add tests for EDE 13 support

Add system test covering EDE 13 being added in the response in case of
SERVFAIL cache hits.

bin/tests/system/sfcache/ns5/named.conf.j2

@@ -13,6 +13,8 @@
 
 // NS5
 
+{% set servfail_ttl = servfail_ttl | default(30) %}
+
 options {
 	query-source address 10.53.0.5;
 	notify-source 10.53.0.5;
@@ -23,7 +25,7 @@ options {
 	listen-on-v6 { none; };
 	recursion yes;
 	dnssec-validation yes;
-	servfail-ttl 30;
+	servfail-ttl @servfail_ttl@;
 };
 
 key rndc_key {

bin/tests/system/sfcache/setup.sh

@@ -18,7 +18,6 @@ set -e
 
 copy_setports ns1/named.conf.in ns1/named.conf
 copy_setports ns2/named.conf.in ns2/named.conf
-copy_setports ns5/named.conf.in ns5/named.conf
 
 cd ns1 && $SHELL sign.sh && cd ..
 cd ns5 && $SHELL sign.sh && cd ..

bin/tests/system/sfcache/tests_sfcache.py

@@ -0,0 +1,48 @@
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# SPDX-License-Identifier: MPL-2.0
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0.  If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+import time
+
+import isctest
+from isctest.compat import EDECode
+
+
+def check_sfcache_ede(ns, ede):
+    msg = isctest.query.create("foo.example.", "A")
+    res = isctest.query.udp(msg, ns.ip)
+    isctest.check.servfail(res)
+    if ede:
+        isctest.check.ede(res, EDECode.CACHED_ERROR)
+    else:
+        isctest.check.noede(res)
+
+
+def test_sfcache_ede(ns5, templates):
+    # Reconfigure the server so servfail-ttl is 1 second
+    templates.render("ns5/named.conf", {"servfail_ttl": 1})
+    with ns5.watch_log_from_here() as watcher:
+        ns5.rndc("reload")
+        watcher.wait_for_line("running")
+
+    # First query do not have a cached SERVFAIL, no EDE
+    check_sfcache_ede(ns5, False)
+
+    # Immediates next queries are cached SERVFAIL, EDE present
+    check_sfcache_ede(ns5, True)
+    check_sfcache_ede(ns5, True)
+
+    # Wait enough time so we know he cached SERVFAIL is removed
+    time.sleep(2)
+
+    # And again, first query is not cached, subsequent ones are.
+    check_sfcache_ede(ns5, False)
+    check_sfcache_ede(ns5, True)
+    check_sfcache_ede(ns5, True)