grong: A Go repository from bortzmeyer

GRONG (Gross and ROugh Nameserver written in Go) is a DNS (Domain Name
System) authoritative name server. It is intended as a research
project and is not probably suitable for use on the wild Internet.

MAY NOT BE SUITABLE ON A PRODUCTION SITE. YOU HAVE BEEN WARNED!!!

Disclaimer: I've never been to this city
<http://en.wikipedia.org/wiki/Grong>

GRONG can only be used as an authoritative name server (like, for
instance, nsd), not as a recursive one.

GRONG provides a general DNS engine, the front-end, which receives
packets, parses them and sends a proper response, and several possible
back-ends (named "responders") which generates a response, given the
query. Some are provided with GRONG and you are welcome to write
others.

The official source is <http://github.com/bortzmeyer/grong>

Usage
*****

./grong [-address="[ADDRESS]:PORT"] [-debug=N] [-nodaemon] [-domain="DOMAIN NAME"]

Run with -help to see the defaults (and the other, less common, options)

The -address option takes either a port (in the syntax ":NNN"), in
that case GRONG listens on all IP addresses, or one address (in the
syntax "x.y.z.T:NNN" for IPv4 and "[xxxx:yyyy::zzzz]:NNN" for
IPv6). There is currently no way to listen on some (but not all) of the IP
addresses.

The -domain option takes a domain name, which will be the name of the
zone for which the name server will be authoritative for. Not all
responders use it.

The back-end is choosen at compile-time only (I have no idea about the
support for dynamic linking in Go)

Among the provided responders:
* rude-responder: responds REFUSED to every query
* reflector-responder: responds with the IP address of the client (for TXT 
  requests, in text form, for A or AAAA requests, as binary). -domain indicates 
  the zone name it uses (e.g. whoami.example.net)
* as112: an AS 112 name server (see <http://www.as112.net/>)

For the person who compiles
**************************

You need a working Go <http://golang.org> environment. Today, only the
gc compiler is supported.

To choose a responder (here, foobar-responder):

make clean
ln -sf foobar-responder.go responder.go
make
mv ./server /where/you/want/grong-foobar


For the person who writes a responder
************************************

The interface of the responder is:

It must be in package "responder" and imports package "types". Read
"types.go" first, it contains useful constants (named from the RFC
1035).

The front-end checks that the request is a query and, if so, calls the
responder. The prototype is:

func Respond(query types.DNSquery, config map[string]interface{}) types.DNSresponse 

To see what is available for you in the query, see the description of
type DNSquery. Important: the query name (Qname) is always in
lowercase, to ease comparisons.

In the DNSresponse, RRs (Resource Records) have to be in the wire
format (the front-end does not know the format of the RR, to keep it
generic). For instance, data in TXT RR has to be {length,
value}. There are some utilities functions in types to help you to do
so.

The map named "config" above gives you access to global variables. You
can never be sure what variables are defined so it is careful to test
their existence before using them. Typical variables (read the source
code of server.go to find others) are:
* debug: an integer for the debug level (0 = no debug, 1 = a bit of
  debug, etc). Always set.
* servername: if set, a string identifying this specific name server
  (for instance "cdg1.a.ns.example.net").
* zonename: if set, the name of the zone currently served (for instance 
  "myself.example.net")

Since the map stores various types (the "interface{}", which means the
empty interface, something which is fulfilled by every possible
object), you often have to convert data with the reflect package. For
instance, to get the integer value of debug:
debug, exists := myconfig["debug"]
if exists {
	debugi := reflect.NewValue(debug).(*reflect.IntValue).Get()
}

The responder must also provide a function:

func Init(firstoption int) 

which will be called at server startup and which can be used to
process additional command-line flags (see as112.go for a good
example) or any other stuff.

Implementation notes
********************

One goroutine is run for every DNS request. Makes the code much
simpler and easier to read but may explain the fact that performance
are behind BIND.

TODO
****

Finish the AS112 responder (SOA and NS records)

The ability to listen to more than one address (but not all). Can I
give several -address option to the flag module? If so, it probably
just means firing several udpListeners and several tcpListeners. Since
it interacts with the IPv4/IPv6 listening abilities, we may have to
wait for the solution of
<http://code.google.com/p/go/issues/detail?id=679>.

Debugging of Go runtime performance issues, hit it harder with
queryperf!

Test with gccgo

Implements version.server (and version.bind and hostname.bind ?)

See if we can replace a good part of package "types" by standard
package net/ <http://golang.org/src/pkg/net/dnsmsg.go> It does not
seem easy, the dns* files do not export anything outside of package
net, they are meant for internal use only.

Daemonizing seems very difficult with Go
<http://groups.google.com/group/golang-nuts/browse_thread/thread/2b29d93b90501a4b/95242bfb7ae0549e>
In the mean time, nohup + & + disown seems the only solution. Provide
an example at least for Debian, using start-stop-daemon?

A name server with data, for instance able to serve a zone with a
simple setup, one SOA, a few NS, and one A record for www.$ORIGIN. The
list of zones (all with identical data) and the IP address of the Web
server being taken from a file or on the command-line.

Configuration file. What is idiomatic in Go? .INI ?
<https://github.com/cthom06/go-rproxy> uses JSON.

Continue hardening against rogue packets. See the example
test-scapy.py in the distribution.

Michael Hoisie had a very good suggestion to turn GRONG into a
package. He plans:
1) all the source files should have a common package, like "grong".
there shouldn't be a main package
2) there could be a Responder interface, that looks like:
type Responder interface {
    Respond(query.DNSquery) DNSresponse
}
And all the various responders would implement this.
3) The Makefile would have a format like (except modified for Grong):
http://github.com/hoisie/web.go/blob/master/Makefile
4) Instead of main() method, there would be a method like Run( resp
Responder ) that takes a responder and starts the server

Rewrite a good part of Grong to use Go DNS? https://github.com/miekg/godns

DNSSEC (no, I'm joking)


Author
******

Stéphane Bortzmeyer <stephane+grong@bortzmeyer.org>


License
*******

This is free software. Free as in free speech, not as in free beer.

See the actual license in LICENSE