Index: head/lib/libc/sys/shutdown.2
===================================================================
--- head/lib/libc/sys/shutdown.2
+++ head/lib/libc/sys/shutdown.2
@@ -29,7 +29,7 @@
 .\"     @(#)shutdown.2	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd March 5, 2007
+.Dd July 27, 2015
 .Dt SHUTDOWN 2
 .Os
 .Sh NAME
@@ -79,40 +79,26 @@
 based on the properties of the socket associated with the file descriptor
 .Fa s .
 .Bl -column ".Dv PF_INET6" ".Dv SOCK_STREAM" ".Dv IPPROTO_SCTP"
-.It Sy Domain Ta Sy Type Ta Sy Protocol Ta Sy Return value and action
+.It Sy Domain Ta Sy Type Ta Sy Protocol Ta Sy Action
 .It Dv PF_INET Ta Dv SOCK_DGRAM Ta Dv IPPROTO_SCTP Ta
-Return \-1.
-The global variable
-.Va errno
-will be set to
-.Er EOPNOTSUPP .
+Failure,
+as socket is not connected.
 .It Dv PF_INET Ta Dv SOCK_DGRAM Ta Dv IPPROTO_UDP Ta
-Return 0.
-ICMP messages will
-.Em not
-be generated.
+Failure,
+as socket is not connected.
 .It Dv PF_INET Ta Dv SOCK_STREAM Ta Dv IPPROTO_SCTP Ta
-Return 0.
 Send queued data and tear down association.
 .It Dv PF_INET Ta Dv SOCK_STREAM Ta Dv IPPROTO_TCP Ta
-Return 0.
 Send queued data, wait for ACK, then send FIN.
 .It Dv PF_INET6 Ta Dv SOCK_DGRAM Ta Dv IPPROTO_SCTP Ta
-Return \-1.
-The global variable
-.Va errno
-will be set to
-.Er EOPNOTSUPP .
+Failure,
+as socket is not connected.
 .It Dv PF_INET6 Ta Dv SOCK_DGRAM Ta Dv IPPROTO_UDP Ta
-Return 0.
-ICMP messages will
-.Em not
-be generated.
+Failure,
+as socket is not connected.
 .It Dv PF_INET6 Ta Dv SOCK_STREAM Ta Dv IPPROTO_SCTP Ta
-Return 0.
 Send queued data and tear down association.
 .It Dv PF_INET6 Ta Dv SOCK_STREAM Ta Dv IPPROTO_TCP Ta
-Return 0.
 Send queued data, wait for ACK, then send FIN.
 .El
 .\"
@@ -131,16 +117,10 @@
 The
 .Fa how
 argument is invalid.
-.It Bq Er EOPNOTSUPP
-The socket associated with the file descriptor
-.Fa s
-does not support this operation.
 .It Bq Er ENOTCONN
 The
 .Fa s
-argument specifies a
-.Dv SOCK_STREAM
-socket which is not connected.
+argument specifies a socket which is not connected.
 .It Bq Er ENOTSOCK
 The
 .Fa s
Index: head/sys/kern/uipc_socket.c
===================================================================
--- head/sys/kern/uipc_socket.c
+++ head/sys/kern/uipc_socket.c
@@ -2334,6 +2334,9 @@
 
 	if (!(how == SHUT_RD || how == SHUT_WR || how == SHUT_RDWR))
 		return (EINVAL);
+	if ((so->so_state &
+	    (SS_ISCONNECTED | SS_ISCONNECTING | SS_ISDISCONNECTING)) == 0)
+		return (ENOTCONN);
 
 	CURVNET_SET(so->so_vnet);
 	if (pr->pr_usrreqs->pru_flush != NULL)
Index: head/sys/kern/uipc_syscalls.c
===================================================================
--- head/sys/kern/uipc_syscalls.c
+++ head/sys/kern/uipc_syscalls.c
@@ -1383,6 +1383,15 @@
 	if (error == 0) {
 		so = fp->f_data;
 		error = soshutdown(so, uap->how);
+		/*
+		 * Previous versions did not return ENOTCONN, but 0 in
+		 * case the socket was not connected. Some important
+		 * programs like syslogd up to r279016, 2015-02-19,
+		 * still depend on this behavior.
+		 */
+		if (error == ENOTCONN &&
+		    td->td_proc->p_osrel < P_OSREL_SHUTDOWN_ENOTCONN)
+			error = 0;
 		fdrop(fp, td);
 	}
 	return (error);
Index: head/sys/sys/param.h
===================================================================
--- head/sys/sys/param.h
+++ head/sys/sys/param.h
@@ -77,12 +77,13 @@
 #define __FreeBSD_kernel__
 
 #ifdef _KERNEL
-#define	P_OSREL_SIGWAIT		700000
-#define	P_OSREL_SIGSEGV		700004
-#define	P_OSREL_MAP_ANON	800104
-#define	P_OSREL_MAP_FSTRICT	1100036
+#define	P_OSREL_SIGWAIT			700000
+#define	P_OSREL_SIGSEGV			700004
+#define	P_OSREL_MAP_ANON		800104
+#define	P_OSREL_MAP_FSTRICT		1100036
+#define	P_OSREL_SHUTDOWN_ENOTCONN	1100077
 
-#define	P_OSREL_MAJOR(x)	((x) / 100000)
+#define	P_OSREL_MAJOR(x)		((x) / 100000)
 #endif
 
 #ifndef LOCORE