epdg: Validate assigned PDP Address and APN

Change-Id: I440a7379c6dab5448d4c57c498ad9d086d0c456b
diff --git a/library/GSUP_Templates.ttcn b/library/GSUP_Templates.ttcn
index 05b8295..10c682c 100644
--- a/library/GSUP_Templates.ttcn
+++ b/library/GSUP_Templates.ttcn
@@ -69,6 +69,15 @@
 }
 template (value) GSUP_PDP_Address ts_EuaIPv4Dyn := ts_GSUP_PDP_Address_IPv4(omit);
 
+template (present) GSUP_PDP_Address tr_GSUP_PDP_Address_IPv4(template OCT4 ip_addr) := {
+	ipv4 := {
+		spare := ?,
+		pdp_typeorg := '0001'B,
+		pdp_typenum := '21'O,
+		ipv4_address := ip_addr
+	}
+}
+
 template GSUP_IE ts_GSUP_IE_AuthTuple2G(octetstring rand, octetstring sres,
 				        octetstring kc) := {
 	tag := OSMO_GSUP_AUTH_TUPLE_IE,