app_dial: Add option "j" to preserve initial stream topology of caller

Resolves: #462

UserNote: The option "j" is now available for the Dial application which
uses the initial stream topology of the caller to create the outgoing
channels.

(cherry picked from commit 366dc1e99f)

apps/app_dial.c

@@ -242,6 +242,10 @@
 					<para>Asterisk will ignore any connected line update requests or any redirecting party
 					update requests it may receive on this dial attempt.</para>
 				</option>
+				<option name="j">
+					<para>Use the initial stream topology of the caller for outgoing channels, even if the caller topology has changed.</para>
+					<para>NOTE: For this option to work, it has to be present in all invocations of Dial that the caller channel goes through.</para>
+				</option>
 				<option name="k">
 					<para>Allow the called party to enable parking of the call by sending
 					the DTMF sequence defined for call parking in <filename>features.conf</filename>.</para>
@@ -705,6 +709,7 @@ enum {
 #define OPT_RING_WITH_EARLY_MEDIA (1LLU << 43)
 #define OPT_HANGUPCAUSE      (1LLU << 44)
 #define OPT_HEARPULSING      (1LLU << 45)
+#define OPT_TOPOLOGY_PRESERVE (1LLU << 46)
 
 enum {
 	OPT_ARG_ANNOUNCE = 0,
@@ -749,6 +754,7 @@ AST_APP_OPTIONS(dial_exec_options, BEGIN_OPTIONS
 	AST_APP_OPTION('H', OPT_CALLER_HANGUP),
 	AST_APP_OPTION('i', OPT_IGNORE_FORWARDING),
 	AST_APP_OPTION('I', OPT_IGNORE_CONNECTEDLINE),
+	AST_APP_OPTION('j', OPT_TOPOLOGY_PRESERVE),
 	AST_APP_OPTION('k', OPT_CALLEE_PARK),
 	AST_APP_OPTION('K', OPT_CALLER_PARK),
 	AST_APP_OPTION_ARG('L', OPT_DURATION_LIMIT, OPT_ARG_DURATION_LIMIT),
@@ -808,6 +814,16 @@ struct chanlist {
 
 AST_LIST_HEAD_NOLOCK(dial_head, chanlist);
 
+static void topology_ds_destroy(void *data) {
+	struct ast_stream_topology *top = data;
+	ast_stream_topology_free(top);
+}
+
+static const struct ast_datastore_info topology_ds_info = {
+	.type = "app_dial_topology_preserve",
+	.destroy = topology_ds_destroy,
+};
+
 static int detect_disconnect(struct ast_channel *chan, char code, struct ast_str **featurecode);
 
 static void chanlist_free(struct chanlist *outgoing)
@@ -2326,6 +2342,7 @@ static int dial_exec_full(struct ast_channel *chan, const char *data, struct ast
 	 */
 	struct ast_party_caller caller;
 	int max_forwards;
+	struct ast_datastore *topology_ds = NULL;
 	SCOPE_ENTER(1, "%s: Data: %s\n", ast_channel_name(chan), data);
 
 	/* Reset all DIAL variables back to blank, to prevent confusion (in case we don't reset all of them). */
@@ -2627,7 +2644,21 @@ static int dial_exec_full(struct ast_channel *chan, const char *data, struct ast
 		 */
 		ast_party_connected_line_copy(&tmp->connected, ast_channel_connected(chan));
 
-		topology = ast_stream_topology_clone(ast_channel_get_stream_topology(chan));
+		if (ast_test_flag64(&opts, OPT_TOPOLOGY_PRESERVE)) {
+			topology_ds = ast_channel_datastore_find(chan, &topology_ds_info, NULL);
+
+			if (!topology_ds && (topology_ds = ast_datastore_alloc(&topology_ds_info, NULL))) {
+				topology_ds->data = ast_stream_topology_clone(ast_channel_get_stream_topology(chan));
+				ast_channel_datastore_add(chan, topology_ds);
+			}
+		}
+
+		if (topology_ds) {
+			ao2_ref(topology_ds->data, +1);
+			topology = topology_ds->data;
+		} else {
+			topology = ast_stream_topology_clone(ast_channel_get_stream_topology(chan));
+		}
 
 		ast_channel_unlock(chan);