TT#14008 rework offer/answer subscriptions

While doing the A/B reassociation during an offer/answer exchange, we
don't (necessarily) want to remove all existing subscriptions. Instead
we cant to unsubscribe all subscribers so we don't do media forking, but
leaving existing subscriptions alone to make early media reception
possible. This mirros the old behaviour.

Change-Id: Ib9e6671ca2d23d1eb4509d7cf939015c816cc622

daemon/call.c

@@ -2692,10 +2692,6 @@ static void __unsubscribe_one_link(struct call_monologue *which, GList *which_cs
 	g_slice_free1(sizeof(*cs), cs);
 	g_slice_free1(sizeof(*rev_cs), rev_cs);
 }
-//static void __unsubscribe_all(struct call_monologue *which) {
-//	while (which->subscriptions.head)
-//		__unsubscribe_one_link(which, which->subscriptions.head);
-//}
 static bool __unsubscribe_one(struct call_monologue *which, struct call_monologue *from) {
 	GList *l = g_hash_table_lookup(which->subscriptions_ht, from);
 	if (!l) {
@@ -2707,15 +2703,15 @@ static bool __unsubscribe_one(struct call_monologue *which, struct call_monologu
 	__unsubscribe_one_link(which, l);
 	return true;
 }
-static void __unsubscribe_all_offer_answer(struct call_monologue *ml) {
-	for (GList *l = ml->subscriptions.head; l; ) {
+static void __unsubscribe_all_offer_answer_subscribers(struct call_monologue *ml) {
+	for (GList *l = ml->subscribers.head; l; ) {
 		struct call_subscription *cs = l->data;
 		if (!cs->offer_answer) {
 			l = l->next;
 			continue;
 		}
 		GList *next = l->next;
-		__unsubscribe_one_link(ml, l);
+		__unsubscribe_one(cs->monologue, ml);
 		l = next;
 	}
 }
@@ -2751,9 +2747,11 @@ void __add_subscription(struct call_monologue *which, struct call_monologue *to,
 	g_hash_table_insert(which->subscriptions_ht, to, to_rev_cs->link);
 	g_hash_table_insert(to->subscribers_ht, which, which_cs->link);
 }
-static void __subscribe_only_one_offer_answer(struct call_monologue *which, struct call_monologue *to) {
-	__unsubscribe_all_offer_answer(which);
-	__add_subscription(which, to, true);
+static void __subscribe_offer_answer_both_ways(struct call_monologue *a, struct call_monologue *b) {
+	__unsubscribe_all_offer_answer_subscribers(a);
+	__unsubscribe_all_offer_answer_subscribers(b);
+	__add_subscription(a, b, true);
+	__add_subscription(b, a, true);
 }
 
 
@@ -3752,8 +3750,7 @@ static int call_get_monologue_new(struct call_monologue *dialogue[2], struct cal
 					goto new_branch;
 				// use existing to-tag
 				__monologue_unkernelize(csm);
-				__subscribe_only_one_offer_answer(ret, csm);
-				__subscribe_only_one_offer_answer(csm, ret);
+				__subscribe_offer_answer_both_ways(ret, csm);
 				break;
 			}
 			break; // there should only be one
@@ -3782,8 +3779,7 @@ static int call_get_monologue_new(struct call_monologue *dialogue[2], struct cal
 	if (os) {
 		/* previously seen branch. use it */
 		__monologue_unkernelize(os);
-		__subscribe_only_one_offer_answer(ret, os);
-		__subscribe_only_one_offer_answer(os, ret);
+		__subscribe_offer_answer_both_ways(ret, os);
 		goto ok_check_tag;
 	}
 
@@ -3792,8 +3788,7 @@ static int call_get_monologue_new(struct call_monologue *dialogue[2], struct cal
 new_branch:
 	__C_DBG("create new \"other side\" monologue for viabranch "STR_FORMAT, STR_FMT0(viabranch));
 	os = __monologue_create(call);
-	__subscribe_only_one_offer_answer(ret, os);
-	__subscribe_only_one_offer_answer(os, ret);
+	__subscribe_offer_answer_both_ways(ret, os);
 	__monologue_viabranch(os, viabranch);
 
 ok_check_tag:
@@ -3883,8 +3878,7 @@ tag_setup:
 
 	__dialogue_unkernelize(ft);
 	__dialogue_unkernelize(tt);
-	__subscribe_only_one_offer_answer(ft, tt);
-	__subscribe_only_one_offer_answer(tt, ft);
+	__subscribe_offer_answer_both_ways(ft, tt);
 	__fix_other_tags(ft);
 
 done: