s/name/unit

1 files changed, 807 insertions, 0 deletions

diff --git a/unit.c b/unit.c
new file mode 100644
index 0000000000..15401e24fe
--- /dev/null
+++ b/unit.c
@@ -0,0 +1,807 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+#include <assert.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/epoll.h>
+#include <sys/timerfd.h>
+#include <sys/poll.h>
+
+#include "set.h"
+#include "unit.h"
+#include "macro.h"
+#include "strv.h"
+#include "load-fragment.h"
+#include "load-dropin.h"
+#include "log.h"
+
+const UnitVTable * const unit_vtable[_UNIT_TYPE_MAX] = {
+        [UNIT_SERVICE] = &service_vtable,
+        [UNIT_TIMER] = &timer_vtable,
+        [UNIT_SOCKET] = &socket_vtable,
+        [UNIT_TARGET] = &target_vtable,
+        [UNIT_DEVICE] = &device_vtable,
+        [UNIT_MOUNT] = &mount_vtable,
+        [UNIT_AUTOMOUNT] = &automount_vtable,
+        [UNIT_SNAPSHOT] = &snapshot_vtable
+};
+
+UnitType unit_name_to_type(const char *n) {
+        UnitType t;
+
+        assert(n);
+
+        for (t = 0; t < _UNIT_TYPE_MAX; t++)
+                if (endswith(n, unit_vtable[t]->suffix))
+                        return t;
+
+        return _UNIT_TYPE_INVALID;
+}
+
+#define VALID_CHARS                             \
+        "0123456789"                            \
+        "abcdefghijklmnopqrstuvwxyz"            \
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"            \
+        "-_"
+
+bool unit_name_is_valid(const char *n) {
+        UnitType t;
+        const char *e, *i;
+
+        assert(n);
+
+        if (strlen(n) >= UNIT_NAME_MAX)
+                return false;
+
+        t = unit_name_to_type(n);
+        if (t < 0 || t >= _UNIT_TYPE_MAX)
+                return false;
+
+        if (!(e = strrchr(n, '.')))
+                return false;
+
+        for (i = n; i < e; i++)
+                if (!strchr(VALID_CHARS, *i))
+                        return false;
+
+        return true;
+}
+
+char *unit_name_change_suffix(const char *n, const char *suffix) {
+        char *e, *r;
+        size_t a, b;
+
+        assert(n);
+        assert(unit_name_is_valid(n));
+        assert(suffix);
+
+        assert_se(e = strrchr(n, '.'));
+        a = e - n;
+        b = strlen(suffix);
+
+        if (!(r = new(char, a + b + 1)))
+                return NULL;
+
+        memcpy(r, n, a);
+        memcpy(r+a, suffix, b+1);
+
+        return r;
+}
+
+Unit *unit_new(Manager *m) {
+        Unit *u;
+
+        assert(m);
+
+        if (!(u = new0(Unit, 1)))
+                return NULL;
+
+        if (!(u->meta.names = set_new(string_hash_func, string_compare_func))) {
+                free(u);
+                return NULL;
+        }
+
+        u->meta.manager = m;
+        u->meta.type = _UNIT_TYPE_INVALID;
+
+        return u;
+}
+
+int unit_add_name(Unit *u, const char *text) {
+        UnitType t;
+        char *s;
+        int r;
+
+        assert(u);
+        assert(text);
+
+        if (!unit_name_is_valid(text))
+                return -EINVAL;
+
+        if ((t = unit_name_to_type(text)) == _UNIT_TYPE_INVALID)
+                return -EINVAL;
+
+        if (u->meta.type != _UNIT_TYPE_INVALID && t != u->meta.type)
+                return -EINVAL;
+
+        if (!(s = strdup(text)))
+                return -ENOMEM;
+
+        if ((r = set_put(u->meta.names, s)) < 0) {
+                free(s);
+
+                if (r == -EEXIST)
+                        return 0;
+
+                return r;
+        }
+
+        if ((r = hashmap_put(u->meta.manager->units, s, u)) < 0) {
+                set_remove(u->meta.names, s);
+                free(s);
+                return r;
+        }
+
+        u->meta.type = t;
+
+        if (!u->meta.id)
+                u->meta.id = s;
+
+        return 0;
+}
+
+void unit_add_to_load_queue(Unit *u) {
+        assert(u);
+
+        if (u->meta.load_state != UNIT_STUB || u->meta.in_load_queue)
+                return;
+
+        LIST_PREPEND(Meta, load_queue, u->meta.manager->load_queue, &u->meta);
+        u->meta.in_load_queue = true;
+}
+
+static void bidi_set_free(Unit *u, Set *s) {
+        Iterator i;
+        Unit *other;
+
+        assert(u);
+
+        /* Frees the set and makes sure we are dropped from the
+         * inverse pointers */
+
+        SET_FOREACH(other, s, i) {
+                UnitDependency d;
+
+                for (d = 0; d < _UNIT_DEPENDENCY_MAX; d++)
+                        set_remove(other->meta.dependencies[d], u);
+        }
+
+        set_free(s);
+}
+
+void unit_free(Unit *u) {
+        UnitDependency d;
+        Iterator i;
+        char *t;
+
+        assert(u);
+
+        /* Detach from next 'bigger' objects */
+
+        SET_FOREACH(t, u->meta.names, i)
+                hashmap_remove_value(u->meta.manager->units, t, u);
+
+        if (u->meta.in_load_queue)
+                LIST_REMOVE(Meta, load_queue, u->meta.manager->load_queue, &u->meta);
+
+        if (u->meta.load_state == UNIT_LOADED)
+                if (UNIT_VTABLE(u)->done)
+                        UNIT_VTABLE(u)->done(u);
+
+        /* Free data and next 'smaller' objects */
+        if (u->meta.job)
+                job_free(u->meta.job);
+
+        for (d = 0; d < _UNIT_DEPENDENCY_MAX; d++)
+                bidi_set_free(u, u->meta.dependencies[d]);
+
+        free(u->meta.description);
+
+        while ((t = set_steal_first(u->meta.names)))
+                free(t);
+        set_free(u->meta.names);
+
+        free(u);
+}
+
+UnitActiveState unit_active_state(Unit *u) {
+        assert(u);
+
+        if (u->meta.load_state != UNIT_LOADED)
+                return UNIT_INACTIVE;
+
+        return UNIT_VTABLE(u)->active_state(u);
+}
+
+static int ensure_merge(Set **s, Set *other) {
+
+        if (!other)
+                return 0;
+
+        if (*s)
+                return set_merge(*s, other);
+
+        if (!(*s = set_copy(other)))
+                return -ENOMEM;
+
+        return 0;
+}
+
+/* FIXME: Does not rollback on failure! */
+int unit_merge(Unit *u, Unit *other) {
+        int r;
+        UnitDependency d;
+
+        assert(u);
+        assert(other);
+        assert(u->meta.manager == other->meta.manager);
+
+        /* This merges 'other' into 'unit'. FIXME: This does not
+         * rollback on failure. */
+
+        if (u->meta.type != u->meta.type)
+                return -EINVAL;
+
+        if (u->meta.load_state != UNIT_STUB)
+                return -EINVAL;
+
+        /* Merge names */
+        if ((r = ensure_merge(&u->meta.names, other->meta.names)) < 0)
+                return r;
+
+        /* Merge dependencies */
+        for (d = 0; d < _UNIT_DEPENDENCY_MAX; d++)
+                /* fixme, the inverse mapping is missing */
+                if ((r = ensure_merge(&u->meta.dependencies[d], other->meta.dependencies[d])) < 0)
+                        return r;
+
+        return 0;
+}
+
+const char* unit_id(Unit *u) {
+        assert(u);
+
+        if (u->meta.id)
+                return u->meta.id;
+
+        return set_first(u->meta.names);
+}
+
+const char *unit_description(Unit *u) {
+        assert(u);
+
+        if (u->meta.description)
+                return u->meta.description;
+
+        return unit_id(u);
+}
+
+void unit_dump(Unit *u, FILE *f, const char *prefix) {
+
+        static const char* const load_state_table[_UNIT_LOAD_STATE_MAX] = {
+                [UNIT_STUB] = "stub",
+                [UNIT_LOADED] = "loaded",
+                [UNIT_FAILED] = "failed"
+        };
+
+        static const char* const active_state_table[_UNIT_ACTIVE_STATE_MAX] = {
+                [UNIT_ACTIVE] = "active",
+                [UNIT_INACTIVE] = "inactive",
+                [UNIT_ACTIVATING] = "activating",
+                [UNIT_DEACTIVATING] = "deactivating"
+        };
+
+        static const char* const dependency_table[_UNIT_DEPENDENCY_MAX] = {
+                [UNIT_REQUIRES] = "Requires",
+                [UNIT_SOFT_REQUIRES] = "SoftRequires",
+                [UNIT_WANTS] = "Wants",
+                [UNIT_REQUISITE] = "Requisite",
+                [UNIT_SOFT_REQUISITE] = "SoftRequisite",
+                [UNIT_REQUIRED_BY] = "RequiredBy",
+                [UNIT_SOFT_REQUIRED_BY] = "SoftRequiredBy",
+                [UNIT_WANTED_BY] = "WantedBy",
+                [UNIT_CONFLICTS] = "Conflicts",
+                [UNIT_BEFORE] = "Before",
+                [UNIT_AFTER] = "After",
+        };
+
+        char *t;
+        UnitDependency d;
+        Iterator i;
+        char *prefix2;
+
+        assert(u);
+
+        if (!prefix)
+                prefix = "";
+        prefix2 = strappend(prefix, "\t");
+        if (!prefix2)
+                prefix2 = "";
+
+        fprintf(f,
+                "%s→ Unit %s:\n"
+                "%s\tDescription: %s\n"
+                "%s\tUnit Load State: %s\n"
+                "%s\tUnit Active State: %s\n",
+                prefix, unit_id(u),
+                prefix, unit_description(u),
+                prefix, load_state_table[u->meta.load_state],
+                prefix, active_state_table[unit_active_state(u)]);
+
+        SET_FOREACH(t, u->meta.names, i)
+                fprintf(f, "%s\tName: %s\n", prefix, t);
+
+        for (d = 0; d < _UNIT_DEPENDENCY_MAX; d++) {
+                Unit *other;
+
+                if (set_isempty(u->meta.dependencies[d]))
+                        continue;
+
+                SET_FOREACH(other, u->meta.dependencies[d], i)
+                        fprintf(f, "%s\t%s: %s\n", prefix, dependency_table[d], unit_id(other));
+        }
+
+        if (UNIT_VTABLE(u)->dump)
+                UNIT_VTABLE(u)->dump(u, f, prefix2);
+
+        if (u->meta.job)
+                job_dump(u->meta.job, f, prefix2);
+
+        free(prefix2);
+}
+
+/* Common implementation for multiple backends */
+int unit_load_fragment_and_dropin(Unit *u) {
+        int r;
+
+        assert(u);
+
+        /* Load a .socket file */
+        if ((r = unit_load_fragment(u)) < 0)
+                return r;
+
+        /* Load drop-in directory data */
+        if ((r = unit_load_dropin(u)) < 0)
+                return r;
+
+        return 0;
+}
+
+int unit_load(Unit *u) {
+        int r;
+
+        assert(u);
+
+        if (u->meta.in_load_queue) {
+                LIST_REMOVE(Meta, load_queue, u->meta.manager->load_queue, &u->meta);
+                u->meta.in_load_queue = false;
+        }
+
+        if (u->meta.load_state != UNIT_STUB)
+                return 0;
+
+        if (UNIT_VTABLE(u)->init)
+                if ((r = UNIT_VTABLE(u)->init(u)) < 0)
+                        goto fail;
+
+        u->meta.load_state = UNIT_LOADED;
+        return 0;
+
+fail:
+        u->meta.load_state = UNIT_FAILED;
+        return r;
+}
+
+/* Errors:
+ *         -EBADR:    This unit type does not support starting.
+ *         -EALREADY: Unit is already started.
+ *         -EAGAIN:   An operation is already in progress. Retry later.
+ */
+int unit_start(Unit *u) {
+        UnitActiveState state;
+
+        assert(u);
+
+        if (!UNIT_VTABLE(u)->start)
+                return -EBADR;
+
+        state = unit_active_state(u);
+        if (UNIT_IS_ACTIVE_OR_RELOADING(state))
+                return -EALREADY;
+
+        /* We don't suppress calls to ->start() here when we are
+         * already starting, to allow this request to be used as a
+         * "hurry up" call, for example when the unit is in some "auto
+         * restart" state where it waits for a holdoff timer to elapse
+         * before it will start again. */
+
+        return UNIT_VTABLE(u)->start(u);
+}
+
+bool unit_can_start(Unit *u) {
+        assert(u);
+
+        return !!UNIT_VTABLE(u)->start;
+}
+
+/* Errors:
+ *         -EBADR:    This unit type does not support stopping.
+ *         -EALREADY: Unit is already stopped.
+ *         -EAGAIN:   An operation is already in progress. Retry later.
+ */
+int unit_stop(Unit *u) {
+        UnitActiveState state;
+
+        assert(u);
+
+        if (!UNIT_VTABLE(u)->stop)
+                return -EBADR;
+
+        state = unit_active_state(u);
+        if (state == UNIT_INACTIVE)
+                return -EALREADY;
+
+        if (state == UNIT_DEACTIVATING)
+                return 0;
+
+        return UNIT_VTABLE(u)->stop(u);
+}
+
+/* Errors:
+ *         -EBADR:    This unit type does not support reloading.
+ *         -ENOEXEC:  Unit is not started.
+ *         -EAGAIN:   An operation is already in progress. Retry later.
+ */
+int unit_reload(Unit *u) {
+        UnitActiveState state;
+
+        assert(u);
+
+        if (!unit_can_reload(u))
+                return -EBADR;
+
+        state = unit_active_state(u);
+        if (unit_active_state(u) == UNIT_ACTIVE_RELOADING)
+                return -EALREADY;
+
+        if (unit_active_state(u) != UNIT_ACTIVE)
+                return -ENOEXEC;
+
+        return UNIT_VTABLE(u)->reload(u);
+}
+
+bool unit_can_reload(Unit *u) {
+        assert(u);
+
+        if (!UNIT_VTABLE(u)->reload)
+                return false;
+
+        if (!UNIT_VTABLE(u)->can_reload)
+                return true;
+
+        return UNIT_VTABLE(u)->can_reload(u);
+}
+
+static void retroactively_start_dependencies(Unit *u) {
+        Iterator i;
+        Unit *other;
+
+        assert(u);
+        assert(UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(u)));
+
+        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRES], i)
+                if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
+                        manager_add_job(u->meta.manager, JOB_START, other, JOB_REPLACE, true, NULL);
+
+        SET_FOREACH(other, u->meta.dependencies[UNIT_SOFT_REQUIRES], i)
+                if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
+                        manager_add_job(u->meta.manager, JOB_START, other, JOB_FAIL, false, NULL);
+
+        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUISITE], i)
+                if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
+                        manager_add_job(u->meta.manager, JOB_START, other, JOB_REPLACE, true, NULL);
+
+        SET_FOREACH(other, u->meta.dependencies[UNIT_WANTS], i)
+                if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
+                        manager_add_job(u->meta.manager, JOB_START, other, JOB_FAIL, false, NULL);
+
+        SET_FOREACH(other, u->meta.dependencies[UNIT_CONFLICTS], i)
+                if (!UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(other)))
+                        manager_add_job(u->meta.manager, JOB_STOP, other, JOB_REPLACE, true, NULL);
+}
+
+static void retroactively_stop_dependencies(Unit *u) {
+        Iterator i;
+        Unit *other;
+
+        assert(u);
+        assert(UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(u)));
+
+        SET_FOREACH(other, u->meta.dependencies[UNIT_REQUIRED_BY], i)
+                if (!UNIT_IS_INACTIVE_OR_DEACTIVATING(unit_active_state(other)))
+                        manager_add_job(u->meta.manager, JOB_STOP, other, JOB_REPLACE, true, NULL);
+}
+
+void unit_notify(Unit *u, UnitActiveState os, UnitActiveState ns) {
+        assert(u);
+        assert(os < _UNIT_ACTIVE_STATE_MAX);
+        assert(ns < _UNIT_ACTIVE_STATE_MAX);
+        assert(!(os == UNIT_ACTIVE && ns == UNIT_ACTIVATING));
+        assert(!(os == UNIT_INACTIVE && ns == UNIT_DEACTIVATING));
+
+        if (os == ns)
+                return;
+
+        if (!UNIT_IS_ACTIVE_OR_RELOADING(os) && UNIT_IS_ACTIVE_OR_RELOADING(ns))
+                u->meta.active_enter_timestamp = now(CLOCK_REALTIME);
+        else if (UNIT_IS_ACTIVE_OR_RELOADING(os) && !UNIT_IS_ACTIVE_OR_RELOADING(ns))
+                u->meta.active_exit_timestamp = now(CLOCK_REALTIME);
+
+        if (u->meta.job) {
+
+                if (u->meta.job->state == JOB_WAITING)
+
+                        /* So we reached a different state for this
+                         * job. Let's see if we can run it now if it
+                         * failed previously due to EAGAIN. */
+                        job_schedule_run(u->meta.job);
+
+                else {
+                        assert(u->meta.job->state == JOB_RUNNING);
+
+                        /* Let's check of this state change
+                         * constitutes a finished job, or maybe
+                         * cotradicts a running job and hence needs to
+                         * invalidate jobs. */
+
+                        switch (u->meta.job->type) {
+
+                        case JOB_START:
+                        case JOB_VERIFY_ACTIVE:
+
+                                if (UNIT_IS_ACTIVE_OR_RELOADING(ns)) {
+                                        job_finish_and_invalidate(u->meta.job, true);
+                                        return;
+                                } else if (ns == UNIT_ACTIVATING)
+                                        return;
+                                else
+                                        job_finish_and_invalidate(u->meta.job, false);
+
+                                break;
+
+                        case JOB_RELOAD:
+                        case JOB_RELOAD_OR_START:
+
+                                if (ns == UNIT_ACTIVE) {
+                                        job_finish_and_invalidate(u->meta.job, true);
+                                        return;
+                                } else if (ns == UNIT_ACTIVATING || ns == UNIT_ACTIVE_RELOADING)
+                                        return;
+                                else
+                                        job_finish_and_invalidate(u->meta.job, false);
+
+                                break;
+
+                        case JOB_STOP:
+                        case JOB_RESTART:
+                        case JOB_TRY_RESTART:
+
+                                if (ns == UNIT_INACTIVE) {
+                                        job_finish_and_invalidate(u->meta.job, true);
+                                        return;
+                                } else if (ns == UNIT_DEACTIVATING)
+                                        return;
+                                else
+                                        job_finish_and_invalidate(u->meta.job, false);
+
+                                break;
+
+                        default:
+                                assert_not_reached("Job type unknown");
+                        }
+                }
+        }
+
+        /* If this state change happened without being requested by a
+         * job, then let's retroactively start or stop dependencies */
+
+        if (UNIT_IS_INACTIVE_OR_DEACTIVATING(os) && UNIT_IS_ACTIVE_OR_ACTIVATING(ns))
+                retroactively_start_dependencies(u);
+        else if (UNIT_IS_ACTIVE_OR_ACTIVATING(os) && UNIT_IS_INACTIVE_OR_DEACTIVATING(ns))
+                retroactively_stop_dependencies(u);
+}
+
+int unit_watch_fd(Unit *u, int fd, uint32_t events) {
+        struct epoll_event ev;
+
+        assert(u);
+        assert(fd >= 0);
+
+        zero(ev);
+        ev.data.fd = fd;
+        ev.data.ptr = u;
+        ev.data.u32 = MANAGER_FD;
+        ev.events = events;
+
+        if (epoll_ctl(u->meta.manager->epoll_fd, EPOLL_CTL_ADD, fd, &ev) >= 0)
+                return 0;
+
+        if (errno == EEXIST)
+                if (epoll_ctl(u->meta.manager->epoll_fd, EPOLL_CTL_MOD, fd, &ev) >= 0)
+                        return 0;
+
+        return -errno;
+}
+
+void unit_unwatch_fd(Unit *u, int fd) {
+        assert(u);
+        assert(fd >= 0);
+
+        assert_se(epoll_ctl(u->meta.manager->epoll_fd, EPOLL_CTL_DEL, fd, NULL) >= 0 || errno == ENOENT);
+}
+
+int unit_watch_pid(Unit *u, pid_t pid) {
+        assert(u);
+        assert(pid >= 1);
+
+        return hashmap_put(u->meta.manager->watch_pids, UINT32_TO_PTR(pid), u);
+}
+
+void unit_unwatch_pid(Unit *u, pid_t pid) {
+        assert(u);
+        assert(pid >= 1);
+
+        hashmap_remove(u->meta.manager->watch_pids, UINT32_TO_PTR(pid));
+}
+
+int unit_watch_timer(Unit *u, usec_t delay, int *id) {
+        struct epoll_event ev;
+        int fd;
+        struct itimerspec its;
+        int flags;
+        bool ours;
+
+        assert(u);
+        assert(id);
+
+        /* This will try to reuse the old timer if there is one */
+
+        if (*id >= 0) {
+                ours = false;
+                fd = *id;
+
+        } else {
+                ours = true;
+
+                if ((fd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK|TFD_CLOEXEC)) < 0)
+                        return -errno;
+        }
+
+        zero(its);
+
+        if (delay <= 0) {
+                /* Set absolute time in the past, but not 0, since we
+                 * don't want to disarm the timer */
+                its.it_value.tv_sec = 0;
+                its.it_value.tv_nsec = 1;
+
+                flags = TFD_TIMER_ABSTIME;
+        } else {
+                timespec_store(&its.it_value, delay);
+                flags = 0;
+        }
+
+        /* This will also flush the elapse counter */
+        if (timerfd_settime(fd, flags, &its, NULL) < 0)
+                goto fail;
+
+        zero(ev);
+        ev.data.fd = fd;
+        ev.data.ptr = u;
+        ev.data.u32 = MANAGER_TIMER;
+        ev.events = POLLIN;
+
+        if (epoll_ctl(u->meta.manager->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0)
+                goto fail;
+
+        *id = fd;
+        return 0;
+
+fail:
+        if (ours)
+                assert_se(close_nointr(fd) == 0);
+
+        return -errno;
+}
+
+void unit_unwatch_timer(Unit *u, int *id) {
+        assert(u);
+        assert(id);
+
+        if (*id < 0)
+                return;
+
+        assert_se(epoll_ctl(u->meta.manager->epoll_fd, EPOLL_CTL_DEL, *id, NULL) >= 0);
+        assert_se(close_nointr(*id) == 0);
+        *id = -1;
+}
+
+bool unit_job_is_applicable(Unit *u, JobType j) {
+        assert(u);
+        assert(j >= 0 && j < _JOB_TYPE_MAX);
+
+        switch (j) {
+
+        case JOB_VERIFY_ACTIVE:
+        case JOB_START:
+                return true;
+
+        case JOB_STOP:
+        case JOB_RESTART:
+        case JOB_TRY_RESTART:
+                return unit_can_start(u);
+
+        case JOB_RELOAD:
+                return unit_can_reload(u);
+
+        case JOB_RELOAD_OR_START:
+                return unit_can_reload(u) && unit_can_start(u);
+
+        default:
+                assert_not_reached("Invalid job type");
+        }
+}
+
+int unit_add_dependency(Unit *u, UnitDependency d, Unit *other) {
+
+        static const UnitDependency inverse_table[_UNIT_DEPENDENCY_MAX] = {
+                [UNIT_REQUIRES] = UNIT_REQUIRED_BY,
+                [UNIT_SOFT_REQUIRES] = UNIT_SOFT_REQUIRED_BY,
+                [UNIT_WANTS] = UNIT_WANTED_BY,
+                [UNIT_REQUISITE] = UNIT_REQUIRED_BY,
+                [UNIT_SOFT_REQUISITE] = UNIT_SOFT_REQUIRED_BY,
+                [UNIT_REQUIRED_BY] = _UNIT_DEPENDENCY_INVALID,
+                [UNIT_SOFT_REQUIRED_BY] = _UNIT_DEPENDENCY_INVALID,
+                [UNIT_WANTED_BY] = _UNIT_DEPENDENCY_INVALID,
+                [UNIT_CONFLICTS] = UNIT_CONFLICTS,
+                [UNIT_BEFORE] = UNIT_AFTER,
+                [UNIT_AFTER] = UNIT_BEFORE
+        };
+        int r;
+
+        assert(u);
+        assert(d >= 0 && d < _UNIT_DEPENDENCY_MAX);
+        assert(inverse_table[d] != _UNIT_DEPENDENCY_INVALID);
+        assert(other);
+
+        /* We won't allow dependencies on ourselves. We will not
+         * consider them an error however. */
+        if (u == other)
+                return 0;
+
+        if ((r = set_ensure_allocated(&u->meta.dependencies[d], trivial_hash_func, trivial_compare_func)) < 0)
+                return r;
+
+        if ((r = set_ensure_allocated(&other->meta.dependencies[inverse_table[d]], trivial_hash_func, trivial_compare_func)) < 0)
+                return r;
+
+        if ((r = set_put(u->meta.dependencies[d], other)) < 0)
+                return r;
+
+        if ((r = set_put(other->meta.dependencies[inverse_table[d]], u)) < 0) {
+                set_remove(u->meta.dependencies[d], other);
+                return r;
+        }
+
+        return 0;
+}