Index: share/man/man9/ifnet.9
===================================================================
--- share/man/man9/ifnet.9
+++ share/man/man9/ifnet.9
@@ -28,7 +28,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd November 14, 2018
+.Dd September 23, 2020
 .Dt IFNET 9
 .Os
 .Sh NAME
@@ -1310,12 +1310,13 @@
 Caller must have appropriate privilege.
 (No call-down to driver.)
 .It Dv SIOCGIFCAP
+.It Dv SIOCGIFDATA
 .It Dv SIOCGIFFIB
 .It Dv SIOCGIFFLAGS
 .It Dv SIOCGIFMETRIC
 .It Dv SIOCGIFMTU
 .It Dv SIOCGIFPHYS
-Get interface capabilities, FIB, flags, metric, MTU, medium selection.
+Get interface capabilities, data, FIB, flags, metric, MTU, medium selection.
 (No call-down to driver.)
 .Pp
 .It Dv SIOCSIFCAP
Index: sys/net/if.c
===================================================================
--- sys/net/if.c
+++ sys/net/if.c
@@ -2518,6 +2518,18 @@
 		ifr->ifr_curcap = ifp->if_capenable;
 		break;
 
+	case SIOCGIFDATA:
+	{
+		struct if_data ifd;
+
+		/* Ensure uninitialised padding is not leaked. */
+		memset(&ifd, 0, sizeof(ifd));
+
+		if_data_copy(ifp, &ifd);
+		error = copyout(&ifd, ifr_data_get_ptr(ifr), sizeof(ifd));
+		break;
+	}
+
 #ifdef MAC
 	case SIOCGIFMAC:
 		error = mac_ifnet_ioctl_get(td->td_ucred, ifr, ifp);
Index: sys/sys/sockio.h
===================================================================
--- sys/sys/sockio.h
+++ sys/sys/sockio.h
@@ -83,6 +83,7 @@
 #define	SIOCSIFDESCR	 _IOW('i', 41, struct ifreq)	/* set ifnet descr */ 
 #define	SIOCGIFDESCR	_IOWR('i', 42, struct ifreq)	/* get ifnet descr */ 
 #define	SIOCAIFADDR	 _IOW('i', 43, struct ifaliasreq)/* add/chg IF alias */
+#define	SIOCGIFDATA	 _IOW('i', 44, struct ifreq)	/* get if_data */
 
 #define	SIOCADDMULTI	 _IOW('i', 49, struct ifreq)	/* add m'cast addr */
 #define	SIOCDELMULTI	 _IOW('i', 50, struct ifreq)	/* del m'cast addr */