iu_client: introduce UE field free_on_release

Allow to free UE ctx when receiving a Iu Release Complete.
In preparation of ranap_iu_tx_release_free() it requires
a field to free the Iu ctx on it's own without depending
on the upstream user.

Change-Id: Iac41cd3cce3232d01b2f7ede0cc46226c2cfb6c0
diff --git a/src/iu_client.c b/src/iu_client.c
index e4eb83e..c309ce4 100644
--- a/src/iu_client.c
+++ b/src/iu_client.c
@@ -129,6 +129,7 @@
 	ctx->rnc = rnc;
 	ctx->conn_id = conn_id;
 	ctx->notification = true;
+	ctx->free_on_release = false;
 	osmo_timer_setup(&ctx->release_timeout,
 			 (void *)(void *) ranap_iu_free_ue,
 			 ctx);
@@ -500,6 +501,7 @@
 			     int timeout)
 {
 	ctx->notification = false;
+	ctx->free_on_release = true;
 	int ret = ranap_iu_tx_release(ctx, cause);
 	if (ret) {
 		ranap_iu_free_ue(ctx);
@@ -851,6 +853,13 @@
 			break;
 
 		global_iu_event(ue, RANAP_IU_EVENT_LINK_INVALIDATED, NULL);
+
+		/* A RANAP_IU_EVENT_LINK_INVALIDATED, can lead to a free */
+		ue = ue_conn_ctx_find(prim->u.disconnect.conn_id);
+		if (!ue)
+			break;
+		if (ue->free_on_release)
+			ranap_iu_free_ue(ue);
 		break;
 	case OSMO_PRIM(OSMO_SCU_PRIM_N_DATA, PRIM_OP_INDICATION):
 		/* connection-oriented data received */