Add USDD code from Mike Haben

This is the initial checkin of the USSD code from Mike Haben.  I didn't
put it in the main branch as I think it still needs some cleanup.

6 files changed, 521 insertions, 2 deletions

diff --git a/openbsc/include/openbsc/gsm_04_80.h b/openbsc/include/openbsc/gsm_04_80.h
new file mode 100644
index 000000000..11962d81d
--- /dev/null
+++ b/openbsc/include/openbsc/gsm_04_80.h
@@ -0,0 +1,132 @@
+#ifndef _GSM_04_80_H
+#define _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 3.6.5 */
+#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
+
+#include <openbsc/msgb.h>
+
+char* gsm0480_rcv_ussd(struct msgb *msg);
+int gsm0480_send_ussd_response(struct msgb *msg, const char* response_text);
+int gsm0480_send_ussd_reject(struct msgb *msg);
+
+#endif
diff --git a/openbsc/include/openbsc/ussd.h b/openbsc/include/openbsc/ussd.h
new file mode 100644
index 000000000..e7bd6d69d
--- /dev/null
+++ b/openbsc/include/openbsc/ussd.h
@@ -0,0 +1,10 @@
+#ifndef _USSD_H
+#define _USSD_H
+
+/* Handler function for mobile-originated USSD messages */
+
+#include <openbsc/msgb.h>
+
+int handle_rcv_ussd(struct msgb *msg);
+
+#endif
diff --git a/openbsc/src/Makefile.am b/openbsc/src/Makefile.am
index 919e07574..2f715bbaf 100644
--- a/openbsc/src/Makefile.am
+++ b/openbsc/src/Makefile.am
@@ -14,7 +14,7 @@ libbsc_a_SOURCES = abis_rsl.c abis_nm.c gsm_data.c gsm_04_08_utils.c \
 
 libmsc_a_SOURCES = gsm_subscriber.c db.c telnet_interface.c \
 		mncc.c rtp_proxy.c gsm_04_08.c gsm_04_11.c transaction.c \
-		token_auth.c rrlp.c
+		token_auth.c rrlp.c gsm_04_80.c ussd.c
 
 libvty_a_SOURCES = vty/buffer.c vty/command.c vty/vector.c vty/vty.c
 
diff --git a/openbsc/src/gsm_04_08.c b/openbsc/src/gsm_04_08.c
index cd883a3fa..23739657d 100644
--- a/openbsc/src/gsm_04_08.c
+++ b/openbsc/src/gsm_04_08.c
@@ -48,6 +48,7 @@
 #include <openbsc/rtp_proxy.h>
 #include <openbsc/talloc.h>
 #include <openbsc/transaction.h>
+#include <openbsc/ussd.h>
 
 #define GSM_MAX_FACILITY       128
 #define GSM_MAX_SSVERSION      128
@@ -3540,10 +3541,12 @@ int gsm0408_rcvmsg(struct msgb *msg, u_int8_t link_id)
 		break;
 	case GSM48_PDISC_MM_GPRS:
 	case GSM48_PDISC_SM_GPRS:
-	case GSM48_PDISC_NC_SS:  /* mobile-originated USSD */
 		fprintf(stderr, "Unimplemented GSM 04.08 discriminator 0x%02x\n",
 			pdisc);
 		break;
+	case GSM48_PDISC_NC_SS:
+		rc = handle_rcv_ussd(msg);
+		break;
 	default:
 		fprintf(stderr, "Unknown GSM 04.08 discriminator 0x%02x\n",
 			pdisc);
diff --git a/openbsc/src/gsm_04_80.c b/openbsc/src/gsm_04_80.c
new file mode 100644
index 000000000..d0dcbc2c3
--- /dev/null
+++ b/openbsc/src/gsm_04_80.c
@@ -0,0 +1,306 @@
+/* GSM Mobile Radio Interface Layer 3 messages on the A-bis interface 
+ * 3GPP TS 04.08 version 7.21.0 Release 1998 / ETSI TS 100 940 V7.21.0 */
+
+/* (C) 2008-2009 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2008, 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2009 by Mike Haben <michael.haben@btinternet.com>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#include <openbsc/msgb.h>
+#include <openbsc/tlv.h>
+#include <openbsc/debug.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/gsm_utils.h>
+#include <openbsc/gsm_04_08.h>
+#include <openbsc/gsm_04_80.h>
+
+static char ussd_string_buff[32];
+static u_int8_t last_transaction_id;
+static u_int8_t last_invoke_id;
+
+/* Forward declarations */
+static int parse_ussd(u_int8_t *ussd);
+static int parse_ussd_information_elements(u_int8_t *ussd_ie);
+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);
+
+	memset(ussd_string_buff, 0, sizeof(ussd_string_buff));
+
+	if ((*parse_ptr & 0x0F) == GSM48_PDISC_NC_SS) {
+	    last_transaction_id = *parse_ptr & 0x70;
+	    rc = parse_ussd(parse_ptr + 1);
+	}
+
+	if (!rc)
+		DEBUGP(DMM, "Error occurred while parsing received USSD!\n"); 
+
+	return ussd_string_buff;
+}
+
+static int parse_ussd(u_int8_t *ussd)
+{
+	int rc = 1;
+	u_int8_t msg_type = ussd[0] & 0xBF;  /* message-type - section 3.4 */
+
+	switch(msg_type) {  
+	case GSM0480_MTYPE_RELEASE_COMPLETE:
+		DEBUGP(DMM, "USS Release Complete\n");  /* could also parse out the optional Cause/Facility data */
+		ussd_string_buff[0] = 0xFF;
+		break;
+	case GSM0480_MTYPE_REGISTER:
+	case GSM0480_MTYPE_FACILITY:
+		rc &= parse_ussd_information_elements(ussd+1);
+		break;
+	default:
+		fprintf(stderr, "Unknown GSM 04.80 message-type field 0x%02x\n",
+			ussd[0]);
+		rc = 0;
+		break;
+	}
+
+	return rc;
+}
+
+static int parse_ussd_information_elements(u_int8_t *ussd_ie)
+{
+	int rc;
+
+	u_int8_t iei = ussd_ie[0];  /* Information Element Identifier - table 3.2 & GSM 04.08 section 10.5 */		
+	u_int8_t iei_length = ussd_ie[1];  
+	switch(iei) {
+	case GSM48_IE_CAUSE:
+		break;
+	case GSM0480_IE_FACILITY:
+		rc = parse_facility_ie(ussd_ie+2, iei_length);
+		break;
+	case GSM0480_IE_SS_VERSION:
+		break;
+	default:
+		fprintf(stderr, "Unhandled GSM 04.08 or 04.80 Information Element Identifier 0x%02x\n",
+			iei);
+		rc = 0;
+		break;
+	}
+
+	return rc;
+}
+
+static int parse_facility_ie(u_int8_t *facility_ie, u_int8_t length)
+{
+	int rc = 1;
+	u_int8_t offset = 0;
+
+	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) {
+		case GSM0480_CTYPE_INVOKE:
+			rc &= parse_ss_invoke(facility_ie+2, component_length);
+			break;
+		case GSM0480_CTYPE_RETURN_RESULT:
+			break;
+		case GSM0480_CTYPE_RETURN_ERROR:
+			break;
+		case GSM0480_CTYPE_REJECT:
+			break;
+		default:
+			fprintf(stderr, "Unknown GSM 04.80 Facility Component Type 0x%02x\n",
+				component_type);
+			rc = 0;
+			break;
+		}
+		offset += (component_length+2);
+	} while(offset < length);
+
+	return rc;
+}
+
+/* Parse an Invoke component - see table 3.3 */
+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 */
+		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 */
+		offset += invoke_data[offset+1] + 2;  /* skip over it */
+		
+	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:
+			rc = parse_process_uss_req(invoke_data + offset + 3, length - offset - 3);
+			break;
+		default:
+			fprintf(stderr, "GSM 04.80 operation code 0x%02x is not yet handled\n",
+				operation_code);
+			rc = 0;
+			break;
+		}
+	} else {
+		fprintf(stderr, "Unexpected GSM 04.80 Component-ID tag 0x%02x (expecting Operation Code tag)\n",
+			invoke_data[0]);
+		rc = 0;
+	}
+
+	return rc;
+}
+
+/* Parse the parameters of a Process UnstructuredSS Request */
+static int parse_process_uss_req(u_int8_t *uss_req_data, u_int8_t length)
+{
+	int rc = 1;
+	int num_chars;
+	u_int8_t dcs;
+
+	/* 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) {
+			dcs = uss_req_data[4];
+			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) {
+		num_chars = uss_req_data[1];
+		memcpy(ussd_string_buff, &(uss_req_data[2]), num_chars);
+	}	
+
+	return rc;
+}
+
+/* Send response to a mobile-originated ProcessUnstructuredSS-Request */
+int gsm0480_send_ussd_response(struct msgb *in_msg, const char* response_text)
+{
+	struct msgb *msg = gsm48_msgb_alloc();
+	struct gsm48_hdr *gh;
+	u_int8_t *ptr8;
+	int response_len;
+
+	response_len = (strlen(response_text) * 7) / 8;
+	if (((strlen(response_text) * 7) % 8) != 0)
+		response_len += 1;
+
+	msg->bts_link = in_msg->bts_link;
+	msg->lchan = in_msg->lchan;
+
+	/* First put the payload text into the message */
+	ptr8 = msgb_put(msg, response_len);
+	gsm_7bit_encode(ptr8, response_text);
+
+	/* Then wrap it as an Octet String */
+	msgb_wrap_with_TL(msg, ASN1_OCTET_STRING_TAG);
+
+	/* Pre-pend the DCS octet string */
+	msgb_push_TLV1(msg, ASN1_OCTET_STRING_TAG, 0x0F);
+
+	/* Then wrap these as a Sequence */
+	msgb_wrap_with_TL(msg, GSM_0480_SEQUENCE_TAG);
+
+	/* Pre-pend the operation code */
+	msgb_push_TLV1(msg, GSM0480_OPERATION_CODE, GSM0480_OP_CODE_PROCESS_USS_REQ);
+
+	/* 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);
+}
+
+int gsm0480_send_ussd_reject(struct msgb *in_msg)
+{
+	struct msgb *msg = gsm48_msgb_alloc();
+	struct gsm48_hdr *gh;
+
+	msg->bts_link = in_msg->bts_link;
+	msg->lchan = in_msg->lchan;
+
+	/* 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);
+
+	/* 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
new file mode 100644
index 000000000..5f9a45725
--- /dev/null
+++ b/openbsc/src/ussd.c
@@ -0,0 +1,68 @@
+/* Network-specific handling of mobile-originated USSDs. */
+
+/* (C) 2008-2009 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2008, 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2009 by Mike Haben <michael.haben@btinternet.com>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+/* This module defines the network-specific handling of mobile-originated USSD messages. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#include <openbsc/gsm_04_80.h>
+#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);
+
+	if(ussd_text_rcvd[0] == 0xFF)  /* Release-Complete */
+	    return 0;
+
+	if(strstr(USSD_TEXT_OWN_NUMBER, ussd_text_rcvd) != NULL) {
+		DEBUGP(DMM, "USSD: Own number requested\n");
+		return send_own_number(msg);
+	} 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\r"; /* Need trailing CR as EOT character */
+
+	char* own_number = msg->lchan->subscr->extension;
+	memcpy(response_string + 18, own_number, 5);
+	return gsm0480_send_ussd_response(msg, response_string);
+}