package main import ( "io/ioutil" "net" "os" "os/signal" "syscall" "github.com/AdguardTeam/golibs/log" "github.com/ameshkov/dnscrypt/v2" "github.com/miekg/dns" "gopkg.in/yaml.v3" ) // ServerArgs - "server" command arguments type ServerArgs struct { Config string `short:"c" long:"config" description:"Path to the DNSCrypt configuration file" required:"true"` Forward string `short:"f" long:"forward" description:"Forwards DNS queries to the specified address" default:"94.140.14.140:53"` ListenAddrs []string `short:"l" long:"listen" description:"Listening addresses" default:"0.0.0.0"` ListenPorts []int `short:"p" long:"port" description:"Listening ports" default:"443"` } // server - runs a DNSCrypt server func server(args ServerArgs) { log.Info("Starting DNSCrypt server") b, err := ioutil.ReadFile(args.Config) if err != nil { log.Fatalf("failed to read the configuration: %v", err) } rc := dnscrypt.ResolverConfig{} err = yaml.Unmarshal(b, &rc) if err != nil { log.Fatalf("failed to deserialize configuration: %v", err) } cert, err := rc.CreateCert() if err != nil { log.Fatalf("failed to generate certificate: %v", err) } s := &dnscrypt.Server{ ProviderName: rc.ProviderName, ResolverCert: cert, Handler: &forwardHandler{addr: args.Forward}, } tcp, udp := createListeners(args) for _, t := range tcp { log.Info("Listening to tcp://%s", t.Addr().String()) listen := t go func() { _ = s.ServeTCP(listen) }() } for _, u := range udp { log.Info("Listening to udp://%s", u.LocalAddr().String()) listen := u go func() { _ = s.ServeUDP(listen) }() } signalChannel := make(chan os.Signal, 1) signal.Notify(signalChannel, syscall.SIGINT, syscall.SIGTERM) <-signalChannel log.Info("Closing all listeners") for _, t := range tcp { _ = t.Close() } for _, u := range udp { _ = u.Close() } } // createListeners - creates listeners for our server func createListeners(args ServerArgs) (tcp []net.Listener, udp []*net.UDPConn) { for _, addr := range args.ListenAddrs { ip := net.ParseIP(addr) if ip == nil { log.Fatalf("invalid listen address: %s", addr) } for _, port := range args.ListenPorts { tcpListen, err := net.ListenTCP("tcp", &net.TCPAddr{IP: ip, Port: port}) if err != nil { log.Fatalf("failed to start TCP listener: %v", err) } udpListen, err := net.ListenUDP("udp", &net.UDPAddr{IP: ip, Port: port}) if err != nil { log.Fatalf("failed to start UDP listener: %v", err) } tcp = append(tcp, tcpListen) udp = append(udp, udpListen) } } return } type forwardHandler struct { addr string } // ServeDNS - implements Handler interface func (f *forwardHandler) ServeDNS(rw dnscrypt.ResponseWriter, r *dns.Msg) error { res, err := dns.Exchange(r, f.addr) if err != nil { return err } return rw.WriteMsg(res) }