newdns
A library for building custom DNS servers in Go.
The newdns library wraps the widely used, but low-level github.com/miekg/dns package with a simple interface to quickly build custom DNS servers. The implemented server only supports a subset of record types (A, AAAA, CNAME, MX, TXT) and is intended to be used as a leaf authoritative name server only. It supports UDP and TCP as transport protocols and implements EDNS0. Conformance is tested by issuing a corpus of tests against a zone in AWS Route53 and comparing the response and behavior.
The intention of this project is not to build a feature-complete alternative to "managed zone" offerings by major cloud platforms. However, some projects may require frequent synchronization of many records between a custom database and a cloud-hosted "managed zone". In this scenario, a custom DNS server that queries the own database might be a lot simpler to manage and operate. Also, the distributed nature of the DNS system offers interesting qualities that could be leveraged by future applications.
Example
// create zone
zone := &newdns.Zone{
Name: "example.com.",
MasterNameServer: "ns1.hostmaster.com.",
AllNameServers: []string{
"ns1.hostmaster.com.",
"ns2.hostmaster.com.",
"ns3.hostmaster.com.",
},
Handler: func(name string) ([]newdns.Set, error) {
// return apex records
if name == "" {
return []newdns.Set{
{
Name: "example.com.",
Type: newdns.A,
Records: []newdns.Record{
{Address: "1.2.3.4"},
},
},
{
Name: "example.com.",
Type: newdns.AAAA,
Records: []newdns.Record{
{Address: "1:2:3:4::"},
},
},
}, nil
}
// return sub records
if name == "foo" {
return []newdns.Set{
{
Name: "foo.example.com.",
Type: newdns.CNAME,
Records: []newdns.Record{
{Address: "bar.example.com."},
},
},
}, nil
}
return nil, nil
},
}
// create server
server := newdns.NewServer(newdns.Config{
Handler: func(name string) (*newdns.Zone, error) {
// check name
if newdns.InZone("example.com.", name) {
return zone, nil
}
return nil, nil
},
Logger: func(e newdns.Event, msg *dns.Msg, err error, reason string) {
fmt.Println(e, err, reason)
},
})
// run server
go func() {
err := server.Run(":1337")
if err != nil {
panic(err)
}
}()
// print info
fmt.Println("Query apex: dig example.com @0.0.0.0 -p 1337")
fmt.Println("Query other: dig foo.example.com @0.0.0.0 -p 1337")
// wait forever
select {}