MINOR: connection: add simple functions to report connection readiness

conn_xprt_ready() reports if the transport layer is ready.
conn_ctrl_ready() reports if the control layer is ready.

The stream interface uses si_conn_ready() to report that the
underlying connection is ready. This will be used for connection
reuse in keep-alive mode.
diff --git a/include/proto/connection.h b/include/proto/connection.h
index a642960..a36906d 100644
--- a/include/proto/connection.h
+++ b/include/proto/connection.h
@@ -43,6 +43,18 @@
 int conn_recv_proxy(struct connection *conn, int flag);
 int make_proxy_line(char *buf, int buf_len, struct sockaddr_storage *src, struct sockaddr_storage *dst);
 
+/* returns true is the transport layer is ready */
+static inline int conn_xprt_ready(struct connection *conn)
+{
+	return (conn->flags & CO_FL_XPRT_READY) && conn->xprt;
+}
+
+/* returns true is the control layer is ready */
+static inline int conn_ctrl_ready(struct connection *conn)
+{
+	return (conn->flags & CO_FL_CTRL_READY);
+}
+
 /* Calls the init() function of the transport layer if any and if not done yet,
  * and sets the CO_FL_XPRT_READY flag to indicate it was properly initialized.
  * Returns <0 in case of error.
diff --git a/include/proto/stream_interface.h b/include/proto/stream_interface.h
index 7ab72ce..5408f1e 100644
--- a/include/proto/stream_interface.h
+++ b/include/proto/stream_interface.h
@@ -149,6 +149,16 @@
 	conn_attach(conn, si, &si_conn_cb);
 }
 
+/* Returns true if a connection is attached to the stream interface <si> and
+ * if this connection is ready.
+ */
+static inline int si_conn_ready(struct stream_interface *si)
+{
+	struct connection *conn = objt_conn(si->end);
+
+	return conn && conn_ctrl_ready(conn) && conn_xprt_ready(conn);
+}
+
 /* Attach appctx <appctx> to the stream interface <si>. The stream interface
  * is configured to work with an applet context. It is left to the caller to
  * call appctx_set_applet() to assign an applet to this context.
diff --git a/src/stream_interface.c b/src/stream_interface.c
index 34438d7..f2650d3 100644
--- a/src/stream_interface.c
+++ b/src/stream_interface.c
@@ -389,7 +389,7 @@
 	if (conn->flags & CO_FL_SOCK_WR_SH)
 		goto out_error;
 
-	if (!(conn->flags & CO_FL_CTRL_READY))
+	if (!conn_ctrl_ready(conn))
 		goto out_error;
 
 	/* If we have a PROXY line to send, we'll use this to validate the
@@ -812,7 +812,7 @@
 			/* quick close, the socket is alredy shut anyway */
 		}
 		else if (si->flags & SI_FL_NOLINGER) {
-			if ((conn->flags & CO_FL_CTRL_READY) && conn->ctrl) {
+			if (conn_ctrl_ready(conn)) {
 				setsockopt(conn->t.sock.fd, SOL_SOCKET, SO_LINGER,
 					   (struct linger *) &nolinger, sizeof(struct linger));
 			}
@@ -833,7 +833,7 @@
 			 */
 			if (!(si->flags & SI_FL_NOHALF) || !(si->ib->flags & (CF_SHUTR|CF_DONT_READ))) {
 				/* We shutdown transport layer */
-				if ((conn->flags & CO_FL_CTRL_READY) && conn->ctrl)
+				if (conn_ctrl_ready(conn))
 					shutdown(conn->t.sock.fd, SHUT_WR);
 
 				if (!(si->ib->flags & (CF_SHUTR|CF_DONT_READ))) {
@@ -931,13 +931,13 @@
 		/* Before calling the data-level operations, we have to prepare
 		 * the polling flags to ensure we properly detect changes.
 		 */
-		if ((conn->flags & CO_FL_CTRL_READY) && conn->ctrl)
+		if (conn_ctrl_ready(conn))
 			fd_want_send(conn->t.sock.fd);
 
 		conn_refresh_polling_flags(conn);
 
 		si_conn_send(conn);
-		if ((conn->flags & CO_FL_CTRL_READY) && (conn->flags & CO_FL_ERROR)) {
+		if (conn_ctrl_ready(conn) && (conn->flags & CO_FL_ERROR)) {
 			/* Write error on the file descriptor */
 			fd_stop_both(conn->t.sock.fd);
 			__conn_data_stop_both(conn);
@@ -1287,7 +1287,7 @@
 		/* we want to immediately forward this close to the write side */
 		if (si->flags & SI_FL_NOLINGER) {
 			si->flags &= ~SI_FL_NOLINGER;
-			if (conn->flags & CO_FL_CTRL_READY)
+			if (conn_ctrl_ready(conn))
 				setsockopt(conn->t.sock.fd, SOL_SOCKET, SO_LINGER,
 				           (struct linger *) &nolinger, sizeof(struct linger));
 		}