machined: flush nscd caches whenever a machine comes/goes

This way, nss-mymachines should always serve authoritative data.

src/machine/machine.c

@@ -398,6 +398,7 @@ int machine_start(Machine *m, sd_bus_message *properties, sd_bus_error *error) {
         machine_save(m);
 
         machine_send_signal(m, true);
+        (void) manager_enqueue_nscd_cache_flush(m->manager);
 
         return 0;
 }
@@ -439,6 +440,7 @@ int machine_stop(Machine *m) {
         m->stopping = true;
 
         machine_save(m);
+        (void) manager_enqueue_nscd_cache_flush(m->manager);
 
         return r;
 }

src/machine/machined-core.c

@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include "machined.h"
+#include "nscd-flush.h"
+#include "strv.h"
+
+static int on_nscd_cache_flush_event(sd_event_source *s, void *userdata) {
+        /* Let's ask glibc's nscd daemon to flush its caches. We request this for the three database machines may show
+         * up in: the hosts database (for resolvable machine names) and the user and group databases (for the user ns
+         * ranges). */
+
+        (void) nscd_flush_cache(STRV_MAKE("passwd", "group", "hosts"));
+        return 0;
+}
+
+int manager_enqueue_nscd_cache_flush(Manager *m) {
+        int r;
+
+        assert(m);
+
+        if (!m->nscd_cache_flush_event) {
+                r = sd_event_add_defer(m->event, &m->nscd_cache_flush_event, on_nscd_cache_flush_event, m);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to allocate NSCD cache flush event: %m");
+
+                sd_event_source_set_description(m->nscd_cache_flush_event, "nscd-cache-flush");
+        }
+
+        r = sd_event_source_set_enabled(m->nscd_cache_flush_event, SD_EVENT_ONESHOT);
+        if (r < 0) {
+                m->nscd_cache_flush_event = sd_event_source_unref(m->nscd_cache_flush_event);
+                return log_error_errno(r, "Failed to enable NSCD cache flush event: %m");
+        }
+
+        return 0;
+}

src/machine/machined.c

@@ -77,6 +77,7 @@ static Manager* manager_unref(Manager *m) {
         hashmap_free(m->image_cache);
 
         sd_event_source_unref(m->image_cache_defer_event);
+        sd_event_source_unref(m->nscd_cache_flush_event);
 
         bus_verify_polkit_async_registry_free(m->polkit_registry);
 

src/machine/machined.h

@@ -35,6 +35,8 @@ struct Manager {
 
         LIST_HEAD(Operation, operations);
         unsigned n_operations;
+
+        sd_event_source *nscd_cache_flush_event;
 };
 
 int manager_add_machine(Manager *m, const char *name, Machine **_machine);
@@ -53,3 +55,5 @@ int manager_kill_unit(Manager *manager, const char *unit, int signo, sd_bus_erro
 int manager_unref_unit(Manager *m, const char *unit, sd_bus_error *error);
 int manager_unit_is_active(Manager *manager, const char *unit);
 int manager_job_is_active(Manager *manager, const char *path);
+
+int manager_enqueue_nscd_cache_flush(Manager *m);

src/machine/meson.build

@@ -9,6 +9,7 @@ libmachine_core_sources = files('''
         machine.c
         machine.h
         machined-dbus.c
+        machined-core.c
         machine-dbus.c
         machine-dbus.h
         image-dbus.c