ACN: Changes specific to the core

Allow passing a topology from the called channel back to the
calling channel.

 * Added a new function ast_queue_answer() that accepts a stream
   topology and queues an ANSWER CONTROL frame with it as the
   data.  This allows the called channel to indicate its resolved
   topology.

 * Added a new virtual function to the channel tech structure
   answer_with_stream_topology() that allows the calling channel
   to receive the called channel's topology.  Added
   ast_raw_answer_with_stream_topology() that invokes that virtual
   function.

 * Modified app_dial.c and features.c to grab the topology from the
   ANSWER frame queued by the answering channel and send it to
   the calling channel with ast_raw_answer_with_stream_topology().

 * Modified frame.c to automatically cleanup the reference
   to the topology on ANSWER frames.

Added a few debugging messages to stream.c.

Change-Id: I0115d2ed68d6bae0f87e85abcf16c771bdaf992c

include/asterisk/channel.h

@@ -707,6 +707,19 @@ struct ast_channel_tech {
 	/*! \brief Answer the channel */
 	int (* const answer)(struct ast_channel *chan);
 
+	/*!
+	 * \brief Answer the channel with topology
+	 * \since 18.0.0
+	 *
+	 * \param chan The channel to answer
+	 * \param topology The topology to use, probably the peer's.
+	 *
+	 * \note The topology may be NULL when the peer doesn't support streams
+	 * or, in the case where transcoding is in effect, when this channel should use
+	 * its existing topology.
+	 */
+	int (* const answer_with_stream_topology)(struct ast_channel *chan, struct ast_stream_topology *topology);
+
 	/*!
 	 * \brief Read a frame (or chain of frames from the same stream), in standard format (see frame.h)
 	 *
@@ -1081,6 +1094,10 @@ struct ast_bridge_config {
 	 * exist when the end_bridge_callback is called, then it needs to be fixed up properly
 	 */
 	void (*end_bridge_callback_data_fixup)(struct ast_bridge_config *bconfig, struct ast_channel *originator, struct ast_channel *terminator);
+	/*! If the bridge answers the channel this topology should be passed to the channel
+	 * and used if the channel supports the answer_with_stream_topology callback.
+	 */
+	struct ast_stream_topology *answer_topology;
 };
 
 struct chanmon;
@@ -1378,6 +1395,17 @@ int ast_queue_control(struct ast_channel *chan, enum ast_control_frame_type cont
 int ast_queue_control_data(struct ast_channel *chan, enum ast_control_frame_type control,
 			   const void *data, size_t datalen);
 
+/*!
+ * \brief Queue an ANSWER control frame with topology
+ *
+ * \param chan channel to queue frame onto
+ * \param topology topology to be passed through the core to the peer channel
+ *
+ * \retval 0 success
+ * \retval non-zero failure
+ */
+int ast_queue_answer(struct ast_channel *chan, const struct ast_stream_topology *topology);
+
 /*!
  * \brief Change channel name
  *
@@ -1801,6 +1829,31 @@ int ast_auto_answer(struct ast_channel *chan);
  */
 int ast_raw_answer(struct ast_channel *chan);
 
+/*!
+ * \brief Answer a channel passing in a stream topology
+ * \since 18.0.0
+ *
+ * \param chan channel to answer
+ * \param topology the peer's stream topology
+ *
+ * This function answers a channel and handles all necessary call
+ * setup functions.
+ *
+ * \note The channel passed does not need to be locked, but is locked
+ * by the function when needed.
+ *
+ * \note Unlike ast_answer(), this function will not wait for media
+ * flow to begin. The caller should be careful before sending media
+ * to the channel before incoming media arrives, as the outgoing
+ * media may be lost.
+ *
+ * \note The topology is usually that of the peer channel and may be NULL.
+ *
+ * \retval 0 on success
+ * \retval non-zero on failure
+ */
+int ast_raw_answer_with_stream_topology(struct ast_channel *chan, struct ast_stream_topology *topology);
+
 /*!
  * \brief Answer a channel, with a selectable delay before returning
  *
@@ -5054,4 +5107,18 @@ int ast_channel_stream_topology_changed_externally(struct ast_channel *chan);
  */
 void *ast_channel_get_stream_topology_change_source(struct ast_channel *chan);
 
+/*!
+ * \brief Checks if a channel's technology implements a particular callback function
+ * \since 18.0.0
+ *
+ * \param chan The channel
+ * \param function The function to look for
+ *
+ * \retval 1 if the channel has a technology set and it implements the function
+ * \retval 0 if the channel doesn't have a technology set or it doesn't implement the function
+ */
+#define ast_channel_has_tech_function(chan, function) \
+	(ast_channel_tech(chan) ? ast_channel_tech(chan)->function != NULL : 0)
+
+
 #endif /* _ASTERISK_CHANNEL_H */

include/asterisk/frame.h

@@ -147,8 +147,12 @@ enum {
 struct ast_frame_subclass {
 	/*! A frame specific code */
 	int integer;
-	/*! The asterisk media format */
-	struct ast_format *format;
+	union {
+		/*! The asterisk media format */
+		struct ast_format *format;
+		/*! The asterisk stream topology */
+		struct ast_stream_topology *topology;
+	};
 	/*! For video formats, an indication that a frame ended */
 	unsigned int frame_ending;
 };