PowerDNS Recursor additional Lua hooks for IPv6 DNS64 and Renumbering

Dear PowerDNS Community,

The PowerDNS Recursor is currently being extended with additional Lua hooks
and extra infrastructure to support flexible DNS64 operations, plus perform
on-the-fly IPv4 or IPv6 renumbering.

DNS64 is described on http://tools.ietf.org/html/draft-ietf-behave-dns64-11
and in brief:

"DNS64 is a mechanism for synthesizing AAAA records from A records. DNS64
is used with an IPv6/IPv4 translator to enable client-server communication
between an IPv6-only client and an IPv4-only server, without requiring any
changes to either the IPv6 or the IPv4 node"

Those of you with an interest in these features are invited to test out the
following *pre-release*, specifically to let us know if the API is sufficient
for your needs:

http://svn.powerdns.com/snapshots/pdns-recursor-3.3-hooks.tar.bz2

It can be compiled like any other PowerDNS Recursor release.

New in the version are the 'nodata()' and 'postresolve()' Lua hooks. Nodata
functions just like nxdomain(), except that it gets called when a domain
exists, but the requested type doesn't. This is where DNS64 happens.

Postresolve() is different, and very powerful - it gets handed the complete
DNS answer as it would be sent out, ready for modification from Lua. This is
where one might for example perform on the fly IP address renumbering.

In the release you can find powerdns-example-script.lua which contains a
working sample for both of the new hooks. This script can also be viewed on
http://wiki.powerdns.com/trac/browser/branches/pdns-dns64/pdns/powerdns-example-script.lua

Note: DO NOT TAKE THIS SCRIPT INTO PRODUCTION - it blacks out important
sites

To get going without disturbing any existing nameservers on your computer,
compile the PowerDNS Recursor, and start like this:
$ ./pdns_recursor --local-address=0.0.0.0 --local-port=5300 --daemon=no
--socket-dir=./ --lua-dns-script=powerdns-example-script.lua

Known defects are:
postresolve() can't yet access the original dns rcode
there is no way for nodata() to set the TTL to the SOA minimum value
as specified by draft-ietf-behave-dns64

Please let us know your thoughts so we can make sure the API has everything
needed for great DNS64 and renumbering operations!

Kind regards,

Bert Hubert

2 comments

  1. filip

    hi bert,i was able to set up a dns64 and nat64 (tayga) service in our corporate environment (testing ofcourse). i notice the pdns is unstable, and every few requests, it crashes:Feb 4 16:25:23 oak pdns_recursor[7456]: STL error: lua error in 'nodata': attempt to index a nil valueFeb 4 16:25:23 oak kernel: [90754.002810] pdns_recursor[7458]: segfault at b789d000 ip b7652b16 sp 08db4d48 error 4 in libc-2.11.2.so[b75de000+140000]we usally use bind and windows dns in our environment, but the powerdns is the first one we tried. not sure whether we are going to keep it, but i thought you wanted to know this.

  2. asq

    same here:Oct 21 12:33:12 From Lua script: postresolve resolveName 1 preRequest from Lua to resolveName 's-static.ak.facebook.com.', 1Result: 0Have 3 answers for Lua, rcode=0Oct 21 12:33:12 From Lua script: postresolve resolveName 1 postOct 21 12:33:17 From Lua script: postresolve resolveName 2 preRequest from Lua to resolveName 's-static.ak.facebook.com.', 1Oct 21 12:33:17 STL error: lua error in 'postresolve': attempt to index a nil valueSegmentation faultKABOOM

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