Indeed, this looks useful.

However, performing the rate limiting in the kernel using firewall rules
can be more efficient and not require any BIND patches.

There are three mechanisms I can think of for performing this rate
limiting today, without waiting for updates:

- Insert iptables hashlimit rules. Here is one suggested rule:
-p udp --dport 53 -m hashlimit --hashlimit-above 200/sec \
 --hashlimit-burst 500 --hashlimit-mode srcip --hashlimit-name DNS-ABUSER \
 --hashlimit-htable-size 8192 --hashlimit-htable-max 32768 -j drop_log_dns_abuse
(The rule was suggested by joerg jungermann in another context at 
http://mailman.powerdns.com/pipermail/pdns-users/2012-September/009235.html )

- Use phreld to dynamically insert DROP rules for hosts that bypass
limits: http://www.digitalgenesis.com/software/phrel/manual/phreld.html
(Sadly, not packaged for Ubuntu.) I know this option is preferred by
some commercial DNS hosts.

- Use ufw limit to add some quick limits. Since this is intended first
and foremost to prevent OpenSSH brute-force connection attempts, the
default limits may be too low for applying to DNS. This might still be
appropriate for very small installations, however. Your mileage my vary.

I hope this helps. Thanks.

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https://bugs.launchpad.net/bugs/1202278

Title:
  bind9 has no rate limit option

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