libmsc/gsm_04_80.c: make the API abstract from ss_request struct

There is no need to pass a pointer to a ss_request struct when
calling the gsm0480_send_ussd_* functions, because they only
use both transaction ID and InvokeID from there, which may
be passed directly.

This change allows one to use this API without parsing the
whole GSM 04.80 message, or when parsing is failed. Moreover,
if InvokeID is not available, one can pass any incorrect,
(e.g. negative) value, so the universal NULL tag will be used.
Finally, setting a TI flag is also up to the caller.

Change-Id: I13d5abbfdcf8238ebaf0566c420f09cd9255b648

1 files changed, 63 insertions, 16 deletions

diff --git a/src/libmsc/gsm_04_80.c b/src/libmsc/gsm_04_80.c
index 8799fcbdc..32e8e23e0 100644
--- a/src/libmsc/gsm_04_80.c
+++ b/src/libmsc/gsm_04_80.c
@@ -59,10 +59,28 @@ static inline unsigned char *msgb_push_TLV1(struct msgb *msgb, uint8_t tag,
 	return data;
 }
 
+static inline unsigned char *msgb_push_NULL(struct msgb *msgb)
+{
+	uint8_t *data = msgb_push(msgb, 2);
 
-/* Send response to a mobile-originated ProcessUnstructuredSS-Request */
+	data[0] = ASN1_NULL_TYPE_TAG;
+	data[1] = 0;
+	return data;
+}
+
+
+/*! Send a MT RELEASE COMPLETE message with USSD-response,
+ *  wrapped into the ReturnResult component (see section 3.6.1).
+ *
+ * \param[in]  conn            Active subscriber connection
+ * \param[in]  transaction_id  Transaction ID with TI flag set
+ * \param[in]  invoke_id       InvokeID of the request
+ * \param[in]  response_text   The response text
+ * \return     result of \ref msc_tx_dtap
+ */
 int gsm0480_send_ussd_response(struct gsm_subscriber_connection *conn,
-			       const char *response_text, const struct ss_request *req)
+			       uint8_t transaction_id, uint8_t invoke_id,
+			       const char *response_text)
 {
 	struct msgb *msg = gsm48_msgb_alloc_name("GSM 04.08 USSD RSP");
 	struct gsm48_hdr *gh;
@@ -91,7 +109,7 @@ int gsm0480_send_ussd_response(struct gsm_subscriber_connection *conn,
 	msgb_wrap_with_TL(msg, GSM_0480_SEQUENCE_TAG);
 
 	/* Pre-pend the invoke ID */
-	msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, req->invoke_id);
+	msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, invoke_id);
 
 	/* Wrap this up as a Return Result component */
 	msgb_wrap_with_TL(msg, GSM0480_CTYPE_RETURN_RESULT);
@@ -101,15 +119,24 @@ int gsm0480_send_ussd_response(struct gsm_subscriber_connection *conn,
 
 	/* And finally pre-pend the L3 header */
 	gh = (struct gsm48_hdr *) msgb_push(msg, sizeof(*gh));
-	gh->proto_discr = GSM48_PDISC_NC_SS | req->transaction_id
-					| (1<<7);  /* TI direction = 1 */
+	gh->proto_discr  = GSM48_PDISC_NC_SS;
+	gh->proto_discr |= transaction_id << 4;
 	gh->msg_type = GSM0480_MTYPE_RELEASE_COMPLETE;
 
 	return msc_tx_dtap(conn, msg);
 }
 
+/*! Send a MT RELEASE COMPLETE message with ReturnError component
+ *  (see section 3.6.1) and given error code (see section 3.6.6).
+ *
+ * \param[in]  conn            Active subscriber connection
+ * \param[in]  transaction_id  Transaction ID with TI flag set
+ * \param[in]  invoke_id       InvokeID of the request
+ * \param[in]  error_code      Error code (section 4.5)
+ * \return     result of \ref msc_tx_dtap
+ */
 int gsm0480_send_ussd_return_error(struct gsm_subscriber_connection *conn,
-	const struct ss_request *req, uint8_t error_code)
+	uint8_t transaction_id, uint8_t invoke_id, uint8_t error_code)
 {
 	struct msgb *msg = gsm48_msgb_alloc_name("GSM 04.08 USSD ERR");
 	struct gsm48_hdr *gh;
@@ -118,7 +145,7 @@ int gsm0480_send_ussd_return_error(struct gsm_subscriber_connection *conn,
 	msgb_push_TLV1(msg, GSM_0480_ERROR_CODE_TAG, error_code);
 
 	/* Before it insert the invoke ID */
-	msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, req->invoke_id);
+	msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, invoke_id);
 
 	/* Wrap this up as a Reject component */
 	msgb_wrap_with_TL(msg, GSM0480_CTYPE_RETURN_ERROR);
@@ -128,25 +155,45 @@ int gsm0480_send_ussd_return_error(struct gsm_subscriber_connection *conn,
 
 	/* And finally pre-pend the L3 header */
 	gh = (struct gsm48_hdr *) msgb_push(msg, sizeof(*gh));
-	gh->proto_discr = GSM48_PDISC_NC_SS;
-	gh->proto_discr |= req->transaction_id | (1<<7);  /* TI direction = 1 */
+	gh->proto_discr  = GSM48_PDISC_NC_SS;
+	gh->proto_discr |= transaction_id << 4;
 	gh->msg_type = GSM0480_MTYPE_RELEASE_COMPLETE;
 
 	return msc_tx_dtap(conn, msg);
 }
 
+/*! Send a MT RELEASE COMPLETE message with Reject component
+ *  (see section 3.6.1) and given error code (see section 3.6.7).
+ *
+ * \param[in]  conn            Active subscriber connection
+ * \param[in]  transaction_id  Transaction ID with TI flag set
+ * \param[in]  invoke_id       InvokeID of the request
+ * \param[in]  problem_tag     Problem code tag (table 3.13)
+ * \param[in]  problem_code    Problem code (tables 3.14-17)
+ * \return     result of \ref msc_tx_dtap
+ *
+ * Note: if InvokeID is not available, e.g. when message parsing
+ * failed, any incorrect value can be passed (0x00 > x > 0xff), so
+ * the universal NULL-tag (see table 3.6) will be used instead.
+ */
 int gsm0480_send_ussd_reject(struct gsm_subscriber_connection *conn,
-			     const struct ss_request *req,
-			     uint8_t error_tag, uint8_t error_code)
+			     uint8_t transaction_id, int invoke_id,
+			     uint8_t problem_tag, uint8_t problem_code)
 {
 	struct msgb *msg = gsm48_msgb_alloc_name("GSM 04.08 USSD REJ");
 	struct gsm48_hdr *gh;
 
 	/* First insert the problem code */
-	msgb_push_TLV1(msg, error_tag, error_code);
+	msgb_push_TLV1(msg, problem_tag, problem_code);
 
-	/* Before it insert the invoke ID */
-	msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, req->invoke_id);
+	/**
+	 * If the Invoke ID is not available, Universal Null
+	 * (table 3.9) with length = 0 shall be used.
+	 */
+	if (invoke_id < 0 || invoke_id > 255)
+		msgb_push_NULL(msg);
+	else
+		msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, invoke_id);
 
 	/* Wrap this up as a Reject component */
 	msgb_wrap_with_TL(msg, GSM0480_CTYPE_REJECT);
@@ -156,8 +203,8 @@ int gsm0480_send_ussd_reject(struct gsm_subscriber_connection *conn,
 
 	/* And finally pre-pend the L3 header */
 	gh = (struct gsm48_hdr *) msgb_push(msg, sizeof(*gh));
-	gh->proto_discr = GSM48_PDISC_NC_SS;
-	gh->proto_discr |= req->transaction_id | (1<<7);  /* TI direction = 1 */
+	gh->proto_discr  = GSM48_PDISC_NC_SS;
+	gh->proto_discr |= transaction_id << 4;
 	gh->msg_type = GSM0480_MTYPE_RELEASE_COMPLETE;
 
 	return msc_tx_dtap(conn, msg);