Merge pull request #28836 from msekletar/aux-scope

core/manager: add dbus API to create auxiliary scope from running service

src/core/cgroup.c

@@ -33,6 +33,7 @@
 #include "process-util.h"
 #include "procfs-util.h"
 #include "restrict-ifaces.h"
+#include "set.h"
 #include "special.h"
 #include "stdio-util.h"
 #include "string-table.h"
@@ -189,6 +190,313 @@ void cgroup_context_init(CGroupContext *c) {
         };
 }
 
+int cgroup_context_add_io_device_weight_dup(CGroupContext *c, CGroupIODeviceWeight *w) {
+        _cleanup_free_ CGroupIODeviceWeight *n = NULL;
+
+        assert(c);
+        assert(w);
+
+        n = new0(CGroupIODeviceWeight, 1);
+        if (!n)
+                return -ENOMEM;
+
+        n->path = strdup(w->path);
+        if (!n->path)
+                return -ENOMEM;
+        n->weight = w->weight;
+
+        LIST_PREPEND(device_weights, c->io_device_weights, TAKE_PTR(n));
+        return 0;
+}
+
+int cgroup_context_add_io_device_limit_dup(CGroupContext *c, CGroupIODeviceLimit *l) {
+        _cleanup_free_ CGroupIODeviceLimit *n = NULL;
+
+        assert(c);
+        assert(l);
+
+        n = new0(CGroupIODeviceLimit, 1);
+        if (!l)
+                return -ENOMEM;
+
+        n->path = strdup(l->path);
+        if (!n->path)
+                return -ENOMEM;
+
+        for (CGroupIOLimitType type = 0; type < _CGROUP_IO_LIMIT_TYPE_MAX; type++)
+                n->limits[type] = l->limits[type];
+
+        LIST_PREPEND(device_limits, c->io_device_limits, TAKE_PTR(n));
+        return 0;
+}
+
+int cgroup_context_add_io_device_latency_dup(CGroupContext *c, CGroupIODeviceLatency *l) {
+        _cleanup_free_ CGroupIODeviceLatency *n = NULL;
+
+        assert(c);
+        assert(l);
+
+        n = new0(CGroupIODeviceLatency, 1);
+        if (!n)
+                return -ENOMEM;
+
+        n->path = strdup(l->path);
+        if (!n->path)
+                return -ENOMEM;
+
+        n->target_usec = l->target_usec;
+
+        LIST_PREPEND(device_latencies, c->io_device_latencies, TAKE_PTR(n));
+        return 0;
+}
+
+int cgroup_context_add_block_io_device_weight_dup(CGroupContext *c, CGroupBlockIODeviceWeight *w) {
+        _cleanup_free_ CGroupBlockIODeviceWeight *n = NULL;
+
+        assert(c);
+        assert(w);
+
+        n = new0(CGroupBlockIODeviceWeight, 1);
+        if (!n)
+                return -ENOMEM;
+
+        n->path = strdup(w->path);
+        if (!n->path)
+                return -ENOMEM;
+
+        n->weight = w->weight;
+
+        LIST_PREPEND(device_weights, c->blockio_device_weights, TAKE_PTR(n));
+        return 0;
+}
+
+int cgroup_context_add_block_io_device_bandwidth_dup(CGroupContext *c, CGroupBlockIODeviceBandwidth *b) {
+        _cleanup_free_ CGroupBlockIODeviceBandwidth *n = NULL;
+
+        assert(c);
+        assert(b);
+
+        n = new0(CGroupBlockIODeviceBandwidth, 1);
+        if (!n)
+                return -ENOMEM;
+
+        *n = (CGroupBlockIODeviceBandwidth) {
+                .rbps = b->rbps,
+                .wbps = b->wbps,
+        };
+
+        LIST_PREPEND(device_bandwidths, c->blockio_device_bandwidths, TAKE_PTR(n));
+        return 0;
+}
+
+int cgroup_context_add_device_allow_dup(CGroupContext *c, CGroupDeviceAllow *a) {
+        _cleanup_free_ CGroupDeviceAllow *n = NULL;
+
+        assert(c);
+        assert(a);
+
+        n = new0(CGroupDeviceAllow, 1);
+        if (!n)
+                return -ENOMEM;
+
+        n->path = strdup(a->path);
+        if (!n->path)
+                return -ENOMEM;
+
+        n->permissions = a->permissions;
+
+        LIST_PREPEND(device_allow, c->device_allow, TAKE_PTR(n));
+        return 0;
+}
+
+static int cgroup_context_add_socket_bind_item_dup(CGroupContext *c, CGroupSocketBindItem *i, CGroupSocketBindItem *h) {
+        _cleanup_free_ CGroupSocketBindItem *n = NULL;
+
+        assert(c);
+        assert(i);
+
+        n = new0(CGroupSocketBindItem, 1);
+        if (!n)
+                return -ENOMEM;
+
+        *n = (CGroupSocketBindItem) {
+                .address_family = i->address_family,
+                .ip_protocol    = i->ip_protocol,
+                .nr_ports       = i->nr_ports,
+                .port_min       = i->port_min,
+        };
+
+        LIST_PREPEND(socket_bind_items, h, TAKE_PTR(n));
+        return 0;
+}
+
+int cgroup_context_add_socket_bind_item_allow_dup(CGroupContext *c, CGroupSocketBindItem *i) {
+        return cgroup_context_add_socket_bind_item_dup(c, i, c->socket_bind_allow);
+}
+
+int cgroup_context_add_socket_bind_item_deny_dup(CGroupContext *c, CGroupSocketBindItem *i) {
+        return cgroup_context_add_socket_bind_item_dup(c, i, c->socket_bind_deny);
+}
+
+int cgroup_context_copy(CGroupContext *dst, const CGroupContext *src) {
+        struct in_addr_prefix *i;
+        char *iface;
+        int r;
+
+        assert(src);
+        assert(dst);
+
+        dst->cpu_accounting = src->cpu_accounting;
+        dst->io_accounting = src->io_accounting;
+        dst->blockio_accounting = src->blockio_accounting;
+        dst->memory_accounting = src->memory_accounting;
+        dst->tasks_accounting = src->tasks_accounting;
+        dst->ip_accounting = src->ip_accounting;
+
+        dst->memory_oom_group = dst->memory_oom_group;
+
+        dst->cpu_weight = src->cpu_weight;
+        dst->startup_cpu_weight = src->startup_cpu_weight;
+        dst->cpu_quota_per_sec_usec = src->cpu_quota_per_sec_usec;
+        dst->cpu_quota_period_usec = src->cpu_quota_period_usec;
+
+        dst->cpuset_cpus = src->cpuset_cpus;
+        dst->startup_cpuset_cpus = src->startup_cpuset_cpus;
+        dst->cpuset_mems = src->cpuset_mems;
+        dst->startup_cpuset_mems = src->startup_cpuset_mems;
+
+        dst->io_weight = src->io_weight;
+        dst->startup_io_weight = src->startup_io_weight;
+
+        LIST_FOREACH_BACKWARDS(device_weights, w, LIST_FIND_TAIL(device_weights, src->io_device_weights)) {
+                r = cgroup_context_add_io_device_weight_dup(dst, w);
+                if (r < 0)
+                        return r;
+        }
+
+        LIST_FOREACH_BACKWARDS(device_limits, l, LIST_FIND_TAIL(device_limits, src->io_device_limits)) {
+                r = cgroup_context_add_io_device_limit_dup(dst, l);
+                if (r < 0)
+                        return r;
+        }
+
+        LIST_FOREACH_BACKWARDS(device_latencies, l, LIST_FIND_TAIL(device_latencies, src->io_device_latencies)) {
+                r = cgroup_context_add_io_device_latency_dup(dst, l);
+                if (r < 0)
+                        return r;
+        }
+
+        dst->default_memory_min = src->default_memory_min;
+        dst->default_memory_low = src->default_memory_low;
+        dst->default_startup_memory_low = src->default_startup_memory_low;
+        dst->memory_min = src->memory_min;
+        dst->memory_low = src->memory_low;
+        dst->startup_memory_low = src->startup_memory_low;
+        dst->memory_high = src->memory_high;
+        dst->startup_memory_high = src->startup_memory_high;
+        dst->memory_max = src->memory_max;
+        dst->startup_memory_max = src->startup_memory_max;
+        dst->memory_swap_max = src->memory_swap_max;
+        dst->startup_memory_swap_max = src->startup_memory_swap_max;
+        dst->memory_zswap_max = src->memory_zswap_max;
+        dst->startup_memory_zswap_max = src->startup_memory_zswap_max;
+
+        dst->default_memory_min_set = src->default_memory_min_set;
+        dst->default_memory_low_set = src->default_memory_low_set;
+        dst->default_startup_memory_low_set = src->default_startup_memory_low_set;
+        dst->memory_min_set = src->memory_min_set;
+        dst->memory_low_set = src->memory_low_set;
+        dst->startup_memory_low_set = src->startup_memory_low_set;
+        dst->startup_memory_high_set = src->startup_memory_high_set;
+        dst->startup_memory_max_set = src->startup_memory_max_set;
+        dst->startup_memory_swap_max_set = src->startup_memory_swap_max_set;
+        dst->startup_memory_zswap_max_set = src->startup_memory_zswap_max_set;
+
+        SET_FOREACH(i, src->ip_address_allow) {
+                r = in_addr_prefix_add(&dst->ip_address_allow, i);
+                if (r < 0)
+                        return r;
+        }
+
+        SET_FOREACH(i, src->ip_address_deny) {
+                r = in_addr_prefix_add(&dst->ip_address_deny, i);
+                if (r < 0)
+                        return r;
+        }
+
+        dst->ip_address_allow_reduced = src->ip_address_allow_reduced;
+        dst->ip_address_deny_reduced = src->ip_address_deny_reduced;
+
+        if (!strv_isempty(src->ip_filters_ingress)) {
+                dst->ip_filters_ingress = strv_copy(src->ip_filters_ingress);
+                if (!dst->ip_filters_ingress)
+                        return -ENOMEM;
+        }
+
+        if (!strv_isempty(src->ip_filters_egress)) {
+                dst->ip_filters_egress = strv_copy(src->ip_filters_egress);
+                if (!dst->ip_filters_egress)
+                        return -ENOMEM;
+        }
+
+        LIST_FOREACH_BACKWARDS(programs, l, LIST_FIND_TAIL(programs, src->bpf_foreign_programs)) {
+                r = cgroup_context_add_bpf_foreign_program_dup(dst, l);
+                if (r < 0)
+                        return r;
+        }
+
+        SET_FOREACH(iface, src->restrict_network_interfaces) {
+                r = set_put_strdup(&dst->restrict_network_interfaces, iface);
+                if (r < 0)
+                        return r;
+        }
+        dst->restrict_network_interfaces_is_allow_list = src->restrict_network_interfaces_is_allow_list;
+
+        dst->cpu_shares = src->cpu_shares;
+        dst->startup_cpu_shares = src->startup_cpu_shares;
+
+        dst->blockio_weight = src->blockio_weight;
+        dst->startup_blockio_weight = src->startup_blockio_weight;
+
+        LIST_FOREACH_BACKWARDS(device_weights, l, LIST_FIND_TAIL(device_weights, src->blockio_device_weights)) {
+                r = cgroup_context_add_block_io_device_weight_dup(dst, l);
+                if (r < 0)
+                        return r;
+        }
+
+        LIST_FOREACH_BACKWARDS(device_bandwidths, l, LIST_FIND_TAIL(device_bandwidths, src->blockio_device_bandwidths)) {
+                r = cgroup_context_add_block_io_device_bandwidth_dup(dst, l);
+                if (r < 0)
+                        return r;
+        }
+
+        dst->memory_limit = src->memory_limit;
+
+        dst->device_policy = src->device_policy;
+        LIST_FOREACH_BACKWARDS(device_allow, l, LIST_FIND_TAIL(device_allow, src->device_allow)) {
+                r = cgroup_context_add_device_allow_dup(dst, l);
+                if (r < 0)
+                        return r;
+        }
+
+        LIST_FOREACH_BACKWARDS(socket_bind_items, l, LIST_FIND_TAIL(socket_bind_items, src->socket_bind_allow)) {
+                r = cgroup_context_add_socket_bind_item_allow_dup(dst, l);
+                if (r < 0)
+                        return r;
+
+        }
+
+        LIST_FOREACH_BACKWARDS(socket_bind_items, l, LIST_FIND_TAIL(socket_bind_items, src->socket_bind_deny)) {
+                r = cgroup_context_add_socket_bind_item_deny_dup(dst, l);
+                if (r < 0)
+                        return r;
+        }
+
+        dst->tasks_max = src->tasks_max;
+
+        return 0;
+}
+
 void cgroup_context_free_device_allow(CGroupContext *c, CGroupDeviceAllow *a) {
         assert(c);
         assert(a);

src/core/cgroup.h

@@ -129,6 +129,7 @@ typedef enum CGroupPressureWatch {
         _CGROUP_PRESSURE_WATCH_INVALID = -EINVAL,
 } CGroupPressureWatch;
 
+/* When adding members make sure to update cgroup_context_copy() accordingly */
 struct CGroupContext {
         bool cpu_accounting;
         bool io_accounting;
@@ -285,6 +286,7 @@ uint64_t cgroup_context_cpu_weight(CGroupContext *c, ManagerState state);
 usec_t cgroup_cpu_adjust_period(usec_t period, usec_t quota, usec_t resolution, usec_t max_period);
 
 void cgroup_context_init(CGroupContext *c);
+int cgroup_context_copy(CGroupContext *dst, const CGroupContext *src);
 void cgroup_context_done(CGroupContext *c);
 void cgroup_context_dump(Unit *u, FILE* f, const char *prefix);
 void cgroup_context_dump_socket_bind_item(const CGroupSocketBindItem *item, FILE *f);
@@ -309,6 +311,18 @@ static inline bool cgroup_context_want_memory_pressure(const CGroupContext *c) {
 int cgroup_context_add_device_allow(CGroupContext *c, const char *dev, CGroupDevicePermissions p);
 int cgroup_context_add_or_update_device_allow(CGroupContext *c, const char *dev, CGroupDevicePermissions p);
 int cgroup_context_add_bpf_foreign_program(CGroupContext *c, uint32_t attach_type, const char *path);
+int cgroup_context_add_io_device_limit_dup(CGroupContext *c, CGroupIODeviceLimit *l);
+int cgroup_context_add_io_device_weight_dup(CGroupContext *c, CGroupIODeviceWeight *w);
+int cgroup_context_add_io_device_latency_dup(CGroupContext *c, CGroupIODeviceLatency *l);
+int cgroup_context_add_block_io_device_weight_dup(CGroupContext *c, CGroupBlockIODeviceWeight *w);
+int cgroup_context_add_block_io_device_bandwidth_dup(CGroupContext *c, CGroupBlockIODeviceBandwidth *b);
+int cgroup_context_add_device_allow_dup(CGroupContext *c, CGroupDeviceAllow *a);
+int cgroup_context_add_socket_bind_item_allow_dup(CGroupContext *c, CGroupSocketBindItem *i);
+int cgroup_context_add_socket_bind_item_deny_dup(CGroupContext *c, CGroupSocketBindItem *i);
+
+static inline int cgroup_context_add_bpf_foreign_program_dup(CGroupContext *c, CGroupBPFForeignProgram *p) {
+        return cgroup_context_add_bpf_foreign_program(c, p->attach_type, p->bpffs_path);
+}
 
 void unit_modify_nft_set(Unit *u, bool add);
 

src/core/dbus-manager.c

@@ -2933,6 +2933,180 @@ static int method_dump_unit_descriptor_store(sd_bus_message *message, void *user
         return method_generic_unit_operation(message, userdata, error, bus_service_method_dump_file_descriptor_store, 0);
 }
 
+static int aux_scope_from_message(Manager *m, sd_bus_message *message, Unit **ret_scope, sd_bus_error *error) {
+        _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *creds = NULL;
+        _cleanup_free_ PidRef *pidrefs = NULL;
+        const char *name;
+        Unit *from, *scope;
+        PidRef *main_pid;
+        CGroupContext *cc;
+        size_t n_pids = 0;
+        uint64_t flags;
+        pid_t pid;
+        int r;
+
+        assert(ret_scope);
+
+        r = sd_bus_query_sender_creds(message, SD_BUS_CREDS_PID, &creds);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_creds_get_pid(creds, &pid);
+        if (r < 0)
+                return r;
+
+        from = manager_get_unit_by_pid(m, pid);
+        if (!from)
+                return sd_bus_error_set(error, BUS_ERROR_NO_SUCH_UNIT, "Client not member of any unit.");
+
+        if (!IN_SET(from->type, UNIT_SERVICE, UNIT_SCOPE))
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                         "Starting auxiliary scope is supported only for service and scope units, refusing.");
+
+        if (!unit_name_is_valid(from->id, UNIT_NAME_PLAIN))
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                         "Auxiliary scope can be started only for non-template service units and scope units, refusing.");
+
+        r = sd_bus_message_read(message, "s", &name);
+        if (r < 0)
+                return r;
+
+        if (!unit_name_is_valid(name, UNIT_NAME_PLAIN))
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                         "Invalid name \"%s\" for auxiliary scope.", name);
+
+        if (unit_name_to_type(name) != UNIT_SCOPE)
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS,
+                                         "Name \"%s\" of auxiliary scope doesn't have .scope suffix.", name);
+
+        main_pid = unit_main_pid(from);
+
+        r = sd_bus_message_enter_container(message, 'a', "h");
+        if (r < 0)
+                return r;
+
+        for (;;) {
+                _cleanup_(pidref_done) PidRef p = PIDREF_NULL;
+                Unit *unit;
+                int fd;
+
+                r = sd_bus_message_read(message, "h", &fd);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                r = pidref_set_pidfd(&p, fd);
+                if (r < 0) {
+                        log_unit_warning_errno(from, r, "Failed to create process reference from PIDFD, ignoring: %m");
+                        continue;
+                }
+
+                unit = manager_get_unit_by_pidref(m, &p);
+                if (!unit) {
+                        log_unit_warning_errno(from, SYNTHETIC_ERRNO(ENOENT), "Failed to get unit from PIDFD, ingoring: %m");
+                        continue;
+                }
+
+                if (!streq(unit->id, from->id)) {
+                        log_unit_warning(from, "PID " PID_FMT " is not running in the same service as the calling process, ignoring.", p.pid);
+                        continue;
+                }
+
+                if (pidref_equal(main_pid, &p)) {
+                        log_unit_warning(from, "Main PID cannot be migrated into auxiliary scope, ignoring.");
+                        continue;
+                }
+
+                if (!GREEDY_REALLOC(pidrefs, n_pids+1))
+                        return -ENOMEM;
+
+                pidrefs[n_pids++] = TAKE_PIDREF(p);
+        }
+
+        if (n_pids == 0)
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "No processes can be migrated to auxiliary scope.");
+
+        r = sd_bus_message_exit_container(message);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_read(message, "t", &flags);
+        if (r < 0)
+                return r;
+
+        if (flags != 0)
+                return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Flags must be zero.");
+
+        r = manager_load_unit(m, name, NULL, error, &scope);
+        if (r < 0)
+                return r;
+
+        if (!unit_is_pristine(scope))
+                return sd_bus_error_setf(error, BUS_ERROR_UNIT_EXISTS,
+                                         "Unit %s was already loaded or has a fragment file.", name);
+
+        r = unit_set_slice(scope, UNIT_GET_SLICE(from));
+        if (r < 0)
+                return r;
+
+        cc = unit_get_cgroup_context(scope);
+
+        r = cgroup_context_copy(cc, unit_get_cgroup_context(from));
+        if (r < 0)
+                return r;
+
+        r = unit_make_transient(scope);
+        if (r < 0)
+                return r;
+
+        r = bus_unit_set_properties(scope, message, UNIT_RUNTIME, true, error);
+        if (r < 0)
+                return r;
+
+        FOREACH_ARRAY(p, pidrefs, n_pids) {
+                r = unit_pid_attachable(scope, p, error);
+                if (r < 0)
+                        return r;
+
+                r = unit_watch_pidref(scope, p, /* exclusive= */ false);
+                if (r < 0 && r != -EEXIST)
+                        return r;
+        }
+
+        /* Now load the missing bits of the unit we just created */
+        unit_add_to_load_queue(scope);
+        manager_dispatch_load_queue(m);
+
+        *ret_scope = TAKE_PTR(scope);
+
+        return 1;
+}
+
+static int method_start_aux_scope(sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        Manager *m = ASSERT_PTR(userdata);
+        Unit *u = NULL; /* avoid false maybe-uninitialized warning */
+        int r;
+
+        assert(message);
+
+        r = mac_selinux_access_check(message, "start", error);
+        if (r < 0)
+                return r;
+
+        r = bus_verify_manage_units_async(m, message, error);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return 1; /* No authorization for now, but the async polkit stuff will call us again when it has it */
+
+        r = aux_scope_from_message(m, message, &u, error);
+        if (r < 0)
+                return r;
+
+        return bus_unit_queue_job(message, u, JOB_START, JOB_REPLACE, 0, error);
+}
+
 const sd_bus_vtable bus_manager_vtable[] = {
         SD_BUS_VTABLE_START(0),
 
@@ -3491,6 +3665,11 @@ const sd_bus_vtable bus_manager_vtable[] = {
                                 SD_BUS_RESULT("a(suuutuusu)", entries),
                                 method_dump_unit_descriptor_store,
                                 SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD_WITH_ARGS("StartAuxiliaryScope",
+                                SD_BUS_ARGS("s", name, "ah", pidfds, "t", flags, "a(sv)", properties),
+                                SD_BUS_RESULT("o", job),
+                                method_start_aux_scope,
+                                SD_BUS_VTABLE_UNPRIVILEGED),
 
         SD_BUS_SIGNAL_WITH_ARGS("UnitNew",
                                 SD_BUS_ARGS("s", id, "o", unit),

src/test/meson.build

@@ -600,4 +600,8 @@ executables += [
                         libudev_basic,
                 ],
         },
+        test_template + {
+                'sources' : files('test-aux-scope.c'),
+                'type' : 'manual',
+        },
 ]

src/test/test-aux-scope.c

@@ -0,0 +1,160 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+
+#include "sd-event.h"
+
+#include "bus-error.h"
+#include "bus-message.h"
+#include "bus-wait-for-jobs.h"
+#include "fd-util.h"
+#include "log.h"
+#include "missing_syscall.h"
+#include "process-util.h"
+#include "tests.h"
+
+static int on_sigusr1(sd_event_source *s, const struct signalfd_siginfo *ssi, void *userdata) {
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *message = NULL, *reply = NULL;
+        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        _cleanup_(bus_wait_for_jobs_freep) BusWaitForJobs *w = NULL;
+        _cleanup_(sd_bus_unrefp) sd_bus *bus = NULL;
+        PidRef *pids = (PidRef *) userdata;
+        const char *job;
+        int r;
+
+        assert(pids);
+
+        r = sd_bus_open_system(&bus);
+        if (r < 0)
+                return log_error_errno(r, "Failed to acquire bus: %m");
+
+        r = sd_bus_message_new_method_call(bus, &message,
+                                           "org.freedesktop.systemd1",
+                                           "/org/freedesktop/systemd1",
+                                           "org.freedesktop.systemd1.Manager",
+                                           "StartAuxiliaryScope");
+        if (r < 0)
+                return log_error_errno(r, "Failed to create bus message: %m");
+
+        r = sd_bus_message_append_basic(message, 's', "test-aux-scope.scope");
+        if (r < 0)
+                return log_error_errno(r, "Failed to attach scope name: %m");
+
+        r = sd_bus_message_open_container(message, 'a', "h");
+        if (r < 0)
+                return log_error_errno(r, "Failed to create array of FDs: %m");
+
+        for (size_t i = 0; i < 10; i++) {
+                r = sd_bus_message_append_basic(message, 'h', &pids[i].fd);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to append PIDFD to message: %m");
+        }
+
+        r = sd_bus_message_close_container(message);
+        if (r < 0)
+                return log_error_errno(r, "Failed to close container: %m");
+
+        r = sd_bus_message_append(message, "ta(sv)", UINT64_C(0), 1, "Description", "s", "Test auxiliary scope");
+        if (r < 0)
+                return log_error_errno(r, "Failed to append unit properties: %m");
+
+        r = sd_bus_call(bus, message, 0, &error, &reply);
+        if (r < 0)
+                return log_error_errno(r, "Failed to start auxiliary scope: %s", bus_error_message(&error, r));
+
+        r = sd_bus_message_read(reply, "o", &job);
+        if (r < 0)
+                return log_error_errno(r, "Failed to read reply: %m");
+
+        r = bus_wait_for_jobs_new(bus, &w);
+        if (r < 0)
+                return log_error_errno(r, "Could not watch jobs: %m");
+
+        r = bus_wait_for_jobs_one(w, job, false, NULL);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static void destroy_pidrefs(PidRef *pids, size_t npids) {
+        assert(pids || npids == 0);
+
+        for (size_t i = 0; i < npids; i++)
+                pidref_done(&pids[i]);
+
+        free(pids);
+}
+
+int main(int argc, char *argv[]) {
+        _cleanup_(sd_event_unrefp) sd_event *event = NULL;
+        PidRef *pids = NULL;
+        size_t npids = 0;
+        int r, fd;
+
+        CLEANUP_ARRAY(pids, npids, destroy_pidrefs);
+
+        test_setup_logging(LOG_INFO);
+
+        fd = pidfd_open(getpid_cached(), 0);
+        if (fd < 0 && (ERRNO_IS_NOT_SUPPORTED(errno) || ERRNO_IS_PRIVILEGE(errno)))
+                return log_tests_skipped("pidfds are not available");
+        else if (fd < 0) {
+                log_error_errno(errno, "pidfd_open() failed: %m");
+                return EXIT_FAILURE;
+        }
+        safe_close(fd);
+
+        r = sd_event_new(&event);
+        if (r < 0) {
+                log_error_errno(r, "Failed to allocate event loop: %m");
+                return EXIT_FAILURE;
+        }
+
+        npids = 10;
+        pids = new0(PidRef, npids);
+        assert(pids);
+
+        r = sd_event_add_signal(event, NULL, SIGUSR1|SD_EVENT_SIGNAL_PROCMASK, on_sigusr1, pids);
+        if (r < 0) {
+                log_error_errno(r, "Failed to setup SIGUSR1 signal handling: %m");
+                return EXIT_FAILURE;
+        }
+
+        for (size_t i = 0; i < npids; i++) {
+                PidRef pidref = PIDREF_NULL;
+                pid_t pid;
+
+                r = safe_fork("(worker)", FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGTERM|FORK_CLOSE_ALL_FDS, &pid);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to fork(): %m");
+                        return EXIT_FAILURE;
+                }
+
+                if (r == 0) {
+                        /* Worker */
+                        sleep(3600);
+                        _exit(EXIT_SUCCESS);
+                }
+
+                r = pidref_set_pid(&pidref, pid);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to initialize PID ref: %m");
+                        return EXIT_FAILURE;
+                }
+
+                assert_se(pidref.pid == pid);
+                assert_se(pidref.fd != -EBADF);
+
+                pids[i] = TAKE_PIDREF(pidref);
+        }
+
+        r = sd_event_loop(event);
+        if (r < 0)
+                return log_error_errno(r, "Failed to run event loop: %m");
+
+        return 0;
+}