diff --git a/sys/net/if.c b/sys/net/if.c
index cfd0c2065888..8de83b2d7bc5 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -2891,6 +2891,7 @@ ifhwioctl(u_long cmd, struct ifnet *ifp, caddr_t data, struct thread *td)
 	case SIOCGIFGENERIC:
 	case SIOCGIFRSSKEY:
 	case SIOCGIFRSSHASH:
+	case SIOCGIFDOWNREASON:
 		if (ifp->if_ioctl == NULL)
 			return (EOPNOTSUPP);
 		error = (*ifp->if_ioctl)(ifp, cmd, data);
diff --git a/sys/net/if.h b/sys/net/if.h
index add4df55a3d9..fbcc06863bd4 100644
--- a/sys/net/if.h
+++ b/sys/net/if.h
@@ -585,6 +585,16 @@ struct ifrsshash {
 
 #define	IFNET_PCP_NONE	0xff	/* PCP disabled */
 
+#define	IFDR_MSG_SIZE		64
+#define	IFDR_REASON_MSG		1
+#define	IFDR_REASON_VENDOR	2
+struct ifdownreason {
+	char		ifdr_name[IFNAMSIZ];
+	uint32_t	ifdr_reason;
+	uint32_t	ifdr_vendor;
+	char		ifdr_msg[IFDR_MSG_SIZE];
+};
+
 #endif /* __BSD_VISIBLE */
 
 #ifdef _KERNEL
diff --git a/sys/sys/sockio.h b/sys/sys/sockio.h
index 89901bd40b44..447e2c884028 100644
--- a/sys/sys/sockio.h
+++ b/sys/sys/sockio.h
@@ -143,4 +143,6 @@
 #define	SIOCGLANPCP	_IOWR('i', 152, struct ifreq)	/* Get (V)LAN PCP */
 #define	SIOCSLANPCP	 _IOW('i', 153, struct ifreq)	/* Set (V)LAN PCP */
 
+#define	SIOCGIFDOWNREASON	_IOWR('i', 154, struct ifdownreason)
+
 #endif /* !_SYS_SOCKIO_H_ */