Merge branch '2250-dns-flag-day-2020-revert-nocookie-udp-size-v9_16' into 'v9_16'

Resolve "DNS Flag Day 2020 - EDNS buffer size configuring does not work anymore"

See merge request isc-projects/bind9!4456

CHANGES

@@ -1,3 +1,6 @@
+5544.	[func]		Restore the default value of nocookie-udp-size to 4096.
+			[GL #2250]
+
 5541.	[func]		Adjust the "max-recursion-queries" default from 75 to
 			100. [GL #2305]
 

bin/named/config.c

@@ -86,7 +86,7 @@ options {\n\
 	memstatistics-file \"named.memstats\";\n\
 #	multiple-cnames <obsolete>;\n\
 #	named-xfer <obsolete>;\n\
-	nocookie-udp-size 1232;\n\
+	nocookie-udp-size 4096;\n\
 	notify-rate 20;\n\
 	nta-lifetime 3600;\n\
 	nta-recheck 300;\n\

doc/arm/reference.rst

@@ -1857,8 +1857,9 @@ Boolean Options
 ``nocookie-udp-size``
    This sets the maximum size of UDP responses that are sent to queries
    without a valid server COOKIE. A value below 128 is silently
-   raised to 128. The default value is 1232, but the ``max-udp-size``
-   option may further limit the response size.
+   raised to 128. The default value is 4096, but the ``max-udp-size``
+   option may further limit the response size as the default for
+   ``max-udp-size`` is 1232.
 
 ``sit-secret``
    This experimental option is obsolete.

doc/notes/notes-current.rst

@@ -46,6 +46,14 @@ Feature Changes
   has a higher chance of being exceeded by non-attack queries, which is the
   main reason for increasing its default value. [GL #2305]
 
+- Restore the ``nocookie-udp-size`` default from 1232 to 4096. Normally the
+  EDNS buffer size is configured by ``max-udp-size``, but this configuration
+  option overrides the value, but most people don't and won't realize there's
+  an extra configuration option that needs to be tweaked. By changing the
+  default here, we allow the the ``max-udp-size`` to be the sole option that
+  needs to be changed when operator wants to change the default EDNS buffer
+  size. [GL #2250]
+
 Bug Fixes
 ~~~~~~~~~