nat: Include LAC/CI as TV values at the end of the 'status' message

Extend the status message and send LAC/CI as part of the status
message. It is using TV to allow sending more fields in the feature.
We only need to encode the data and this is why there is no tlv
description yet.
diff --git a/openbsc/src/osmo-bsc_nat/bsc_ussd.c b/openbsc/src/osmo-bsc_nat/bsc_ussd.c
index f972ba5..59f76e4 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_ussd.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_ussd.c
@@ -38,6 +38,9 @@
 #include <string.h>
 #include <unistd.h>
 
+#define USSD_LAC_IE	0
+#define USSD_CI_IE	1
+
 static void ussd_auth_con(struct tlv_parsed *, struct bsc_nat_ussd_con *);
 
 static struct bsc_nat_ussd_con *bsc_nat_ussd_alloc(struct bsc_nat *nat)
@@ -292,6 +295,7 @@
 	struct msgb *msg, *copy;
 	struct ipac_msgt_sccp_state *state;
 	struct bsc_nat_ussd_con *ussd;
+	uint16_t lac, ci;
 
 	if (!con->bsc->nat->ussd_con)
 		return -1;
@@ -323,6 +327,12 @@
 	memcpy(&state->dst_ref, &con->real_ref, sizeof(con->real_ref));
 	memcpy(state->imsi, con->imsi, strlen(con->imsi));
 
+	/* add additional tag/values */
+	lac = htons(con->lac);
+	ci = htons(con->ci);
+	msgb_tv_fixed_put(msg, USSD_LAC_IE, sizeof(lac), &lac);
+	msgb_tv_fixed_put(msg, USSD_CI_IE, sizeof(ci), &ci);
+
 	ussd = con->bsc->nat->ussd_con;
 	bsc_do_write(&ussd->queue, msg, IPAC_PROTO_IPACCESS);
 	bsc_do_write(&ussd->queue, copy, IPAC_PROTO_SCCP);