tree-wide: Add more socket units (#37991)

src/login/logind-varlink.c

@@ -2,8 +2,10 @@
 
 #include "sd-bus.h"
 #include "sd-event.h"
+
 #include "alloc-util.h"
 #include "cgroup-util.h"
+#include "fd-util.h"
 #include "format-util.h"
 #include "hashmap.h"
 #include "json-util.h"
@@ -326,8 +328,9 @@ static int vl_method_release_session(sd_varlink *link, sd_json_variant *paramete
         return sd_varlink_reply(link, NULL);
 }
 
-int manager_varlink_init(Manager *m) {
+int manager_varlink_init(Manager *m, int fd) {
         _cleanup_(sd_varlink_server_unrefp) sd_varlink_server *s = NULL;
+        _unused_ _cleanup_close_ int fd_close = fd;
         int r;
 
         assert(m);
@@ -361,10 +364,15 @@ int manager_varlink_init(Manager *m) {
         if (r < 0)
                 return log_error_errno(r, "Failed to register varlink methods: %m");
 
-        r = sd_varlink_server_listen_address(s, "/run/systemd/io.systemd.Login", 0666);
+        if (fd < 0)
+                r = sd_varlink_server_listen_address(s, "/run/systemd/io.systemd.Login", /* mode= */ 0666);
+        else
+                r = sd_varlink_server_listen_fd(s, fd);
         if (r < 0)
                 return log_error_errno(r, "Failed to bind to varlink socket: %m");
 
+        TAKE_FD(fd_close);
+
         r = sd_varlink_server_attach_event(s, m->event, SD_EVENT_PRIORITY_NORMAL);
         if (r < 0)
                 return log_error_errno(r, "Failed to attach varlink connection to event loop: %m");

src/login/logind-varlink.h

@@ -3,7 +3,7 @@
 
 #include "logind-forward.h"
 
-int manager_varlink_init(Manager *m);
+int manager_varlink_init(Manager *m, int fd);
 void manager_varlink_done(Manager *m);
 
 int session_send_create_reply_varlink(Session *s, const sd_bus_error *error);

src/login/logind.c

@@ -525,9 +525,8 @@ fail_close:
 }
 
 static int manager_enumerate_sessions(Manager *m) {
-        _cleanup_strv_free_ char **fdnames = NULL;
         _cleanup_closedir_ DIR *d = NULL;
-        int r = 0, n;
+        int r = 0;
 
         assert(m);
 
@@ -560,6 +559,16 @@ static int manager_enumerate_sessions(Manager *m) {
                         RET_GATHER(r, log_warning_errno(k, "Failed to deserialize session '%s', ignoring: %m", s->id));
         }
 
+        return r;
+}
+
+static int manager_enumerate_fds(Manager *m, int *ret_varlink_fd) {
+        _cleanup_strv_free_ char **fdnames = NULL;
+        int varlink_fd = -EBADF, n, r = 0;
+
+        assert(m);
+        assert(ret_varlink_fd);
+
         n = sd_listen_fds_with_names(/* unset_environment = */ true, &fdnames);
         if (n < 0)
                 return log_error_errno(n, "Failed to acquire passed fd list: %m");
@@ -567,9 +576,18 @@ static int manager_enumerate_sessions(Manager *m) {
         for (int i = 0; i < n; i++) {
                 int fd = SD_LISTEN_FDS_START + i;
 
+                if (streq(fdnames[i], "varlink")) {
+                        assert(varlink_fd < 0);
+                        varlink_fd = fd;
+                        continue;
+                }
+
                 RET_GATHER(r, manager_attach_session_fd_one_consume(m, fdnames[i], fd));
         }
 
+        if (r >= 0)
+                *ret_varlink_fd = varlink_fd;
+
         return r;
 }
 
@@ -1171,6 +1189,7 @@ static int manager_dispatch_reload_signal(sd_event_source *s, const struct signa
 }
 
 static int manager_startup(Manager *m) {
+        _cleanup_close_ int varlink_fd = -EBADF;
         int r;
         Seat *seat;
         Session *session;
@@ -1202,10 +1221,6 @@ static int manager_startup(Manager *m) {
         if (r < 0)
                 return r;
 
-        r = manager_varlink_init(m);
-        if (r < 0)
-                return r;
-
         /* Instantiate magic seat 0 */
         r = manager_add_seat(m, "seat0", &m->seat0);
         if (r < 0)
@@ -1232,6 +1247,10 @@ static int manager_startup(Manager *m) {
         if (r < 0)
                 log_warning_errno(r, "Session enumeration failed: %m");
 
+        r = manager_enumerate_fds(m, &varlink_fd);
+        if (r < 0)
+                log_warning_errno(r, "File descriptor enumeration failed: %m");
+
         r = manager_enumerate_inhibitors(m);
         if (r < 0)
                 log_warning_errno(r, "Inhibitor enumeration failed: %m");
@@ -1240,6 +1259,10 @@ static int manager_startup(Manager *m) {
         if (r < 0)
                 log_warning_errno(r, "Button enumeration failed: %m");
 
+        r = manager_varlink_init(m, TAKE_FD(varlink_fd));
+        if (r < 0)
+                return r;
+
         manager_load_scheduled_shutdown(m);
 
         /* Remove stale objects before we start them */

src/network/networkd-manager-varlink.c

@@ -259,8 +259,9 @@ static int vl_method_set_persistent_storage(sd_varlink *vlink, sd_json_variant *
         return sd_varlink_reply(vlink, NULL);
 }
 
-int manager_connect_varlink(Manager *m) {
+int manager_connect_varlink(Manager *m, int fd) {
         _cleanup_(sd_varlink_server_unrefp) sd_varlink_server *s = NULL;
+        _unused_ _cleanup_close_ int fd_close = fd;
         int r;
 
         assert(m);
@@ -297,10 +298,15 @@ int manager_connect_varlink(Manager *m) {
         if (r < 0)
                 return log_error_errno(r, "Failed to register varlink methods: %m");
 
-        r = sd_varlink_server_listen_address(s, "/run/systemd/netif/io.systemd.Network", 0666);
+        if (fd < 0)
+                r = sd_varlink_server_listen_address(s, "/run/systemd/netif/io.systemd.Network", /* mode= */ 0666);
+        else
+                r = sd_varlink_server_listen_fd(s, fd);
         if (r < 0)
                 return log_error_errno(r, "Failed to bind to varlink socket: %m");
 
+        TAKE_FD(fd_close);
+
         r = sd_varlink_server_attach_event(s, m->event, SD_EVENT_PRIORITY_NORMAL);
         if (r < 0)
                 return log_error_errno(r, "Failed to attach varlink connection to event loop: %m");
@@ -313,5 +319,4 @@ void manager_varlink_done(Manager *m) {
         assert(m);
 
         m->varlink_server = sd_varlink_server_unref(m->varlink_server);
-        (void) unlink("/run/systemd/netif/io.systemd.Network");
 }

src/network/networkd-manager-varlink.h

@@ -3,5 +3,5 @@
 
 #include "networkd-forward.h"
 
-int manager_connect_varlink(Manager *m);
+int manager_connect_varlink(Manager *m, int fd);
 void manager_varlink_done(Manager *m);

src/network/networkd-manager.c

@@ -205,12 +205,13 @@ static int manager_connect_udev(Manager *m) {
         return 0;
 }
 
-static int manager_listen_fds(Manager *m, int *ret_rtnl_fd) {
+static int manager_listen_fds(Manager *m, int *ret_rtnl_fd, int *ret_varlink_fd) {
         _cleanup_strv_free_ char **names = NULL;
-        int n, rtnl_fd = -EBADF;
+        int n, rtnl_fd = -EBADF, varlink_fd = -EBADF;
 
         assert(m);
         assert(ret_rtnl_fd);
+        assert(ret_varlink_fd);
 
         n = sd_listen_fds_with_names(/* unset_environment = */ true, &names);
         if (n < 0)
@@ -221,7 +222,7 @@ static int manager_listen_fds(Manager *m, int *ret_rtnl_fd) {
 
                 if (sd_is_socket(fd, AF_NETLINK, SOCK_RAW, -1) > 0) {
                         if (rtnl_fd >= 0) {
-                                log_debug("Received multiple netlink socket, ignoring.");
+                                log_debug("Received multiple netlink sockets, ignoring.");
                                 goto unused;
                         }
 
@@ -229,6 +230,11 @@ static int manager_listen_fds(Manager *m, int *ret_rtnl_fd) {
                         continue;
                 }
 
+                if (streq(names[i], "varlink")) {
+                        varlink_fd = fd;
+                        continue;
+                }
+
                 if (manager_set_serialization_fd(m, fd, names[i]) >= 0)
                         continue;
 
@@ -243,6 +249,8 @@ static int manager_listen_fds(Manager *m, int *ret_rtnl_fd) {
         }
 
         *ret_rtnl_fd = rtnl_fd;
+        *ret_varlink_fd = varlink_fd;
+
         return 0;
 }
 
@@ -513,7 +521,7 @@ static int manager_set_keep_configuration(Manager *m) {
 }
 
 int manager_setup(Manager *m) {
-        _cleanup_close_ int rtnl_fd = -EBADF;
+        _cleanup_close_ int rtnl_fd = -EBADF, varlink_fd = -EBADF;
         int r;
 
         assert(m);
@@ -537,7 +545,7 @@ int manager_setup(Manager *m) {
         if (r < 0)
                 return r;
 
-        r = manager_listen_fds(m, &rtnl_fd);
+        r = manager_listen_fds(m, &rtnl_fd, &varlink_fd);
         if (r < 0)
                 return r;
 
@@ -552,7 +560,7 @@ int manager_setup(Manager *m) {
         if (m->test_mode)
                 return 0;
 
-        r = manager_connect_varlink(m);
+        r = manager_connect_varlink(m, TAKE_FD(varlink_fd));
         if (r < 0)
                 return r;
 

src/udev/udev-manager.c

@@ -1405,11 +1405,13 @@ static int manager_setup_event(Manager *manager) {
         return 0;
 }
 
-static int manager_listen_fds(Manager *manager) {
+static int manager_listen_fds(Manager *manager, int *ret_varlink_fd) {
         _cleanup_strv_free_ char **names = NULL;
+        int varlink_fd = -EBADF;
         int r;
 
         assert(manager);
+        assert(ret_varlink_fd);
 
         int n = sd_listen_fds_with_names(/* unset_environment = */ true, &names);
         if (n < 0)
@@ -1418,9 +1420,10 @@ static int manager_listen_fds(Manager *manager) {
         for (int i = 0; i < n; i++) {
                 int fd = SD_LISTEN_FDS_START + i;
 
-                if (streq(names[i], "varlink"))
-                        r = 0; /* The fd will be handled by sd_varlink_server_listen_auto(). */
-                else if (streq(names[i], "systemd-udevd-control.socket"))
+                if (streq(names[i], "varlink")) {
+                        varlink_fd = fd;
+                        r = 0;
+                } else if (streq(names[i], "systemd-udevd-control.socket"))
                         r = manager_init_ctrl(manager, fd);
                 else if (streq(names[i], "systemd-udevd-kernel.socket"))
                         r = manager_init_device_monitor(manager, fd);
@@ -1437,10 +1440,13 @@ static int manager_listen_fds(Manager *manager) {
                         close_and_notify_warn(fd, names[i]);
         }
 
+        *ret_varlink_fd = varlink_fd;
+
         return 0;
 }
 
 int manager_main(Manager *manager) {
+        _cleanup_close_ int varlink_fd = -EBADF;
         int r;
 
         assert(manager);
@@ -1458,7 +1464,7 @@ int manager_main(Manager *manager) {
         if (r < 0)
                 return r;
 
-        r = manager_listen_fds(manager);
+        r = manager_listen_fds(manager, &varlink_fd);
         if (r < 0)
                 return r;
 
@@ -1466,7 +1472,7 @@ int manager_main(Manager *manager) {
         if (r < 0)
                 return r;
 
-        r = manager_start_varlink_server(manager);
+        r = manager_start_varlink_server(manager, TAKE_FD(varlink_fd));
         if (r < 0)
                 return r;
 

src/udev/udev-varlink.c

@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include "fd-util.h"
 #include "json-util.h"
 #include "log.h"
 #include "string-util.h"
@@ -165,8 +166,9 @@ static int vl_method_exit(sd_varlink *link, sd_json_variant *parameters, sd_varl
         return sd_varlink_reply(link, NULL);
 }
 
-int manager_start_varlink_server(Manager *manager) {
+int manager_start_varlink_server(Manager *manager, int fd) {
         _cleanup_(sd_varlink_server_unrefp) sd_varlink_server *v = NULL;
+        _cleanup_close_ int fd_close = fd;
         int r;
 
         assert(manager);
@@ -183,14 +185,14 @@ int manager_start_varlink_server(Manager *manager) {
         if (r < 0)
                 return log_error_errno(r, "Failed to attach Varlink connection to event loop: %m");
 
-        r = sd_varlink_server_listen_auto(v);
-        if (r < 0)
-                return log_error_errno(r, "Failed to bind to passed Varlink socket: %m");
-        if (r == 0) {
+        if (fd < 0)
                 r = sd_varlink_server_listen_address(v, UDEV_VARLINK_ADDRESS, 0600);
-                if (r < 0)
-                        return log_error_errno(r, "Failed to bind to Varlink socket: %m");
-        }
+        else
+                r = sd_varlink_server_listen_fd(v, fd);
+        if (r < 0)
+                return log_error_errno(r, "Failed to bind to Varlink socket: %m");
+
+        TAKE_FD(fd_close);
 
         r = sd_varlink_server_add_interface_many(
                         v,

src/udev/udev-varlink.h

@@ -3,5 +3,5 @@
 
 #include "udev-forward.h"
 
-int manager_start_varlink_server(Manager *manager);
+int manager_start_varlink_server(Manager *manager, int fd);
 int udev_varlink_connect(sd_varlink **ret, usec_t timeout);

test/units/TEST-74-AUX-UTILS.varlinkctl.sh

@@ -66,6 +66,20 @@ if [[ -x /usr/lib/systemd/systemd-pcrextend ]]; then
     varlinkctl introspect /usr/lib/systemd/systemd-pcrextend
 fi
 
+# Test various varlink socket units to make sure that we can still connect to the varlink sockets even if the
+# services are currently stopped (or restarting).
+systemctl stop \
+    systemd-networkd.service \
+    systemd-hostnamed.service \
+    systemd-machined.service \
+    systemd-udevd.service
+varlinkctl introspect /run/systemd/netif/io.systemd.Network
+varlinkctl introspect /run/systemd/io.systemd.Hostname
+varlinkctl introspect /run/systemd/machine/io.systemd.Machine
+if ! systemd-detect-virt -qc; then
+    varlinkctl introspect /run/udev/io.systemd.Udev
+fi
+
 # SSH transport
 SSHBINDIR="$(mktemp -d)"
 

units/meson.build

@@ -472,6 +472,11 @@ units = [
           'conditions' : ['ENABLE_LOCALED'],
           'symlinks' : ['dbus-org.freedesktop.locale1.service'],
         },
+        {
+          'file': 'systemd-logind-varlink.socket',
+          'conditions': ['ENABLE_LOGIND'],
+          'symlinks' : ['sockets.target.wants/'],
+        },
         {
           'file' : 'systemd-logind.service.in',
           'conditions' : ['ENABLE_LOGIND'],
@@ -502,6 +507,10 @@ units = [
           'file' : 'systemd-networkd-persistent-storage.service',
           'conditions' : ['ENABLE_NETWORKD'],
         },
+        {
+          'file' : 'systemd-networkd-varlink.socket',
+          'conditions' : ['ENABLE_NETWORKD'],
+        },
         {
           'file' : 'systemd-networkd-wait-online.service.in',
           'conditions' : ['ENABLE_NETWORKD'],

units/systemd-logind-varlink.socket

@@ -0,0 +1,18 @@
+#  SPDX-License-Identifier: LGPL-2.1-or-later
+#
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+[Unit]
+Description=User Login Management Varlink Socket
+Documentation=man:systemd-logind.service(8)
+
+[Socket]
+ListenStream=/run/systemd/io.systemd.Login
+FileDescriptorName=varlink
+SocketMode=0666
+Service=systemd-logind.service

units/systemd-networkd-varlink.socket

@@ -0,0 +1,25 @@
+#  SPDX-License-Identifier: LGPL-2.1-or-later
+#
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+[Unit]
+Description=Network Service Varlink Socket
+Documentation=man:systemd-networkd.service(8)
+ConditionCapability=CAP_NET_ADMIN
+DefaultDependencies=no
+Before=sockets.target shutdown.target
+Conflicts=shutdown.target
+
+[Socket]
+ListenStream=/run/systemd/netif/io.systemd.Network
+FileDescriptorName=varlink
+SocketMode=0666
+Service=systemd-networkd.service
+
+[Install]
+WantedBy=sockets.target

units/systemd-networkd.service.in

@@ -46,7 +46,7 @@ RestrictRealtime=yes
 RestrictSUIDSGID=yes
 RuntimeDirectory=systemd/netif
 RuntimeDirectoryPreserve=yes
-Sockets=systemd-networkd.socket
+Sockets=systemd-networkd.socket systemd-networkd-varlink.socket
 SystemCallArchitectures=native
 SystemCallErrorNumber=EPERM
 SystemCallFilter=@system-service bpf
@@ -56,7 +56,7 @@ User=systemd-network
 
 [Install]
 WantedBy=multi-user.target
-Also=systemd-networkd.socket
+Also=systemd-networkd.socket systemd-networkd-varlink.socket
 Alias=dbus-org.freedesktop.network1.service
 
 # The output from this generator is used by udevd and networkd. Enable it by