If we come into vcl_error{} with a non-3-digit error status, for instance

because vcl_recv does "return(error);", force the status to 501.

Fixes: #558


git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4240 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_center.c

@@ -344,6 +344,9 @@ cnt_error(struct sess *sp)
 	CHECK_OBJ_NOTNULL(sp->obj, OBJECT_MAGIC);
 	h = sp->obj->http;
 
+	if (sp->err_code < 100 || sp->err_code > 999)
+		sp->err_code = 501;
+
 	http_PutProtocol(w, sp->fd, h, "HTTP/1.1");
 	http_PutStatus(w, sp->fd, h, sp->err_code);
 	TIM_format(TIM_real(), date);