Implement support for receiving BSSMAP CommonID from MSC

The MSC may at any time send a BSSMAP CommonID message via a
SCCP connection to inform us of the IMSI of the subscriber.  Let's
make use of that information by associating a related bsc_subscr
and updating the identity of the bsc_subscr_conn_fsm for improved
logging / filtering.

Closes: OS#2969
Change-Id: I52c43fb940f0db796adf4c0adb2260321c721c39

5 files changed, 52 insertions, 1 deletions

diff --git a/include/osmocom/bsc/bsc_msc_data.h b/include/osmocom/bsc/bsc_msc_data.h
index b1fe14d2f..43ace2532 100644
--- a/include/osmocom/bsc/bsc_msc_data.h
+++ b/include/osmocom/bsc/bsc_msc_data.h
@@ -64,6 +64,7 @@ enum {
 	MSC_CTR_BSSMAP_RX_DT1_HANDOVER_CMD,
 	MSC_CTR_BSSMAP_RX_DT1_CLASSMARK_RQST,
 	MSC_CTR_BSSMAP_RX_DT1_CONFUSION,
+	MSC_CTR_BSSMAP_RX_DT1_COMMON_ID,
 	MSC_CTR_BSSMAP_RX_DT1_UNKNOWN,
 	MSC_CTR_BSSMAP_RX_DT1_DTAP,
 	MSC_CTR_BSSMAP_RX_DT1_DTAP_ERROR,
diff --git a/include/osmocom/bsc/bsc_subscr_conn_fsm.h b/include/osmocom/bsc/bsc_subscr_conn_fsm.h
index 78937353f..354c5ee93 100644
--- a/include/osmocom/bsc/bsc_subscr_conn_fsm.h
+++ b/include/osmocom/bsc/bsc_subscr_conn_fsm.h
@@ -14,6 +14,8 @@ enum gscon_fsm_event {
 	GSCON_EV_A_CLEAR_CMD,
 	/* MSC SCCP disconnect indication */
 	GSCON_EV_A_DISC_IND,
+	/* MSC has sent a BSSMAP COMMON ID */
+	GSCON_EV_A_COMMON_ID_IND,
 
 	GSCON_EV_ASSIGNMENT_START,
 	GSCON_EV_ASSIGNMENT_END,
diff --git a/src/osmo-bsc/bsc_subscr_conn_fsm.c b/src/osmo-bsc/bsc_subscr_conn_fsm.c
index 6a35c755d..bd0b53468 100644
--- a/src/osmo-bsc/bsc_subscr_conn_fsm.c
+++ b/src/osmo-bsc/bsc_subscr_conn_fsm.c
@@ -73,6 +73,7 @@ static const struct value_string gscon_fsm_event_names[] = {
 	{GSCON_EV_A_CONN_CFM, "MO-CONNECT.cfm"},
 	{GSCON_EV_A_CLEAR_CMD, "CLEAR_CMD"},
 	{GSCON_EV_A_DISC_IND, "DISCONNET.ind"},
+	{GSCON_EV_A_COMMON_ID_IND, "COMMON_ID.ind"},
 	{GSCON_EV_ASSIGNMENT_START, "ASSIGNMENT_START"},
 	{GSCON_EV_ASSIGNMENT_END, "ASSIGNMENT_END"},
 	{GSCON_EV_HANDOVER_START, "HANDOVER_START"},
@@ -759,6 +760,7 @@ static void gscon_fsm_allstate(struct osmo_fsm_inst *fi, uint32_t event, void *d
 {
 	struct gsm_subscriber_connection *conn = fi->priv;
 	const struct gscon_clear_cmd_data *ccd;
+	struct osmo_mobile_identity *mi_imsi;
 
 	/* Regular allstate event processing */
 	switch (event) {
@@ -805,6 +807,18 @@ static void gscon_fsm_allstate(struct osmo_fsm_inst *fi, uint32_t event, void *d
 		break;
 	case GSCON_EV_LCLS_FAIL:
 		break;
+	case GSCON_EV_A_COMMON_ID_IND:
+		OSMO_ASSERT(data);
+		mi_imsi = data;
+		if (!conn->bsub)
+			conn->bsub = bsc_subscr_find_or_create_by_imsi(conn->network->bsc_subscribers, mi_imsi->imsi);
+		else {
+			/* we already have a bsc_subscr associated; maybe that subscriber has no IMSI yet? */
+			if (!conn->bsub->imsi[0])
+				bsc_subscr_set_imsi(conn->bsub, mi_imsi->imsi);
+		}
+		gscon_update_id(conn);
+		break;
 	default:
 		OSMO_ASSERT(false);
 		break;
@@ -898,7 +912,8 @@ static struct osmo_fsm gscon_fsm = {
 	.name = "SUBSCR_CONN",
 	.states = gscon_fsm_states,
 	.num_states = ARRAY_SIZE(gscon_fsm_states),
-	.allstate_event_mask = S(GSCON_EV_A_DISC_IND) | S(GSCON_EV_A_CLEAR_CMD) | S(GSCON_EV_RSL_CONN_FAIL) |
+	.allstate_event_mask = S(GSCON_EV_A_DISC_IND) | S(GSCON_EV_A_CLEAR_CMD) | S(GSCON_EV_A_COMMON_ID_IND) |
+	    S(GSCON_EV_RSL_CONN_FAIL) |
 	    S(GSCON_EV_LCLS_FAIL) |
 	    S(GSCON_EV_FORGET_LCHAN) |
 	    S(GSCON_EV_FORGET_MGW_ENDPOINT),
diff --git a/src/osmo-bsc/osmo_bsc_bssap.c b/src/osmo-bsc/osmo_bsc_bssap.c
index bf38d107d..a253b01f1 100644
--- a/src/osmo-bsc/osmo_bsc_bssap.c
+++ b/src/osmo-bsc/osmo_bsc_bssap.c
@@ -1073,6 +1073,34 @@ static int bssmap_handle_confusion(struct gsm_subscriber_connection *conn,
 	return 0;
 }
 
+/* Common ID; 3GPP TS 48.008 3.2.1.68 */
+static int bssmap_handle_common_id(struct gsm_subscriber_connection *conn,
+				   struct msgb *msg, unsigned int length)
+{
+	struct tlv_parsed tp;
+	struct osmo_mobile_identity mi_imsi;
+
+	osmo_bssap_tlv_parse(&tp, msg->l4h + 1, length - 1);
+
+	/* Check for the mandatory elements */
+	if (!TLVP_PRESENT(&tp, GSM0808_IE_IMSI)) {
+		LOGPFSML(conn->fi, LOGL_ERROR,
+		         "CommonID: missing mandatory IMSI IE: %s\n",
+		         osmo_hexdump(msg->l4h, length));
+		return -EINVAL;
+	}
+
+	if (osmo_mobile_identity_decode(&mi_imsi, TLVP_VAL(&tp, GSM0808_IE_IMSI), TLVP_LEN(&tp, GSM0808_IE_IMSI), false)
+	    || mi_imsi.type != GSM_MI_TYPE_IMSI) {
+		LOGPFSML(conn->fi, LOGL_ERROR, "CommonID: could not parse IMSI\n");
+		return -EINVAL;
+	}
+
+	osmo_fsm_inst_dispatch(conn->fi, GSCON_EV_A_COMMON_ID_IND, &mi_imsi);
+
+	return 0;
+}
+
 static int bssmap_rcvmsg_udt(struct bsc_msc_data *msc,
 			     struct msgb *msg, unsigned int length)
 {
@@ -1153,6 +1181,10 @@ static int bssmap_rcvmsg_dt1(struct gsm_subscriber_connection *conn,
 		rate_ctr_inc(&ctrs[MSC_CTR_BSSMAP_RX_DT1_CONFUSION]);
 		ret = bssmap_handle_confusion(conn, msg, length);
 		break;
+	case BSS_MAP_MSG_COMMON_ID:
+		rate_ctr_inc(&ctrs[MSC_CTR_BSSMAP_RX_DT1_COMMON_ID]);
+		ret = bssmap_handle_common_id(conn, msg, length);
+		break;
 	default:
 		rate_ctr_inc(&ctrs[MSC_CTR_BSSMAP_RX_DT1_UNKNOWN]);
 		LOGP(DMSC, LOGL_NOTICE, "Unimplemented msg type: %s\n",
diff --git a/src/osmo-bsc/osmo_bsc_msc.c b/src/osmo-bsc/osmo_bsc_msc.c
index 5e02b4a39..b1bb24530 100644
--- a/src/osmo-bsc/osmo_bsc_msc.c
+++ b/src/osmo-bsc/osmo_bsc_msc.c
@@ -58,6 +58,7 @@ static const struct rate_ctr_desc msc_ctr_description[] = {
 	[MSC_CTR_BSSMAP_RX_DT1_HANDOVER_CMD] =      {"bssmap:rx:dt1:handover:cmd", "Number of received BSSMAP DT1 HANDOVER CMD messages"},
 	[MSC_CTR_BSSMAP_RX_DT1_CLASSMARK_RQST] =    {"bssmap:rx:dt1:classmark:rqst", "Number of received BSSMAP DT1 CLASSMARK RQST messages"},
 	[MSC_CTR_BSSMAP_RX_DT1_CONFUSION] =         {"bssmap:rx:dt1:confusion", "Number of received BSSMAP DT1 CONFUSION messages"},
+	[MSC_CTR_BSSMAP_RX_DT1_COMMON_ID] =         {"bssmap:rx:dt1:common_id", "Number of received BSSMAP DT1 COMMON ID messages"},
 	[MSC_CTR_BSSMAP_RX_DT1_UNKNOWN] =           {"bssmap:rx:dt1:err_unknown", "Number of received BSSMAP unknown DT1 messages"},
 	[MSC_CTR_BSSMAP_RX_DT1_DTAP] =              {"bssmap:rx:dt1:dtap:good", "Number of received BSSMAP DTAP messages"},
 	[MSC_CTR_BSSMAP_RX_DT1_DTAP_ERROR] =        {"bssmap:rx:dt1:dtap:error", "Number of received BSSMAP DTAP messages with errors"},