Add CHANGES and release notes for GL #1712 and GL #1829

CHANGES

@@ -1,3 +1,10 @@
+5484.	[func]		Expire the 0 TTL RRSet quickly rather using them for
+			stale answers. [GL #1829]
+
+5483.	[func]		Keeping "stale" answers in cache has been disabled by
+			default and can be re-enabled with a new configuration
+			option "stale-cache-enable". [GL #1712]
+
 5482.	[bug]		BIND 9 would fail to bind to IPv6 addresses in a
 			tentative state when a new IPv6 address was added to the
 			system, but the Duplicate Address Detection (DAD)

bin/named/server.c

@@ -4366,6 +4366,10 @@ configure_view(dns_view_t *view, dns_viewlist_t *viewlist, cfg_obj_t *config,
 		INSIST(result == ISC_R_SUCCESS);
 		max_stale_ttl = ISC_MAX(cfg_obj_asduration(obj), 1);
 	}
+	/*
+	 * If 'stale-cache-enable' is false, max_stale_ttl is set to 0,
+	 * meaning keeping stale RRsets in cache is disabled.
+	 */
 
 	obj = NULL;
 	result = named_config_get(maps, "stale-answer-enable", &obj);

doc/notes/notes-current.rst

@@ -36,6 +36,9 @@ New Features
 - Statistics channels have also been updated to use the new BIND network
   manager API. [GL #2022]
 
+- A new configuration option ``stale-cache-enable`` has been introduced to
+  enable or disable the keeping of stale answers in cache. [GL #1712]
+
 Feature Changes
 ~~~~~~~~~~~~~~~
 
@@ -46,6 +49,11 @@ Feature Changes
   prevents interruption to query resolution when the hash tables need to be
   increased in size. [GL #1775]
 
+- Keeping stale answers in cache has been disabled by default.
+
+- The resource records received with 0 TTL are no longer kept in the cache
+  to be used for stale answers. [GL #1829]
+
 Bug Fixes
 ~~~~~~~~~