Support cipher mode reject with extended cause

* add function to generate cipher mode reject with extended (2-byte)
  Cause IE
* add function to get (extended) Cause value
* add corresponding (extended cause) test
* update existing (non-extended cause) test
* use enum as a parameter for existing non-extended version to make
  interface more unified

Change-Id: Id5509b94a18180a44f45300caaa02b843c166fa3
Related: OS#3187

7 files changed, 89 insertions, 1 deletions

diff --git a/include/osmocom/gsm/gsm0808.h b/include/osmocom/gsm/gsm0808.h
index 66f7c277..9b19d691 100644
--- a/include/osmocom/gsm/gsm0808.h
+++ b/include/osmocom/gsm/gsm0808.h
@@ -51,6 +51,7 @@ struct msgb *gsm0808_create_cipher(const struct gsm0808_encrypt_info *ei,
 				   const uint8_t *cipher_response_mode);
 struct msgb *gsm0808_create_cipher_complete(struct msgb *layer3, uint8_t alg_id);
 struct msgb *gsm0808_create_cipher_reject(enum gsm0808_cause cause);
+struct msgb *gsm0808_create_cipher_reject_ext(enum gsm0808_cause_class class, uint8_t ext);
 struct msgb *gsm0808_create_classmark_request();
 struct msgb *gsm0808_create_classmark_update(const uint8_t *cm2, uint8_t cm2_len,
 					     const uint8_t *cm3, uint8_t cm3_len);
diff --git a/include/osmocom/gsm/gsm0808_utils.h b/include/osmocom/gsm/gsm0808_utils.h
index b56e2635..c22d0a9b 100644
--- a/include/osmocom/gsm/gsm0808_utils.h
+++ b/include/osmocom/gsm/gsm0808_utils.h
@@ -120,6 +120,8 @@ static inline bool gsm0808_cause_ext(enum gsm0808_cause cause)
 	return (cause & 0x80) && !(cause & 0x0F);
 }
 
+int gsm0808_get_cipher_reject_cause(const struct tlv_parsed *tp);
+
 /*! \returns 3GPP TS 48.008 3.2.2.49 Current Channel Type 1 from enum gsm_chan_t. */
 static inline uint8_t gsm0808_current_channel_type_1(enum gsm_chan_t type)
 {
diff --git a/src/gsm/gsm0808.c b/src/gsm/gsm0808.c
index c413688c..a84e717d 100644
--- a/src/gsm/gsm0808.c
+++ b/src/gsm/gsm0808.c
@@ -283,6 +283,30 @@ struct msgb *gsm0808_create_cipher_reject(enum gsm0808_cause cause)
 	return msg;
 }
 
+/*! Create BSSMAP Cipher Mode Reject message
+ *  \param[in] class 3GPP TS 08.08 §3.2.2.5 cause's class
+ *  \param[in] ext 3GPP TS 08.08 §3.2.2.5 cause value (national application extension)
+ *  \returns callee-allocated msgb with BSSMAP Cipher Mode Reject message */
+struct msgb *gsm0808_create_cipher_reject_ext(enum gsm0808_cause_class class, uint8_t ext)
+{
+	uint8_t c[2];
+	struct msgb *msg = msgb_alloc_headroom(BSSMAP_MSG_SIZE, BSSMAP_MSG_HEADROOM,
+					       "bssmap: cipher mode reject");
+	if (!msg)
+		return NULL;
+
+	c[0] = 0x80 | (class << 4); /* set the high bit to indicate extended cause */
+	c[1] = ext;
+
+	msgb_v_put(msg, BSS_MAP_MSG_CIPHER_MODE_REJECT);
+
+	msgb_tlv_put(msg, GSM0808_IE_CAUSE, 2, c);
+
+	msg->l3h = msgb_tv_push(msg, BSSAP_MSG_BSS_MANAGEMENT, msgb_length(msg));
+
+	return msg;
+}
+
 /*! Create BSSMAP LCLS CONNECT CONTROL message (TS 48.008 3.2.1.91).
  *  \param[in] config LCLS Configuration
  *  \param[in] control LCLS Connection Status Control
diff --git a/src/gsm/gsm0808_utils.c b/src/gsm/gsm0808_utils.c
index 2348105d..c58d8284 100644
--- a/src/gsm/gsm0808_utils.c
+++ b/src/gsm/gsm0808_utils.c
@@ -1235,6 +1235,22 @@ void gsm48_mr_cfg_from_gsm0808_sc_cfg(struct gsm48_multi_rate_conf *cfg,
 	cfg->icmi = 1;
 }
 
+int gsm0808_get_cipher_reject_cause(const struct tlv_parsed *tp)
+{
+	const uint8_t *buf = TLVP_VAL_MINLEN(tp, GSM0808_IE_CAUSE, 1);
+
+	if (!buf)
+		return -EBADMSG;
+
+	if (TLVP_LEN(tp, GSM0808_IE_CAUSE) > 1) {
+		if (!gsm0808_cause_ext(buf[0]))
+			return -EINVAL;
+		return buf[1];
+	}
+
+	return buf[0];
+}
+
 /*! Print a human readable name of the cell identifier to the char buffer.
  * This is useful both for struct gsm0808_cell_id and struct gsm0808_cell_id_list2.
  * See also gsm0808_cell_id_name() and gsm0808_cell_id_list_name().
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 32e4ce95..217dcc39 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -157,6 +157,8 @@ gsm0808_create_ass_fail;
 gsm0808_create_cipher;
 gsm0808_create_cipher_complete;
 gsm0808_create_cipher_reject;
+gsm0808_create_cipher_reject_ext;
+gsm0808_get_cipher_reject_cause;
 gsm0808_create_classmark_request;
 gsm0808_create_classmark_update;
 gsm0808_create_clear_command;
diff --git a/tests/gsm0808/gsm0808_test.c b/tests/gsm0808/gsm0808_test.c
index 671b8399..197ec06d 100644
--- a/tests/gsm0808/gsm0808_test.c
+++ b/tests/gsm0808/gsm0808_test.c
@@ -250,14 +250,55 @@ static void test_create_cipher_complete()
 	msgb_free(l3);
 }
 
+static inline void parse_cipher_reject(struct msgb *msg, uint8_t exp)
+{
+	struct tlv_parsed tp;
+	int rc;
+
+	/* skip header and message type so we can parse Cause IE directly */
+	msg->l2h = msgb_data(msg) + sizeof(struct bssmap_header) + 1;
+
+	rc = osmo_bssap_tlv_parse(&tp, msg->l2h, msgb_l2len(msg));
+	if (rc < 0)
+		printf("FIXME: failed (%d) to parse created message %s\n", rc, msgb_hexdump(msg));
+
+	rc = gsm0808_get_cipher_reject_cause(&tp);
+	if (rc < 0)
+		printf("FIXME: failed (%s) to extract Cause from created message %s\n",
+		       strerror(-rc), msgb_hexdump(msg));
+
+	if (exp != (enum gsm0808_cause)rc)
+		printf("FIXME: wrong Cause %d != %u (" OSMO_BIN_SPEC ") extracted from created message %s\n",
+		       rc, exp, OSMO_BIT_PRINT(exp), msgb_hexdump(msg));
+}
+
 static void test_create_cipher_reject()
 {
 	static const uint8_t res[] = { 0x00, 0x04, 0x59, 0x04, 0x01, 0x23 };
+	enum gsm0808_cause cause = GSM0808_CAUSE_CCCH_OVERLOAD;
 	struct msgb *msg;
 
 	printf("Testing creating Cipher Reject\n");
-	msg = gsm0808_create_cipher_reject(GSM0808_CAUSE_CCCH_OVERLOAD);
+	msg = gsm0808_create_cipher_reject(cause);
+	VERIFY(msg, res, ARRAY_SIZE(res));
+
+	parse_cipher_reject(msg, cause);
+
+	msgb_free(msg);
+}
+
+static void test_create_cipher_reject_ext()
+{
+	static const uint8_t res[] = { 0x00, 0x05, 0x59, 0x04, 0x02, 0xd0, 0xFA };
+	uint8_t cause = 0xFA;
+	struct msgb *msg;
+
+	printf("Testing creating Cipher Reject (extended)\n");
+	msg = gsm0808_create_cipher_reject_ext(GSM0808_CAUSE_CLASS_INVAL, cause);
 	VERIFY(msg, res, ARRAY_SIZE(res));
+
+	parse_cipher_reject(msg, cause);
+
 	msgb_free(msg);
 }
 
@@ -1738,6 +1779,7 @@ int main(int argc, char **argv)
 	test_create_cipher();
 	test_create_cipher_complete();
 	test_create_cipher_reject();
+	test_create_cipher_reject_ext();
 	test_create_cm_u();
 	test_create_sapi_reject();
 	test_create_ass();
diff --git a/tests/gsm0808/gsm0808_test.ok b/tests/gsm0808/gsm0808_test.ok
index 58bc5099..a48cf1d5 100644
--- a/tests/gsm0808/gsm0808_test.ok
+++ b/tests/gsm0808/gsm0808_test.ok
@@ -8,6 +8,7 @@ Testing creating Clear Complete
 Testing creating Chipher Mode Command
 Testing creating Cipher Complete
 Testing creating Cipher Reject
+Testing creating Cipher Reject (extended)
 Testing creating CM U
 Testing creating SAPI Reject
 Testing creating Assignment Request