mirror of
https://github.com/miekg/dns.git
synced 2025-08-11 20:16:58 +02:00
139 lines
2.8 KiB
Go
139 lines
2.8 KiB
Go
/*
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* A name server which sends back the IP address of its client, the
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* recursive resolver. When queried for type TXT, it sends back the text
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* form of the address. When queried for type A (resp. AAAA), it sends
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* back the IPv4 (resp. v6) address.
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*
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* Similar services: whoami.ultradns.net, whoami.akamai.net. Also (but it
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* is not their normal goal): rs.dns-oarc.net, porttest.dns-oarc.net,
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* amiopen.openresolvers.org.
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*
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* Stephane Bortzmeyer <stephane+grong@bortzmeyer.org>
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*
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* Adapted to Go DNS (i.e. completely rewritten)
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* Miek Gieben <miek@miek.nl>
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*/
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package main
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import (
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"os"
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"os/signal"
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"net"
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"dns"
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"fmt"
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"strconv"
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)
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func reply(a net.Addr, in *dns.Msg, tcp bool) *dns.Msg {
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if in.MsgHdr.Response == true {
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return nil // Don't answer responses
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}
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m := new(dns.Msg)
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m.MsgHdr.Id = in.MsgHdr.Id
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m.MsgHdr.Authoritative = true
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m.MsgHdr.Response = true
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m.MsgHdr.Opcode = dns.OpcodeQuery
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m.MsgHdr.Rcode = dns.RcodeSuccess
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m.Question = make([]dns.Question, 1)
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m.Answer = make([]dns.RR, 1)
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m.Extra = make([]dns.RR, 1)
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r := new(dns.RR_A)
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r.Hdr = dns.RR_Header{Name: "whoami.miek.nl.", Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 0}
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ip, _ := net.ResolveUDPAddr(a.String())
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r.A = ip.IP
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t := new(dns.RR_TXT)
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t.Hdr = dns.RR_Header{Name: "whoami.miek.nl.", Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}
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if tcp {
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t.Txt = "Port: " + strconv.Itoa(ip.Port) + " (tcp)"
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} else {
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t.Txt = "Port: " + strconv.Itoa(ip.Port) + " (udp)"
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}
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m.Question[0] = in.Question[0]
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m.Answer[0] = r
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m.Extra[0] = t
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return m
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}
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func replyUDP(c *net.UDPConn, a net.Addr, in *dns.Msg) {
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m := reply(a, in, false)
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if m == nil {
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return
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}
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fmt.Fprintf(os.Stderr, "%v\n", m)
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out, ok := m.Pack()
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if !ok {
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println("Failed to pack")
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return
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}
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dns.SendUDP(out, c, a)
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}
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func replyTCP(c *net.TCPConn, a net.Addr, in *dns.Msg) {
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m := reply(a, in, true)
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if m == nil {
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return
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}
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fmt.Fprintf(os.Stderr, "%v\n", m)
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out, ok := m.Pack()
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if !ok {
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println("Failed to pack")
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return
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}
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dns.SendTCP(out, c, a)
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}
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func tcp(addr string, e chan os.Error) {
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a, err := net.ResolveTCPAddr(addr)
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if err != nil {
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e <- err
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}
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l, err := net.ListenTCP("tcp", a)
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if err != nil {
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e <- err
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}
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err = dns.ServeTCP(l, replyTCP)
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e <- err
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return
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}
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func udp(addr string, e chan os.Error) {
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a, err := net.ResolveUDPAddr(addr)
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if err != nil {
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e <- err
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}
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l, err := net.ListenUDP("udp", a)
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if err != nil {
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e <- err
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}
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err = dns.ServeUDP(l, replyUDP)
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e <- err
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return
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}
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func main() {
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e := make(chan os.Error)
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go udp("127.0.0.1:8053", e)
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go udp("[::1]:8053", e)
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go tcp("127.0.0.1:8053", e)
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go tcp("[::1]:8053", e)
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forever:
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for {
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// Wait for a signal to stop
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select {
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case err := <-e:
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fmt.Printf("Error received, stopping: %s\n", err.String())
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break forever
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case <-signal.Incoming:
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fmt.Printf("Signal received, stopping\n")
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break forever
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}
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}
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close(e)
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}
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