Index: lib/libc/sys/getsockopt.2
===================================================================
--- lib/libc/sys/getsockopt.2
+++ lib/libc/sys/getsockopt.2
@@ -28,7 +28,7 @@
 .\"     @(#)getsockopt.2	8.4 (Berkeley) 5/2/95
 .\" $FreeBSD$
 .\"
-.Dd May 9, 2018
+.Dd August 18, 2018
 .Dt GETSOCKOPT 2
 .Os
 .Sh NAME
@@ -172,6 +172,7 @@
 .It Dv SO_TIMESTAMP Ta "enables reception of a timestamp with datagrams"
 .It Dv SO_BINTIME Ta "enables reception of a timestamp with datagrams"
 .It Dv SO_ACCEPTCONN Ta "get listening status of the socket (get only)"
+.It Dv SO_DOMAIN Ta "get the domain of the socket (get only)"
 .It Dv SO_TYPE Ta "get the type of the socket (get only)"
 .It Dv SO_PROTOCOL Ta "get the protocol number for the socket (get only)"
 .It Dv SO_PROTOTYPE Ta "SunOS alias for the Linux SO_PROTOCOL (get only)"
Index: sys/kern/uipc_socket.c
===================================================================
--- sys/kern/uipc_socket.c
+++ sys/kern/uipc_socket.c
@@ -3008,6 +3008,10 @@
 			error = sooptcopyout(sopt, &optval, sizeof optval);
 			break;
 
+		case SO_DOMAIN:
+			optval = so->so_proto->pr_domain->dom_family;
+			goto integer;
+
 		case SO_TYPE:
 			optval = so->so_type;
 			goto integer;
Index: sys/sys/socket.h
===================================================================
--- sys/sys/socket.h
+++ sys/sys/socket.h
@@ -171,6 +171,7 @@
 #define	SO_PROTOTYPE	SO_PROTOCOL	/* alias for SO_PROTOCOL (SunOS name) */
 #define	SO_TS_CLOCK	0x1017		/* clock type used for SO_TIMESTAMP */
 #define	SO_MAX_PACING_RATE	0x1018	/* socket's max TX pacing rate (Linux name) */
+#define	SO_DOMAIN	0x1019		/* get socket domain */
 #endif
 
 #if __BSD_VISIBLE