networkctl,networkd: add --no-reconfigure flag to networkctl reload

Add a new --no-reconfigure flag to 'networkctl reload' that reloads
.network and .netdev files from disk without reconfiguring any network
interfaces. This may be useful to avoid reconfiguring multiple interfaces
simultaneously when multiple .network files are updated, or when an updated
.network file is applied to multiple interfaces.

On the networkd side, manager_reload() gains a reconfigure_links parameter
that gates the per-link reconfiguration loop. A new io.systemd.Network.Reload
varlink method is added that exposes this as an optional reconfigureLinks
boolean (defaults to true). Both plain 'networkctl reload' and
'--no-reconfigure' now unconditionally call this method first. If an older
networkd returns MethodNotFound, plain reload falls back to
io.systemd.service.Reload for backward compatibility; '--no-reconfigure'
fails with a clear error in that case.

src/network/networkctl-config-file.c

@@ -411,7 +411,7 @@ static int reload_daemons(ReloadFlags flags) {
                 if (!networkd_is_running())
                         log_debug("systemd-networkd is not running, skipping reload.");
                 else
-                        RET_GATHER(ret, reload_networkd());
+                        RET_GATHER(ret, reload_networkd(/* reconfigure_links= */ true));
         }
 
         return ret;

src/network/networkctl-misc.c

@@ -123,7 +123,7 @@ int verb_link_varlink_simple_method(int argc, char *argv[], uintptr_t _data, voi
 }
 
 int verb_reload(int argc, char *argv[], uintptr_t _data, void *userdata) {
-        return reload_networkd();
+        return reload_networkd(!arg_no_reconfigure);
 }
 
 int verb_persistent_storage(int argc, char *argv[], uintptr_t _data, void *userdata) {

src/network/networkctl-util.c

@@ -60,7 +60,7 @@ int varlink_connect_networkd(sd_varlink **ret_varlink) {
         return 0;
 }
 
-int reload_networkd(void) {
+int reload_networkd(bool reconfigure_links) {
         _cleanup_(sd_varlink_flush_close_unrefp) sd_varlink *vl = NULL;
         int r;
 
@@ -70,11 +70,39 @@ int reload_networkd(void) {
 
         (void) polkit_agent_open_if_enabled(BUS_TRANSPORT_LOCAL, arg_ask_password);
 
-        return varlink_callbo_and_log(
+        sd_json_variant *reply = NULL;
+        const char *error_id = NULL;
+        r = sd_varlink_callbo(
                         vl,
-                        "io.systemd.service.Reload",
-                        /* reply= */ NULL,
+                        "io.systemd.Network.Reload",
+                        &reply,
+                        &error_id,
+                        SD_JSON_BUILD_PAIR_BOOLEAN("reconfigureLinks", reconfigure_links),
                         SD_JSON_BUILD_PAIR_BOOLEAN("allowInteractiveAuthentication", arg_ask_password));
+        if (r < 0)
+                return log_error_errno(r, "Failed to call io.systemd.Network.Reload varlink method: %m");
+
+        if (error_id) {
+                if (streq(error_id, SD_VARLINK_ERROR_METHOD_NOT_FOUND)) {
+                        if (!reconfigure_links)
+                                return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
+                                                       "Installed version of systemd-networkd does not support --no-reconfigure.");
+
+                        /* Older networkd without io.systemd.Network.Reload, fall back to io.systemd.service.Reload. */
+                        return varlink_callbo_and_log(
+                                        vl,
+                                        "io.systemd.service.Reload",
+                                        /* reply= */ NULL,
+                                        SD_JSON_BUILD_PAIR_BOOLEAN("allowInteractiveAuthentication", arg_ask_password));
+                }
+
+                r = sd_varlink_error_to_errno(error_id, reply);
+                if (r != -EBADR)
+                        return log_error_errno(r, "Failed to call io.systemd.Network.Reload varlink method: %m");
+                return log_error_errno(r, "Failed to call io.systemd.Network.Reload varlink method: %s", error_id);
+        }
+
+        return 0;
 }
 
 int reload_udevd(void) {

src/network/networkctl-util.h

@@ -4,7 +4,7 @@
 #include "forward.h"
 
 int varlink_connect_networkd(sd_varlink **ret_varlink);
-int reload_networkd(void);
+int reload_networkd(bool reconfigure_links);
 int reload_udevd(void);
 bool networkd_is_running(void);
 

src/network/networkctl.c

@@ -28,6 +28,7 @@
 PagerFlags arg_pager_flags = 0;
 bool arg_legend = true;
 bool arg_no_reload = false;
+bool arg_no_reconfigure = false;
 bool arg_all = false;
 bool arg_stats = false;
 bool arg_full = false;
@@ -167,6 +168,11 @@ static int parse_argv(int argc, char *argv[], char ***remaining_args) {
                         arg_no_reload = true;
                         break;
 
+                OPTION_LONG("no-reconfigure", NULL,
+                            "Only reload config files, do not reconfigure network interfaces"):
+                        arg_no_reconfigure = true;
+                        break;
+
                 OPTION_LONG("drop-in", "NAME",
                             "Edit specified drop-in instead of main config file"):
                         if (isempty(opts.arg))

src/network/networkctl.h

@@ -7,6 +7,7 @@
 extern PagerFlags arg_pager_flags;
 extern bool arg_legend;
 extern bool arg_no_reload;
+extern bool arg_no_reconfigure;
 extern bool arg_all;
 extern bool arg_stats;
 extern bool arg_full;

src/network/networkd-manager-bus.c

@@ -215,7 +215,7 @@ static int bus_method_reload(sd_bus_message *message, void *userdata, sd_bus_err
         if (r == 0)
                 return 1; /* Polkit will call us back */
 
-        r = manager_reload(manager, message, /* varlink= */ NULL);
+        r = manager_reload(manager, message, /* varlink= */ NULL, /* reconfigure_links= */ true);
         if (r < 0)
                 return r;
 

src/network/networkd-manager-varlink.c

@@ -18,6 +18,7 @@
 #include "networkd-manager.h"
 #include "networkd-manager-varlink.h"
 #include "stat-util.h"
+#include "string-util.h"
 #include "varlink-io.systemd.Network.h"
 #include "varlink-io.systemd.Network.Link.h"
 #include "varlink-io.systemd.service.h"
@@ -237,6 +238,12 @@ static int vl_method_set_persistent_storage(sd_varlink *vlink, sd_json_variant *
 }
 
 static int vl_method_reload(sd_varlink *vlink, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) {
+        static const sd_json_dispatch_field dispatch_table[] = {
+                { "reconfigureLinks", SD_JSON_VARIANT_BOOLEAN, sd_json_dispatch_tristate, 0, SD_JSON_NULLABLE },
+                VARLINK_DISPATCH_POLKIT_FIELD,
+                {}
+        };
+
         Manager *m = ASSERT_PTR(userdata);
         int r;
 
@@ -245,7 +252,18 @@ static int vl_method_reload(sd_varlink *vlink, sd_json_variant *parameters, sd_v
         if (m->reloading > 0)
                 return sd_varlink_error(vlink, "io.systemd.Network.AlreadyReloading", NULL);
 
-        r = sd_varlink_dispatch(vlink, parameters, dispatch_table_polkit_only, /* userdata= */ NULL);
+        const char *method;
+        r = sd_varlink_get_current_method(vlink, &method);
+        if (r < 0)
+                return r;
+
+        bool is_network_reload = streq(method, "io.systemd.Network.Reload");
+        int reconfigure_links = -1; /* tristate: -1 = unset (defaults to true) */
+        r = sd_varlink_dispatch(
+                        vlink,
+                        parameters,
+                        is_network_reload ? dispatch_table : dispatch_table_polkit_only,
+                        &reconfigure_links);
         if (r != 0)
                 return r;
 
@@ -258,7 +276,7 @@ static int vl_method_reload(sd_varlink *vlink, sd_json_variant *parameters, sd_v
         if (r <= 0)
                 return r;
 
-        r = manager_reload(m, /* message= */ NULL, vlink);
+        r = manager_reload(m, /* message= */ NULL, vlink, /* reconfigure_links= */ reconfigure_links != 0);
         if (r < 0)
                 return log_error_errno(r, "Failed to reload: %m");
 
@@ -302,6 +320,7 @@ int manager_varlink_init(Manager *m, int fd) {
                         "io.systemd.Network.GetStates",            vl_method_get_states,
                         "io.systemd.Network.GetNamespaceId",       vl_method_get_namespace_id,
                         "io.systemd.Network.GetLLDPNeighbors",     vl_method_get_lldp_neighbors,
+                        "io.systemd.Network.Reload",               vl_method_reload,
                         "io.systemd.Network.SetPersistentStorage", vl_method_set_persistent_storage,
                         "io.systemd.Network.Link.Describe",        vl_method_link_describe,
                         "io.systemd.Network.Link.Up",              vl_method_link_up,

src/network/networkd-manager.c

@@ -535,7 +535,7 @@ static int signal_restart_callback(sd_event_source *s, const struct signalfd_sig
 static int signal_reload_callback(sd_event_source *s, const struct signalfd_siginfo *si, void *userdata) {
         Manager *m = ASSERT_PTR(userdata);
 
-        (void) manager_reload(m, /* message= */ NULL, /* varlink= */ NULL);
+        (void) manager_reload(m, /* message= */ NULL, /* varlink= */ NULL, /* reconfigure_links= */ true);
 
         return 0;
 }
@@ -1266,7 +1266,7 @@ int manager_set_timezone(Manager *m, const char *tz) {
         return 0;
 }
 
-int manager_reload(Manager *m, sd_bus_message *message, sd_varlink *varlink) {
+int manager_reload(Manager *m, sd_bus_message *message, sd_varlink *varlink, bool reconfigure_links) {
         Link *link;
         int r;
 
@@ -1288,13 +1288,14 @@ int manager_reload(Manager *m, sd_bus_message *message, sd_varlink *varlink) {
                 goto finish;
         }
 
-        HASHMAP_FOREACH(link, m->links_by_index)
-                (void) link_reconfigure_full(
-                                link,
-                                /* flags= */ 0,
-                                message,
-                                varlink,
-                                /* counter= */ (message || varlink) ? &m->reloading : NULL);
+        if (reconfigure_links)
+                HASHMAP_FOREACH(link, m->links_by_index)
+                        (void) link_reconfigure_full(
+                                        link,
+                                        /* flags= */ 0,
+                                        message,
+                                        varlink,
+                                        /* counter= */ (message || varlink) ? &m->reloading : NULL);
 
         log_debug("Reloaded.");
         r = 0;

src/network/networkd-manager.h

@@ -159,7 +159,7 @@ int manager_enumerate(Manager *m);
 int manager_set_hostname(Manager *m, const char *hostname);
 int manager_set_timezone(Manager *m, const char *tz);
 
-int manager_reload(Manager *m, sd_bus_message *message, sd_varlink *varlink);
+int manager_reload(Manager *m, sd_bus_message *message, sd_varlink *varlink, bool reconfigure_links);
 
 static inline Hashmap** manager_get_sysctl_shadow(Manager *manager) {
 #if ENABLE_SYSCTL_BPF