[master] DDoS mitigation features

3938.	[func]		Added quotas to be used in recursive resolvers
			that are under high query load for names in zones
			whose authoritative servers are nonresponsive or
			are experiencing a denial of service attack.

			- "fetches-per-server" limits the number of
			  simultaneous queries that can be sent to any
			  single authoritative server.  The configured
			  value is a starting point; it is automatically
			  adjusted downward if the server is partially or
			  completely non-responsive. The algorithm used to
			  adjust the quota can be configured via the
			  "fetch-quota-params" option.
			- "fetches-per-zone" limits the number of
			  simultaneous queries that can be sent for names
			  within a single domain.  (Note: Unlike
			  "fetches-per-server", this value is not
			  self-tuning.)
			- New stats counters have been added to count
			  queries spilled due to these quotas.

			See the ARM for details of these options. [RT #37125]

bin/tests/system/fetchlimit/ns1/root.db

@@ -0,0 +1,29 @@
+; Copyright (C) 2014  Internet Systems Consortium, Inc. ("ISC")
+;
+; Permission to use, copy, modify, and/or distribute this software for any
+; purpose with or without fee is hereby granted, provided that the above
+; copyright notice and this permission notice appear in all copies.
+;
+; THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+; REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+; AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+; INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+; LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+; OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+; PERFORMANCE OF THIS SOFTWARE.
+
+; $Id$
+
+$TTL 300
+. 			IN SOA	gson.nominum.com. a.root.servers.nil. (
+				2000042100   	; serial
+				600         	; refresh
+				600         	; retry
+				1200    	; expire
+				600       	; minimum
+				)
+.			NS	a.root-servers.nil.
+a.root-servers.nil.	A	10.53.0.1
+
+example.		NS	ns2.example.
+ns2.example.		A	10.53.0.2