Make global UNIX socket non-blocking for ctrl_iface

This keeps wpa_supplicant from hanging forever if the other end of the
socket dies. This is similar to the earlier commit
4fdc8def8855ce9b90ffbbdc47152ce46ccdcb1e to make the global control
interface befave in the same way.

Signed-hostap: Jouni Malinen <j@w1.fi>

wpa_supplicant/ctrl_iface_unix.c

@@ -722,6 +722,7 @@ wpa_supplicant_global_ctrl_iface_init(struct wpa_global *global)
 	struct ctrl_iface_global_priv *priv;
 	struct sockaddr_un addr;
 	const char *ctrl = global->params.ctrl_interface;
+	int flags;
 
 	priv = os_zalloc(sizeof(*priv));
 	if (priv == NULL)
@@ -864,6 +865,20 @@ wpa_supplicant_global_ctrl_iface_init(struct wpa_global *global)
 	}
 
 havesock:
+
+	/*
+	 * Make socket non-blocking so that we don't hang forever if
+	 * target dies unexpectedly.
+	 */
+	flags = fcntl(priv->sock, F_GETFL);
+	if (flags >= 0) {
+		flags |= O_NONBLOCK;
+		if (fcntl(priv->sock, F_SETFL, flags) < 0) {
+			perror("fcntl(ctrl, O_NONBLOCK)");
+			/* Not fatal, continue on.*/
+		}
+	}
+
 	eloop_register_read_sock(priv->sock,
 				 wpa_supplicant_global_ctrl_iface_receive,
 				 global, priv);