bsc: f_establish_fully(): Support non-assignment cases

If it's a pure signalling procedure (like LU), the MSC will never
even send a BSSMAP ASSIGNMENT CMD.  Our test suite should be able
to produce this kind of behavior by passing "omit" as assignment
comamnd to the f_establish_fully() function.

Change-Id: I9bb5c8c19518905cf1ce121aa0b433886ec594d5
diff --git a/bsc/MSC_ConnectionHandler.ttcn b/bsc/MSC_ConnectionHandler.ttcn
index fe524dc..991a693 100644
--- a/bsc/MSC_ConnectionHandler.ttcn
+++ b/bsc/MSC_ConnectionHandler.ttcn
@@ -675,8 +675,25 @@
 }
 
 /* establish a channel fully, expecting an assignment matching 'exp' */
-function f_establish_fully_ret(PDU_BSSAP ass_cmd, template PDU_BSSAP exp_ass_cpl)
-runs on MSC_ConnHdlr return PDU_BSSAP {
+function f_establish_fully(template (omit) PDU_BSSAP ass_tpl, template PDU_BSSAP exp_ass_cpl)
+runs on MSC_ConnHdlr {
+	f_MscConnHdlr_init(1, "127.0.0.2", "127.0.0.3");
+
+	f_create_chan_and_exp();
+	/* we should now have a COMPL_L3 at the MSC */
+	BSSAP.receive(tr_BSSMAP_ComplL3);
+
+	/* start ciphering, if requested */
+	if (ispresent(g_pars.encr)) {
+		f_cipher_mode(g_pars.encr.enc_alg, g_pars.encr.enc_key);
+	}
+
+	/* bail out early if no assignment requested */
+	if (istemplatekind(ass_tpl, "omit")) {
+		return;
+	}
+
+	var PDU_BSSAP ass_cmd := valueof(ass_tpl);
 	var PDU_BSSAP bssap;
 	timer T := 10.0;
 	var boolean exp_compl := ischosen(exp_ass_cpl.pdu.bssmap.assignmentComplete);
@@ -696,17 +713,6 @@
 		st.is_assignment := true;
 	}
 
-	f_MscConnHdlr_init(1, "127.0.0.2", "127.0.0.3");
-
-	f_create_chan_and_exp();
-	/* we should now have a COMPL_L3 at the MSC */
-	BSSAP.receive(tr_BSSMAP_ComplL3);
-
-	/* start ciphering, if requested */
-	if (ispresent(g_pars.encr)) {
-		f_cipher_mode(g_pars.encr.enc_alg, g_pars.encr.enc_key);
-	}
-
 	f_create_mgcp_expect(mgcpcrit);
 	BSSAP.send(ass_cmd);
 
@@ -751,12 +757,6 @@
 	if (not isbound(bssap)) {
 		self.stop;
 	}
-	return bssap;
-}
-
-function f_establish_fully(PDU_BSSAP ass_cmd, template PDU_BSSAP exp_ass_cpl)
-runs on MSC_ConnHdlr {
-	var PDU_BSSAP unused := f_establish_fully_ret(ass_cmd, exp_ass_cpl);
 }
 
 type record HandoverState {