├── setup.go ├── README.md ├── demo.go └── LICENSE /setup.go: -------------------------------------------------------------------------------- 1 | package demo 2 | 3 | import ( 4 | "github.com/coredns/caddy" 5 | "github.com/coredns/coredns/core/dnsserver" 6 | "github.com/coredns/coredns/plugin" 7 | ) 8 | 9 | func init() { 10 | caddy.RegisterPlugin("demo", caddy.Plugin{ 11 | ServerType: "dns", 12 | Action: setup, 13 | }) 14 | } 15 | 16 | func setup(c *caddy.Controller) error { 17 | c.Next() // 'demo' 18 | if c.NextArg() { 19 | return plugin.Error("demo", c.ArgErr()) 20 | } 21 | 22 | dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler { 23 | return Demo{} 24 | }) 25 | 26 | return nil 27 | } 28 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # demo 2 | 3 | ## Name 4 | 5 | *demo* - returns `1.1.1.1` for `172.0.0.0/8` or `127.0.0.0/8` and `8.8.8.8` otherwise 6 | 7 | ## Description 8 | 9 | This demo plugin showcases the implementation of source IP based service discovery. 10 | It is intended as a boilerplate code, so that anyone that is interested in coredns 11 | implementation could build their plugin on top of this demo plugin. 12 | 13 | This demo plugin and its full code has been walked through in past KubeCon talks 14 | 15 | Note: In order to add a new plugin, an additional step of `make gen` is needed. Therefore, 16 | to build the coredns with demo plugin the following should be used: 17 | ``` 18 | docker run -it --rm -v $PWD:/v -w /v golang:1.16 sh -c 'make gen && make' 19 | ``` 20 | 21 | ## Syntax 22 | 23 | ~~~ txt 24 | demo 25 | ~~~ 26 | 27 | ## Also See 28 | 29 | See the [manual](https://coredns.io/manual). 30 | -------------------------------------------------------------------------------- /demo.go: -------------------------------------------------------------------------------- 1 | // Package demo implements a plugin. 2 | package demo 3 | 4 | import ( 5 | "context" 6 | "fmt" 7 | "net" 8 | "strings" 9 | 10 | "github.com/coredns/coredns/request" 11 | 12 | "github.com/miekg/dns" 13 | ) 14 | 15 | // Demo is a plugin in CoreDNS 16 | type Demo struct{} 17 | 18 | // ServeDNS implements the plugin.Handler interface. 19 | func (p Demo) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) { 20 | state := request.Request{W: w, Req: r} 21 | qname := state.Name() 22 | 23 | reply := "8.8.8.8" 24 | if strings.HasPrefix(state.IP(), "172.") || strings.HasPrefix(state.IP(), "127.") { 25 | reply = "1.1.1.1" 26 | } 27 | fmt.Printf("Received query %s from %s, expected to reply %s\n", qname, state.IP(), reply) 28 | 29 | answers := []dns.RR{} 30 | 31 | if state.QType() != dns.TypeA { 32 | return dns.RcodeNameError, nil 33 | } 34 | 35 | rr := new(dns.A) 36 | rr.Hdr = dns.RR_Header{Name: qname, Rrtype: dns.TypeA, Class: dns.ClassINET} 37 | rr.A = net.ParseIP(reply).To4() 38 | 39 | answers = append(answers, rr) 40 | 41 | m := new(dns.Msg) 42 | m.SetReply(r) 43 | m.Authoritative = true 44 | m.Answer = answers 45 | 46 | w.WriteMsg(m) 47 | return dns.RcodeSuccess, nil 48 | } 49 | 50 | // Name implements the Handler interface. 51 | func (p Demo) Name() string { return "demo" } 52 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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