--- kern/uipc_sockbuf.c	(revision 255139)
+++ kern/uipc_sockbuf.c	(working copy)
@@ -688,23 +688,16 @@ 
 	return (retval);
 }
 
-int
+void
 sbappendcontrol_locked(struct sockbuf *sb, struct mbuf *m0,
     struct mbuf *control)
 {
-	struct mbuf *m, *n, *mlast;
-	int space;
+	struct mbuf *m, *mlast;
 
 	SOCKBUF_LOCK_ASSERT(sb);
 
-	if (control == 0)
-		panic("sbappendcontrol_locked");
-	space = m_length(control, &n) + m_length(m0, NULL);
+	m_last(control)->m_next = m0;		/* concatenate data to control */
 
-	if (space > sbspace(sb))
-		return (0);
-	n->m_next = m0;			/* concatenate data to control */
-
 	SBLASTRECORDCHK(sb);
 
 	for (m = control; m->m_next; m = m->m_next)
@@ -717,18 +710,14 @@ 
 	SBLASTMBUFCHK(sb);
 
 	SBLASTRECORDCHK(sb);
-	return (1);
 }
 
-int
+void
 sbappendcontrol(struct sockbuf *sb, struct mbuf *m0, struct mbuf *control)
 {
-	int retval;
-
 	SOCKBUF_LOCK(sb);
-	retval = sbappendcontrol_locked(sb, m0, control);
+	sbappendcontrol_locked(sb, m0, control);
 	SOCKBUF_UNLOCK(sb);
-	return (retval);
 }
 
 /*
--- kern/uipc_socket.c	(revision 255139)
+++ kern/uipc_socket.c	(working copy)
@@ -1102,6 +1102,11 @@ 
 	KASSERT(so->so_proto->pr_flags & PR_ATOMIC,
 	    ("sosend_dgram: !PR_ATOMIC"));
 
+	if (so->so_proto->pr_usrreqs->pru_finalizecontrol &&
+	    (error = (*so->so_proto->pr_usrreqs->pru_finalizecontrol)(so,
+	        flags, &control, td)))
+		goto out;
+
 	if (uio != NULL)
 		resid = uio->uio_resid;
 	else
@@ -1168,6 +1173,10 @@ 
 	space = sbspace(&so->so_snd);
 	if (flags & MSG_OOB)
 		space += 1024;
+	if (clen > space) {
+		error = EMSGSIZE;
+		goto out;
+	}
 	space -= clen;
 	SOCKBUF_UNLOCK(&so->so_snd);
 	if (resid > space) {
@@ -1269,6 +1278,11 @@ 
 	int clen = 0, error, dontroute;
 	int atomic = sosendallatonce(so) || top;
 
+	if (so->so_proto->pr_usrreqs->pru_finalizecontrol &&
+	    (error = (*so->so_proto->pr_usrreqs->pru_finalizecontrol)(so,
+	        flags, &control, td)))
+		goto out;
+
 	if (uio != NULL)
 		resid = uio->uio_resid;
 	else
@@ -1361,6 +1375,10 @@ 
 			goto restart;
 		}
 		SOCKBUF_UNLOCK(&so->so_snd);
+		if (clen > space) {
+			error = EMSGSIZE;
+			goto release;
+		}
 		space -= clen;
 		do {
 			if (uio == NULL) {
@@ -1426,8 +1444,11 @@ 
 				so->so_options &= ~SO_DONTROUTE;
 				SOCK_UNLOCK(so);
 			}
-			clen = 0;
-			control = NULL;
+			if (control) {
+				control = NULL;
+				space += clen;
+				clen = 0;
+			}
 			top = NULL;
 			if (error)
 				goto release;
--- kern/uipc_usrreq.c	(revision 255139)
+++ kern/uipc_usrreq.c	(working copy)
@@ -290,7 +290,7 @@ 
 static void	unp_internalize_fp(struct file *);
 static int	unp_externalize(struct mbuf *, struct mbuf **, int);
 static int	unp_externalize_fp(struct file *);
-static struct mbuf	*unp_addsockcred(struct thread *, struct mbuf *);
+static int	unp_addsockcred(struct mbuf **, struct thread *);
 static void	unp_process_defers(void * __unused, int);
 
 /*
@@ -782,6 +782,47 @@ 
 }
 
 static int
+uipc_finalizecontrol(struct socket *so, int flags, struct mbuf **pcontrol,
+    struct thread *td)
+{
+	struct unpcb *unp, *unp2;
+	int error = 0;
+
+	unp = sotounpcb(so);
+	KASSERT(unp != NULL, ("uipc_finalizecontrol: unp == NULL"));
+
+	UNP_PCB_LOCK(unp);
+	unp2 = unp->unp_conn;
+
+	if (*pcontrol != NULL && (error = unp_internalize(pcontrol, td))) {
+		UNP_PCB_UNLOCK(unp);
+		return (error);
+	}
+
+	/* Lockless read. */
+	if (unp2->unp_flags & UNP_WANTCRED) {
+		switch (so->so_type) {
+		case SOCK_SEQPACKET:
+		case SOCK_STREAM:
+			/* Credentials are passed only once on SOCK_STREAM. */
+			UNP_PCB_LOCK(unp2);
+			if (unp2->unp_flags & UNP_WANTCRED) {
+				unp2->unp_flags &= ~UNP_WANTCRED;
+				error = unp_addsockcred(pcontrol, td);
+			}
+			UNP_PCB_UNLOCK(unp2);
+			break;
+		case SOCK_DGRAM:
+			error = unp_addsockcred(pcontrol, td);
+			break;
+		}
+	}
+
+	UNP_PCB_UNLOCK(unp);
+	return (error);
+}
+
+static int
 uipc_rcvd(struct socket *so, int flags)
 {
 	struct unpcb *unp, *unp2;
@@ -845,8 +886,6 @@ 
 		error = EOPNOTSUPP;
 		goto release;
 	}
-	if (control != NULL && (error = unp_internalize(&control, td)))
-		goto release;
 	if ((nam != NULL) || (flags & PRUS_EOF))
 		UNP_LINK_WLOCK();
 	else
@@ -880,9 +919,6 @@ 
 			error = ENOTCONN;
 			break;
 		}
-		/* Lockless read. */
-		if (unp2->unp_flags & UNP_WANTCRED)
-			control = unp_addsockcred(td, control);
 		UNP_PCB_LOCK(unp);
 		if (unp->unp_addr != NULL)
 			from = (struct sockaddr *)unp->unp_addr;
@@ -949,14 +985,6 @@ 
 		so2 = unp2->unp_socket;
 		UNP_PCB_LOCK(unp2);
 		SOCKBUF_LOCK(&so2->so_rcv);
-		if (unp2->unp_flags & UNP_WANTCRED) {
-			/*
-			 * Credentials are passed only once on SOCK_STREAM
-			 * and SOCK_SEQPACKET.
-			 */
-			unp2->unp_flags &= ~UNP_WANTCRED;
-			control = unp_addsockcred(td, control);
-		}
 		/*
 		 * Send to paired receive port, and then reduce send buffer
 		 * hiwater marks to maintain backpressure.  Wake up readers.
@@ -964,9 +992,8 @@ 
 		switch (so->so_type) {
 		case SOCK_STREAM:
 			if (control != NULL) {
-				if (sbappendcontrol_locked(&so2->so_rcv, m,
-				    control))
-					control = NULL;
+				sbappendcontrol_locked(&so2->so_rcv, m, control);
+				control = NULL;
 			} else
 				sbappend_locked(&so2->so_rcv, m);
 			break;
@@ -1114,6 +1141,7 @@ 
 	.pru_disconnect =	uipc_disconnect,
 	.pru_listen =		uipc_listen,
 	.pru_peeraddr =		uipc_peeraddr,
+	.pru_finalizecontrol =	uipc_finalizecontrol,
 	.pru_rcvd =		uipc_rcvd,
 	.pru_send =		uipc_send,
 	.pru_sense =		uipc_sense,
@@ -1136,6 +1164,7 @@ 
 	.pru_disconnect =	uipc_disconnect,
 	.pru_listen =		uipc_listen,
 	.pru_peeraddr =		uipc_peeraddr,
+	.pru_finalizecontrol =	uipc_finalizecontrol,
 	.pru_rcvd =		uipc_rcvd,
 	.pru_send =		uipc_send,
 	.pru_sense =		uipc_sense,
@@ -1158,6 +1187,7 @@ 
 	.pru_disconnect =	uipc_disconnect,
 	.pru_listen =		uipc_listen,
 	.pru_peeraddr =		uipc_peeraddr,
+	.pru_finalizecontrol =	uipc_finalizecontrol,
 	.pru_rcvd =		uipc_rcvd,
 	.pru_send =		uipc_send,
 	.pru_sense =		uipc_sense,
@@ -1747,7 +1777,7 @@ 
 			    SCM_RIGHTS, SOL_SOCKET);
 			if (*controlp == NULL) {
 				FILEDESC_XUNLOCK(fdesc);
-				error = E2BIG;
+				error = ENOBUFS;
 				unp_freerights(fdep, newfds);
 				goto next;
 			}
@@ -1928,7 +1958,7 @@ 
 			    SCM_RIGHTS, SOL_SOCKET);
 			if (*controlp == NULL) {
 				FILEDESC_SUNLOCK(fdesc);
-				error = E2BIG;
+				error = ENOBUFS;
 				goto out;
 			}
 			fdp = data;
@@ -1992,9 +2022,10 @@ 
 	return (error);
 }
 
-static struct mbuf *
-unp_addsockcred(struct thread *td, struct mbuf *control)
+static int
+unp_addsockcred(struct mbuf **pcontrol, struct thread *td)
 {
+	struct mbuf *control = *pcontrol;
 	struct mbuf *m, *n, *n_prev;
 	struct sockcred *sc;
 	const struct cmsghdr *cm;
@@ -2004,7 +2035,7 @@ 
 	ngroups = MIN(td->td_ucred->cr_ngroups, CMGROUP_MAX);
 	m = sbcreatecontrol(NULL, SOCKCREDSIZE(ngroups), SCM_CREDS, SOL_SOCKET);
 	if (m == NULL)
-		return (control);
+		return (ENOBUFS);
 
 	sc = (struct sockcred *) CMSG_DATA(mtod(m, struct cmsghdr *));
 	sc->sc_uid = td->td_ucred->cr_ruid;
@@ -2038,7 +2069,8 @@ 
 
 	/* Prepend it to the head. */
 	m->m_next = control;
-	return (m);
+	*pcontrol = m;
+	return (0);
 }
 
 static struct unpcb *
--- sys/protosw.h	(revision 255139)
+++ sys/protosw.h	(working copy)
@@ -201,6 +201,8 @@ 
 	int	(*pru_listen)(struct socket *so, int backlog,
 		    struct thread *td);
 	int	(*pru_peeraddr)(struct socket *so, struct sockaddr **nam);
+	int	(*pru_finalizecontrol)(struct socket *so, int flags, struct mbuf **pcontrol,
+		    struct thread *td);
 	int	(*pru_rcvd)(struct socket *so, int flags);
 	int	(*pru_rcvoob)(struct socket *so, struct mbuf *m, int flags);
 	int	(*pru_send)(struct socket *so, int flags, struct mbuf *m,
--- sys/sockbuf.h	(revision 255139)
+++ sys/sockbuf.h	(working copy)
@@ -127,9 +127,9 @@ 
 	    struct mbuf *m0, struct mbuf *control);
 int	sbappendaddr_locked(struct sockbuf *sb, const struct sockaddr *asa,
 	    struct mbuf *m0, struct mbuf *control);
-int	sbappendcontrol(struct sockbuf *sb, struct mbuf *m0,
+void	sbappendcontrol(struct sockbuf *sb, struct mbuf *m0,
 	    struct mbuf *control);
-int	sbappendcontrol_locked(struct sockbuf *sb, struct mbuf *m0,
+void	sbappendcontrol_locked(struct sockbuf *sb, struct mbuf *m0,
 	    struct mbuf *control);
 void	sbappendrecord(struct sockbuf *sb, struct mbuf *m0);
 void	sbappendrecord_locked(struct sockbuf *sb, struct mbuf *m0);