/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  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 "log.h"
#include "macro.h"
#include "mkdir.h"
#include "path-lookup.h"
#include "path-util.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;

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

        assert(path);

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

        STRV_FOREACH(i, search)
                if (path_equal(parent, *i))
                        return true;

        return false;
}

static int get_config_path(UnitFileScope scope, bool runtime, const char *root_dir, char **ret) {
        char *p = NULL;
        int r;

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

        /* This determines where we shall create or remove our
         * installation ("configuration") symlinks */

        switch (scope) {

        case UNIT_FILE_SYSTEM:

                if (runtime)
                        p = path_join(root_dir, "/run/systemd/system", NULL);
                else
                        p = path_join(root_dir, SYSTEM_CONFIG_UNIT_PATH, NULL);
                break;

        case UNIT_FILE_GLOBAL:

                if (root_dir)
                        return -EINVAL;

                if (runtime)
                        p = strdup("/run/systemd/user");
                else
                        p = strdup(USER_CONFIG_UNIT_PATH);
                break;

        case UNIT_FILE_USER:

                if (root_dir)
                        return -EINVAL;

                if (runtime)
                        r = user_runtime_dir(&p);
                else
                        r = user_config_home(&p);
                if (r < 0)
                        return r;
                if (r == 0)
                        return -ENOENT;

                break;

        default:
                assert_not_reached("Bad scope");
        }

        if (!p)
                return -ENOMEM;

        *ret = p;
        return 0;
}

static bool is_config_path(UnitFileScope scope, const char *path) {
        int r;

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

        /* Checks whether the specified path is intended for
         * configuration or is outside of it */

        switch (scope) {

        case UNIT_FILE_SYSTEM:
        case UNIT_FILE_GLOBAL:
                return path_startswith(path, "/etc") ||
                        path_startswith(path, SYSTEM_CONFIG_UNIT_PATH) ||
                        path_startswith(path, "/run");


        case UNIT_FILE_USER: {
                _cleanup_free_ char *p = NULL;

                r = user_config_home(&p);
                if (r < 0)
                        return r;
                if (r > 0 && path_startswith(path, p))
                        return true;

                p = mfree(p);

                r = user_runtime_dir(&p);
                if (r < 0)
                        return r;
                if (r > 0 && path_startswith(path, p))
                        return true;

                return false;
        }

        default:
                assert_not_reached("Bad scope");
        }
}


static int verify_root_dir(UnitFileScope scope, const char **root_dir) {
        int r;

        assert(root_dir);

        /* Verifies that the specified root directory to operate on
         * makes sense. Reset it to NULL if it is the root directory
         * or set to empty */

        if (isempty(*root_dir) || path_equal(*root_dir, "/")) {
                *root_dir = NULL;
                return 0;
        }

        if (scope != UNIT_FILE_SYSTEM)
                return -EINVAL;

        r = is_dir(*root_dir, true);
        if (r < 0)
                return r;
        if (r == 0)
                return -ENOTDIR;

        return 0;
}

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

        UnitFileChange *c;
        unsigned i;

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

        if (!changes)
                return 0;

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

        *changes = c;
        i = *n_changes;

        c[i].type = type;
        c[i].path = strdup(path);
        if (!c[i].path)
                return -ENOMEM;

        path_kill_slashes(c[i].path);

        if (source) {
                c[i].source = strdup(source);
                if (!c[i].source) {
                        free(c[i].path);
                        return -ENOMEM;
                }

                path_kill_slashes(c[i].path);
        } else
                c[i].source = NULL;

        *n_changes = i+1;
        return 0;
}

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

        assert(changes || n_changes == 0);

        if (!changes)
                return;

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

        free(changes);
}

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

        _cleanup_free_ char *dest = NULL;
        int r;

        assert(old_path);
        assert(new_path);

        /* Actually create a symlink, and remember that we did. Is
         * smart enough to check if there's already a valid symlink in
         * place. */

        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 0;
        }

        if (errno != EEXIST)
                return -errno;

        r = readlink_malloc(new_path, &dest);
        if (r < 0)
                return r;

        if (path_equal(dest, old_path))
                return 0;

        if (!force)
                return -EEXIST;

        r = symlink_atomic(old_path, new_path);
        if (r < 0)
                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 0;
}

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,
                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(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, 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;
                        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;

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

                                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 (unlink(p) < 0 && errno != ENOENT) {
                                if (r == 0)
                                        r = -errno;
                                continue;
                        }

                        path_kill_slashes(p);
                        (void) rmdir_parents(p, config_path);

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

                        q = mark_symlink_for_removal(&remove_symlinks_to, p);
                        if (q < 0)
                                return q;
                        if (q > 0)
                                *restart = true;
                }
        }

        return r;
}

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

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

        assert(config_path);

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

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

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

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

        _cleanup_free_ char *normal_path = NULL, *runtime_path = NULL;
        bool same_name_link_runtime = false, same_name_link = false;
        int r;

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

        /* First look in the normal config path */
        r = get_config_path(scope, false, root_dir, &normal_path);
        if (r < 0)
                return r;

        r = find_symlinks(root_dir, name, normal_path, &same_name_link);
        if (r < 0)
                return r;
        if (r > 0) {
                *state = UNIT_FILE_ENABLED;
                return r;
        }

        /* Then look in runtime config path */
        r = get_config_path(scope, true, root_dir, &runtime_path);
        if (r < 0)
                return r;

        r = find_symlinks(root_dir, name, runtime_path, &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_add(
                InstallContext *c,
                const char *name,
                const char *path,
                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) {
                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->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 0;

fail:
        install_info_free(i);
        return r;
}

static int install_info_add_auto(
                InstallContext *c,
                const char *name_or_path,
                UnitFileInstallInfo **ret) {

        assert(c);
        assert(name_or_path);

        if (path_is_absolute(name_or_path))
                return install_info_add(c, NULL, name_or_path, ret);
        else
                return install_info_add(c, name_or_path, NULL, ret);
}

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 *i = userdata;
        InstallContext *c = data;
        int r;

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

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

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

                r = install_info_add(c, word, NULL, NULL);
                if (r < 0)
                        return r;

                r = strv_push(&i->also, word);
                if (r < 0)
                        return r;

                word = 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;
        char *printed;
        int r;

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

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

        if (!unit_instance_is_valid(printed)) {
                free(printed);
                return -EINVAL;
        }

        free(i->default_instance);
        i->default_instance = printed;

        return 0;
}

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

        const ConfigTableItem items[] = {
                { "Install", "Alias",           config_parse_strv,             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                        },
                {}
        };

        _cleanup_fclose_ FILE *f = NULL;
        _cleanup_close_ int fd = -1;
        struct stat st;
        int r;

        assert(c);
        assert(info);
        assert(path);

        path = prefix_roota(root_dir, path);

        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;
        }

        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 r;

        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 *np = NULL;
        int r;

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

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

        r = readlink_and_make_absolute_root(root_dir, path, &np);
        if (r < 0)
                return r;

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

                bn = basename(np);

                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;

                info->type = UNIT_FILE_TYPE_SYMLINK;
                info->symlink_target = np;
                np = NULL;
        }

        return 0;
}

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

        char **p;
        int r;

        assert(c);
        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, root_dir, flags);

        assert(info->name);

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

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

                r = unit_file_load_or_readlink(c, info, path, root_dir, flags);
                if (r < 0) {
                        if (r != -ENOENT)
                                return r;
                } else {
                        info->path = path;
                        path = NULL;
                        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. */

                _cleanup_free_ char *template = NULL;

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

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

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

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

        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(i->path);
        i->path = i->symlink_target;
        i->symlink_target = NULL;
        i->type = _UNIT_FILE_TYPE_INVALID;

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

static int install_info_traverse(
                UnitFileScope scope,
                InstallContext *c,
                const char *root_dir,
                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, root_dir, 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) && is_config_path(scope, i->path))
                        return -ELOOP;

                r = install_info_follow(c, i, root_dir, flags);
                if (r < 0) {
                        _cleanup_free_ char *buffer = NULL;
                        const char *bn;

                        if (r != -EXDEV)
                                return r;

                        /* 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, &i);
                        if (r < 0)
                                return r;

                        r = unit_file_search(c, i, paths, root_dir, flags);
                        if (r < 0)
                                return r;
                }

                /* Try again, with the new target we found. */
        }

        if (ret)
                *ret = i;

        return 0;
}

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

        UnitFileInstallInfo *i;
        int r;

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

        r = install_info_add_auto(c, name, &i);
        if (r < 0)
                return r;

        return install_info_traverse(scope, c, root_dir, paths, i, flags, ret);
}

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

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

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

        return r;
}

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

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

        assert(i);
        assert(config_path);

        if (unit_name_is_valid(i->name, UNIT_NAME_TEMPLATE)) {

                /* Don't install any symlink if there's no default
                 * instance configured */

                if (!i->default_instance)
                        return 0;

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

                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, NULL);
                if (!path)
                        return -ENOMEM;

                q = create_symlink(i->path, path, force, 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,
                const char *root_dir,
                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(i->path, paths->unit_path);
        if (r != 0)
                return r;

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

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

static int install_info_apply(
                UnitFileInstallInfo *i,
                const LookupPaths *paths,
                const char *config_path,
                const char *root_dir,
                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, config_path, force, changes, n_changes);

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

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

        q = install_info_symlink_link(i, paths, config_path, root_dir, force, changes, n_changes);
        if (r == 0)
                r = q;

        return r;
}

static int install_context_apply(
                UnitFileScope scope,
                InstallContext *c,
                const LookupPaths *paths,
                const char *config_path,
                const char *root_dir,
                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, root_dir, paths, i, flags, NULL);
                if (r < 0)
                        return r;

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

                q = install_info_apply(i, paths, config_path, root_dir, 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,
                const char *root_dir) {

        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, root_dir, paths, i, SEARCH_LOAD|SEARCH_FOLLOW_CONFIG_SYMLINKS, NULL);
                if (r < 0)
                        return r;

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

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

        return 0;
}

int unit_file_mask(
                UnitFileScope scope,
                bool runtime,
                const char *root_dir,
                char **files,
                bool force,
                UnitFileChange **changes,
                unsigned *n_changes) {

        _cleanup_free_ char *prefix = NULL;
        char **i;
        int r;

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

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

        r = get_config_path(scope, runtime, root_dir, &prefix);
        if (r < 0)
                return r;

        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, prefix);
                if (!path)
                        return -ENOMEM;

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

        return r;
}

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

        _cleanup_set_free_free_ Set *remove_symlinks_to = NULL;
        _cleanup_free_ char *config_path = NULL;
        _cleanup_free_ char **todo = NULL;
        size_t n_todo = 0, n_allocated = 0;
        char **i;
        int r, q;

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

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

        r = get_config_path(scope, runtime, root_dir, &config_path);
        if (r < 0)
                return r;

        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++] = *i;
        }

        strv_uniq(todo);

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

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

                if (unlink(path) < 0) {
                        if (errno != -ENOENT && r >= 0)
                                r = -errno;
                } else {
                        q = mark_symlink_for_removal(&remove_symlinks_to, path);
                        if (q < 0)
                                return q;

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

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

        return r;
}

int unit_file_link(
                UnitFileScope scope,
                bool runtime,
                const char *root_dir,
                char **files,
                bool force,
                UnitFileChange **changes,
                unsigned *n_changes) {

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

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

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

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

        r = get_config_path(scope, runtime, root_dir, &config_path);
        if (r < 0)
                return r;

        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(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(*i, paths.unit_path);
                if (q < 0)
                        return q;
                if (q > 0)
                        continue;

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

                todo[n_todo++] = *i;
        }

        strv_uniq(todo);

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

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

                q = create_symlink(*i, path, force, changes, n_changes);
                if (q < 0 && r >= 0)
                        r = q;
        }

        return r;
}

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

        _cleanup_lookup_paths_free_ LookupPaths paths = {};
        _cleanup_(install_context_done) InstallContext c = {};
        _cleanup_free_ char *config_path = NULL;
        UnitFileInstallInfo *i, *target_info;
        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 = verify_root_dir(scope, &root_dir);
        if (r < 0)
                return r;

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

        r = get_config_path(scope, runtime, root_dir, &config_path);
        if (r < 0)
                return r;

        r = install_info_discover(scope, &c, root_dir, &paths, target, SEARCH_FOLLOW_CONFIG_SYMLINKS, &target_info);
        if (r < 0)
                return r;
        if (target_info->type == UNIT_FILE_TYPE_MASKED)
                return -ESHUTDOWN;

        assert(target_info->type == UNIT_FILE_TYPE_REGULAR);

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

                r = install_info_discover(scope, &c, root_dir, &paths, *f, SEARCH_FOLLOW_CONFIG_SYMLINKS, &i);
                if (r < 0)
                        return r;
                if (i->type == UNIT_FILE_TYPE_MASKED)
                        return -ESHUTDOWN;

                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, root_dir, force, SEARCH_FOLLOW_CONFIG_SYMLINKS, changes, n_changes);
}

int unit_file_enable(
                UnitFileScope scope,
                bool runtime,
                const char *root_dir,
                char **files,
                bool force,
                UnitFileChange **changes,
                unsigned *n_changes) {

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

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

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

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

        r = get_config_path(scope, runtime, root_dir, &config_path);
        if (r < 0)
                return r;

        STRV_FOREACH(f, files) {
                r = install_info_discover(scope, &c, root_dir, &paths, *f, SEARCH_LOAD, &i);
                if (r < 0)
                        return r;
                if (i->type == UNIT_FILE_TYPE_MASKED)
                        return -ESHUTDOWN;

                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, root_dir, force, SEARCH_LOAD, changes, n_changes);
}

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

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

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

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

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

        r = get_config_path(scope, runtime, root_dir, &config_path);
        if (r < 0)
                return r;

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

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

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

        return remove_marked_symlinks(remove_symlinks_to, config_path, changes, n_changes);
}

int unit_file_reenable(
                UnitFileScope scope,
                bool runtime,
                const char *root_dir,
                char **files,
                bool force,
                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, runtime, root_dir, n, changes, n_changes);
        if (r < 0)
                return r;

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

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

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

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

        if (unit_name_to_type(name) != UNIT_TARGET)
                return -EINVAL;
        if (streq(name, SPECIAL_DEFAULT_TARGET))
                return -EINVAL;

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

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

        r = get_config_path(scope, false, root_dir, &config_path);
        if (r < 0)
                return r;

        r = install_info_discover(scope, &c, root_dir, &paths, name, 0, &i);
        if (r < 0)
                return r;
        if (i->type == UNIT_FILE_TYPE_MASKED)
                return -ESHUTDOWN;

        path = strjoina(config_path, "/" SPECIAL_DEFAULT_TARGET);

        return create_symlink(i->path, path, 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 = verify_root_dir(scope, &root_dir);
        if (r < 0)
                return r;

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

        r = install_info_discover(scope, &c, root_dir, &paths, SPECIAL_DEFAULT_TARGET, SEARCH_FOLLOW_CONFIG_SYMLINKS, &i);
        if (r < 0)
                return r;
        if (i->type == UNIT_FILE_TYPE_MASKED)
                return -ESHUTDOWN;

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

        *name = n;
        return 0;
}

int unit_file_lookup_state(
                UnitFileScope scope,
                const char *root_dir,
                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 = verify_root_dir(scope, &root_dir);
        if (r < 0)
                return r;

        r = install_info_discover(scope, &c, root_dir, paths, name, SEARCH_LOAD|SEARCH_FOLLOW_CONFIG_SYMLINKS, &i);
        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:
                state = path_startswith(i->path, "/run") ? UNIT_FILE_MASKED_RUNTIME : UNIT_FILE_MASKED;
                break;

        case UNIT_FILE_TYPE_REGULAR:
                r = find_symlinks_in_scope(scope, root_dir, 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 = verify_root_dir(scope, &root_dir);
        if (r < 0)
                return r;

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

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

int unit_file_query_preset(UnitFileScope scope, const char *root_dir, const char *name) {
        _cleanup_strv_free_ char **files = NULL;
        char **p;
        int r;

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

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

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

        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
                return 1; /* Default is "enable" */

        if (r < 0)
                return r;

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

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

                        return -errno;
                }

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

                        l = strstrip(line);

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

                        parameter = first_word(l, "enable");
                        if (parameter) {
                                if (fnmatch(parameter, name, FNM_NOESCAPE) == 0) {
                                        log_debug("Preset file says enable %s.", name);
                                        return 1;
                                }

                                continue;
                        }

                        parameter = first_word(l, "disable");
                        if (parameter) {
                                if (fnmatch(parameter, name, FNM_NOESCAPE) == 0) {
                                        log_debug("Preset file says disable %s.", name);
                                        return 0;
                                }

                                continue;
                        }

                        log_debug("Couldn't parse line '%s'", l);
                }
        }

        /* Default is "enable" */
        log_debug("Preset file doesn't say anything about %s, enabling.", name);
        return 1;
}

static int execute_preset(
                UnitFileScope scope,
                InstallContext *plus,
                InstallContext *minus,
                const LookupPaths *paths,
                const char *config_path,
                const char *root_dir,
                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, root_dir);
                if (r < 0)
                        return r;

                r = remove_marked_symlinks(remove_symlinks_to, config_path, 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, root_dir, 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 *root_dir,
                UnitFilePresetMode mode,
                const char *name) {

        UnitFileInstallInfo *i;
        int r;

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

        r = unit_file_query_preset(scope, root_dir, name);
        if (r < 0)
                return r;

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

                if (i->type == UNIT_FILE_TYPE_MASKED)
                        return -ESHUTDOWN;
        } else
                r = install_info_discover(scope, minus, root_dir, paths, name, SEARCH_FOLLOW_CONFIG_SYMLINKS, &i);

        return r;
}

int unit_file_preset(
                UnitFileScope scope,
                bool runtime,
                const char *root_dir,
                char **files,
                UnitFilePresetMode mode,
                bool force,
                UnitFileChange **changes,
                unsigned *n_changes) {

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

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

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

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

        r = get_config_path(scope, runtime, root_dir, &config_path);
        if (r < 0)
                return r;

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

                r = preset_prepare_one(scope, &plus, &minus, &paths, root_dir, mode, *i);
                if (r < 0)
                        return r;
        }

        return execute_preset(scope, &plus, &minus, &paths, config_path, root_dir, files, mode, force, changes, n_changes);
}

int unit_file_preset_all(
                UnitFileScope scope,
                bool runtime,
                const char *root_dir,
                UnitFilePresetMode mode,
                bool force,
                UnitFileChange **changes,
                unsigned *n_changes) {

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

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

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

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

        r = get_config_path(scope, runtime, root_dir, &config_path);
        if (r < 0)
                return r;

        STRV_FOREACH(i, paths.unit_path) {
                _cleanup_closedir_ DIR *d = NULL;
                _cleanup_free_ char *units_dir;
                struct dirent *de;

                units_dir = path_join(root_dir, *i, NULL);
                if (!units_dir)
                        return -ENOMEM;

                d = opendir(units_dir);
                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;

                        r = preset_prepare_one(scope, &plus, &minus, &paths, root_dir, mode, de->d_name);
                        if (r < 0)
                                return r;
                }
        }

        return execute_preset(scope, &plus, &minus, &paths, config_path, root_dir, NULL, mode, 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) {

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

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

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

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

        STRV_FOREACH(i, paths.unit_path) {
                _cleanup_closedir_ DIR *d = NULL;
                _cleanup_free_ char *units_dir;
                struct dirent *de;

                units_dir = path_join(root_dir, *i, NULL);
                if (!units_dir)
                        return -ENOMEM;

                d = opendir(units_dir);
                if (!d) {
                        if (errno == ENOENT)
                                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 (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, units_dir);
                        if (!f->path)
                                return -ENOMEM;

                        r = unit_file_lookup_state(scope, root_dir, &paths, basename(f->path), &f->state);
                        if (r < 0)
                                f->state = UNIT_FILE_BAD;

                        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_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",
};

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);
