core: Add stream topology changing primitives with tests.

This change adds a few things to facilitate stream topology changing:

1. Control frame types have been added for use by the channel driver
to notify the application that the channel wants to change the stream
topology or that a stream topology change has been accepted. They are
also used by the indicate interface to the channel that the application
uses to indicate it wants to do the same.

2. Legacy behavior has been adopted in ast_read() such that if a
channel requests a stream topology change it is denied automatically
and the current stream topology is preserved if the application is
not capable of handling streams.

Tests have also been written which confirm the multistream and
non-multistream behavior.

ASTERISK-26839

Change-Id: Ia68ef22bca8e8457265ca4f0f9de600cbcc10bc9

1 files changed, 41 insertions, 0 deletions

diff --git a/main/channel.c b/main/channel.c
index 12a30e048..15c7fa406 100644
--- a/main/channel.c
+++ b/main/channel.c
@@ -4068,6 +4068,19 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio, int
 				}
 				ast_frfree(f);
 				f = &ast_null_frame;
+			} else if (f->subclass.integer == AST_CONTROL_STREAM_TOPOLOGY_REQUEST_CHANGE && dropnondefault) {
+				/* The caller of this function is incapable of handling streams so we don't accept the change request
+				 * and stick to the streams currently on the channel.
+				 */
+				ast_channel_stream_topology_changed(chan, ast_channel_get_stream_topology(chan));
+				ast_frfree(f);
+				f = &ast_null_frame;
+			} else if (f->subclass.integer == AST_CONTROL_STREAM_TOPOLOGY_CHANGED && dropnondefault) {
+				/* The caller of this function is incapable of handling streams so we absord the notification that the
+				 * stream topology has changed.
+				 */
+				ast_frfree(f);
+				f = &ast_null_frame;
 			}
 			break;
 		case AST_FRAME_DTMF_END:
@@ -4494,6 +4507,8 @@ static int attribute_const is_visible_indication(enum ast_control_frame_type con
 	case AST_CONTROL_UPDATE_RTP_PEER:
 	case AST_CONTROL_PVT_CAUSE_CODE:
 	case AST_CONTROL_MASQUERADE_NOTIFY:
+	case AST_CONTROL_STREAM_TOPOLOGY_REQUEST_CHANGE:
+	case AST_CONTROL_STREAM_TOPOLOGY_CHANGED:
 	case AST_CONTROL_STREAM_STOP:
 	case AST_CONTROL_STREAM_SUSPEND:
 	case AST_CONTROL_STREAM_REVERSE:
@@ -4792,6 +4807,8 @@ static int indicate_data_internal(struct ast_channel *chan, int _condition, cons
 	case AST_CONTROL_MCID:
 	case AST_CONTROL_MASQUERADE_NOTIFY:
 	case AST_CONTROL_UPDATE_RTP_PEER:
+	case AST_CONTROL_STREAM_TOPOLOGY_REQUEST_CHANGE:
+	case AST_CONTROL_STREAM_TOPOLOGY_CHANGED:
 	case AST_CONTROL_STREAM_STOP:
 	case AST_CONTROL_STREAM_SUSPEND:
 	case AST_CONTROL_STREAM_REVERSE:
@@ -11147,3 +11164,27 @@ enum ast_channel_error ast_channel_errno(void)
 {
 	return ast_channel_internal_errno();
 }
+
+int ast_channel_request_stream_topology_change(struct ast_channel *chan, struct ast_stream_topology *topology)
+{
+	ast_assert(chan != NULL);
+	ast_assert(topology != NULL);
+
+	if (!ast_channel_is_multistream(chan) || !ast_channel_tech(chan)->indicate) {
+		return -1;
+	}
+
+	return ast_channel_tech(chan)->indicate(chan, AST_CONTROL_STREAM_TOPOLOGY_REQUEST_CHANGE, topology, sizeof(topology));
+}
+
+int ast_channel_stream_topology_changed(struct ast_channel *chan, struct ast_stream_topology *topology)
+{
+	ast_assert(chan != NULL);
+	ast_assert(topology != NULL);
+
+	if (!ast_channel_is_multistream(chan) || !ast_channel_tech(chan)->indicate) {
+		return -1;
+	}
+
+	return ast_channel_tech(chan)->indicate(chan, AST_CONTROL_STREAM_TOPOLOGY_CHANGED, topology, sizeof(topology));
+}