_info_add(
                InstallContext *c,
                const char *name,
                const char *path,
                bool auxiliary,
                UnitFileInstallInfo **ret) {

        UnitFileInstallInfo *i = NULL;
        int r;

        assert(c);
        assert(name || path);

        if (!name)
                name = basename(path);

        if (!unit_name_is_valid(name, UNIT_NAME_ANY))
                return -EINVAL;

        i = install_info_find(c, name);
        if (i) {
                i->auxiliary = i->auxiliary && auxiliary;

                if (ret)
                        *ret = i;
                return 0;
        }

        r = ordered_hashmap_ensure_allocated(&c->will_process, &string_hash_ops);
        if (r < 0)
                return r;

        i = new0(UnitFileInstallInfo, 1);
        if (!i)
                return -ENOMEM;
        i->type = _UNIT_FILE_TYPE_INVALID;
        i->auxiliary = auxiliary;

        i->name = strdup(name);
        if (!i->name) {
                r = -ENOMEM;
                goto fail;
        }

        if (path) {
                i->path = strdup(path);
                if (!i->path) {
                        r = -ENOMEM;
                        goto fail;
                }
        }

        r = ordered_hashmap_put(c->will_process, i->name, i);
        if (r < 0)
                goto fail;

        if (ret)
                *ret = i;

        return 1;

fail:
        install_info_free(i);
        return r;
}

static int config_parse_alias(
                const char *unit,
                const char *filename,
                unsigned line,
                const char *section,
                unsigned section_line,
                const char *lvalue,
                int ltype,
                const char *rvalue,
                void *data,
                void *userdata) {

        const char *name;
        UnitType type;

        assert(filename);
        assert(lvalue);
        assert(rvalue);

        name = basename(filename);
        type = unit_name_to_type(name);
        if (!unit_type_may_alias(type))
                return log_syntax(unit, LOG_WARNING, filename, line, 0,
                                  "Alias= is not allowed for %s units, ignoring.",
                                  unit_type_to_string(type));

        return config_parse_strv(unit, filename, line, section, section_line,
                                 lvalue, ltype, rvalue, data, userdata);
}

static int config_parse_also(
                const char *unit,
                const char *filename,
                unsigned line,
                const char *section,
                unsigned section_line,
                const char *lvalue,
                int ltype,
                const char *rvalue,
                void *data,
                void *userdata) {

        UnitFileInstallInfo *info = userdata, *alsoinfo = NULL;
        InstallContext *c = data;
        int r;

        assert(filename);
        assert(lvalue);
        assert(rvalue);

        for (;;) {
                _cleanup_free_ char *word = NULL, *printed = NULL;

                r = extract_first_word(&rvalue, &word, NULL, 0);
                if (r < 0)
                        return r;
                if (r == 0)
                        break;

                r = install_full_printf(info, word, &printed);
                if (r < 0)
                        return r;

                if (!unit_name_is_valid(printed, UNIT_NAME_ANY))
                        return -EINVAL;

                r = install_info_add(c, printed, NULL, true, &alsoinfo);
                if (r < 0)
                        return r;

                r = strv_push(&info->also, printed);
                if (r < 0)
                        return r;

                printed = NULL;
        }

        return 0;
}

static int config_parse_default_instance(
                const char *unit,
                const char *filename,
                unsigned line,
                const char *section,
                unsigned section_line,
                const char *lvalue,
                int ltype,
                const char *rvalue,
                void *data,
                void *userdata) {

        UnitFileInstallInfo *i = data;
        const char *name;
        _cleanup_free_ char *printed = NULL;
        int r;

        assert(filename);
        assert(lvalue);
        assert(rvalue);

        name = basename(filename);
        if (unit_name_is_valid(name, UNIT_NAME_INSTANCE))
                /* When enabling an instance, we might be using a template unit file,
                 * but we should ignore DefaultInstance silently. */
                return 0;
        if (!unit_name_is_valid(name, UNIT_NAME_TEMPLATE))
                return log_syntax(unit, LOG_WARNING, filename, line, 0,
                                  "DefaultInstance= only makes sense for template units, ignoring.");

        r = install_full_printf(i, rvalue, &printed);
        if (r < 0)
                return r;

        if (!unit_instance_is_valid(printed))
                return -EINVAL;

        return free_and_replace(i->default_instance, printed);
}

static int unit_file_load(
                InstallContext *c,
                UnitFileInstallInfo *info,
                const char *path,
                SearchFlags flags) {

        const ConfigTableItem items[] = {
                { "Install", "Alias",           config_parse_alias,            0, &info->aliases           },
                { "Install", "WantedBy",        config_parse_strv,             0, &info->wanted_by         },
                { "Install", "RequiredBy",      config_parse_strv,             0, &info->required_by       },
                { "Install", "DefaultInstance", config_parse_default_instance, 0, info                     },
                { "Install", "Also",            config_parse_also,             0, c                        },
                {}
        };

        const char *name;
        UnitType type;
        _cleanup_fclose_ FILE *f = NULL;
        _cleanup_close_ int fd = -1;
        struct stat st;
        int r;

        assert(info);
        assert(path);

        name = basename(path);
        type = unit_name_to_type(name);
        if (unit_name_is_valid(name, UNIT_NAME_TEMPLATE|UNIT_NAME_INSTANCE) &&
            !unit_type_may_template(type))
                return log_error_errno(EINVAL, "Unit type %s cannot be templated.", unit_type_to_string(type));

        if (!(flags & SEARCH_LOAD)) {
                r = lstat(path, &st);
                if (r < 0)
                        return -errno;

                if (null_or_empty(&st))
                        info->type = UNIT_FILE_TYPE_MASKED;
                else if (S_ISREG(st.st_mode))
                        info->type = UNIT_FILE_TYPE_REGULAR;
                else if (S_ISLNK(st.st_mode))
                        return -ELOOP;
                else if (S_ISDIR(st.st_mode))
                        return -EISDIR;
                else
                        return -ENOTTY;

                return 0;
        }

        /* c is only needed if we actually load the file */
        assert(c);

        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
        if (fd < 0)
                return -errno;
        if (fstat(fd, &st) < 0)
                return -errno;
        if (null_or_empty(&st)) {
                info->type = UNIT_FILE_TYPE_MASKED;
                return 0;
        }
        if (S_ISDIR(st.st_mode))
                return -EISDIR;
        if (!S_ISREG(st.st_mode))
                return -ENOTTY;

        f = fdopen(fd, "re");
        if (!f)
                return -errno;
        fd = -1;

        r = config_parse(NULL, path, f,
                         NULL,
                         config_item_table_lookup, items,
                         true, true, false, info);
        if (r < 0)
                return log_debug_errno(r, "Failed to parse %s: %m", info->name);

        info->type = UNIT_FILE_TYPE_REGULAR;

        return
                (int) strv_length(info->aliases) +
                (int) strv_length(info->wanted_by) +
                (int) strv_length(info->required_by);
}

static int unit_file_load_or_readlink(
                InstallContext *c,
                UnitFileInstallInfo *info,
                const char *path,
                const char *root_dir,
                SearchFlags flags) {

        _cleanup_free_ char *target = NULL;
        int r;

        r = unit_file_load(c, info, path, flags);
        if (r != -ELOOP)
                return r;

        /* This is a symlink, let's read it. */

        r = readlink_malloc(path, &target);
        if (r < 0)
                return r;

        if (path_equal(target, "/dev/null"))
                info->type = UNIT_FILE_TYPE_MASKED;
        else {
                const char *bn;
                UnitType a, b;

                bn = basename(target);

                if (unit_name_is_valid(info->name, UNIT_NAME_PLAIN)) {

                        if (!unit_name_is_valid(bn, UNIT_NAME_PLAIN))
                                return -EINVAL;

                } else if (unit_name_is_valid(info->name, UNIT_NAME_INSTANCE)) {

                        if (!unit_name_is_valid(bn, UNIT_NAME_INSTANCE|UNIT_NAME_TEMPLATE))
                                return -EINVAL;

                } else if (unit_name_is_valid(info->name, UNIT_NAME_TEMPLATE)) {

                        if (!unit_name_is_valid(bn, UNIT_NAME_TEMPLATE))
                                return -EINVAL;
                } else
                        return -EINVAL;

                /* Enforce that the symlink destination does not
                 * change the unit file type. */

                a = unit_name_to_type(info->name);
                b = unit_name_to_type(bn);
                if (a < 0 || b < 0 || a != b)
                        return -EINVAL;

                if (path_is_absolute(target))
                        /* This is an absolute path, prefix the root so that we always deal with fully qualified paths */
                        info->symlink_target = prefix_root(root_dir, target);
                else
                        /* This is a relative path, take it relative to the dir the symlink is located in. */
                        info->symlink_target = file_in_same_dir(path, target);
                if (!info->symlink_target)
                        return -ENOMEM;

                info->type = UNIT_FILE_TYPE_SYMLINK;
        }

        return 0;
}

static int unit_file_search(
                InstallContext *c,
                UnitFileInstallInfo *info,
                const LookupPaths *paths,
                SearchFlags flags) {

        _cleanup_free_ char *template = NULL;
        char **p;
        int r;

        assert(info);
        assert(paths);

        /* Was this unit already loaded? */
        if (info->type != _UNIT_FILE_TYPE_INVALID)
                return 0;

        if (info->path)
                return unit_file_load_or_readlink(c, info, info->path, paths->root_dir, flags);

        assert(info->name);

        STRV_FOREACH(p, paths->search_path) {
                _cleanup_free_ char *path = NULL;

                path = strjoin(*p, "/", info->name);
                if (!path)
                        return -ENOMEM;

                r = unit_file_load_or_readlink(c, info, path, paths->root_dir, flags);
                if (r >= 0) {
                        info->path = path;
                        path = NULL;
                        return r;
                } else if (!IN_SET(r, -ENOENT, -ENOTDIR, -EACCES))
                        return r;
        }

        if (unit_name_is_valid(info->name, UNIT_NAME_INSTANCE)) {
                /* Unit file doesn't exist, however instance
                 * enablement was requested.  We will check if it is
                 * possible to load template unit file. */

                r = unit_name_template(info->name, &template);
                if (r < 0)
                        return r;

                STRV_FOREACH(p, paths->search_path) {
                        _cleanup_free_ char *path = NULL;

                        path = strjoin(*p, "/", template);
                        if (!path)
                                return -ENOMEM;

                        r = unit_file_load_or_readlink(c, info, path, paths->root_dir, flags);
                        if (r >= 0) {
                                info->path = path;
                                path = NULL;
                                return r;
                        } else if (!IN_SET(r, -ENOENT, -ENOTDIR, -EACCES))
                                return r;
                }
        }

        log_debug("Cannot find unit %s%s%s.", info->name, template ? " or " : "", strempty(template));
        return -ENOENT;
}

static int install_info_follow(
                InstallContext *c,
                UnitFileInstallInfo *i,
                const char *root_dir,
                SearchFlags flags) {

        assert(c);
        assert(i);

        if (i->type != UNIT_FILE_TYPE_SYMLINK)
                return -EINVAL;
        if (!i->symlink_target)
                return -EINVAL;

        /* If the basename doesn't match, the caller should add a
         * complete new entry for this. */

        if (!streq(basename(i->symlink_target), i->name))
                return -EXDEV;

        free_and_replace(i->path, i->symlink_target);
        i->type = _UNIT_FILE_TYPE_INVALID;

        return unit_file_load_or_readlink(c, i, i->path, root_dir, flags);
}

/**
 * Search for the unit file. If the unit name is a symlink, follow the symlink to the
 * target, maybe more than once. Propagate the instance name if present.
 */
static int install_info_traverse(
                UnitFileScope scope,
                InstallContext *c,
                const LookupPaths *paths,
                UnitFileInstallInfo *start,
                SearchFlags flags,
                UnitFileInstallInfo **ret) {

        UnitFileInstallInfo *i;
        unsigned k = 0;
        int r;

        assert(paths);
        assert(start);
        assert(c);

        r = unit_file_search(c, start, paths, flags);
        if (r < 0)
                return r;

        i = start;
        while (i->type == UNIT_FILE_TYPE_SYMLINK) {
                /* Follow the symlink */

                if (++k > UNIT_FILE_FOLLOW_SYMLINK_MAX)
                        return -ELOOP;

                if (!(flags & SEARCH_FOLLOW_CONFIG_SYMLINKS)) {
                        r = path_is_config(paths, i->path);
                        if (r < 0)
                                return r;
                        if (r > 0)
                                return -ELOOP;
                }

                r = install_info_follow(c, i, paths->root_dir, flags);
                if (r == -EXDEV) {
                        _cleanup_free_ char *buffer = NULL;
                        const char *bn;

                        /* Target has a different name, create a new
                         * install info object for that, and continue
                         * with that. */

                        bn = basename(i->symlink_target);

                        if (unit_name_is_valid(i->name, UNIT_NAME_INSTANCE) &&
                            unit_name_is_valid(bn, UNIT_NAME_TEMPLATE)) {

                                _cleanup_free_ char *instance = NULL;

                                r = unit_name_to_instance(i->name, &instance);
                                if (r < 0)
                                        return r;

                                r = unit_name_replace_instance(bn, instance, &buffer);
                                if (r < 0)
                                        return r;

                                bn = buffer;
                        }

                        r = install_info_add(c, bn, NULL, false, &i);
                        if (r < 0)
                                return r;

                        /* Try again, with the new target we found. */
                        r = unit_file_search(c, i, paths, flags);
                        if (r == -ENOENT)
                                /* Translate error code to highlight this specific case */
                                return -ENOLINK;
                }

                if (r < 0)
                        return r;
        }

        if (ret)
                *ret = i;

        return 0;
}

/**
 * Call install_info_add() with name_or_path as the path (if name_or_path starts with "/")
 * or the name (otherwise). root_dir is prepended to the path.
 */
static int install_info_add_auto(
                InstallContext *c,
                const LookupPaths *paths,
                const char *name_or_path,
                UnitFileInstallInfo **ret) {

        assert(c);
        assert(name_or_path);

        if (path_is_absolute(name_or_path)) {
                const char *pp;

                pp = prefix_roota(paths->root_dir, name_or_path);

                return install_info_add(c, NULL, pp, false, ret);
        } else
                return install_info_add(c, name_or_path, NULL, false, ret);
}

static int install_info_discover(
                UnitFileScope scope,
                InstallContext *c,
                const LookupPaths *paths,
                const char *name,
                SearchFlags flags,
                UnitFileInstallInfo **ret,
                UnitFileChange **changes,
                unsigned *n_changes) {

        UnitFileInstallInfo *i;
        int r;

        assert(c);
        assert(paths);
        assert(name);

        r = install_info_add_auto(c, paths, name, &i);
        if (r >= 0)
                r = install_info_traverse(scope, c, paths, i, flags, ret);

        if (r < 0)
                unit_file_changes_add(changes, n_changes, r, name, NULL);
        return r;
}

static int install_info_symlink_alias(
                UnitFileInstallInfo *i,
                const LookupPaths *paths,
                const char *config_path,
                bool force,
                UnitFileChange **changes,
                unsigned *n_changes) {

        char **s;
        int r = 0, q;

        assert(i);
        assert(paths);
        assert(config_path);

        STRV_FOREACH(s, i->aliases) {
                _cleanup_free_ char *alias_path = NULL, *dst = NULL;

                q = install_full_printf(i, *s, &dst);
                if (q < 0)
                        return q;

                alias_path = path_make_absolute(dst, config_path);
                if (!alias_path)
                        return -ENOMEM;

                q = create_symlink(paths, i->path, alias_path, force, changes, n_changes);
                if (r == 0)
                        r = q;
        }

        return r;
}

static int install_info_symlink_wants(
                UnitFileInstallInfo *i,
                const LookupPaths *paths,
                const char *config_path,
                char **list,
                const char *suffix,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_free_ char *buf = NULL;
        const char *n;
        char **s;
        int r = 0, q;

        assert(i);
        assert(paths);
        assert(config_path);

        if (strv_isempty(list))
                return 0;

        if (unit_name_is_valid(i->name, UNIT_NAME_TEMPLATE) && i->default_instance) {
                UnitFileInstallInfo instance = {
                        .type = _UNIT_FILE_TYPE_INVALID,
                };
                _cleanup_free_ char *path = NULL;

                r = unit_name_replace_instance(i->name, i->default_instance, &buf);
                if (r < 0)
                        return r;

                instance.name = buf;
                r = unit_file_search(NULL, &instance, paths, SEARCH_FOLLOW_CONFIG_SYMLINKS);
                if (r < 0)
                        return r;

                path = instance.path;
                instance.path = NULL;

                if (instance.type == UNIT_FILE_TYPE_MASKED) {
                        unit_file_changes_add(changes, n_changes, -ERFKILL, path, NULL);
                        return -ERFKILL;
                }

                n = buf;
        } else
                n = i->name;

        STRV_FOREACH(s, list) {
                _cleanup_free_ char *path = NULL, *dst = NULL;

                q = install_full_printf(i, *s, &dst);
                if (q < 0)
                        return q;

                if (!unit_name_is_valid(dst, UNIT_NAME_ANY)) {
                        r = -EINVAL;
                        continue;
                }

                path = strjoin(config_path, "/", dst, suffix, n);
                if (!path)
                        return -ENOMEM;

                q = create_symlink(paths, i->path, path, true, changes, n_changes);
                if (r == 0)
                        r = q;
        }

        return r;
}

static int install_info_symlink_link(
                UnitFileInstallInfo *i,
                const LookupPaths *paths,
                const char *config_path,
                bool force,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_free_ char *path = NULL;
        int r;

        assert(i);
        assert(paths);
        assert(config_path);
        assert(i->path);

        r = in_search_path(paths, i->path);
        if (r < 0)
                return r;
        if (r > 0)
                return 0;

        path = strjoin(config_path, "/", i->name);
        if (!path)
                return -ENOMEM;

        return create_symlink(paths, i->path, path, force, changes, n_changes);
}

static int install_info_apply(
                UnitFileInstallInfo *i,
                const LookupPaths *paths,
                const char *config_path,
                bool force,
                UnitFileChange **changes,
                unsigned *n_changes) {

        int r, q;

        assert(i);
        assert(paths);
        assert(config_path);

        if (i->type != UNIT_FILE_TYPE_REGULAR)
                return 0;

        r = install_info_symlink_alias(i, paths, config_path, force, changes, n_changes);

        q = install_info_symlink_wants(i, paths, config_path, i->wanted_by, ".wants/", changes, n_changes);
        if (r == 0)
                r = q;

        q = install_info_symlink_wants(i, paths, config_path, i->required_by, ".requires/", changes, n_changes);
        if (r == 0)
                r = q;

        q = install_info_symlink_link(i, paths, config_path, force, changes, n_changes);
        /* Do not count links to the unit file towards the "carries_install_info" count */
        if (r == 0 && q < 0)
                r = q;

        return r;
}

static int install_context_apply(
                UnitFileScope scope,
                InstallContext *c,
                const LookupPaths *paths,
                const char *config_path,
                bool force,
                SearchFlags flags,
                UnitFileChange **changes,
                unsigned *n_changes) {

        UnitFileInstallInfo *i;
        int r;

        assert(c);
        assert(paths);
        assert(config_path);

        if (ordered_hashmap_isempty(c->will_process))
                return 0;

        r = ordered_hashmap_ensure_allocated(&c->have_processed, &string_hash_ops);
        if (r < 0)
                return r;

        r = 0;
        while ((i = ordered_hashmap_first(c->will_process))) {
                int q;

                q = ordered_hashmap_move_one(c->have_processed, c->will_process, i->name);
                if (q < 0)
                        return q;

                r = install_info_traverse(scope, c, paths, i, flags, NULL);
                if (r < 0) {
                        unit_file_changes_add(changes, n_changes, r, i->name, NULL);
                        return r;
                }

                /* We can attempt to process a masked unit when a different unit
                 * that we were processing specifies it in Also=. */
                if (i->type == UNIT_FILE_TYPE_MASKED) {
                        unit_file_changes_add(changes, n_changes, UNIT_FILE_IS_MASKED, i->path, NULL);
                        if (r >= 0)
                                /* Assume that something *could* have been enabled here,
                                 * avoid "empty [Install] section" warning. */
                                r += 1;
                        continue;
                }

                if (i->type != UNIT_FILE_TYPE_REGULAR)
                        continue;

                q = install_info_apply(i, paths, config_path, force, changes, n_changes);
                if (r >= 0) {
                        if (q < 0)
                                r = q;
                        else
                                r += q;
                }
        }

        return r;
}

static int install_context_mark_for_removal(
                UnitFileScope scope,
                InstallContext *c,
                const LookupPaths *paths,
                Set **remove_symlinks_to,
                const char *config_path) {

        UnitFileInstallInfo *i;
        int r;

        assert(c);
        assert(paths);
        assert(config_path);

        /* Marks all items for removal */

        if (ordered_hashmap_isempty(c->will_process))
                return 0;

        r = ordered_hashmap_ensure_allocated(&c->have_processed, &string_hash_ops);
        if (r < 0)
                return r;

        while ((i = ordered_hashmap_first(c->will_process))) {

                r = ordered_hashmap_move_one(c->have_processed, c->will_process, i->name);
                if (r < 0)
                        return r;

                r = install_info_traverse(scope, c, paths, i, SEARCH_LOAD|SEARCH_FOLLOW_CONFIG_SYMLINKS, NULL);
                if (r == -ENOLINK) {
                        log_debug_errno(r, "Name %s leads to a dangling symlink, ignoring.", i->name);
                        continue;
                } else if (r == -ENOENT && i->auxiliary) {
                        /* some unit specified in Also= or similar is missing */
                        log_debug_errno(r, "Auxiliary unit %s not found, ignoring.", i->name);
                        continue;
                } else if (r < 0)
                        return log_debug_errno(r, "Failed to find unit %s: %m", i->name);

                if (i->type != UNIT_FILE_TYPE_REGULAR) {
                        log_debug("Unit %s has type %s, ignoring.",
                                  i->name,
                                  unit_file_type_to_string(i->type) ?: "invalid");
                        continue;
                }

                r = mark_symlink_for_removal(remove_symlinks_to, i->name);
                if (r < 0)
                        return r;
        }

        return 0;
}

int unit_file_mask(
                UnitFileScope scope,
                UnitFileFlags flags,
                const char *root_dir,
                char **files,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        const char *config_path;
        char **i;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        config_path = (flags & UNIT_FILE_RUNTIME) ? paths.runtime_config : paths.persistent_config;

        STRV_FOREACH(i, files) {
                _cleanup_free_ char *path = NULL;
                int q;

                if (!unit_name_is_valid(*i, UNIT_NAME_ANY)) {
                        if (r == 0)
                                r = -EINVAL;
                        continue;
                }

                path = path_make_absolute(*i, config_path);
                if (!path)
                        return -ENOMEM;

                q = create_symlink(&paths, "/dev/null", path, !!(flags & UNIT_FILE_FORCE), changes, n_changes);
                if (q < 0 && r >= 0)
                        r = q;
        }

        return r;
}

int unit_file_unmask(
                UnitFileScope scope,
                UnitFileFlags flags,
                const char *root_dir,
                char **files,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;
        _cleanup_strv_free_ char **todo = NULL;
        size_t n_todo = 0, n_allocated = 0;
        const char *config_path;
        char **i;
        bool dry_run;
        int r, q;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        config_path = (flags & UNIT_FILE_RUNTIME) ? paths.runtime_config : paths.persistent_config;
        dry_run = !!(flags & UNIT_FILE_DRY_RUN);

        STRV_FOREACH(i, files) {
                _cleanup_free_ char *path = NULL;

                if (!unit_name_is_valid(*i, UNIT_NAME_ANY))
                        return -EINVAL;

                path = path_make_absolute(*i, config_path);
                if (!path)
                        return -ENOMEM;

                r = null_or_empty_path(path);
                if (r == -ENOENT)
                        continue;
                if (r < 0)
                        return r;
                if (r == 0)
                        continue;

                if (!GREEDY_REALLOC0(todo, n_allocated, n_todo + 2))
                        return -ENOMEM;

                todo[n_todo++] = strdup(*i);
        }

        strv_uniq(todo);

        r = 0;
        STRV_FOREACH(i, todo) {
                _cleanup_free_ char *path = NULL;
                const char *rp;

                path = path_make_absolute(*i, config_path);
                if (!path)
                        return -ENOMEM;

                if (!dry_run && unlink(path) < 0) {
                        if (errno != ENOENT) {
                                if (r >= 0)
                                        r = -errno;
                                unit_file_changes_add(changes, n_changes, -errno, path, NULL);
                        }

                        continue;
                }

                unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, path, NULL);

                rp = skip_root(&paths, path);
                q = mark_symlink_for_removal(&remove_symlinks_to, rp ?: path);
                if (q < 0)
                        return q;
        }

        q = remove_marked_symlinks(remove_symlinks_to, config_path, &paths, dry_run, changes, n_changes);
        if (r >= 0)
                r = q;

        return r;
}

int unit_file_link(
                UnitFileScope scope,
                UnitFileFlags flags,
                const char *root_dir,
                char **files,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_strv_free_ char **todo = NULL;
        size_t n_todo = 0, n_allocated = 0;
        const char *config_path;
        char **i;
        int r, q;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        config_path = (flags & UNIT_FILE_RUNTIME) ? paths.runtime_config : paths.persistent_config;

        STRV_FOREACH(i, files) {
                _cleanup_free_ char *full = NULL;
                struct stat st;
                char *fn;

                if (!path_is_absolute(*i))
                        return -EINVAL;

                fn = basename(*i);
                if (!unit_name_is_valid(fn, UNIT_NAME_ANY))
                        return -EINVAL;

                full = prefix_root(paths.root_dir, *i);
                if (!full)
                        return -ENOMEM;

                if (lstat(full, &st) < 0)
                        return -errno;
                if (S_ISLNK(st.st_mode))
                        return -ELOOP;
                if (S_ISDIR(st.st_mode))
                        return -EISDIR;
                if (!S_ISREG(st.st_mode))
                        return -ENOTTY;

                q = in_search_path(&paths, *i);
                if (q < 0)
                        return q;
                if (q > 0)
                        continue;

                if (!GREEDY_REALLOC0(todo, n_allocated, n_todo + 2))
                        return -ENOMEM;

                todo[n_todo] = strdup(*i);
                if (!todo[n_todo])
                        return -ENOMEM;

                n_todo++;
        }

        strv_uniq(todo);

        r = 0;
        STRV_FOREACH(i, todo) {
                _cleanup_free_ char *new_path = NULL;

                new_path = path_make_absolute(basename(*i), config_path);
                if (!new_path)
                        return -ENOMEM;

                q = create_symlink(&paths, *i, new_path, !!(flags & UNIT_FILE_FORCE), changes, n_changes);
                if (q < 0 && r >= 0)
                        r = q;
        }

        return r;
}

static int path_shall_revert(const LookupPaths *paths, const char *path) {
        int r;

        assert(paths);
        assert(path);

        /* Checks whether the path is one where the drop-in directories shall be removed. */

        r = path_is_config(paths, path);
        if (r != 0)
                return r;

        r = path_is_control(paths, path);
        if (r != 0)
                return r;

        return path_is_transient(paths, path);
}

int unit_file_revert(
                UnitFileScope scope,
                const char *root_dir,
                char **files,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;
        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_strv_free_ char **todo = NULL;
        size_t n_todo = 0, n_allocated = 0;
        char **i;
        int r, q;

        /* Puts a unit file back into vendor state. This means:
         *
         * a) we remove all drop-in snippets added by the user ("config"), add to transient units ("transient"), and
         *    added via "systemctl set-property" ("control"), but not if the drop-in is generated ("generated").
         *
         * c) if there's a vendor unit file (i.e. one in /usr) we remove any configured overriding unit files (i.e. in
         *    "config", but not in "transient" or "control" or even "generated").
         *
         * We remove all that in both the runtime and the persistent directories, if that applies.
         */

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        STRV_FOREACH(i, files) {
                bool has_vendor = false;
                char **p;

                if (!unit_name_is_valid(*i, UNIT_NAME_ANY))
                        return -EINVAL;

                STRV_FOREACH(p, paths.search_path) {
                        _cleanup_free_ char *path = NULL, *dropin = NULL;
                        struct stat st;

                        path = path_make_absolute(*i, *p);
                        if (!path)
                                return -ENOMEM;

                        r = lstat(path, &st);
                        if (r < 0) {
                                if (errno != ENOENT)
                                        return -errno;
                        } else if (S_ISREG(st.st_mode)) {
                                /* Check if there's a vendor version */
                                r = path_is_vendor(&paths, path);
                                if (r < 0)
                                        return r;
                                if (r > 0)
                                        has_vendor = true;
                        }

                        dropin = strappend(path, ".d");
                        if (!dropin)
                                return -ENOMEM;

                        r = lstat(dropin, &st);
                        if (r < 0) {
                                if (errno != ENOENT)
                                        return -errno;
                        } else if (S_ISDIR(st.st_mode)) {
                                /* Remove the drop-ins */
                                r = path_shall_revert(&paths, dropin);
                                if (r < 0)
                                        return r;
                                if (r > 0) {
                                        if (!GREEDY_REALLOC0(todo, n_allocated, n_todo + 2))
                                                return -ENOMEM;

                                        todo[n_todo++] = dropin;
                                        dropin = NULL;
                                }
                        }
                }

                if (!has_vendor)
                        continue;

                /* OK, there's a vendor version, hence drop all configuration versions */
                STRV_FOREACH(p, paths.search_path) {
                        _cleanup_free_ char *path = NULL;
                        struct stat st;

                        path = path_make_absolute(*i, *p);
                        if (!path)
                                return -ENOMEM;

                        r = lstat(path, &st);
                        if (r < 0) {
                                if (errno != ENOENT)
                                        return -errno;
                        } else if (S_ISREG(st.st_mode) || S_ISLNK(st.st_mode)) {
                                r = path_is_config(&paths, path);
                                if (r < 0)
                                        return r;
                                if (r > 0) {
                                        if (!GREEDY_REALLOC0(todo, n_allocated, n_todo + 2))
                                                return -ENOMEM;

                                        todo[n_todo++] = path;
                                        path = NULL;
                                }
                        }
                }
        }

        strv_uniq(todo);

        r = 0;
        STRV_FOREACH(i, todo) {
                _cleanup_strv_free_ char **fs = NULL;
                const char *rp;
                char **j;

                (void) get_files_in_directory(*i, &fs);

                q = rm_rf(*i, REMOVE_ROOT|REMOVE_PHYSICAL);
                if (q < 0 && q != -ENOENT && r >= 0) {
                        r = q;
                        continue;
                }

                STRV_FOREACH(j, fs) {
                        _cleanup_free_ char *t = NULL;

                        t = strjoin(*i, "/", *j);
                        if (!t)
                                return -ENOMEM;

                        unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, t, NULL);
                }

                unit_file_changes_add(changes, n_changes, UNIT_FILE_UNLINK, *i, NULL);

                rp = skip_root(&paths, *i);
                q = mark_symlink_for_removal(&remove_symlinks_to, rp ?: *i);
                if (q < 0)
                        return q;
        }

        q = remove_marked_symlinks(remove_symlinks_to, paths.runtime_config, &paths, false, changes, n_changes);
        if (r >= 0)
                r = q;

        q = remove_marked_symlinks(remove_symlinks_to, paths.persistent_config, &paths, false, changes, n_changes);
        if (r >= 0)
                r = q;

        return r;
}

int unit_file_add_dependency(
                UnitFileScope scope,
                UnitFileFlags flags,
                const char *root_dir,
                char **files,
                const char *target,
                UnitDependency dep,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_(install_context_done) InstallContext c = {};
        UnitFileInstallInfo *i, *target_info;
        const char *config_path;
        char **f;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);
        assert(target);

        if (!IN_SET(dep, UNIT_WANTS, UNIT_REQUIRES))
                return -EINVAL;

        if (!unit_name_is_valid(target, UNIT_NAME_ANY))
                return -EINVAL;

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        config_path = (flags & UNIT_FILE_RUNTIME) ? paths.runtime_config : paths.persistent_config;

        r = install_info_discover(scope, &c, &paths, target, SEARCH_FOLLOW_CONFIG_SYMLINKS,
                                  &target_info, changes, n_changes);
        if (r < 0)
                return r;
        r = install_info_may_process(target_info, &paths, changes, n_changes);
        if (r < 0)
                return r;

        assert(target_info->type == UNIT_FILE_TYPE_REGULAR);

        STRV_FOREACH(f, files) {
                char ***l;

                r = install_info_discover(scope, &c, &paths, *f, SEARCH_FOLLOW_CONFIG_SYMLINKS,
                                          &i, changes, n_changes);
                if (r < 0)
                        return r;
                r = install_info_may_process(i, &paths, changes, n_changes);
                if (r < 0)
                        return r;

                assert(i->type == UNIT_FILE_TYPE_REGULAR);

                /* We didn't actually load anything from the unit
                 * file, but instead just add in our new symlink to
                 * create. */

                if (dep == UNIT_WANTS)
                        l = &i->wanted_by;
                else
                        l = &i->required_by;

                strv_free(*l);
                *l = strv_new(target_info->name, NULL);
                if (!*l)
                        return -ENOMEM;
        }

        return install_context_apply(scope, &c, &paths, config_path, !!(flags & UNIT_FILE_FORCE), SEARCH_FOLLOW_CONFIG_SYMLINKS, changes, n_changes);
}

int unit_file_enable(
                UnitFileScope scope,
                UnitFileFlags flags,
                const char *root_dir,
                char **files,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_(install_context_done) InstallContext c = {};
        const char *config_path;
        UnitFileInstallInfo *i;
        char **f;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        config_path = (flags & UNIT_FILE_RUNTIME) ? paths.runtime_config : paths.persistent_config;

        STRV_FOREACH(f, files) {
                r = install_info_discover(scope, &c, &paths, *f, SEARCH_LOAD|SEARCH_FOLLOW_CONFIG_SYMLINKS,
                                          &i, changes, n_changes);
                if (r < 0)
                        return r;
                r = install_info_may_process(i, &paths, changes, n_changes);
                if (r < 0)
                        return r;

                assert(i->type == UNIT_FILE_TYPE_REGULAR);
        }

        /* This will return the number of symlink rules that were
           supposed to be created, not the ones actually created. This
           is useful to determine whether the passed files had any
           installation data at all. */

        return install_context_apply(scope, &c, &paths, config_path, !!(flags & UNIT_FILE_FORCE), SEARCH_LOAD, changes, n_changes);
}

int unit_file_disable(
                UnitFileScope scope,
                UnitFileFlags flags,
                const char *root_dir,
                char **files,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_(install_context_done) InstallContext c = {};
        _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;
        const char *config_path;
        char **i;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        config_path = (flags & UNIT_FILE_RUNTIME) ? paths.runtime_config : paths.persistent_config;

        STRV_FOREACH(i, files) {
                if (!unit_name_is_valid(*i, UNIT_NAME_ANY))
                        return -EINVAL;

                r = install_info_add(&c, *i, NULL, false, NULL);
                if (r < 0)
                        return r;
        }

        r = install_context_mark_for_removal(scope, &c, &paths, &remove_symlinks_to, config_path);
        if (r < 0)
                return r;

        return remove_marked_symlinks(remove_symlinks_to, config_path, &paths, !!(flags & UNIT_FILE_DRY_RUN), changes, n_changes);
}

int unit_file_reenable(
                UnitFileScope scope,
                UnitFileFlags flags,
                const char *root_dir,
                char **files,
                UnitFileChange **changes,
                unsigned *n_changes) {

        char **n;
        int r;
        size_t l, i;

        /* First, we invoke the disable command with only the basename... */
        l = strv_length(files);
        n = newa(char*, l+1);
        for (i = 0; i < l; i++)
                n[i] = basename(files[i]);
        n[i] = NULL;

        r = unit_file_disable(scope, flags, root_dir, n, changes, n_changes);
        if (r < 0)
                return r;

        /* But the enable command with the full name */
        return unit_file_enable(scope, flags, root_dir, files, changes, n_changes);
}

int unit_file_set_default(
                UnitFileScope scope,
                UnitFileFlags flags,
                const char *root_dir,
                const char *name,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_(install_context_done) InstallContext c = {};
        UnitFileInstallInfo *i;
        const char *new_path;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);
        assert(name);

        if (unit_name_to_type(name) != UNIT_TARGET) /* this also validates the name */
                return -EINVAL;
        if (streq(name, SPECIAL_DEFAULT_TARGET))
                return -EINVAL;

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        r = install_info_discover(scope, &c, &paths, name, 0, &i, changes, n_changes);
        if (r < 0)
                return r;
        r = install_info_may_process(i, &paths, changes, n_changes);
        if (r < 0)
                return r;

        new_path = strjoina(paths.persistent_config, "/" SPECIAL_DEFAULT_TARGET);
        return create_symlink(&paths, i->path, new_path, !!(flags & UNIT_FILE_FORCE), changes, n_changes);
}

int unit_file_get_default(
                UnitFileScope scope,
                const char *root_dir,
                char **name) {

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_(install_context_done) InstallContext c = {};
        UnitFileInstallInfo *i;
        char *n;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);
        assert(name);

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        r = install_info_discover(scope, &c, &paths, SPECIAL_DEFAULT_TARGET, SEARCH_FOLLOW_CONFIG_SYMLINKS,
                                  &i, NULL, NULL);
        if (r < 0)
                return r;
        r = install_info_may_process(i, &paths, NULL, 0);
        if (r < 0)
                return r;

        n = strdup(i->name);
        if (!n)
                return -ENOMEM;

        *name = n;
        return 0;
}

static int unit_file_lookup_state(
                UnitFileScope scope,
                const LookupPaths *paths,
                const char *name,
                UnitFileState *ret) {

        _cleanup_(install_context_done) InstallContext c = {};
        UnitFileInstallInfo *i;
        UnitFileState state;
        int r;

        assert(paths);
        assert(name);

        if (!unit_name_is_valid(name, UNIT_NAME_ANY))
                return -EINVAL;

        r = install_info_discover(scope, &c, paths, name, SEARCH_LOAD|SEARCH_FOLLOW_CONFIG_SYMLINKS,
                                  &i, NULL, NULL);
        if (r < 0)
                return r;

        /* Shortcut things, if the caller just wants to know if this unit exists. */
        if (!ret)
                return 0;

        switch (i->type) {

        case UNIT_FILE_TYPE_MASKED:
                r = path_is_runtime(paths, i->path);
                if (r < 0)
                        return r;

                state = r > 0 ? UNIT_FILE_MASKED_RUNTIME : UNIT_FILE_MASKED;
                break;

        case UNIT_FILE_TYPE_REGULAR:
                r = path_is_generator(paths, i->path);
                if (r < 0)
                        return r;
                if (r > 0) {
                        state = UNIT_FILE_GENERATED;
                        break;
                }

                r = path_is_transient(paths, i->path);
                if (r < 0)
                        return r;
                if (r > 0) {
                        state = UNIT_FILE_TRANSIENT;
                        break;
                }

                r = find_symlinks_in_scope(scope, paths, i->name, &state);
                if (r < 0)
                        return r;
                if (r == 0) {
                        if (UNIT_FILE_INSTALL_INFO_HAS_RULES(i))
                                state = UNIT_FILE_DISABLED;
                        else if (UNIT_FILE_INSTALL_INFO_HAS_ALSO(i))
                                state = UNIT_FILE_INDIRECT;
                        else
                                state = UNIT_FILE_STATIC;
                }

                break;

        default:
                assert_not_reached("Unexpect unit file type.");
        }

        *ret = state;
        return 0;
}

int unit_file_get_state(
                UnitFileScope scope,
                const char *root_dir,
                const char *name,
                UnitFileState *ret) {

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);
        assert(name);

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        return unit_file_lookup_state(scope, &paths, name, ret);
}

int unit_file_exists(UnitFileScope scope, const LookupPaths *paths, const char *name) {
        _cleanup_(install_context_done) InstallContext c = {};
        int r;

        assert(paths);
        assert(name);

        if (!unit_name_is_valid(name, UNIT_NAME_ANY))
                return -EINVAL;

        r = install_info_discover(scope, &c, paths, name, 0, NULL, NULL, NULL);
        if (r == -ENOENT)
                return 0;
        if (r < 0)
                return r;

        return 1;
}

static int read_presets(UnitFileScope scope, const char *root_dir, Presets *presets) {
        _cleanup_(presets_freep) Presets ps = {};
        size_t n_allocated = 0;
        _cleanup_strv_free_ char **files = NULL;
        char **p;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);
        assert(presets);

        if (scope == UNIT_FILE_SYSTEM)
                r = conf_files_list(&files, ".preset", root_dir,
                                    "/etc/systemd/system-preset",
                                    "/usr/local/lib/systemd/system-preset",
                                    "/usr/lib/systemd/system-preset",
#ifdef HAVE_SPLIT_USR
                                    "/lib/systemd/system-preset",
#endif
                                    NULL);
        else if (scope == UNIT_FILE_GLOBAL)
                r = conf_files_list(&files, ".preset", root_dir,
                                    "/etc/systemd/user-preset",
                                    "/usr/local/lib/systemd/user-preset",
                                    "/usr/lib/systemd/user-preset",
                                    NULL);
        else {
                *presets = (Presets){};

                return 0;
        }

        if (r < 0)
                return r;

        STRV_FOREACH(p, files) {
                _cleanup_fclose_ FILE *f;
                char line[LINE_MAX];
                int n = 0;

                f = fopen(*p, "re");
                if (!f) {
                        if (errno == ENOENT)
                                continue;

                        return -errno;
                }

                FOREACH_LINE(line, f, return -errno) {
                        PresetRule rule = {};
                        const char *parameter;
                        char *l;

                        l = strstrip(line);
                        n++;

                        if (isempty(l))
                                continue;
                        if (strchr(COMMENTS, *l))
                                continue;

                        parameter = first_word(l, "enable");
                        if (parameter) {
                                char *pattern;

                                pattern = strdup(parameter);
                                if (!pattern)
                                        return -ENOMEM;

                                rule = (PresetRule) {
                                        .pattern = pattern,
                                        .action = PRESET_ENABLE,
                                };
                        }

                        parameter = first_word(l, "disable");
                        if (parameter) {
                                char *pattern;

                                pattern = strdup(parameter);
                                if (!pattern)
                                        return -ENOMEM;

                                rule = (PresetRule) {
                                        .pattern = pattern,
                                        .action = PRESET_DISABLE,
                                };
                        }

                        if (rule.action) {
                                if (!GREEDY_REALLOC(ps.rules, n_allocated, ps.n_rules + 1))
                                        return -ENOMEM;

                                ps.rules[ps.n_rules++] = rule;
                                continue;
                        }

                        log_syntax(NULL, LOG_WARNING, *p, n, 0, "Couldn't parse line '%s'. Ignoring.", line);
                }
        }

        *presets = ps;
        ps = (Presets){};

        return 0;
}

static int query_presets(const char *name, const Presets presets) {
        PresetAction action = PRESET_UNKNOWN;
        size_t i;

        if (!unit_name_is_valid(name, UNIT_NAME_ANY))
                return -EINVAL;

        for (i = 0; i < presets.n_rules; i++)
                if (fnmatch(presets.rules[i].pattern, name, FNM_NOESCAPE) == 0) {
                        action = presets.rules[i].action;
                        break;
                }

        switch (action) {
        case PRESET_UNKNOWN:
                log_debug("Preset files don't specify rule for %s. Enabling.", name);
                return 1;
        case PRESET_ENABLE:
                log_debug("Preset files say enable %s.", name);
                return 1;
        case PRESET_DISABLE:
                log_debug("Preset files say disable %s.", name);
                return 0;
        default:
                assert_not_reached("invalid preset action");
        }
}

int unit_file_query_preset(UnitFileScope scope, const char *root_dir, const char *name) {
        _cleanup_(presets_freep) Presets presets = {};
        int r;

        r = read_presets(scope, root_dir, &presets);
        if (r < 0)
                return r;

        return query_presets(name, presets);
}

static int execute_preset(
                UnitFileScope scope,
                InstallContext *plus,
                InstallContext *minus,
                const LookupPaths *paths,
                const char *config_path,
                char **files,
                UnitFilePresetMode mode,
                bool force,
                UnitFileChange **changes,
                unsigned *n_changes) {

        int r;

        assert(plus);
        assert(minus);
        assert(paths);
        assert(config_path);

        if (mode != UNIT_FILE_PRESET_ENABLE_ONLY) {
                _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;

                r = install_context_mark_for_removal(scope, minus, paths, &remove_symlinks_to, config_path);
                if (r < 0)
                        return r;

                r = remove_marked_symlinks(remove_symlinks_to, config_path, paths, false, changes, n_changes);
        } else
                r = 0;

        if (mode != UNIT_FILE_PRESET_DISABLE_ONLY) {
                int q;

                /* Returns number of symlinks that where supposed to be installed. */
                q = install_context_apply(scope, plus, paths, config_path, force, SEARCH_LOAD, changes, n_changes);
                if (r >= 0) {
                        if (q < 0)
                                r = q;
                        else
                                r += q;
                }
        }

        return r;
}

static int preset_prepare_one(
                UnitFileScope scope,
                InstallContext *plus,
                InstallContext *minus,
                LookupPaths *paths,
                const char *name,
                Presets presets,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_(install_context_done) InstallContext tmp = {};
        UnitFileInstallInfo *i;
        int r;

        if (install_info_find(plus, name) || install_info_find(minus, name))
                return 0;

        r = install_info_discover(scope, &tmp, paths, name, SEARCH_FOLLOW_CONFIG_SYMLINKS,
                                  &i, changes, n_changes);
        if (r < 0)
                return r;
        if (!streq(name, i->name)) {
                log_debug("Skipping %s because is an alias for %s", name, i->name);
                return 0;
        }

        r = query_presets(name, presets);
        if (r < 0)
                return r;

        if (r > 0) {
                r = install_info_discover(scope, plus, paths, name, SEARCH_LOAD|SEARCH_FOLLOW_CONFIG_SYMLINKS,
                                          &i, changes, n_changes);
                if (r < 0)
                        return r;

                r = install_info_may_process(i, paths, changes, n_changes);
                if (r < 0)
                        return r;
        } else
                r = install_info_discover(scope, minus, paths, name, SEARCH_FOLLOW_CONFIG_SYMLINKS,
                                          &i, changes, n_changes);

        return r;
}

int unit_file_preset(
                UnitFileScope scope,
                UnitFileFlags flags,
                const char *root_dir,
                char **files,
                UnitFilePresetMode mode,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_(install_context_done) InstallContext plus = {}, minus = {};
        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_(presets_freep) Presets presets = {};
        const char *config_path;
        char **i;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);
        assert(mode < _UNIT_FILE_PRESET_MAX);

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        config_path = (flags & UNIT_FILE_RUNTIME) ? paths.runtime_config : paths.persistent_config;

        r = read_presets(scope, root_dir, &presets);
        if (r < 0)
                return r;

        STRV_FOREACH(i, files) {
                r = preset_prepare_one(scope, &plus, &minus, &paths, *i, presets, changes, n_changes);
                if (r < 0)
                        return r;
        }

        return execute_preset(scope, &plus, &minus, &paths, config_path, files, mode, !!(flags & UNIT_FILE_FORCE), changes, n_changes);
}

int unit_file_preset_all(
                UnitFileScope scope,
                UnitFileFlags flags,
                const char *root_dir,
                UnitFilePresetMode mode,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_(install_context_done) InstallContext plus = {}, minus = {};
        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_(presets_freep) Presets presets = {};
        const char *config_path = NULL;
        char **i;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);
        assert(mode < _UNIT_FILE_PRESET_MAX);

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        config_path = (flags & UNIT_FILE_RUNTIME) ? paths.runtime_config : paths.persistent_config;

        r = read_presets(scope, root_dir, &presets);
        if (r < 0)
                return r;

        STRV_FOREACH(i, paths.search_path) {
                _cleanup_closedir_ DIR *d = NULL;
                struct dirent *de;

                d = opendir(*i);
                if (!d) {
                        if (errno == ENOENT)
                                continue;

                        return -errno;
                }

                FOREACH_DIRENT(de, d, return -errno) {

                        if (!unit_name_is_valid(de->d_name, UNIT_NAME_ANY))
                                continue;

                        dirent_ensure_type(d, de);

                        if (!IN_SET(de->d_type, DT_LNK, DT_REG))
                                continue;

                        /* we don't pass changes[] in, because we want to handle errors on our own */
                        r = preset_prepare_one(scope, &plus, &minus, &paths, de->d_name, presets, NULL, 0);
                        if (r == -ERFKILL)
                                r = unit_file_changes_add(changes, n_changes,
                                                          UNIT_FILE_IS_MASKED, de->d_name, NULL);
                        else if (r == -ENOLINK)
                                r = unit_file_changes_add(changes, n_changes,
                                                          UNIT_FILE_IS_DANGLING, de->d_name, NULL);
                        if (r < 0)
                                return r;
                }
        }

        return execute_preset(scope, &plus, &minus, &paths, config_path, NULL, mode, !!(flags & UNIT_FILE_FORCE), changes, n_changes);
}

static void unit_file_list_free_one(UnitFileList *f) {
        if (!f)
                return;

        free(f->path);
        free(f);
}

Hashmap* unit_file_list_free(Hashmap *h) {
        UnitFileList *i;

        while ((i = hashmap_steal_first(h)))
                unit_file_list_free_one(i);

        return hashmap_free(h);
}

DEFINE_TRIVIAL_CLEANUP_FUNC(UnitFileList*, unit_file_list_free_one);

int unit_file_get_list(
                UnitFileScope scope,
                const char *root_dir,
                Hashmap *h,
                char **states,
                char **patterns) {

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        char **i;
        int r;

        assert(scope >= 0);
        assert(scope < _UNIT_FILE_SCOPE_MAX);
        assert(h);

        r = lookup_paths_init(&paths, scope, 0, root_dir);
        if (r < 0)
                return r;

        STRV_FOREACH(i, paths.search_path) {
                _cleanup_closedir_ DIR *d = NULL;
                struct dirent *de;

                d = opendir(*i);
                if (!d) {
                        if (errno == ENOENT)
                                continue;
                        if (IN_SET(errno, ENOTDIR, EACCES)) {
                                log_debug("Failed to open \"%s\": %m", *i);
                                continue;
                        }

                        return -errno;
                }

                FOREACH_DIRENT(de, d, return -errno) {
                        _cleanup_(unit_file_list_free_onep) UnitFileList *f = NULL;

                        if (!unit_name_is_valid(de->d_name, UNIT_NAME_ANY))
                                continue;

                        if (!strv_fnmatch_or_empty(patterns, de->d_name, FNM_NOESCAPE))
                                continue;

                        if (hashmap_get(h, de->d_name))
                                continue;

                        dirent_ensure_type(d, de);

                        if (!IN_SET(de->d_type, DT_LNK, DT_REG))
                                continue;

                        f = new0(UnitFileList, 1);
                        if (!f)
                                return -ENOMEM;

                        f->path = path_make_absolute(de->d_name, *i);
                        if (!f->path)
                                return -ENOMEM;

                        r = unit_file_lookup_state(scope, &paths, de->d_name, &f->state);
                        if (r < 0)
                                f->state = UNIT_FILE_BAD;

                        if (!strv_isempty(states) &&
                            !strv_contains(states, unit_file_state_to_string(f->state)))
                                continue;

                        r = hashmap_put(h, basename(f->path), f);
                        if (r < 0)
                                return r;

                        f = NULL; /* prevent cleanup */
                }
        }

        return 0;
}

static const char* const unit_file_state_table[_UNIT_FILE_STATE_MAX] = {
        [UNIT_FILE_ENABLED] = "enabled",
        [UNIT_FILE_ENABLED_RUNTIME] = "enabled-runtime",
        [UNIT_FILE_LINKED] = "linked",
        [UNIT_FILE_LINKED_RUNTIME] = "linked-runtime",
        [UNIT_FILE_MASKED] = "masked",
        [UNIT_FILE_MASKED_RUNTIME] = "masked-runtime",
        [UNIT_FILE_STATIC] = "static",
        [UNIT_FILE_DISABLED] = "disabled",
        [UNIT_FILE_INDIRECT] = "indirect",
        [UNIT_FILE_GENERATED] = "generated",
        [UNIT_FILE_TRANSIENT] = "transient",
        [UNIT_FILE_BAD] = "bad",
};

DEFINE_STRING_TABLE_LOOKUP(unit_file_state, UnitFileState);

static const char* const unit_file_change_type_table[_UNIT_FILE_CHANGE_TYPE_MAX] = {
        [UNIT_FILE_SYMLINK] = "symlink",
        [UNIT_FILE_UNLINK] = "unlink",
        [UNIT_FILE_IS_MASKED] = "masked",
        [UNIT_FILE_IS_DANGLING] = "dangling",
};

DEFINE_STRING_TABLE_LOOKUP(unit_file_change_type, UnitFileChangeType);

static const char* const unit_file_preset_mode_table[_UNIT_FILE_PRESET_MAX] = {
        [UNIT_FILE_PRESET_FULL] = "full",
        [UNIT_FILE_PRESET_ENABLE_ONLY] = "enable-only",
        [UNIT_FILE_PRESET_DISABLE_ONLY] = "disable-only",
};

DEFINE_STRING_TABLE_LOOKUP(unit_file_preset_mode, UnitFilePresetMode);