Index: uipc_usrreq.c
===================================================================
RCS file: /zoo/cvsup/FreeBSD-CVS/src/sys/kern/uipc_usrreq.c,v
retrieving revision 1.182
diff -u -r1.182 uipc_usrreq.c
--- uipc_usrreq.c	26 Jul 2006 19:16:34 -0000	1.182
+++ uipc_usrreq.c	31 Jul 2006 17:51:45 -0000
@@ -605,7 +605,18 @@
 				break;
 			}
 		}
+		/*
+		 * Because connect() and send() are non-atomic in a sendto()
+		 * with a target address, it's possible that the socket will
+		 * have disconnected before the send() can run.  In that case
+		 * return the slightly counter-intuitive but otherwise
+		 * correct error that the socket is not connected.
+		 */
 		unp2 = unp->unp_conn;
+		if (unp2 == NULL) {
+			error = ENOTCONN;
+			break;
+		}
 		so2 = unp2->unp_socket;
 		if (unp->unp_addr != NULL)
 			from = (struct sockaddr *)unp->unp_addr;
@@ -650,9 +661,18 @@
 			error = EPIPE;
 			break;
 		}
+		/*
+		 * Because connect() and send() are non-atomic in a sendto()
+		 * with a target address, it's possible that the socket will
+		 * have disconnected before the send() can run.  In that case
+		 * return the slightly counter-intuitive but otherwise
+		 * correct error that the socket is not connected.
+		 */
 		unp2 = unp->unp_conn;
-		if (unp2 == NULL)
-			panic("uipc_send connected but no connection?");
+		if (unp2 == NULL) {
+			error = ENOTCONN;
+			break;
+		}
 		so2 = unp2->unp_socket;
 		SOCKBUF_LOCK(&so2->so_rcv);
 		if (unp2->unp_flags & UNP_WANTCRED) {