# Go DNS and AXFR


I've implemented `axfr` in my [Go DNS
library](https://github.com/miekg/godns) in nice and Go-like way (at
least that's what I like to think).
Starting an `axfr` results in a channel which can then be used with
the `range` keyword to loop over it, until the entire `axfr` is
received.

# Using it
First the normal begin of a Go program:

    package main
    import (
        "fmt"
        "dns"           // DNS package
    )

Then we start the main function in which we define a new resolver and
a channel for receiving the `axfr` messages. The channels will
send `dns.xfr` messages which is defined as:

    type Xfr struct {
        Add bool // true is to be added, otherwise false
        RR
     }

This is facilitate IXFR handling, for an AXFR the bool is always set to `true`.

    func main() {
        res := new(resolver.Resolver)
        res.FromFile("/etc/resolv.conf")

        ch := make(chan dns.xfr) 

Next we setup the server and the `axfr` query:

        res.Servers = []string{"127.0.0.1"}
        m := new(dns.Msg)
        m.Question = make([]dns.Question, 1)
        // We are asking for an AXFR of atoom.net in the IN class
        m.Question[0] = dns.Question{"atoom.net", dns.TypeAXFR, dns.ClassINET}

And now the fun part:

        // Ask the server to start the AXFR
        go res.Axfr(m, ch)

        // And then loop over the answers and print them
        for x := range ch {
            fmt.Printf("%v\n",x.RR)
        }
        // Done with axfr, note the channel is now closed
    }

And that's it.