ARI: allow other operations to happen while bridged

This patch changes ARI bridging to allow other channel operations to
happen while the channel is bridged.

ARI channel operations are designed to queue up and execute
sequentially. This meant, though, that while a channel was bridged,
any other channel operations would queue up and execute only after the
channel left the bridge.

This patch changes ARI bridging so that channel commands can execute
while the channel is bridged. For most operations, things simply work
as expected. The one thing that ended up being a bit odd is recording.

The current recording implementation will fail when one attempts to
record a channel that's in a bridge. Note that the bridge itself may
be recording; it's recording a specific channel in the bridge that
fails. While this is an annoying limitation, channel recording is
still very useful for use cases such as voice mail, and bridge
recording makes up much of the difference for other use cases.

(closes issue ASTERISK-22084)
Review: https://reviewboard.asterisk.org/r/2726/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@396568 65c4cc65-6c06-0410-ace0-fbb531ad65f3

2 files changed, 248 insertions, 14 deletions

diff --git a/res/stasis/control.c b/res/stasis/control.c
index dcc029701..df279165f 100644
--- a/res/stasis/control.c
+++ b/res/stasis/control.c
@@ -33,62 +33,99 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #include "control.h"
 #include "asterisk/dial.h"
 #include "asterisk/bridge.h"
+#include "asterisk/bridge_after.h"
 #include "asterisk/bridge_basic.h"
 #include "asterisk/frame.h"
 #include "asterisk/pbx.h"
 #include "asterisk/musiconhold.h"
 
 struct stasis_app_control {
+	ast_cond_t wait_cond;
 	/*! Queue of commands to dispatch on the channel */
 	struct ao2_container *command_queue;
 	/*!
-	 * When set, /c app_stasis should exit and continue in the dialplan.
-	 */
-	int is_done:1;
-	/*!
 	 * The associated channel.
 	 * Be very careful with the threading associated w/ manipulating
 	 * the channel.
 	 */
 	struct ast_channel *channel;
+	/*!
+	 * When a channel is in a bridge, the bridge that it is in.
+	 */
+	struct ast_bridge *bridge;
+	/*!
+	 * Holding place for channel's PBX while imparted to a bridge.
+	 */
+	struct ast_pbx *pbx;
+	/*!
+	 * When set, /c app_stasis should exit and continue in the dialplan.
+	 */
+	int is_done:1;
 };
 
+static void control_dtor(void *obj)
+{
+	struct stasis_app_control *control = obj;
+
+	ao2_cleanup(control->command_queue);
+	ast_cond_destroy(&control->wait_cond);
+}
+
 struct stasis_app_control *control_create(struct ast_channel *channel)
 {
-	struct stasis_app_control *control;
+	RAII_VAR(struct stasis_app_control *, control, NULL, ao2_cleanup);
+	int res;
 
-	control = ao2_alloc(sizeof(*control), NULL);
+	control = ao2_alloc(sizeof(*control), control_dtor);
 	if (!control) {
 		return NULL;
 	}
 
+	res = ast_cond_init(&control->wait_cond, NULL);
+	if (res != 0) {
+		ast_log(LOG_ERROR, "Error initializing ast_cond_t: %s\n",
+			strerror(errno));
+		return NULL;
+	}
+
 	control->command_queue = ao2_container_alloc_list(
 		AO2_ALLOC_OPT_LOCK_MUTEX, 0, NULL, NULL);
 
 	if (!control->command_queue) {
-		ao2_cleanup(control);
 		return NULL;
 	}
 
 	control->channel = channel;
 
+	ao2_ref(control, +1);
 	return control;
 }
 
+static void *noop_cb(struct stasis_app_control *control,
+	struct ast_channel *chan, void *data)
+{
+	return NULL;
+}
+
+
 static struct stasis_app_command *exec_command(
 	struct stasis_app_control *control, stasis_app_command_cb command_fn,
 	void *data)
 {
 	RAII_VAR(struct stasis_app_command *, command, NULL, ao2_cleanup);
 
+	command_fn = command_fn ? : noop_cb;
+
 	command = command_create(command_fn, data);
 
 	if (!command) {
 		return NULL;
 	}
 
-	/* command_queue is a thread safe list; no lock needed */
-	ao2_link(control->command_queue, command);
+	ao2_lock(control->command_queue);
+	ao2_link_flags(control->command_queue, command, OBJ_NOLOCK);
+	ast_cond_signal(&control->wait_cond);
+	ao2_unlock(control->command_queue);
 
 	ao2_ref(command, +1);
 	return command;
@@ -195,6 +232,14 @@ static void *app_control_continue(struct stasis_app_control *control,
 {
 	RAII_VAR(struct stasis_app_control_continue_data *, continue_data, data, ast_free);
 
+	ast_assert(control->channel != NULL);
+
+	/* If we're in a Stasis bridge, depart it before going back to the
+	 * dialplan */
+	if (stasis_app_get_bridge(control)) {
+		ast_bridge_depart(control->channel);
+	}
+
 	/* Called from stasis_app_exec thread; no lock needed */
 	ast_explicit_goto(control->channel, continue_data->context, continue_data->extension, continue_data->priority);
 
@@ -422,6 +467,161 @@ int stasis_app_send_command_async(struct stasis_app_control *control,
 	return 0;
 }
 
+struct ast_bridge *stasis_app_get_bridge(struct stasis_app_control *control)
+{
+	if (!control) {
+		return NULL;
+	} else {
+		SCOPED_AO2LOCK(lock, control);
+		return control->bridge;
+	}
+}
+
+
+static void bridge_after_cb(struct ast_channel *chan, void *data)
+{
+	struct stasis_app_control *control = data;
+	SCOPED_AO2LOCK(lock, control);
+
+	ast_debug(3, "%s, %s: Channel leaving bridge\n",
+		ast_channel_uniqueid(chan), control->bridge->uniqueid);
+
+	ast_assert(chan == control->channel);
+
+	/* Restore the channel's PBX */
+	ast_channel_pbx_set(control->channel, control->pbx);
+	control->pbx = NULL;
+
+	/* No longer in the bridge */
+	control->bridge = NULL;
+
+	/* Wakeup the command_queue loop */
+	exec_command(control, NULL, NULL);
+}
+
+static void bridge_after_cb_failed(enum ast_bridge_after_cb_reason reason,
+	void *data)
+{
+	struct stasis_app_control *control = data;
+
+	bridge_after_cb(control->channel, data);
+
+	ast_debug(3, "  reason: %s\n",
+		ast_bridge_after_cb_reason_string(reason));
+}
+
+static void *app_control_add_channel_to_bridge(
+	struct stasis_app_control *control,
+	struct ast_channel *chan, void *data)
+{
+	struct ast_bridge *bridge = data;
+	int res;
+
+	if (!control || !bridge) {
+		return NULL;
+	}
+
+	ast_debug(3, "%s: Adding to bridge %s\n",
+		stasis_app_control_get_channel_id(control),
+		bridge->uniqueid);
+
+	ast_assert(chan != NULL);
+
+	/* Depart whatever Stasis bridge we're currently in. */
+	if (stasis_app_get_bridge(control)) {
+		/* Note that it looks like there's a race condition here, since
+		 * we don't have control locked. But this happens from the
+		 * control callback thread, so there won't be any other
+		 * concurrent attempts to bridge.
+		 */
+		ast_bridge_depart(chan);
+	}
+
+
+	res = ast_bridge_set_after_callback(chan, bridge_after_cb,
+		bridge_after_cb_failed, control);
+	if (res != 0) {
+		ast_log(LOG_ERROR, "Error setting after-bridge callback\n");
+		return NULL;
+	}
+
+	{
+		/* pbx and bridge are modified by the bridging impart thread.
+		 * It shouldn't happen concurrently, but we still need to lock
+		 * for the memory fence.
+		 */
+		SCOPED_AO2LOCK(lock, control);
+
+		/* Save off the channel's PBX */
+		ast_assert(control->pbx == NULL);
+		if (!control->pbx) {
+			control->pbx = ast_channel_pbx(chan);
+			ast_channel_pbx_set(chan, NULL);
+		}
+
+		res = ast_bridge_impart(bridge,
+			chan,
+			NULL, /* swap channel */
+			NULL, /* features */
+			0); /* independent - false allows us to ast_bridge_depart() */
+
+		if (res != 0) {
+			ast_log(LOG_ERROR, "Error adding channel to bridge\n");
+			ast_channel_pbx_set(chan, control->pbx);
+			control->pbx = NULL;
+			return NULL;
+		}
+
+		ast_assert(stasis_app_get_bridge(control) == NULL);
+		control->bridge = bridge;
+	}
+	return NULL;
+}
+
+void stasis_app_control_add_channel_to_bridge(
+	struct stasis_app_control *control, struct ast_bridge *bridge)
+{
+	ast_debug(3, "%s: Sending channel add_to_bridge command\n",
+			stasis_app_control_get_channel_id(control));
+	stasis_app_send_command_async(control,
+		app_control_add_channel_to_bridge, bridge);
+}
+
+static void *app_control_remove_channel_from_bridge(
+	struct stasis_app_control *control,
+	struct ast_channel *chan, void *data)
+{
+	struct ast_bridge *bridge = data;
+
+	if (!control) {
+		return NULL;
+	}
+
+	/* We should only depart from our own bridge */
+	ast_debug(3, "%s: Departing bridge %s\n",
+		stasis_app_control_get_channel_id(control),
+		bridge->uniqueid);
+
+	if (bridge != stasis_app_get_bridge(control)) {
+		ast_log(LOG_WARNING, "%s: Not in bridge %s; not removing\n",
+			stasis_app_control_get_channel_id(control),
+			bridge->uniqueid);
+		return NULL;
+	}
+
+	ast_bridge_depart(chan);
+	return NULL;
+}
+
+void stasis_app_control_remove_channel_from_bridge(
+	struct stasis_app_control *control, struct ast_bridge *bridge)
+{
+	ast_debug(3, "%s: Sending channel remove_from_bridge command\n",
+			stasis_app_control_get_channel_id(control));
+	stasis_app_send_command_async(control,
+		app_control_remove_channel_from_bridge, bridge);
+}
+
 const char *stasis_app_control_get_channel_id(
 	const struct stasis_app_control *control)
 {
@@ -464,9 +664,22 @@ int control_dispatch_all(struct stasis_app_control *control,
 	return count;
 }
 
-/* Must be defined here since it must operate on the channel outside of the queue */
-int stasis_app_control_remove_channel_from_bridge(
-	struct stasis_app_control *control, struct ast_bridge *bridge)
+void control_wait(struct stasis_app_control *control)
 {
-	return ast_bridge_remove(bridge, control->channel);
+	if (!control) {
+		return;
+	}
+
+	ast_assert(control->command_queue != NULL);
+
+	ao2_lock(control->command_queue);
+	while (ao2_container_count(control->command_queue) == 0) {
+		int res = ast_cond_wait(&control->wait_cond,
+			ao2_object_get_lockaddr(control->command_queue));
+		if (res < 0) {
+			ast_log(LOG_ERROR, "Error waiting on command queue\n");
+			break;
+		}
+	}
+	ao2_unlock(control->command_queue);
 }
diff --git a/res/stasis/control.h b/res/stasis/control.h
index 9a4243be1..9e580b860 100644
--- a/res/stasis/control.h
+++ b/res/stasis/control.h
@@ -48,8 +48,29 @@ struct stasis_app_control *control_create(struct ast_channel *channel);
 int control_dispatch_all(struct stasis_app_control *control,
 	struct ast_channel *chan);
 
-int control_is_done(struct stasis_app_control *control);
+/*!
+ * \brief Blocks until \a control's command queue has a command available.
+ *
+ * \param control Control to block on.
+ */
+void control_wait(struct stasis_app_control *control);
 
+/*!
+ * \brief Signals that a control object should finish and exit back to the
+ * dialplan.
+ *
+ * \param control Control object to continue.
+ */
 void control_continue(struct stasis_app_control *control);
 
+/*!
+ * \brief Returns true if control_continue() has been called on this \a control.
+ *
+ * \param control Control to query.
+ * \return True (non-zero) if control_continue() has been called.
+ * \return False (zero) otherwise.
+ */
+int control_is_done(struct stasis_app_control *control);
+
+
 #endif /* _ASTERISK_RES_STASIS_CONTROL_H */