Index: sys/net80211/ieee80211_ioctl.h
===================================================================
--- sys/net80211/ieee80211_ioctl.h
+++ sys/net80211/ieee80211_ioctl.h
@@ -704,6 +704,7 @@
 #define	IEEE80211_IOC_GREENFIELD	112	/* Greenfield (on, off) */
 #define	IEEE80211_IOC_STBC		113	/* STBC Tx/RX (on, off) */
 #define	IEEE80211_IOC_LDPC		114	/* LDPC Tx/RX (on, off) */
+#define IEEE80211_IOC_UNIT		115	/* interface identifier */
 
 /* VHT */
 #define	IEEE80211_IOC_VHTCONF		130	/* VHT config (off, on; widths) */
Index: sys/net80211/ieee80211_ioctl.c
===================================================================
--- sys/net80211/ieee80211_ioctl.c
+++ sys/net80211/ieee80211_ioctl.c
@@ -1143,6 +1143,11 @@
 		if (vap->iv_flags_ht & IEEE80211_FHT_LDPC_RX)
 			ireq->i_val |= 2;
 		break;
+	case IEEE80211_IOC_UNIT:
+		ireq->i_val = vap->iv_ifp->if_dunit;
+		if (ireq->i_val != vap->iv_ifp->if_dunit)
+			error = EOVERFLOW;
+		break;
 
 	/* VHT */
 	case IEEE80211_IOC_VHTCONF: