wait-online: request that at least one managed online interface exists

Fixes a regression caused by ab3aed4.

I thought the commit does not cause any severe regression. However,
drivers for network interfaces may be loaded later. So, we should wait
if no network interface is found.

Fixes #27822.

(cherry picked from commit 2f96a29)

Author: yuwata

src/network/wait-online/manager.c

@@ -162,12 +162,13 @@ bool manager_configured(Manager *m) {
                                 return true;
                 }
 
-                /* With '--any'   : no interface is ready
-                 * Without '--any': all interfaces are ready */
+                /* With '--any'   : no interface is ready    → return false
+                 * Without '--any': all interfaces are ready → return true */
                 return !m->any;
         }
 
         /* wait for all links networkd manages */
+        bool has_online = false;
         HASHMAP_FOREACH(l, m->links_by_index) {
                 if (manager_ignore_link(m, l)) {
                         log_link_debug(l, "link is ignored");
@@ -179,13 +180,20 @@ bool manager_configured(Manager *m) {
                                                                          _LINK_OPERSTATE_INVALID });
                 if (r < 0 && !m->any) /* Unlike the above loop, unmanaged interfaces are ignored here. */
                         return false;
-                if (r > 0 && m->any)
-                        return true;
+                if (r > 0) {
+                        if (m->any)
+                                return true;
+                        has_online = true;
+                }
         }
 
-        /* With '--any'   : no interface is ready
-         * Without '--any': all interfaces are ready or unmanaged */
-        return !m->any;
+        /* With '--any'   : no interface is ready → return false
+         * Without '--any': all interfaces are ready or unmanaged
+         *
+         * In this stage, drivers for interfaces may not be loaded yet, and there may be only lo.
+         * To avoid that wait-online exits earlier than that drivers are loaded, let's request at least one
+         * managed online interface exists. See issue #27822. */
+        return !m->any && has_online;
 }
 
 static int manager_process_link(sd_netlink *rtnl, sd_netlink_message *mm, void *userdata) {

test/test-network/systemd-networkd-tests.py

@@ -1149,10 +1149,6 @@ def setUp(self):
     def tearDown(self):
         tear_down_common()
 
-    def test_wait_online_all_unmanaged(self):
-        start_networkd()
-        self.wait_online([])
-
     def test_wait_online_any(self):
         copy_network_unit('25-bridge.netdev', '25-bridge.network', '11-dummy.netdev', '11-dummy.network')
         start_networkd()