MT#61372 add explicit support for 18x responses

Allow to-tag updates in answers only until a non-provisional response is
received. Add a flag to optionally suppress this feature.

Change-Id: I67110ede662f618ba5a355500d3d84050e6318cc

daemon/call.c

@@ -3005,6 +3005,13 @@ int monologue_offer_answer(struct call_monologue *monologues[2], sdp_streams_q *
 
 	__C_DBG("this="STR_FORMAT" other="STR_FORMAT, STR_FMT(&receiver_ml->tag), STR_FMT(&sender_ml->tag));
 
+	if (flags->opmode == OP_OFFER)
+		ML_CLEAR(receiver_ml, FINAL_RESPONSE);
+	else if (flags->opmode == OP_ANSWER && flags->message_type == SIP_REPLY && flags->code >= 200)
+		ML_SET(sender_ml, FINAL_RESPONSE);
+	else
+		ML_CLEAR(sender_ml, FINAL_RESPONSE);
+
 	for (__auto_type sp_iter = streams->head; sp_iter; sp_iter = sp_iter->next) {
 		struct stream_params *sp = sp_iter->data;
 		__C_DBG("processing media stream #%u", sp->index);
@@ -4812,7 +4819,8 @@ static int call_get_dialogue(struct call_monologue *monologues[2], call_t *call,
 		// Allow an updated/changed to-tag in answers unless the flag to
 		// suppress this feature is set. A changed to-tag will be stored
 		// as a tag alias.
-		if (!flags || flags->opmode != OP_ANSWER || flags->new_branch)
+		if (!flags || flags->opmode != OP_ANSWER || flags->new_branch
+				|| (ML_ISSET(ft, FINAL_RESPONSE) && !flags->provisional))
 			ft = __monologue_create(call);
 	}
 

daemon/call_interfaces.c

@@ -1147,6 +1147,9 @@ void call_ng_flags_flags(str *s, unsigned int idx, helper_arg arg) {
 		case CSH_LOOKUP("port-latching"):
 			out->port_latching = 1;
 			break;
+		case CSH_LOOKUP("provisional"):
+			out->provisional = 1;
+			break;
 		case CSH_LOOKUP("record-call"):
 			out->record_call = 1;
 			break;

docs/ng_control_protocol.md

@@ -1081,6 +1081,13 @@ Spaces in each string may be replaced by hyphens.
 	Forces *rtpengine* to retain its local ports during a signalling exchange even when the
 	remote endpoint changes its port.
 
+* `provisional`
+
+    Disables special behaviour when operating on a message that was triggered
+    by a SIP response with a non-provisional (>= 200) status code.
+    Specifically, setting this flag allows for changed or updated to-tag even
+    after a final SIP response has been received.
+
 * `record call`
 
 	Identical to setting `record call` to `on` (see below).

include/call.h

@@ -219,7 +219,7 @@ enum {
 #define ML_FLAG_DTMF_INJECTION_ACTIVE		0x00040000
 #define ML_FLAG_DETECT_DTMF			0x00080000
 #define ML_FLAG_NO_RECORDING			0x00100000
-/* unused					0x00200000 */
+#define ML_FLAG_FINAL_RESPONSE			0x00200000
 #define ML_FLAG_BLOCK_SHORT			0x00400000
 #define ML_FLAG_BLOCK_MEDIA			0x00800000
 #define ML_FLAG_SILENCE_MEDIA			0x01000000

include/call_interfaces.h

@@ -237,6 +237,7 @@ struct sdp_ng_flags {
 		     directional:1,
 		     fatal:1,
 		     new_branch:1,
+		     provisional:1,
 		     /* to_tag is used especially by delete handling */
 		     to_tag_flag:1;
 };