Index: sys/kern/init_sysent.c
===================================================================
--- sys/kern/init_sysent.c
+++ sys/kern/init_sysent.c
@@ -174,7 +174,7 @@
 	{ AS(flock_args), (sy_call_t *)sys_flock, AUE_FLOCK, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 131 = flock */
 	{ AS(mkfifo_args), (sy_call_t *)sys_mkfifo, AUE_MKFIFO, NULL, 0, 0, 0, SY_THR_STATIC },	/* 132 = mkfifo */
 	{ AS(sendto_args), (sy_call_t *)sys_sendto, AUE_SENDTO, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 133 = sendto */
-	{ AS(shutdown_args), (sy_call_t *)sys_shutdown, AUE_SHUTDOWN, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 134 = shutdown */
+	{ AS(oshutdown_args), (sy_call_t *)sys_oshutdown, AUE_SHUTDOWN, NULL, 0, 0, 0, SY_THR_STATIC },	/* 134 = oshutdown */
 	{ AS(socketpair_args), (sy_call_t *)sys_socketpair, AUE_SOCKETPAIR, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 135 = socketpair */
 	{ AS(mkdir_args), (sy_call_t *)sys_mkdir, AUE_MKDIR, NULL, 0, 0, 0, SY_THR_STATIC },	/* 136 = mkdir */
 	{ AS(rmdir_args), (sy_call_t *)sys_rmdir, AUE_RMDIR, NULL, 0, 0, 0, SY_THR_STATIC },	/* 137 = rmdir */
@@ -588,4 +588,5 @@
 	{ AS(ppoll_args), (sy_call_t *)sys_ppoll, AUE_POLL, NULL, 0, 0, 0, SY_THR_STATIC },	/* 545 = ppoll */
 	{ AS(futimens_args), (sy_call_t *)sys_futimens, AUE_FUTIMES, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 546 = futimens */
 	{ AS(utimensat_args), (sy_call_t *)sys_utimensat, AUE_FUTIMESAT, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 547 = utimensat */
+	{ AS(shutdown_args), (sy_call_t *)sys_shutdown, AUE_SHUTDOWN, NULL, 0, 0, SYF_CAPENABLED, SY_THR_STATIC },	/* 548 = shutdown */
 };
Index: sys/kern/syscalls.c
===================================================================
--- sys/kern/syscalls.c
+++ sys/kern/syscalls.c
@@ -141,7 +141,7 @@
 	"flock",			/* 131 = flock */
 	"mkfifo",			/* 132 = mkfifo */
 	"sendto",			/* 133 = sendto */
-	"shutdown",			/* 134 = shutdown */
+	"oshutdown",			/* 134 = oshutdown */
 	"socketpair",			/* 135 = socketpair */
 	"mkdir",			/* 136 = mkdir */
 	"rmdir",			/* 137 = rmdir */
@@ -555,4 +555,5 @@
 	"ppoll",			/* 545 = ppoll */
 	"futimens",			/* 546 = futimens */
 	"utimensat",			/* 547 = utimensat */
+	"shutdown",			/* 548 = shutdown */
 };
Index: sys/kern/syscalls.master
===================================================================
--- sys/kern/syscalls.master
+++ sys/kern/syscalls.master
@@ -273,7 +273,7 @@
 132	AUE_MKFIFO	STD	{ int mkfifo(char *path, int mode); }
 133	AUE_SENDTO	STD	{ int sendto(int s, caddr_t buf, size_t len, \
 				    int flags, caddr_t to, int tolen); }
-134	AUE_SHUTDOWN	STD	{ int shutdown(int s, int how); }
+134	AUE_SHUTDOWN	STD	{ int oshutdown(int s, int how); }
 135	AUE_SOCKETPAIR	STD	{ int socketpair(int domain, int type, \
 				    int protocol, int *rsv); }
 136	AUE_MKDIR	STD	{ int mkdir(char *path, int mode); }
@@ -988,5 +988,6 @@
 547	AUE_FUTIMESAT	STD	{ int utimensat(int fd, \
 				    char *path, \
 				    struct timespec *times, int flag); }
+548	AUE_SHUTDOWN	STD	{ int shutdown(int s, int how); }
 ; Please copy any additions and changes to the following compatability tables:
 ; sys/compat/freebsd32/syscalls.master
Index: sys/kern/systrace_args.c
===================================================================
--- sys/kern/systrace_args.c
+++ sys/kern/systrace_args.c
@@ -766,9 +766,9 @@
 		*n_args = 6;
 		break;
 	}
-	/* shutdown */
+	/* oshutdown */
 	case 134: {
-		struct shutdown_args *p = params;
+		struct oshutdown_args *p = params;
 		iarg[0] = p->s; /* int */
 		iarg[1] = p->how; /* int */
 		*n_args = 2;
@@ -3337,6 +3337,14 @@
 		*n_args = 4;
 		break;
 	}
+	/* shutdown */
+	case 548: {
+		struct shutdown_args *p = params;
+		iarg[0] = p->s; /* int */
+		iarg[1] = p->how; /* int */
+		*n_args = 2;
+		break;
+	}
 	default:
 		*n_args = 0;
 		break;
@@ -4554,7 +4562,7 @@
 			break;
 		};
 		break;
-	/* shutdown */
+	/* oshutdown */
 	case 134:
 		switch(ndx) {
 		case 0:
@@ -8883,6 +8891,19 @@
 			break;
 		};
 		break;
+	/* shutdown */
+	case 548:
+		switch(ndx) {
+		case 0:
+			p = "int";
+			break;
+		case 1:
+			p = "int";
+			break;
+		default:
+			break;
+		};
+		break;
 	default:
 		break;
 	};
@@ -9330,7 +9351,7 @@
 		if (ndx == 0 || ndx == 1)
 			p = "int";
 		break;
-	/* shutdown */
+	/* oshutdown */
 	case 134:
 		if (ndx == 0 || ndx == 1)
 			p = "int";
@@ -10806,6 +10827,11 @@
 		if (ndx == 0 || ndx == 1)
 			p = "int";
 		break;
+	/* shutdown */
+	case 548:
+		if (ndx == 0 || ndx == 1)
+			p = "int";
+		break;
 	default:
 		break;
 	};
Index: sys/kern/uipc_socket.c
===================================================================
--- sys/kern/uipc_socket.c
+++ 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: sys/kern/uipc_syscalls.c
===================================================================
--- sys/kern/uipc_syscalls.c
+++ sys/kern/uipc_syscalls.c
@@ -1363,6 +1363,25 @@
 	return (error);
 }
 
+/*
+ * The old shutdown() system call 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.
+ */
+int
+sys_oshutdown(struct thread *td, struct oshutdown_args *uap)
+{
+	struct shutdown_args nuap;
+	int error;
+
+	nuap.s = uap->s;
+	nuap.how = uap->how;
+	error = sys_shutdown(td, &nuap);
+	if (error == ENOTCONN)
+		error = 0;
+	return (error);
+}
+
 /* ARGSUSED */
 int
 sys_shutdown(td, uap)
Index: sys/sys/syscall.h
===================================================================
--- sys/sys/syscall.h
+++ sys/sys/syscall.h
@@ -137,7 +137,7 @@
 #define	SYS_flock	131
 #define	SYS_mkfifo	132
 #define	SYS_sendto	133
-#define	SYS_shutdown	134
+#define	SYS_oshutdown	134
 #define	SYS_socketpair	135
 #define	SYS_mkdir	136
 #define	SYS_rmdir	137
@@ -465,4 +465,5 @@
 #define	SYS_ppoll	545
 #define	SYS_futimens	546
 #define	SYS_utimensat	547
-#define	SYS_MAXSYSCALL	548
+#define	SYS_shutdown	548
+#define	SYS_MAXSYSCALL	549
Index: sys/sys/syscall.mk
===================================================================
--- sys/sys/syscall.mk
+++ sys/sys/syscall.mk
@@ -99,7 +99,7 @@
 	flock.o \
 	mkfifo.o \
 	sendto.o \
-	shutdown.o \
+	oshutdown.o \
 	socketpair.o \
 	mkdir.o \
 	rmdir.o \
@@ -412,4 +412,5 @@
 	procctl.o \
 	ppoll.o \
 	futimens.o \
-	utimensat.o
+	utimensat.o \
+	shutdown.o
Index: sys/sys/sysproto.h
===================================================================
--- sys/sys/sysproto.h
+++ sys/sys/sysproto.h
@@ -444,7 +444,7 @@
 	char to_l_[PADL_(caddr_t)]; caddr_t to; char to_r_[PADR_(caddr_t)];
 	char tolen_l_[PADL_(int)]; int tolen; char tolen_r_[PADR_(int)];
 };
-struct shutdown_args {
+struct oshutdown_args {
 	char s_l_[PADL_(int)]; int s; char s_r_[PADR_(int)];
 	char how_l_[PADL_(int)]; int how; char how_r_[PADR_(int)];
 };
@@ -1790,6 +1790,10 @@
 	char times_l_[PADL_(struct timespec *)]; struct timespec * times; char times_r_[PADR_(struct timespec *)];
 	char flag_l_[PADL_(int)]; int flag; char flag_r_[PADR_(int)];
 };
+struct shutdown_args {
+	char s_l_[PADL_(int)]; int s; char s_r_[PADR_(int)];
+	char how_l_[PADL_(int)]; int how; char how_r_[PADR_(int)];
+};
 int	nosys(struct thread *, struct nosys_args *);
 void	sys_sys_exit(struct thread *, struct sys_exit_args *);
 int	sys_fork(struct thread *, struct fork_args *);
@@ -1885,7 +1889,7 @@
 int	sys_flock(struct thread *, struct flock_args *);
 int	sys_mkfifo(struct thread *, struct mkfifo_args *);
 int	sys_sendto(struct thread *, struct sendto_args *);
-int	sys_shutdown(struct thread *, struct shutdown_args *);
+int	sys_oshutdown(struct thread *, struct oshutdown_args *);
 int	sys_socketpair(struct thread *, struct socketpair_args *);
 int	sys_mkdir(struct thread *, struct mkdir_args *);
 int	sys_rmdir(struct thread *, struct rmdir_args *);
@@ -2178,6 +2182,7 @@
 int	sys_ppoll(struct thread *, struct ppoll_args *);
 int	sys_futimens(struct thread *, struct futimens_args *);
 int	sys_utimensat(struct thread *, struct utimensat_args *);
+int	sys_shutdown(struct thread *, struct shutdown_args *);
 
 #ifdef COMPAT_43
 
@@ -2611,7 +2616,7 @@
 #define	SYS_AUE_flock	AUE_FLOCK
 #define	SYS_AUE_mkfifo	AUE_MKFIFO
 #define	SYS_AUE_sendto	AUE_SENDTO
-#define	SYS_AUE_shutdown	AUE_SHUTDOWN
+#define	SYS_AUE_oshutdown	AUE_SHUTDOWN
 #define	SYS_AUE_socketpair	AUE_SOCKETPAIR
 #define	SYS_AUE_mkdir	AUE_MKDIR
 #define	SYS_AUE_rmdir	AUE_RMDIR
@@ -2931,6 +2936,7 @@
 #define	SYS_AUE_ppoll	AUE_POLL
 #define	SYS_AUE_futimens	AUE_FUTIMES
 #define	SYS_AUE_utimensat	AUE_FUTIMESAT
+#define	SYS_AUE_shutdown	AUE_SHUTDOWN
 
 #undef PAD_
 #undef PADL_