wifi: add callback to nm_supplicant_interface_request_scan()

While we request a scan, we are not yet actually scanning. That means, the supplicant's
"scanning" property will only change to TRUE a while after we initiate the scan. It may
even never happen.

We thus need to handle that the request is currently pending and react when the
request completes.

2 files changed, 85 insertions, 16 deletions

diff --git a/src/supplicant/nm-supplicant-interface.c b/src/supplicant/nm-supplicant-interface.c
index bfee298445..099c3bf2ca 100644
--- a/src/supplicant/nm-supplicant-interface.c
+++ b/src/supplicant/nm-supplicant-interface.c
@@ -2337,40 +2337,82 @@ nm_supplicant_interface_assoc (NMSupplicantInterface *self,
 
 /*****************************************************************************/
 
+typedef struct {
+	NMSupplicantInterface *self;
+	GCancellable *cancellable;
+	NMSupplicantInterfaceRequestScanCallback callback;
+	gpointer user_data;
+} ScanRequestData;
+
 static void
 scan_request_cb (GObject *source, GAsyncResult *result, gpointer user_data)
 {
+	gs_unref_object NMSupplicantInterface *self_keep_alive = NULL;
 	NMSupplicantInterface *self;
 	gs_unref_variant GVariant *res = NULL;
 	gs_free_error GError *error = NULL;
+	ScanRequestData *data = user_data;
+	gboolean cancelled = FALSE;
 
 	res = g_dbus_connection_call_finish (G_DBUS_CONNECTION (source), result, &error);
-	if (nm_utils_error_is_cancelled (error))
-		return;
-
-	self = NM_SUPPLICANT_INTERFACE (user_data);
-	if (error) {
-		if (_nm_dbus_error_has_name (error, "fi.w1.wpa_supplicant1.Interface.ScanError"))
-			_LOGD ("request-scan: could not get scan request result: %s", error->message);
-		else {
-			g_dbus_error_strip_remote_error (error);
-			_LOGW ("request-scan: could not get scan request result: %s", error->message);
+	if (nm_utils_error_is_cancelled (error)) {
+		if (!data->callback) {
+			/* the self instance was not kept alive. We also must not touch it. Return. */
+			nm_g_object_unref (data->cancellable);
+			nm_g_slice_free (data);
+			return;
 		}
-	} else
-		_LOGT ("request-scan: request scanning success");
+		cancelled = TRUE;
+	}
+
+	self = data->self;
+	if (data->callback) {
+		/* the self instance was kept alive. Balance the reference count. */
+		self_keep_alive = self;
+	}
+
+	/* we don't propagate the error/success. That is, because either answer is not
+	 * reliable. What is important to us is whether the request completed, and
+	 * the current nm_supplicant_interface_get_scanning() state. */
+	if (cancelled)
+		_LOGD ("request-scan: request cancelled");
+	else {
+		if (error) {
+			if (_nm_dbus_error_has_name (error, "fi.w1.wpa_supplicant1.Interface.ScanError"))
+				_LOGD ("request-scan: could not get scan request result: %s", error->message);
+			else {
+				g_dbus_error_strip_remote_error (error);
+				_LOGW ("request-scan: could not get scan request result: %s", error->message);
+			}
+		} else
+			_LOGT ("request-scan: request scanning success");
+	}
+
+	if (data->callback)
+		data->callback (self, data->cancellable, data->user_data);
+
+	nm_g_object_unref (data->cancellable);
+	nm_g_slice_free (data);
 }
 
 void
 nm_supplicant_interface_request_scan (NMSupplicantInterface *self,
                                       GBytes *const*ssids,
-                                      guint ssids_len)
+                                      guint ssids_len,
+                                      GCancellable *cancellable,
+                                      NMSupplicantInterfaceRequestScanCallback callback,
+                                      gpointer user_data)
 {
 	NMSupplicantInterfacePrivate *priv;
 	GVariantBuilder builder;
+	ScanRequestData *data;
 	guint i;
 
 	g_return_if_fail (NM_IS_SUPPLICANT_INTERFACE (self));
 
+	nm_assert (   (!cancellable && !callback)
+	           || (G_IS_CANCELLABLE (cancellable) && callback));
+
 	priv = NM_SUPPLICANT_INTERFACE_GET_PRIVATE (self);
 
 	_LOGT ("request-scan: request scanning (%u ssids)...", ssids_len);
@@ -2390,6 +2432,26 @@ nm_supplicant_interface_request_scan (NMSupplicantInterface *self,
 		g_variant_builder_add (&builder, "{sv}", "SSIDs", g_variant_builder_end (&ssids_builder));
 	}
 
+	data = g_slice_new (ScanRequestData);
+	*data = (ScanRequestData) {
+		.self            = self,
+		.callback        = callback,
+		.user_data       = user_data,
+		.cancellable     = nm_g_object_ref (cancellable),
+	};
+
+	if (callback) {
+		/* A callback was provided. This keeps @self alive. The caller
+		 * must provide a cancellable as the caller must never leave an asynchronous
+		 * operation pending indefinitely. */
+		nm_assert (G_IS_CANCELLABLE (cancellable));
+		g_object_ref (self);
+	} else {
+		/* We don't keep @self alive, and we don't accept a cancellable either. */
+		nm_assert (!cancellable);
+		cancellable = priv->main_cancellable;
+	}
+
 	_dbus_connection_call (self,
 	                       NM_WPAS_DBUS_IFACE_INTERFACE,
 	                       "Scan",
@@ -2397,9 +2459,9 @@ nm_supplicant_interface_request_scan (NMSupplicantInterface *self,
 	                       G_VARIANT_TYPE ("()"),
 	                       G_DBUS_CALL_FLAGS_NONE,
 	                       DBUS_TIMEOUT_MSEC,
-	                       priv->main_cancellable,
+	                       cancellable,
 	                       scan_request_cb,
-	                       self);
+	                       data);
 }
 
 /*****************************************************************************/
diff --git a/src/supplicant/nm-supplicant-interface.h b/src/supplicant/nm-supplicant-interface.h
index eb414f26f5..9ef198167f 100644
--- a/src/supplicant/nm-supplicant-interface.h
+++ b/src/supplicant/nm-supplicant-interface.h
@@ -128,9 +128,16 @@ nm_supplicant_interface_disconnect_async (NMSupplicantInterface * self,
                                           NMSupplicantInterfaceDisconnectCb callback,
                                           gpointer user_data);
 
+typedef void (*NMSupplicantInterfaceRequestScanCallback) (NMSupplicantInterface *self,
+                                                          GCancellable *cancellable,
+                                                          gpointer user_data);
+
 void nm_supplicant_interface_request_scan (NMSupplicantInterface *self,
                                            GBytes *const*ssids,
-                                           guint ssids_len);
+                                           guint ssids_len,
+                                           GCancellable *cancellable,
+                                           NMSupplicantInterfaceRequestScanCallback callback,
+                                           gpointer user_data);
 
 NMSupplicantInterfaceState nm_supplicant_interface_get_state (NMSupplicantInterface * self);