wwan: mark modems that are taken by a NMDevice as "claimed"

NMModem-s are either used by NMDeviceModem or by NMDeviceBt.
The mechanism how that is coordinated it odd:

  - the factory emits component-added, and then NMDeviceBt
    might take the device (and claim it). In that case, component-added
    would return TRUE to indicate that the modem should not be also
    used by NMDeviceModem.

  - next, if the modem has a driver that looks like bluetooth, NMDeviceModem
    ignores it too.

  - finally, NMDeviceModem claims the modem (which is now considered to
    be non-bluetooth).

I think the first problem is that the device factory tries to have this
generic mechanism of "component-added". It's literally only used to
cover this special case. Note that NMDeviceBt is aware of modems. So,
abstracting this just adds lots of code that could be solved better
by handling the case (of giving the modem to either NMDeviceBt or
NMDeviceModem) specifically.

NMWWanFactory itself registers to the NM_MODEM_MANAGER_MODEM_ADDED
signal and emits nm_device_factory_emit_component_added().
We could just have NMWWanFactory and NMDeviceBt both register to
that signal. Signals even support priorities, so we could have
NMDeviceBt be called first to claim the device.

Anyway, as the modem can only have one owner, the modem should have
a flag that indicates whether it's claimed or not. That will allow
multiple components all look at the same modem and moderate who is
going to take ownership.

src/devices/bluetooth/nm-device-bt.c

@@ -577,7 +577,7 @@ modem_cleanup (NMDeviceBt *self)
 
 	if (priv->modem) {
 		g_signal_handlers_disconnect_matched (priv->modem, G_SIGNAL_MATCH_DATA, 0, 0, NULL, NULL, self);
-		g_clear_object (&priv->modem);
+		nm_clear_pointer (&priv->modem, nm_modem_unclaim);
 	}
 }
 
@@ -646,6 +646,10 @@ component_added (NMDevice *device, GObject *component)
 		return FALSE;
 
 	modem = NM_MODEM (component);
+
+	if (nm_modem_is_claimed (modem))
+		return FALSE;
+
 	if (!priv->rfcomm_iface)
 		return FALSE;
 
@@ -675,12 +679,9 @@ component_added (NMDevice *device, GObject *component)
 	_LOGI (LOGD_BT | LOGD_MB,
 	       "Activation: (bluetooth) Stage 2 of 5 (Device Configure) modem found.");
 
-	if (priv->modem) {
-		g_warn_if_reached ();
-		modem_cleanup (self);
-	}
+	modem_cleanup (self);
 
-	priv->modem = g_object_ref (modem);
+	priv->modem = nm_modem_claim (modem);
 	g_signal_connect (modem, NM_MODEM_PPP_STATS, G_CALLBACK (ppp_stats), self);
 	g_signal_connect (modem, NM_MODEM_PPP_FAILED, G_CALLBACK (ppp_failed), self);
 	g_signal_connect (modem, NM_MODEM_PREPARE_RESULT, G_CALLBACK (modem_prepare_result), self);

src/devices/wwan/libnm-wwan.ver

@@ -3,6 +3,7 @@ global:
 	nm_modem_act_stage1_prepare;
 	nm_modem_act_stage2_config;
 	nm_modem_check_connection_compatible;
+	nm_modem_claim;
 	nm_modem_complete_connection;
 	nm_modem_deactivate;
 	nm_modem_deactivate_async;
@@ -14,14 +15,15 @@ global:
 	nm_modem_get_device_id;
 	nm_modem_get_driver;
 	nm_modem_get_iid;
-	nm_modem_get_path;
 	nm_modem_get_ip_ifindex;
 	nm_modem_get_operator_code;
+	nm_modem_get_path;
 	nm_modem_get_secrets;
 	nm_modem_get_state;
 	nm_modem_get_type;
 	nm_modem_get_uid;
 	nm_modem_ip4_pre_commit;
+	nm_modem_is_claimed;
 	nm_modem_manager_get;
 	nm_modem_manager_get_type;
 	nm_modem_manager_name_owner_get;
@@ -32,6 +34,7 @@ global:
 	nm_modem_stage3_ip4_config_start;
 	nm_modem_stage3_ip6_config_start;
 	nm_modem_state_to_string;
+	nm_modem_unclaim;
 local:
 	*;
 };

src/devices/wwan/nm-device-modem.c

@@ -716,7 +716,7 @@ set_modem (NMDeviceModem *self, NMModem *modem)
 
 	g_return_if_fail (modem != NULL);
 
-	priv->modem = g_object_ref (modem);
+	priv->modem = nm_modem_claim (modem);
 
 	g_signal_connect (modem, NM_MODEM_PPP_FAILED, G_CALLBACK (ppp_failed), self);
 	g_signal_connect (modem, NM_MODEM_PREPARE_RESULT, G_CALLBACK (modem_prepare_result), self);
@@ -844,7 +844,7 @@ dispose (GObject *object)
 
 	if (priv->modem) {
 		g_signal_handlers_disconnect_by_data (priv->modem, NM_DEVICE_MODEM (object));
-		g_clear_object (&priv->modem);
+		nm_clear_pointer (&priv->modem, nm_modem_unclaim);
 	}
 
 	g_clear_pointer (&priv->device_id, g_free);

src/devices/wwan/nm-modem.c

@@ -97,6 +97,8 @@ typedef struct _NMModemPrivate {
 	/* PPP stats */
 	guint32 in_bytes;
 	guint32 out_bytes;
+
+	bool claimed:1;
 } NMModemPrivate;
 
 G_DEFINE_TYPE (NMModem, nm_modem, G_TYPE_OBJECT)
@@ -174,6 +176,53 @@ nm_modem_state_to_string (NMModemState state)
 	return NULL;
 }
 
+/*****************************************************************************/
+
+gboolean
+nm_modem_is_claimed (NMModem *self)
+{
+	g_return_val_if_fail (NM_IS_MODEM (self), FALSE);
+
+	return NM_MODEM_GET_PRIVATE (self)->claimed;
+}
+
+NMModem *
+nm_modem_claim (NMModem *self)
+{
+	NMModemPrivate *priv;
+
+	g_return_val_if_fail (NM_IS_MODEM (self), NULL);
+
+	priv = NM_MODEM_GET_PRIVATE (self);
+
+	g_return_val_if_fail (!priv->claimed, NULL);
+
+	priv->claimed = TRUE;
+	return g_object_ref (self);
+}
+
+void
+nm_modem_unclaim (NMModem *self)
+{
+	NMModemPrivate *priv;
+
+	g_return_if_fail (NM_IS_MODEM (self));
+
+	priv = NM_MODEM_GET_PRIVATE (self);
+
+	g_return_if_fail (priv->claimed);
+
+	/* we don't actually unclaim the instance. This instance should not be re-used
+	 * by another owner, that is because we only claim modems as we receive them.
+	 * There is no mechanism that somebody else would later re-use them again.
+	 *
+	 * // priv->claimed = FALSE; */
+
+	g_object_unref (self);
+}
+
+/*****************************************************************************/
+
 NMModemState
 nm_modem_get_state (NMModem *self)
 {

src/devices/wwan/nm-modem.h

@@ -154,6 +154,10 @@ typedef struct {
 
 GType nm_modem_get_type (void);
 
+gboolean nm_modem_is_claimed (NMModem *modem);
+NMModem *nm_modem_claim (NMModem *modem);
+void nm_modem_unclaim (NMModem *modem);
+
 const char *nm_modem_get_path            (NMModem *modem);
 const char *nm_modem_get_uid             (NMModem *modem);
 const char *nm_modem_get_control_port    (NMModem *modem);

src/devices/wwan/nm-wwan-factory.c

@@ -64,13 +64,16 @@ modem_added_cb (NMModemManager *manager,
                 gpointer user_data)
 {
 	NMWwanFactory *self = NM_WWAN_FACTORY (user_data);
-	NMDevice *device;
+	gs_unref_object NMDevice *device = NULL;
 	const char *driver;
 
 	/* Do nothing if the modem was consumed by some other plugin */
 	if (nm_device_factory_emit_component_added (NM_DEVICE_FACTORY (self), G_OBJECT (modem)))
 		return;
 
+	if (nm_modem_is_claimed (modem))
+		return;
+
 	driver = nm_modem_get_driver (modem);
 
 	/* If it was a Bluetooth modem and no bluetooth device claimed it, ignore
@@ -85,9 +88,7 @@ modem_added_cb (NMModemManager *manager,
 
 	/* Make the new modem device */
 	device = nm_device_modem_new (modem);
-	g_assert (device);
 	g_signal_emit_by_name (self, NM_DEVICE_FACTORY_DEVICE_ADDED, device);
-	g_object_unref (device);
 }
 
 static NMDevice *