ggsn: Verify presence of DNS addresses in IPCP of PCO

If we request DNS in IPCP in PCO, we also expect a corresponding result.
diff --git a/ggsn_tests/GGSN_Tests.ttcn b/ggsn_tests/GGSN_Tests.ttcn
index dd9acbc..8b0d5e4 100644
--- a/ggsn_tests/GGSN_Tests.ttcn
+++ b/ggsn_tests/GGSN_Tests.ttcn
@@ -8,6 +8,7 @@
 	import from GTP_CodecPort_CtrlFunct all;
 	import from GTPC_Types all;
 	import from GTPU_Types all;
+	import from IPCP_Types all;
 	import from IP_Types all;
 	import from ICMPv6_Types all;
 	import from Native_Functions all;
@@ -400,6 +401,15 @@
 		}
 	}
 
+	template ProtocolElement tr_PCO_Proto(OCT2 prot_id) := {
+		protocolID := prot_id,
+		lengthProtoID := ?,
+		protoIDContents := ?
+	}
+	template ProtConfigOptions tr_PCO_Contains(OCT2 prot_id) modifies tr_PCO := {
+		protocols := { *, tr_PCO_Proto(prot_id), * }
+	}
+
 	template ProtConfigOptions ts_PCO_IPv4_DNS_CONT modifies ts_PCO := {
 		protocols := {
 			{ protocolID := '000d'O, lengthProtoID := 0, protoIDContents := ''O }
@@ -411,6 +421,41 @@
 		}
 	}
 
+	/* extract a given protocol payload from PCO */
+	function f_PCO_extract_proto(ProtConfigOptions pco, OCT2 protocol) return octetstring {
+		var integer i;
+		for (i := 0; i < lengthof(pco.protocols); i := i + 1) {
+			if (pco.protocols[i].protocolID == protocol) {
+				return pco.protocols[i].protoIDContents;
+			}
+		}
+		setverdict(fail);
+		return ''O;
+	}
+
+	template IpcpPacket tr_IPCP(template LcpCode code, template uint8_t identifier,
+				    template IpcpOptionList opts) := {
+		code := code,
+		identifier := identifier,
+		len := ?,
+		options := opts
+	}
+	template IpcpOption tr_IPCP_PrimaryDns(template OCT4 addr) := {
+		code := IPCP_OPT_PrimaryDNS,
+		len := 6,
+		data := addr
+	}
+	template IpcpOption tr_IPCP_SecondaryDns(template OCT4 addr) := {
+		code := IPCP_OPT_SecondaryDNS,
+		len := 6,
+		data := addr
+	}
+
+	template IpcpPacket tr_IPCP_Ack_DNS(template uint8_t identifier := ?, template OCT4 dns1 := ?,
+					    template OCT4 dns2 := ?) :=
+		tr_IPCP(LCP_Configure_Ack, identifier,
+				{ *, tr_IPCP_PrimaryDns(dns1), *, tr_IPCP_SecondaryDns(dns2), * });
+
 
 	function f_teardown_ind_IE(in template BIT1 ind) return template TearDownInd {
 /*
@@ -937,6 +982,15 @@
 		var PdpContext ctx := valueof(t_DefinePDP(f_rnd_imsi('26242'H), '1234'O, c_ApnInternet, valueof(t_EuaIPv4Dyn)));
 		ctx.pco_req := valueof(ts_PCO_IPv4_DNS_IPCP);
 		f_pdp_ctx_act(ctx);
+		/* verify IPCP is at all contained */
+		if (not match(ctx.pco_neg, tr_PCO_Contains('8021'O))) {
+			setverdict(fail, "IPCP not found in PCO");
+		}
+		/* verify IPCP contains both primary and secondary DNS */
+		var IpcpPacket ipcp := dec_IpcpPacket(f_PCO_extract_proto(ctx.pco_neg, '8021'O));
+		if (not match(ipcp, tr_IPCP_Ack_DNS)) {
+			setverdict(fail, "Primary/Secondary DNS not found in IPCP");
+		}
 		f_pdp_ctx_del(ctx, '1'B);
 	}