/* SPDX-License-Identifier: LGPL-2.1+ */

#include <fcntl.h>

#include <unistd.h>

#include "alloc-util.h"

#include "bus-common-errors.h"

#include "bus-error.h"

#include "terminal-util.h"

#include "transaction.h"

#include "dbus-unit.h"

static void transaction_unlink_job(Transaction *tr, Job *j, bool delete_dependencies);

static void transaction_delete_job(Transaction *tr, Job *j, bool delete_dependencies) {

        assert(tr);

        assert(j);

        /* Deletes one job from the transaction */

        transaction_unlink_job(tr, j, delete_dependencies);

        job_free(j);

}

static void transaction_delete_unit(Transaction *tr, Unit *u) {

        Job *j;

        /* Deletes all jobs associated with a certain unit from the

         * transaction */

        while ((j = hashmap_get(tr->jobs, u)))

                transaction_delete_job(tr, j, true);

}

void transaction_abort(Transaction *tr) {

        Job *j;

        assert(tr);

        while ((j = hashmap_first(tr->jobs)))

                transaction_delete_job(tr, j, false);

        assert(hashmap_isempty(tr->jobs));

}

static void transaction_find_jobs_that_matter_to_anchor(Job *j, unsigned generation) {

        JobDependency *l;

        /* A recursive sweep through the graph that marks all units

         * that matter to the anchor job, i.e. are directly or

         * indirectly a dependency of the anchor job via paths that

         * are fully marked as mattering. */

        j->matters_to_anchor = true;

        j->generation = generation;

        LIST_FOREACH(subject, l, j->subject_list) {

                /* This link does not matter */

                if (!l->matters)

                        continue;

                /* This unit has already been marked */

                if (l->object->generation == generation)

                        continue;

                transaction_find_jobs_that_matter_to_anchor(l->object, generation);

        }

}

static void transaction_merge_and_delete_job(Transaction *tr, Job *j, Job *other, JobType t) {

        JobDependency *l, *last;

        assert(j);

        assert(other);

        assert(j->unit == other->unit);

        assert(!j->installed);

        /* Merges 'other' into 'j' and then deletes 'other'. */

        j->type = t;

        j->state = JOB_WAITING;

        j->irreversible = j->irreversible || other->irreversible;

        j->matters_to_anchor = j->matters_to_anchor || other->matters_to_anchor;

        /* Patch us in as new owner of the JobDependency objects */

        last = NULL;

        LIST_FOREACH(subject, l, other->subject_list) {

                assert(l->subject == other);

                l->subject = j;

                last = l;

        }

        /* Merge both lists */

        if (last) {

                last->subject_next = j->subject_list;

                if (j->subject_list)

                        j->subject_list->subject_prev = last;

                j->subject_list = other->subject_list;

        }

        /* Patch us in as new owner of the JobDependency objects */

        last = NULL;

        LIST_FOREACH(object, l, other->object_list) {

                assert(l->object == other);

                l->object = j;

                last = l;

        }

        /* Merge both lists */

        if (last) {

                last->object_next = j->object_list;

                if (j->object_list)

                        j->object_list->object_prev = last;

                j->object_list = other->object_list;

        }

        /* Kill the other job */

        other->subject_list = NULL;

        other->object_list = NULL;

        transaction_delete_job(tr, other, true);

}

_pure_ static bool job_is_conflicted_by(Job *j) {

        JobDependency *l;

        assert(j);

        /* Returns true if this job is pulled in by a least one

         * ConflictedBy dependency. */

        LIST_FOREACH(object, l, j->object_list)

                if (l->conflicts)

                        return true;

        return false;

}

static int delete_one_unmergeable_job(Transaction *tr, Job *j) {

        Job *k;

        assert(j);

        /* Tries to delete one item in the linked list

         * j->transaction_next->transaction_next->... that conflicts

         * with another one, in an attempt to make an inconsistent

         * transaction work. */

        /* We rely here on the fact that if a merged with b does not

         * merge with c, either a or b merge with c neither */

        LIST_FOREACH(transaction, j, j)

                LIST_FOREACH(transaction, k, j->transaction_next) {

                        Job *d;

                        /* Is this one mergeable? Then skip it */

                        if (job_type_is_mergeable(j->type, k->type))

                                continue;

                        /* Ok, we found two that conflict, let's see if we can

                         * drop one of them */

                        if (!j->matters_to_anchor && !k->matters_to_anchor) {

                                /* Both jobs don't matter, so let's

                                 * find the one that is smarter to

                                 * remove. Let's think positive and

                                 * rather remove stops then starts --

                                 * except if something is being

                                 * stopped because it is conflicted by

                                 * another unit in which case we

                                 * rather remove the start. */

                                log_unit_debug(j->unit,

                                               "Looking at job %s/%s conflicted_by=%s",

                                               j->unit->id, job_type_to_string(j->type),

                                               yes_no(j->type == JOB_STOP && job_is_conflicted_by(j)));

                                log_unit_debug(k->unit,

                                               "Looking at job %s/%s conflicted_by=%s",

                                               k->unit->id, job_type_to_string(k->type),

                                               yes_no(k->type == JOB_STOP && job_is_conflicted_by(k)));

                                if (j->type == JOB_STOP) {

                                        if (job_is_conflicted_by(j))

                                                d = k;

                                        else

                                                d = j;

                                } else if (k->type == JOB_STOP) {

                                        if (job_is_conflicted_by(k))

                                                d = j;

                                        else

                                                d = k;

                                } else

                                        d = j;

                        } else if (!j->matters_to_anchor)

                                d = j;

                        else if (!k->matters_to_anchor)

                                d = k;

                        else

                                return -ENOEXEC;

                        /* Ok, we can drop one, so let's do so. */

                        log_unit_debug(d->unit,

                                       "Fixing conflicting jobs %s/%s,%s/%s by deleting job %s/%s",

                                       j->unit->id, job_type_to_string(j->type),

                                       k->unit->id, job_type_to_string(k->type),

                                       d->unit->id, job_type_to_string(d->type));

                        transaction_delete_job(tr, d, true);

                        return 0;

                }

        return -EINVAL;

}

static int transaction_merge_jobs(Transaction *tr, sd_bus_error *e) {

        Job *j;

        Iterator i;

        int r;

        assert(tr);

        /* First step, check whether any of the jobs for one specific

         * task conflict. If so, try to drop one of them. */

        HASHMAP_FOREACH(j, tr->jobs, i) {

                JobType t;

                Job *k;

                t = j->type;

                LIST_FOREACH(transaction, k, j->transaction_next) {

                        if (job_type_merge_and_collapse(&t, k->type, j->unit) >= 0)

                                continue;

                        /* OK, we could not merge all jobs for this

                         * action. Let's see if we can get rid of one

                         * of them */

                        r = delete_one_unmergeable_job(tr, j);

                        if (r >= 0)

                                /* Ok, we managed to drop one, now

                                 * let's ask our callers to call us

                                 * again after garbage collecting */

                                return -EAGAIN;

                        /* We couldn't merge anything. Failure */

                        return sd_bus_error_setf(e, BUS_ERROR_TRANSACTION_JOBS_CONFLICTING,

                                                 "Transaction contains conflicting jobs '%s' and '%s' for %s. "

                                                 "Probably contradicting requirement dependencies configured.",

                                                 job_type_to_string(t),

                                                 job_type_to_string(k->type),

                                                 k->unit->id);

                }

        }

        /* Second step, merge the jobs. */

        HASHMAP_FOREACH(j, tr->jobs, i) {

                JobType t = j->type;

                Job *k;

                /* Merge all transaction jobs for j->unit */

                LIST_FOREACH(transaction, k, j->transaction_next)

                        assert_se(job_type_merge_and_collapse(&t, k->type, j->unit) == 0);

                while ((k = j->transaction_next)) {

                        if (tr->anchor_job == k) {

                                transaction_merge_and_delete_job(tr, k, j, t);

                                j = k;

                        } else

                                transaction_merge_and_delete_job(tr, j, k, t);

                }

                assert(!j->transaction_next);

                assert(!j->transaction_prev);

        }

        return 0;

}

static void transaction_drop_redundant(Transaction *tr) {

        bool again;

        /* Goes through the transaction and removes all jobs of the units whose jobs are all noops. If not

         * all of a unit's jobs are redundant, they are kept. */

        assert(tr);

        do {

                Iterator i;

                Job *j;

                again = false;

                HASHMAP_FOREACH(j, tr->jobs, i) {

                        bool keep = false;

                        Job *k;

                        LIST_FOREACH(transaction, k, j)

                                if (tr->anchor_job == k ||

                                    !job_type_is_redundant(k->type, unit_active_state(k->unit)) ||

                                    (k->unit->job && job_type_is_conflicting(k->type, k->unit->job->type))) {

                                        keep = true;

                                        break;

                                }

                        if (!keep) {

                                log_trace("Found redundant job %s/%s, dropping from transaction.",

                                          j->unit->id, job_type_to_string(j->type));

                                transaction_delete_job(tr, j, false);

                                again = true;

                                break;

                        }

                }

        } while (again);

}

_pure_ static bool unit_matters_to_anchor(Unit *u, Job *j) {

        assert(u);

        assert(!j->transaction_prev);

        /* Checks whether at least one of the jobs for this unit

         * matters to the anchor. */

        LIST_FOREACH(transaction, j, j)

                if (j->matters_to_anchor)

                        return true;

        return false;

}

static char* merge_unit_ids(const char* unit_log_field, char **pairs) {

        char **unit_id, **job_type, *ans = NULL;

        size_t alloc = 0, size = 0, next;

        STRV_FOREACH_PAIR(unit_id, job_type, pairs) {

                next = strlen(unit_log_field) + strlen(*unit_id);

                if (!GREEDY_REALLOC(ans, alloc, size + next + 1)) {

                        return mfree(ans);

                }

                sprintf(ans + size, "%s%s", unit_log_field, *unit_id);

                if (*(unit_id+1))

                        ans[size + next] =  '\n';

                size += next + 1;

        }

        return ans;

}

static int transaction_verify_order_one(Transaction *tr, Job *j, Job *from, unsigned generation, sd_bus_error *e) {

        Iterator i;

        Unit *u;

        void *v;

        int r;

        assert(tr);

        assert(j);

        assert(!j->transaction_prev);

        /* Does a recursive sweep through the ordering graph, looking

         * for a cycle. If we find a cycle we try to break it. */

        /* Have we seen this before? */

        if (j->generation == generation) {

                Job *k, *delete = NULL;

                _cleanup_free_ char **array = NULL, *unit_ids = NULL;

                char **unit_id, **job_type;

                /* If the marker is NULL we have been here already and

                 * decided the job was loop-free from here. Hence

                 * shortcut things and return right-away. */

                if (!j->marker)

                        return 0;

                /* So, the marker is not NULL and we already have been here. We have

                 * a cycle. Let's try to break it. We go backwards in our path and

                 * try to find a suitable job to remove. We use the marker to find

                 * our way back, since smart how we are we stored our way back in

                 * there. */

                for (k = from; k; k = ((k->generation == generation && k->marker != k) ? k->marker : NULL)) {

                        /* For logging below */

                        if (strv_push_pair(&array, k->unit->id, (char*) job_type_to_string(k->type)) < 0)

                                log_oom();

                        if (!delete && hashmap_get(tr->jobs, k->unit) && !unit_matters_to_anchor(k->unit, k))

                                /* Ok, we can drop this one, so let's do so. */

                                delete = k;

                        /* Check if this in fact was the beginning of the cycle */

                        if (k == j)

                                break;

                }

                unit_ids = merge_unit_ids(j->manager->unit_log_field, array); /* ignore error */

                STRV_FOREACH_PAIR(unit_id, job_type, array)

                        /* logging for j not k here to provide a consistent narrative */

                        log_struct(LOG_WARNING,

                                   "MESSAGE=%s: Found %s on %s/%s",

                                   j->unit->id,

                                   unit_id == array ? "ordering cycle" : "dependency",

                                   *unit_id, *job_type,

                                   unit_ids);

                if (delete) {

                        const char *status;

                        /* logging for j not k here to provide a consistent narrative */

                        log_struct(LOG_ERR,

                                   "MESSAGE=%s: Job %s/%s deleted to break ordering cycle starting with %s/%s",

                                   j->unit->id, delete->unit->id, job_type_to_string(delete->type),

                                   j->unit->id, job_type_to_string(j->type),

                                   unit_ids);

                        if (log_get_show_color())

                                status = ANSI_HIGHLIGHT_RED " SKIP " ANSI_NORMAL;

                        else

                                status = " SKIP ";

                        unit_status_printf(delete->unit, status,

                                           "Ordering cycle found, skipping %s");

                        transaction_delete_unit(tr, delete->unit);

                        return -EAGAIN;

                }

                log_struct(LOG_ERR,

                           "MESSAGE=%s: Unable to break cycle starting with %s/%s",

                           j->unit->id, j->unit->id, job_type_to_string(j->type),

                           unit_ids);

                return sd_bus_error_setf(e, BUS_ERROR_TRANSACTION_ORDER_IS_CYCLIC,

                                         "Transaction order is cyclic. See system logs for details.");

        }

        /* Make the marker point to where we come from, so that we can

         * find our way backwards if we want to break a cycle. We use

         * a special marker for the beginning: we point to

         * ourselves. */

        j->marker = from ? from : j;

        j->generation = generation;

        /* We assume that the dependencies are bidirectional, and

         * hence can ignore UNIT_AFTER */

        HASHMAP_FOREACH_KEY(v, u, j->unit->dependencies[UNIT_BEFORE], i) {

                Job *o;

                /* Is there a job for this unit? */

                o = hashmap_get(tr->jobs, u);

                if (!o) {

                        /* Ok, there is no job for this in the

                         * transaction, but maybe there is already one

                         * running? */

                        o = u->job;

                        if (!o)

                                continue;

                }

                r = transaction_verify_order_one(tr, o, j, generation, e);

                if (r < 0)

                        return r;

        }

        /* Ok, let's backtrack, and remember that this entry is not on

         * our path anymore. */

        j->marker = NULL;

        return 0;

}

static int transaction_verify_order(Transaction *tr, unsigned *generation, sd_bus_error *e) {

        Job *j;

        int r;

        Iterator i;

        unsigned g;

        assert(tr);

        assert(generation);

        /* Check if the ordering graph is cyclic. If it is, try to fix

         * that up by dropping one of the jobs. */

        g = (*generation)++;

        HASHMAP_FOREACH(j, tr->jobs, i) {

                r = transaction_verify_order_one(tr, j, NULL, g, e);

                if (r < 0)

                        return r;

        }

        return 0;

}

static void transaction_collect_garbage(Transaction *tr) {

        bool again;

        assert(tr);

        /* Drop jobs that are not required by any other job */

        do {

                Iterator i;

                Job *j;

                again = false;

                HASHMAP_FOREACH(j, tr->jobs, i) {

                        if (tr->anchor_job == j)

                                continue;

                        if (!j->object_list) {

                                log_trace("Garbage collecting job %s/%s", j->unit->id, job_type_to_string(j->type));

                                transaction_delete_job(tr, j, true);

                                again = true;

                                break;

                        }

                        log_trace("Keeping job %s/%s because of %s/%s",

                                  j->unit->id, job_type_to_string(j->type),

                                  j->object_list->subject ? j->object_list->subject->unit->id : "root",

                                  j->object_list->subject ? job_type_to_string(j->object_list->subject->type) : "root");

                }

        } while (again);

}

static int transaction_is_destructive(Transaction *tr, JobMode mode, sd_bus_error *e) {

        Iterator i;

        Job *j;

        assert(tr);

        /* Checks whether applying this transaction means that

         * existing jobs would be replaced */

        HASHMAP_FOREACH(j, tr->jobs, i) {

                /* Assume merged */

                assert(!j->transaction_prev);

                assert(!j->transaction_next);

                if (j->unit->job && (mode == JOB_FAIL || j->unit->job->irreversible) &&

                    job_type_is_conflicting(j->unit->job->type, j->type))

                        return sd_bus_error_setf(e, BUS_ERROR_TRANSACTION_IS_DESTRUCTIVE,

                                                 "Transaction for %s/%s is destructive (%s has '%s' job queued, but '%s' is included in transaction).",

                                                 tr->anchor_job->unit->id, job_type_to_string(tr->anchor_job->type),

                                                 j->unit->id, job_type_to_string(j->unit->job->type), job_type_to_string(j->type));

        }

        return 0;

}

static void transaction_minimize_impact(Transaction *tr) {

        Job *j;

        Iterator i;

        assert(tr);

        /* Drops all unnecessary jobs that reverse already active jobs

         * or that stop a running service. */

rescan:

        HASHMAP_FOREACH(j, tr->jobs, i) {

                LIST_FOREACH(transaction, j, j) {

                        bool stops_running_service, changes_existing_job;

                        /* If it matters, we shouldn't drop it */

                        if (j->matters_to_anchor)

                                continue;

                        /* Would this stop a running service?

                         * Would this change an existing job?

                         * If so, let's drop this entry */

                        stops_running_service =

                                j->type == JOB_STOP && UNIT_IS_ACTIVE_OR_ACTIVATING(unit_active_state(j->unit));

                        changes_existing_job =

                                j->unit->job &&

                                job_type_is_conflicting(j->type, j->unit->job->type);

                        if (!stops_running_service && !changes_existing_job)

                                continue;

                        if (stops_running_service)

                                log_unit_debug(j->unit,

                                               "%s/%s would stop a running service.",

                                               j->unit->id, job_type_to_string(j->type));

                        if (changes_existing_job)

                                log_unit_debug(j->unit,

                                               "%s/%s would change existing job.",

                                               j->unit->id, job_type_to_string(j->type));

                        /* Ok, let's get rid of this */

                        log_unit_debug(j->unit,

                                       "Deleting %s/%s to minimize impact.",

                                       j->unit->id, job_type_to_string(j->type));

                        transaction_delete_job(tr, j, true);

                        goto rescan;

                }

        }

}

static int transaction_apply(

                Transaction *tr,

                Manager *m,

                JobMode mode,

                Set *affected_jobs) {

        Iterator i;

        Job *j;

        int r;

        /* Moves the transaction jobs to the set of active jobs */

        if (IN_SET(mode, JOB_ISOLATE, JOB_FLUSH)) {

                /* When isolating first kill all installed jobs which

                 * aren't part of the new transaction */

                HASHMAP_FOREACH(j, m->jobs, i) {

                        assert(j->installed);

                        if (j->unit->ignore_on_isolate)

                                continue;

                        if (hashmap_get(tr->jobs, j->unit))

                                continue;

                        /* Not invalidating recursively. Avoids triggering

                         * OnFailure= actions of dependent jobs. Also avoids

                         * invalidating our iterator. */

                        job_finish_and_invalidate(j, JOB_CANCELED, false, false);

                }

        }

        HASHMAP_FOREACH(j, tr->jobs, i) {

                /* Assume merged */

                assert(!j->transaction_prev);

                assert(!j->transaction_next);

                r = hashmap_put(m->jobs, UINT32_TO_PTR(j->id), j);

                if (r < 0)

                        goto rollback;

        }

        while ((j = hashmap_steal_first(tr->jobs))) {

                Job *installed_job;

                /* Clean the job dependencies */

                transaction_unlink_job(tr, j, false);

                installed_job = job_install(j);

                if (installed_job != j) {

                        /* j has been merged into a previously installed job */

                        if (tr->anchor_job == j)

                                tr->anchor_job = installed_job;

                        hashmap_remove(m->jobs, UINT32_TO_PTR(j->id));

                        job_free(j);

                        j = installed_job;

                }

                job_add_to_run_queue(j);

                job_add_to_dbus_queue(j);

                job_start_timer(j, false);

                job_shutdown_magic(j);

                /* When 'affected' is specified, let's track all in it all jobs that were touched because of

                 * this transaction. */

                if (affected_jobs)

                        (void) set_put(affected_jobs, j);

        }

        return 0;

rollback:

        HASHMAP_FOREACH(j, tr->jobs, i)

                hashmap_remove(m->jobs, UINT32_TO_PTR(j->id));

        return r;

}

int transaction_activate(

                Transaction *tr,

                Manager *m,

                JobMode mode,

                Set *affected_jobs,

                sd_bus_error *e) {

        Iterator i;

        Job *j;

        int r;

        unsigned generation = 1;

        assert(tr);

        /* This applies the changes recorded in tr->jobs to

         * the actual list of jobs, if possible. */

        /* Reset the generation counter of all installed jobs. The detection of cycles

         * looks at installed jobs. If they had a non-zero generation from some previous

         * walk of the graph, the algorithm would break. */

        HASHMAP_FOREACH(j, m->jobs, i)

                j->generation = 0;

        /* First step: figure out which jobs matter */

        transaction_find_jobs_that_matter_to_anchor(tr->anchor_job, generation++);

        /* Second step: Try not to stop any running services if

         * we don't have to. Don't try to reverse running

         * jobs if we don't have to. */

        if (mode == JOB_FAIL)

                transaction_minimize_impact(tr);

        /* Third step: Drop redundant jobs */

        transaction_drop_redundant(tr);

        for (;;) {

                /* Fourth step: Let's remove unneeded jobs that might

                 * be lurking. */

                if (mode != JOB_ISOLATE)

                        transaction_collect_garbage(tr);

                /* Fifth step: verify order makes sense and correct

                 * cycles if necessary and possible */

                r = transaction_verify_order(tr, &generation, e);

                if (r >= 0)

                        break;

                if (r != -EAGAIN)

                        return log_warning_errno(r, "Requested transaction contains an unfixable cyclic ordering dependency: %s", bus_error_message(e, r));

                /* Let's see if the resulting transaction ordering

                 * graph is still cyclic... */

        }

        for (;;) {

                /* Sixth step: let's drop unmergeable entries if

                 * necessary and possible, merge entries we can

                 * merge */

                r = transaction_merge_jobs(tr, e);

                if (r >= 0)

                        break;

                if (r != -EAGAIN)

                        return log_warning_errno(r, "Requested transaction contains unmergeable jobs: %s", bus_error_message(e, r));

                /* Seventh step: an entry got dropped, let's garbage

                 * collect its dependencies. */

                if (mode != JOB_ISOLATE)

                        transaction_collect_garbage(tr);

                /* Let's see if the resulting transaction still has

                 * unmergeable entries ... */

        }

        /* Eights step: Drop redundant jobs again, if the merging now allows us to drop more. */

        transaction_drop_redundant(tr);

        /* Ninth step: check whether we can actually apply this */

        r = transaction_is_destructive(tr, mode, e);

        if (r < 0)

                return log_notice_errno(r, "Requested transaction contradicts existing jobs: %s", bus_error_message(e, r));

        /* Tenth step: apply changes */

        r = transaction_apply(tr, m, mode, affected_jobs);

        if (r < 0)

                return log_warning_errno(r, "Failed to apply transaction: %m");

        assert(hashmap_isempty(tr->jobs));

        if (!hashmap_isempty(m->jobs)) {

                /* Are there any jobs now? Then make sure we have the

                 * idle pipe around. We don't really care too much

                 * whether this works or not, as the idle pipe is a

                 * feature for cosmetics, not actually useful for

                 * anything beyond that. */

                if (m->idle_pipe[0] < 0 && m->idle_pipe[1] < 0 &&

                    m->idle_pipe[2] < 0 && m->idle_pipe[3] < 0) {

                        (void) pipe2(m->idle_pipe, O_NONBLOCK|O_CLOEXEC);

                        (void) pipe2(m->idle_pipe + 2, O_NONBLOCK|O_CLOEXEC);

                }

        }

        return 0;

}

static Job* transaction_add_one_job(Transaction *tr, JobType type, Unit *unit, bool *is_new) {

        Job *j, *f;

        assert(tr);

        assert(unit);

        /* Looks for an existing prospective job and returns that. If

         * it doesn't exist it is created and added to the prospective

         * jobs list. */

        f = hashmap_get(tr->jobs, unit);

        LIST_FOREACH(transaction, j, f) {

                assert(j->unit == unit);

                if (j->type == type) {

                        if (is_new)

                                *is_new = false;

                        return j;

                }

        }

        j = job_new(unit, type);

        if (!j)

                return NULL;

        j->generation = 0;

        j->marker = NULL;

        j->matters_to_anchor = false;

        j->irreversible = tr->irreversible;

        LIST_PREPEND(transaction, f, j);

        if (hashmap_replace(tr->jobs, unit, f) < 0) {

                LIST_REMOVE(transaction, f, j);

                job_free(j);

                return NULL;

        }

        if (is_new)

                *is_new = true;

        log_trace("Added job %s/%s to transaction.", unit->id, job_type_to_string(type));

        return j;

}