[PATCH] Changes to USSD support modules following initial review Signed-off-by: Mike Haben <michael.haben at btinternet.com>

This is merely a historical archive of years 2008-2021, before the migration to mailman3.

A maintained and still updated list archive can be found at https://lists.osmocom.org/hyperkitty/list/OpenBSC@lists.osmocom.org/.

Mike Haben michael.haben at btinternet.com
Fri Oct 9 17:24:21 UTC 2009


---
 openbsc/include/openbsc/gsm_04_80.h |  129 +++++++++++++++++--
 openbsc/include/openbsc/ussd.h      |    2 +
 openbsc/src/gsm_04_80.c             |  246 ++++++++++------------------------
 openbsc/src/ussd.c                  |   16 ++-
 4 files changed, 201 insertions(+), 192 deletions(-)

diff --git a/openbsc/include/openbsc/gsm_04_80.h b/openbsc/include/openbsc/gsm_04_80.h
index 43b5b74..11962d8 100755
--- a/openbsc/include/openbsc/gsm_04_80.h
+++ b/openbsc/include/openbsc/gsm_04_80.h
@@ -1,24 +1,129 @@
 #ifndef _GSM_04_80_H
 #define _GSM_04_80_H
 
-#include <openbsc/msgb.h>
+/* GSM TS 04.80  definitions (Supplementary Services Specification, Formats and Coding) */
+
+/* Section 3.4 */
+#define GSM0480_MTYPE_RELEASE_COMPLETE	0x2A
+#define GSM0480_MTYPE_FACILITY			0x3A
+#define GSM0480_MTYPE_REGISTER			0x3B
+
+/* Section 3.5 */
+#define GSM0480_IE_FACILITY			0x1C
+#define GSM0480_IE_SS_VERSION			0x7F
+
+/* Section 3.6.2 */
+#define GSM0480_CTYPE_INVOKE			0xA1
+#define GSM0480_CTYPE_RETURN_RESULT		0xA2
+#define GSM0480_CTYPE_RETURN_ERROR		0xA3
+#define GSM0480_CTYPE_REJECT			0xA4
+
+/* Section 3.6.3 */
+#define GSM0480_COMPIDTAG_INVOKE_ID		0x02
+#define GSM0480_COMPIDTAG_LINKED_ID		0x80
+
+/* Section 3.6.4 */
+#define GSM0480_OPERATION_CODE			0x02
 
-/* GSM TS 04.80  definitions (Supplementary Services specification, Formats and coding */
 /* Section 3.6.5 */
 #define GSM_0480_SEQUENCE_TAG			0x30
 #define GSM_0480_SET_TAG			0x31
 
+/* Section 3.6.6 */
+#define GSM_0480_ERROR_CODE_TAG			0x02
+
+/* Section 3.6.7 */
+/* Table 3.13 */
+#define GSM_0480_PROBLEM_CODE_TAG_GENERAL	0x80
+#define GSM_0480_PROBLEM_CODE_TAG_INVOKE	0x81
+#define GSM_0480_PROBLEM_CODE_TAG_RETURN_RESULT	0x82
+#define GSM_0480_PROBLEM_CODE_TAG_RETURN_ERROR	0x83
+
+/* Table 3.14 */
+#define GSM_0480_GEN_PROB_CODE_UNRECOGNISED	0x00
+#define GSM_0480_GEN_PROB_CODE_MISTYPED		0x01
+#define GSM_0480_GEN_PROB_CODE_BAD_STRUCTURE	0x02
+
+/* Table 3.15 */
+#define GSM_0480_INVOKE_PROB_CODE_DUPLICATE_INVOKE_ID		0x00
+#define GSM_0480_INVOKE_PROB_CODE_UNRECOGNISED_OPERATION	0x01
+#define GSM_0480_INVOKE_PROB_CODE_MISTYPED_PARAMETER		0x02
+#define GSM_0480_INVOKE_PROB_CODE_RESOURCE_LIMITATION		0x03
+#define GSM_0480_INVOKE_PROB_CODE_INITIATING_RELEASE		0x04
+#define GSM_0480_INVOKE_PROB_CODE_UNRECOGNISED_LINKED_ID	0x05
+#define GSM_0480_INVOKE_PROB_CODE_UNEXPECTED_LINKED_RESPONSE	0x06
+#define GSM_0480_INVOKE_PROB_CODE_UNEXPECTED_LINKED_OPERATION	0x07
+
+/* Table 3.16 */
+#define GSM_0480_RESULT_PROB_CODE_UNRECOGNISED_INVOKE_ID	0x00
+#define GSM_0480_RESULT_PROB_CODE_RETURN_RESULT_UNEXPECTED	0x01
+#define GSM_0480_RESULT_PROB_CODE_MISTYPED_PARAMETER		0x02
+
+/* Table 3.17 */
+#define GSM_0480_ERROR_PROB_CODE_UNRECOGNISED_INVOKE_ID		0x00
+#define GSM_0480_ERROR_PROB_CODE_RETURN_ERROR_UNEXPECTED	0x01
+#define GSM_0480_ERROR_PROB_CODE_UNRECOGNISED_ERROR		0x02
+#define GSM_0480_ERROR_PROB_CODE_UNEXPECTED_ERROR		0x03
+#define GSM_0480_ERROR_PROB_CODE_MISTYPED_PARAMETER		0x04
+
+/* Section 4.5 */
+#define GSM0480_OP_CODE_REGISTER_SS		0x0A
+#define GSM0480_OP_CODE_ERASE_SS		0x0B
+#define GSM0480_OP_CODE_ACTIVATE_SS		0x0C
+#define GSM0480_OP_CODE_DEACTIVATE_SS		0x0D
+#define GSM0480_OP_CODE_INTERROGATE_SS		0x0E
+#define GSM0480_OP_CODE_NOTIFY_SS		0x10
+#define GSM0480_OP_CODE_REGISTER_PASSWORD	0x11
+#define GSM0480_OP_CODE_GET_PASSWORD		0x12
+#define GSM0480_OP_CODE_PROCESS_USS_DATA	0x13
+#define GSM0480_OP_CODE_FORWARD_CHECK_SS_IND	0x26
+#define GSM0480_OP_CODE_PROCESS_USS_REQ		0x3B
+#define GSM0480_OP_CODE_USS_REQUEST		0x3C
+#define GSM0480_OP_CODE_USS_NOTIFY		0x3D
+#define GSM0480_OP_CODE_FORWARD_CUG_INFO	0x78
+#define GSM0480_OP_CODE_SPLIT_MPTY		0x79
+#define GSM0480_OP_CODE_RETRIEVE_MPTY		0x7A
+#define GSM0480_OP_CODE_HOLD_MPTY		0x7B
+#define GSM0480_OP_CODE_BUILD_MPTY		0x7C
+#define GSM0480_OP_CODE_FORWARD_CHARGE_ADVICE	0x7D
+
+#define GSM0480_ERR_CODE_UNKNOWN_SUBSCRIBER			0x01
+#define GSM0480_ERR_CODE_ILLEGAL_SUBSCRIBER			0x09
+#define GSM0480_ERR_CODE_BEARER_SERVICE_NOT_PROVISIONED		0x0A
+#define GSM0480_ERR_CODE_TELESERVICE_NOT_PROVISIONED		0x0B
+#define GSM0480_ERR_CODE_ILLEGAL_EQUIPMENT			0x0C
+#define GSM0480_ERR_CODE_CALL_BARRED				0x0D
+#define GSM0480_ERR_CODE_ILLEGAL_SS_OPERATION			0x10
+#define GSM0480_ERR_CODE_SS_ERROR_STATUS			0x11
+#define GSM0480_ERR_CODE_SS_NOT_AVAILABLE			0x12
+#define GSM0480_ERR_CODE_SS_SUBSCRIPTION_VIOLATION		0x13
+#define GSM0480_ERR_CODE_SS_INCOMPATIBILITY			0x14
+#define GSM0480_ERR_CODE_FACILITY_NOT_SUPPORTED			0x15
+#define GSM0480_ERR_CODE_ABSENT_SUBSCRIBER			0x1B
+#define GSM0480_ERR_CODE_SYSTEM_FAILURE				0x22
+#define GSM0480_ERR_CODE_DATA_MISSING				0x23
+#define GSM0480_ERR_CODE_UNEXPECTED_DATA_VALUE			0x24
+#define GSM0480_ERR_CODE_PW_REGISTRATION_FAILURE		0x25
+#define GSM0480_ERR_CODE_NEGATIVE_PW_CHECK			0x26
+#define GSM0480_ERR_CODE_NUM_PW_ATTEMPTS_VIOLATION		0x2B
+#define GSM0480_ERR_CODE_UNKNOWN_ALPHABET			0x47
+#define GSM0480_ERR_CODE_USSD_BUSY				0x48
+#define GSM0480_ERR_CODE_MAX_MPTY_PARTICIPANTS			0x7E
+#define GSM0480_ERR_CODE_RESOURCES_NOT_AVAILABLE		0x7F
+
 /* ASN.1 type-tags */
-#define ASN1_BOOLEAN_TAG			0x01
-#define ASN1_INTEGER_TAG			0x02
-#define ASN1_BIT_STRING_TAG			0x03
-#define ASN1_OCTET_STRING_TAG			0x04
-#define ASN1_NULL_TYPE_TAG			0x05
-#define ASN1_OBJECT_ID_TAG			0x06
-#define ASN1_UTF8_STRING_TAG			0x0C
-#define ASN1_PRINTABLE_STRING_TAG		0x13
-#define ASN1_IA5_STRING_TAG			0x16
-#define ASN1_UNICODE_STRING_TAG			0x1E
+#define ASN1_BOOLEAN_TAG		0x01
+#define ASN1_INTEGER_TAG		0x02
+#define ASN1_BIT_STRING_TAG		0x03
+#define ASN1_OCTET_STRING_TAG		0x04
+#define ASN1_NULL_TYPE_TAG		0x05
+#define ASN1_OBJECT_ID_TAG		0x06
+#define ASN1_UTF8_STRING_TAG		0x0C
+#define ASN1_PRINTABLE_STRING_TAG	0x13
+#define ASN1_IA5_STRING_TAG		0x16
+#define ASN1_UNICODE_STRING_TAG		0x1E
+
+#include <openbsc/msgb.h>
 
 char* gsm0480_rcv_ussd(struct msgb *msg);
 int gsm0480_send_ussd_response(struct msgb *msg, const char* response_text);
diff --git a/openbsc/include/openbsc/ussd.h b/openbsc/include/openbsc/ussd.h
index dfd34f3..e7bd6d6 100755
--- a/openbsc/include/openbsc/ussd.h
+++ b/openbsc/include/openbsc/ussd.h
@@ -1,6 +1,8 @@
 #ifndef _USSD_H
 #define _USSD_H
 
+/* Handler function for mobile-originated USSD messages */
+
 #include <openbsc/msgb.h>
 
 int handle_rcv_ussd(struct msgb *msg);
diff --git a/openbsc/src/gsm_04_80.c b/openbsc/src/gsm_04_80.c
index a6dffa8..d922ae5 100755
--- a/openbsc/src/gsm_04_80.c
+++ b/openbsc/src/gsm_04_80.c
@@ -3,6 +3,7 @@
 
 /* (C) 2008-2009 by Harald Welte <laforge at gnumonks.org>
  * (C) 2008, 2009 by Holger Hans Peter Freyther <zecke at selfish.org>
+ * (C) 2009 by Mike Haben <michael.haben at btinternet.com>
  *
  * All Rights Reserved
  *
@@ -36,112 +37,6 @@
 #include <openbsc/gsm_04_08.h>
 #include <openbsc/gsm_04_80.h>
 
-/* GSM TS 04.80  definitions (Supplementary Services specification, Formats and coding */
-
-/* Section 3.4 */
-#define GSM0480_MTYPE_RELEASE_COMPLETE		0x2A
-#define GSM0480_MTYPE_FACILITY			0x3A
-#define GSM0480_MTYPE_REGISTER			0x3B
-
-/* Section 3.5 */
-#define GSM0480_IE_FACILITY			0x1C
-#define GSM0480_IE_SS_VERSION			0x7F
-
-/* Section 3.6.2 */
-#define GSM0480_CTYPE_INVOKE			0xA1
-#define GSM0480_CTYPE_RETURN_RESULT		0xA2
-#define GSM0480_CTYPE_RETURN_ERROR		0xA3
-#define GSM0480_CTYPE_REJECT			0xA4
-
-/* Section 3.6.3 */
-#define GSM0480_COMPIDTAG_INVOKE_ID		0x02
-#define GSM0480_COMPIDTAG_LINKED_ID		0x80
-
-/* Section 3.6.4 */
-#define GSM0480_OPERATION_CODE			0x02
-
-/* Section 3.6.6 */
-#define GSM_0480_ERROR_CODE_TAG			0x02
-
-/* Section 3.6.7 */
-/* Table 3.13 */
-#define GSM_0480_PROBLEM_CODE_TAG_GENERAL	0x80
-#define GSM_0480_PROBLEM_CODE_TAG_INVOKE	0x81
-#define GSM_0480_PROBLEM_CODE_TAG_RETURN_RESULT	0x82
-#define GSM_0480_PROBLEM_CODE_TAG_RETURN_ERROR	0x83
-
-/* Table 3.14 */
-#define GSM_0480_GEN_PROB_CODE_UNRECOGNISED	0x00
-#define GSM_0480_GEN_PROB_CODE_MISTYPED		0x01
-#define GSM_0480_GEN_PROB_CODE_BAD_STRUCTURE	0x02
-
-/* Table 3.15 */
-#define GSM_0480_INVOKE_PROB_CODE_DUPLICATE_INVOKE_ID		0x00
-#define GSM_0480_INVOKE_PROB_CODE_UNRECOGNISED_OPERATION	0x01
-#define GSM_0480_INVOKE_PROB_CODE_MISTYPED_PARAMETER		0x02
-#define GSM_0480_INVOKE_PROB_CODE_RESOURCE_LIMITATION		0x03
-#define GSM_0480_INVOKE_PROB_CODE_INITIATING_RELEASE		0x04
-#define GSM_0480_INVOKE_PROB_CODE_UNRECOGNISED_LINKED_ID	0x05
-#define GSM_0480_INVOKE_PROB_CODE_UNEXPECTED_LINKED_RESPONSE	0x06
-#define GSM_0480_INVOKE_PROB_CODE_UNEXPECTED_LINKED_OPERATION	0x07
-
-/* Table 3.16 */
-#define GSM_0480_RESULT_PROB_CODE_UNRECOGNISED_INVOKE_ID	0x00
-#define GSM_0480_RESULT_PROB_CODE_RETURN_RESULT_UNEXPECTED	0x01
-#define GSM_0480_RESULT_PROB_CODE_MISTYPED_PARAMETER		0x02
-
-/* Table 3.17 */
-#define GSM_0480_ERROR_PROB_CODE_UNRECOGNISED_INVOKE_ID		0x00
-#define GSM_0480_ERROR_PROB_CODE_RETURN_ERROR_UNEXPECTED	0x01
-#define GSM_0480_ERROR_PROB_CODE_UNRECOGNISED_ERROR		0x02
-#define GSM_0480_ERROR_PROB_CODE_UNEXPECTED_ERROR		0x03
-#define GSM_0480_ERROR_PROB_CODE_MISTYPED_PARAMETER		0x04
-
-/* Section 4.5 */
-#define GSM0480_OP_CODE_REGISTER_SS		0x0A
-#define GSM0480_OP_CODE_ERASE_SS		0x0B
-#define GSM0480_OP_CODE_ACTIVATE_SS		0x0C
-#define GSM0480_OP_CODE_DEACTIVATE_SS		0x0D
-#define GSM0480_OP_CODE_INTERROGATE_SS		0x0E
-#define GSM0480_OP_CODE_NOTIFY_SS		0x10
-#define GSM0480_OP_CODE_REGISTER_PASSWORD	0x11
-#define GSM0480_OP_CODE_GET_PASSWORD		0x12
-#define GSM0480_OP_CODE_PROCESS_USS_DATA	0x13
-#define GSM0480_OP_CODE_FORWARD_CHECK_SS_IND	0x26
-#define GSM0480_OP_CODE_PROCESS_USS_REQ		0x3B
-#define GSM0480_OP_CODE_USS_REQUEST		0x3C
-#define GSM0480_OP_CODE_USS_NOTIFY		0x3D
-#define GSM0480_OP_CODE_FORWARD_CUG_INFO	0x78
-#define GSM0480_OP_CODE_SPLIT_MPTY		0x79
-#define GSM0480_OP_CODE_RETRIEVE_MPTY		0x7A
-#define GSM0480_OP_CODE_HOLD_MPTY		0x7B
-#define GSM0480_OP_CODE_BUILD_MPTY		0x7C
-#define GSM0480_OP_CODE_FORWARD_CHARGE_ADVICE	0x7D
-
-#define GSM0480_ERR_CODE_UNKNOWN_SUBSCRIBER		0x01
-#define GSM0480_ERR_CODE_ILLEGAL_SUBSCRIBER		0x09
-#define GSM0480_ERR_CODE_BEARER_SERVICE_NOT_PROVISIONED	0x0A
-#define GSM0480_ERR_CODE_TELESERVICE_NOT_PROVISIONED	0x0B
-#define GSM0480_ERR_CODE_ILLEGAL_EQUIPMENT		0x0C
-#define GSM0480_ERR_CODE_CALL_BARRED			0x0D
-#define GSM0480_ERR_CODE_ILLEGAL_SS_OPERATION		0x10
-#define GSM0480_ERR_CODE_SS_ERROR_STATUS		0x11
-#define GSM0480_ERR_CODE_SS_NOT_AVAILABLE		0x12
-#define GSM0480_ERR_CODE_SS_SUBSCRIPTION_VIOLATION	0x13
-#define GSM0480_ERR_CODE_SS_INCOMPATIBILITY		0x14
-#define GSM0480_ERR_CODE_FACILITY_NOT_SUPPORTED		0x15
-#define GSM0480_ERR_CODE_ABSENT_SUBSCRIBER		0x1B
-#define GSM0480_ERR_CODE_SYSTEM_FAILURE			0x22
-#define GSM0480_ERR_CODE_DATA_MISSING			0x23
-#define GSM0480_ERR_CODE_UNEXPECTED_DATA_VALUE		0x24
-#define GSM0480_ERR_CODE_PW_REGISTRATION_FAILURE	0x25
-#define GSM0480_ERR_CODE_NEGATIVE_PW_CHECK		0x26
-#define GSM0480_ERR_CODE_NUM_PW_ATTEMPTS_VIOLATION	0x2B
-#define GSM0480_ERR_CODE_UNKNOWN_ALPHABET		0x47
-#define GSM0480_ERR_CODE_USSD_BUSY			0x48
-#define GSM0480_ERR_CODE_MAX_MPTY_PARTICIPANTS		0x7E
-#define GSM0480_ERR_CODE_RESOURCES_NOT_AVAILABLE	0x7F
-
 static char ussd_string_buff[32];
 static u_int8_t last_transaction_id;
 static u_int8_t last_invoke_id;
@@ -153,23 +48,40 @@ static int parse_facility_ie(u_int8_t *facility_ie, u_int8_t length);
 static int parse_ss_invoke(u_int8_t *invoke_data, u_int8_t length);
 static int parse_process_uss_req(u_int8_t *uss_req_data, u_int8_t length);
 
+static inline unsigned char *msgb_wrap_with_TL(struct msgb *msgb, u_int8_t tag)
+{
+	msgb->data -= 2;
+	msgb->data[0] = tag;
+	msgb->data[1] = msgb->len;
+	msgb->len += 2;
+	return msgb->data;
+}
+
+static inline unsigned char *msgb_push_TLV1(struct msgb *msgb, u_int8_t tag, u_int8_t value)
+{
+	msgb->data -= 3;
+	msgb->len += 3;
+	msgb->data[0] = tag;
+	msgb->data[1] = 1;
+	msgb->data[2] = value;
+	return msgb->data;
+}
+
+
 /* Receive a mobile-originated USSD message and return the decoded text */
 char* gsm0480_rcv_ussd(struct msgb *msg)
 {
 	int rc = 0;
 	u_int8_t* parse_ptr = msgb_l3(msg);
 
-//	DEBUGP(DMM, "USSD %s\n", hexdump(msg->data, msg->len));  // temporary, just see what we're receiving...
-
 	memset(ussd_string_buff, 0, sizeof(ussd_string_buff));
 
-	if((*parse_ptr & 0x0F) == GSM48_PDISC_NC_SS)
-	{
-	    last_transaction_id = *parse_ptr & 0xF0;
+	if ((*parse_ptr & 0x0F) == GSM48_PDISC_NC_SS) {
+	    last_transaction_id = *parse_ptr & 0x70;
 	    rc = parse_ussd(parse_ptr + 1);
 	}
 
-	if(!rc)
+	if (!rc)
 		DEBUGP(DMM, "Error occurred while parsing received USSD!\n"); 
 
 	return ussd_string_buff;
@@ -228,8 +140,7 @@ static int parse_facility_ie(u_int8_t *facility_ie, u_int8_t length)
 	int rc = 1;
 	u_int8_t offset = 0;
 
-	do
-	{
+	do {
 		u_int8_t component_type = facility_ie[offset]; // Component Type tag - table 3.7 
 		u_int8_t component_length = facility_ie[offset+1];
 		switch(component_type) {
@@ -248,10 +159,8 @@ static int parse_facility_ie(u_int8_t *facility_ie, u_int8_t length)
 			rc = 0;
 			break;
 		}
-
 		offset += (component_length+2);
-	}
-	while(offset < length);
+	} while(offset < length);
 
 	return rc;
 }
@@ -261,19 +170,17 @@ static int parse_ss_invoke(u_int8_t *invoke_data, u_int8_t length)
 {
 	int rc = 1;
 	
-	if(invoke_data[0] != GSM0480_COMPIDTAG_INVOKE_ID)  // mandatory part
-	{
+	if (invoke_data[0] != GSM0480_COMPIDTAG_INVOKE_ID) {  /* mandatory part */
 		fprintf(stderr, "Unexpected GSM 04.80 Component-ID tag 0x%02x (expecting Invoke ID tag)\n",
 				invoke_data[0]);
 	}
 	u_int8_t offset = invoke_data[1] + 2;
 	last_invoke_id = invoke_data[2];
 
-	if(invoke_data[offset] == GSM0480_COMPIDTAG_LINKED_ID)  // optional part
+	if (invoke_data[offset] == GSM0480_COMPIDTAG_LINKED_ID)  /* optional part */
 		offset += invoke_data[offset+1] + 2;  // skip over it
 		
-	if(invoke_data[offset] == GSM0480_OPERATION_CODE)  // mandatory part
-	{
+	if (invoke_data[offset] == GSM0480_OPERATION_CODE) {  /* mandatory part */
 		u_int8_t operation_code = invoke_data[offset+2];
 		switch(operation_code) {
 		case GSM0480_OP_CODE_PROCESS_USS_REQ:
@@ -285,11 +192,9 @@ static int parse_ss_invoke(u_int8_t *invoke_data, u_int8_t length)
 			rc = 0;
 			break;
 		}
-	}
-	else
-	{
+	} else {
 		fprintf(stderr, "Unexpected GSM 04.80 Component-ID tag 0x%02x (expecting Operation Code tag)\n",
-				invoke_data[0]);
+			invoke_data[0]);
 		rc = 0;
 	}
 
@@ -306,21 +211,16 @@ static int parse_process_uss_req(u_int8_t *uss_req_data, u_int8_t length)
 //	DEBUGP(DMM, "USSD request params %s\n", hexdump(uss_req_data, length));
 	/* FIXME: most phones send USSD text as a 7-bit encoded octet string; the following code
 	also handles the case of plain ASCII text (IA5String), but other encodings might be used */
-	if(uss_req_data[0] == GSM_0480_SEQUENCE_TAG)
-	{
-		if(uss_req_data[2] == ASN1_OCTET_STRING_TAG)
-		{
+	if (uss_req_data[0] == GSM_0480_SEQUENCE_TAG) {
+		if (uss_req_data[2] == ASN1_OCTET_STRING_TAG) {
 			dcs = uss_req_data[4];
 //			DEBUGP(DMM, "Data coding scheme = 0x%2.2X\n", dcs);
-			if((dcs == 0x0F) && (uss_req_data[5] == ASN1_OCTET_STRING_TAG))
-			{
+			if ((dcs == 0x0F) && (uss_req_data[5] == ASN1_OCTET_STRING_TAG)) {
 				num_chars = (uss_req_data[6] * 8) / 7;
 				gsm_7bit_decode(ussd_string_buff, &(uss_req_data[7]), num_chars);
 			}
 		}
-	}
-	else if(uss_req_data[0] == ASN1_IA5_STRING_TAG)
-	{
+	} else if (uss_req_data[0] == ASN1_IA5_STRING_TAG) {
 		num_chars = uss_req_data[1];
 		memcpy(ussd_string_buff, &(uss_req_data[2]), num_chars);
 	}	
@@ -340,30 +240,32 @@ int gsm0480_send_ussd_response(struct msgb *in_msg, const char* response_text)
 	msg->bts_link = in_msg->bts_link;
 	msg->lchan = in_msg->lchan;
 
-	gh = (struct gsm48_hdr *) msgb_put(msg, sizeof(*gh));
-	gh->proto_discr = GSM48_PDISC_NC_SS | last_transaction_id | 0x80;  // TI direction = 1
-	gh->msg_type = GSM0480_MTYPE_RELEASE_COMPLETE;
-
-	ptr8 = msgb_put(msg, 14);
-	ptr8[0] = GSM0480_IE_FACILITY;
-	ptr8[1] = response_len + 12;
-	ptr8[2] = GSM0480_CTYPE_RETURN_RESULT;
-	ptr8[3] = response_len + 10;
-	ptr8[4] = GSM0480_COMPIDTAG_INVOKE_ID;
-	ptr8[5] = 1;
-	ptr8[6] = last_invoke_id;
-	ptr8[7] = GSM_0480_SEQUENCE_TAG;
-	ptr8[8] = response_len + 5;
-	ptr8[9] = GSM0480_OPERATION_CODE;
-	ptr8[10] = 1;
-	ptr8[11] = GSM0480_OP_CODE_PROCESS_USS_DATA;
-	ptr8[12] = ASN1_IA5_STRING_TAG;
-	ptr8[13] = response_len;
-
+	/* First put the payload text into the message */
 	ptr8 = msgb_put(msg, response_len);
 	memcpy(ptr8, response_text, response_len);
 
-//	DEBUGP(DMM, "USSD response %s\n", hexdump(msg->data, msg->len));  // temporary, just to see what we're sending back
+	/* Then wrap it as an IA5 String */
+	msgb_wrap_with_TL(msg, ASN1_IA5_STRING_TAG);
+
+	/* Pre-pend the operation code */
+	msgb_push_TLV1(msg, GSM0480_OPERATION_CODE, GSM0480_OP_CODE_PROCESS_USS_DATA);
+
+	/* Wrap the operation code and IA5 string as a sequence */
+	msgb_wrap_with_TL(msg, GSM_0480_SEQUENCE_TAG);
+
+	/* Pre-pend the invoke ID */
+	msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, last_invoke_id);
+
+	/* Wrap this up as a Return Result component */
+	msgb_wrap_with_TL(msg, GSM0480_CTYPE_RETURN_RESULT);
+
+	/* Wrap the component in a Facility message */
+	msgb_wrap_with_TL(msg, GSM0480_IE_FACILITY);
+
+	/* And finally pre-pend the L3 header */
+	gh = (struct gsm48_hdr *) msgb_push(msg, sizeof(*gh));
+	gh->proto_discr = GSM48_PDISC_NC_SS | last_transaction_id | (1<<7);  /* TI direction = 1 */
+	gh->msg_type = GSM0480_MTYPE_RELEASE_COMPLETE;
 
 	return gsm48_sendmsg(msg, NULL);
 }
@@ -372,28 +274,26 @@ int gsm0480_send_ussd_reject(struct msgb *in_msg)
 {
 	struct msgb *msg = gsm48_msgb_alloc();
 	struct gsm48_hdr *gh;
-	u_int8_t *ptr8;
 
 	msg->bts_link = in_msg->bts_link;
 	msg->lchan = in_msg->lchan;
 
-	gh = (struct gsm48_hdr *) msgb_put(msg, sizeof(*gh));
-	gh->proto_discr = GSM48_PDISC_NC_SS | last_transaction_id | 0x80;  // TI direction = 1
-	gh->msg_type = GSM0480_MTYPE_RELEASE_COMPLETE;
+	/* First insert the problem code */
+	msgb_push_TLV1(msg, GSM_0480_PROBLEM_CODE_TAG_GENERAL, GSM_0480_GEN_PROB_CODE_UNRECOGNISED);
+
+	/* Before it insert the invoke ID */
+	msgb_push_TLV1(msg, GSM0480_COMPIDTAG_INVOKE_ID, last_invoke_id);
 
-	ptr8 = msgb_put(msg, 10);
-	ptr8[0] = GSM0480_IE_FACILITY;
-	ptr8[1] = 8;
-	ptr8[2] = GSM0480_CTYPE_REJECT;
-	ptr8[3] = 6;
-	ptr8[4] = GSM0480_COMPIDTAG_INVOKE_ID;
-	ptr8[5] = 1;
-	ptr8[6] = last_invoke_id;
-	ptr8[7] = GSM_0480_PROBLEM_CODE_TAG_GENERAL;
-	ptr8[8] = 1;
-	ptr8[9] = GSM_0480_GEN_PROB_CODE_UNRECOGNISED;
-
-//	DEBUGP(DMM, "USSD reject %s\n", hexdump(msg->data, msg->len));  // temporary, just to see what we're sending back
+	/* Wrap this up as a Reject component */
+	msgb_wrap_with_TL(msg, GSM0480_CTYPE_REJECT);
+
+	/* Wrap the component in a Facility message */
+	msgb_wrap_with_TL(msg, GSM0480_IE_FACILITY);
+
+	/* And finally pre-pend the L3 header */
+	gh = (struct gsm48_hdr *) msgb_push(msg, sizeof(*gh));
+	gh->proto_discr = GSM48_PDISC_NC_SS | last_transaction_id | (1<<7);  /* TI direction = 1 */
+	gh->msg_type = GSM0480_MTYPE_RELEASE_COMPLETE;
 
 	return gsm48_sendmsg(msg, NULL);
 }
diff --git a/openbsc/src/ussd.c b/openbsc/src/ussd.c
index 761a0e7..ba2f045 100755
--- a/openbsc/src/ussd.c
+++ b/openbsc/src/ussd.c
@@ -2,6 +2,7 @@
 
 /* (C) 2008-2009 by Harald Welte <laforge at gnumonks.org>
  * (C) 2008, 2009 by Holger Hans Peter Freyther <zecke at selfish.org>
+ * (C) 2009 by Mike Haben <michael.haben at btinternet.com>
  *
  * All Rights Reserved
  *
@@ -21,6 +22,7 @@
  *
  */
 
+/* This module defines the network-specific handling of mobile-originated USSD messages. */
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -31,10 +33,14 @@
 #include <openbsc/gsm_subscriber.h>
 #include <openbsc/debug.h>
 
+/* Declarations of USSD strings to be recognised */
 const char USSD_TEXT_OWN_NUMBER[] = "*#100#";
 
+/* Forward declarations of network-specific handler functions */
 static int send_own_number(struct msgb *msg);
 
+
+/* Entrypoint - handler function common to all mobile-originated USSDs */
 int handle_rcv_ussd(struct msgb *msg)
 {
 	char* ussd_text_rcvd = gsm0480_rcv_ussd(msg);
@@ -42,20 +48,16 @@ int handle_rcv_ussd(struct msgb *msg)
 	if(ussd_text_rcvd[0] == 0xFF)  // Release-Complete
 	    return 0;
 
-	DEBUGP(DMM, "Received USSD text %s\n", ussd_text_rcvd);  // show text payload entered on MS
-
-	if(strstr(USSD_TEXT_OWN_NUMBER, ussd_text_rcvd) != NULL)
-	{
+	if(strstr(USSD_TEXT_OWN_NUMBER, ussd_text_rcvd) != NULL) {
 		DEBUGP(DMM, "USSD: Own number requested\n");
 		return send_own_number(msg);
-	}
-	else
-	{
+	} else {
 		DEBUGP(DMM, "Unhandled USSD %s\n", ussd_text_rcvd);
 		return gsm0480_send_ussd_reject(msg);
 	}
 }
 
+/* A network-specific handler function */
 static int send_own_number(struct msgb *msg)
 {
 	char response_string[] = "Your extension is xxxxx";
-- 
1.6.0.4


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