core: use hostnamed to set the transient hostnamebg/sethostname-hostnamed

In commit 6dc35e66d45e ("settings: add hostnamed support") we started
to use systemd-hostnamed for setting the system static hostname
(i.e. the one written to /etc/hostname), but nm-policy.c still called
sethostname() to set the transient (dynamic) hostname when this needs
to be changed, for example after a reverse lookup of our dynamic IP
address.

Thus, when using systemd the hostname change failed because process'
capabilities are restricted and sethostname() requires CAP_SYS_ADMIN.

We should set also the transient hostname through hostnamed when this
is available.

https://bugzilla.redhat.com/show_bug.cgi?id=1308974

3 files changed, 98 insertions, 16 deletions

diff --git a/src/nm-policy.c b/src/nm-policy.c
index 05f7edf4db..e6abbc5428 100644
--- a/src/nm-policy.c
+++ b/src/nm-policy.c
@@ -120,9 +120,32 @@ get_best_ip6_device (NMPolicy *self, gboolean fully_activated)
 
 #define FALLBACK_HOSTNAME4 "localhost.localdomain"
 
-static gboolean
-set_system_hostname (const char *new_hostname, const char *msg)
+static void settings_set_hostname_cb (char *hostname, gboolean result)
 {
+	int ret = 0;
+
+	if (!result) {
+		ret = sethostname (hostname, strlen (hostname));
+		if (ret != 0) {
+			int errsv = errno;
+
+			nm_log_warn (LOGD_DNS, "couldn't set the system hostname to '%s': (%d) %s",
+			             hostname, errsv, strerror (errsv));
+			if (errsv == EPERM)
+				nm_log_warn (LOGD_DNS, "You should use hostnamed when systemd hardening is in effect!");
+		}
+	}
+
+	if (!ret)
+		nm_dispatcher_call (DISPATCHER_ACTION_HOSTNAME, NULL, NULL, NULL, NULL, NULL, NULL);
+
+	g_free (hostname);
+}
+
+static void
+set_system_hostname (NMPolicy *self, const char *new_hostname, const char *msg)
+{
+	NMPolicyPrivate *priv = NM_POLICY_GET_PRIVATE (self);
 	char old_hostname[HOST_NAME_MAX + 1];
 	const char *name;
 	int ret;
@@ -140,23 +163,14 @@ set_system_hostname (const char *new_hostname, const char *msg)
 		/* Don't set the hostname if it isn't actually changing */
 		if (   (new_hostname && !strcmp (old_hostname, new_hostname))
 		       || (!new_hostname && !strcmp (old_hostname, FALLBACK_HOSTNAME4)))
-			return FALSE;
+			return;
 	}
 
 	name = (new_hostname && strlen (new_hostname)) ? new_hostname : FALLBACK_HOSTNAME4;
-
 	nm_log_info (LOGD_DNS, "Setting system hostname to '%s' (%s)", name, msg);
-	ret = sethostname (name, strlen (name));
-	if (ret != 0) {
-		int errsv = errno;
-
-		nm_log_warn (LOGD_DNS, "couldn't set the system hostname to '%s': (%d) %s",
-		             name, errsv, strerror (errsv));
-		if (errsv == EPERM)
-			nm_log_warn (LOGD_DNS, "You should use hostnamed when systemd hardening is in effect!");
-	}
+	nm_settings_set_transient_hostname (priv->settings, g_strdup (name), settings_set_hostname_cb);
 
-	return (ret == 0);
+	return;
 }
 
 static void
@@ -198,8 +212,7 @@ _set_hostname (NMPolicy *policy,
 
 	nm_dns_manager_set_hostname (priv->dns_manager, priv->cur_hostname);
 
-	if (set_system_hostname (priv->cur_hostname, msg))
-		nm_dispatcher_call (DISPATCHER_ACTION_HOSTNAME, NULL, NULL, NULL, NULL, NULL, NULL);
+	set_system_hostname (policy, priv->cur_hostname, msg);
 }
 
 static void
diff --git a/src/settings/nm-settings.c b/src/settings/nm-settings.c
index 377d52793c..280670e535 100644
--- a/src/settings/nm-settings.c
+++ b/src/settings/nm-settings.c
@@ -1526,6 +1526,71 @@ impl_settings_reload_connections (NMSettings *self,
 	g_dbus_method_invocation_return_value (context, g_variant_new ("(b)", TRUE));
 }
 
+typedef struct {
+	char *hostname;
+	NMSettingsSetHostnameCb cb;
+} SetHostnameInfo;
+
+static void
+set_transient_hostname_done (GObject *object,
+                             GAsyncResult *res,
+                             gpointer user_data)
+{
+	GDBusProxy *proxy = G_DBUS_PROXY (object);
+	SetHostnameInfo *info = user_data;
+	GError *error = NULL;
+	GVariant *result;
+
+	result = g_dbus_proxy_call_finish (proxy,
+	                                   res,
+	                                   &error);
+
+	if (error) {
+		nm_log_warn (LOGD_DNS,
+		             "couldn't set the system hostname to '%s' using hostnamed: %s",
+		             info->hostname, error->message);
+	}
+
+	info->cb (info->hostname, !error);
+
+	if (error)
+		g_error_free (error);
+	g_variant_unref (result);
+	g_free (info);
+}
+
+void
+nm_settings_set_transient_hostname (NMSettings *self,
+                                    char *hostname,
+                                    NMSettingsSetHostnameCb cb)
+{
+	gs_unref_variant GVariant *var = NULL;
+	gs_free_error GError *error = NULL;
+	NMSettingsPrivate *priv;
+	SetHostnameInfo *info;
+
+	g_return_if_fail (NM_IS_SETTINGS (self));
+	priv = NM_SETTINGS_GET_PRIVATE (self);
+
+	if (!priv->hostname.hostnamed_proxy) {
+		cb (hostname, FALSE);
+		return;
+	}
+
+	info = g_new0 (SetHostnameInfo, 1);
+	info->hostname = hostname;
+	info->cb = cb;
+
+	g_dbus_proxy_call (priv->hostname.hostnamed_proxy,
+	                   "SetHostname",
+	                    g_variant_new ("(sb)", hostname, FALSE),
+	                    G_DBUS_CALL_FLAGS_NONE,
+	                    -1,
+	                    NULL,
+	                    set_transient_hostname_done,
+	                    info);
+}
+
 static gboolean
 write_hostname (NMSettingsPrivate *priv, const char *hostname)
 {
diff --git a/src/settings/nm-settings.h b/src/settings/nm-settings.h
index 923b164b04..07e36c44c1 100644
--- a/src/settings/nm-settings.h
+++ b/src/settings/nm-settings.h
@@ -71,6 +71,8 @@ typedef struct {
 	void (*agent_registered) (NMSettings *self, NMSecretAgent *agent);
 } NMSettingsClass;
 
+typedef void (*NMSettingsSetHostnameCb) (char *name, gboolean result);
+
 GType nm_settings_get_type (void);
 
 NMSettings *nm_settings_new (void);
@@ -127,4 +129,6 @@ gint nm_settings_sort_connections (gconstpointer a, gconstpointer b);
 
 gboolean nm_settings_get_startup_complete (NMSettings *self);
 
+void nm_settings_set_transient_hostname (NMSettings *self, char *hostname, NMSettingsSetHostnameCb cb);
+
 #endif  /* __NM_SETTINGS_H__ */