add dns proxy server

cmd/gost/cfg.go

@@ -223,9 +223,7 @@ func parseResolver(cfg string) gost.Resolver {
 					Addr:     s,
 					Protocol: "https",
 				}
-				if err := ns.Init(); err == nil {
 				nss = append(nss, ns)
-				}
 				continue
 			}
 
@@ -234,20 +232,16 @@ func parseResolver(cfg string) gost.Resolver {
 				ns := gost.NameServer{
 					Addr: ss[0],
 				}
-				if err := ns.Init(); err == nil {
 				nss = append(nss, ns)
 			}
-			}
 			if len(ss) == 2 {
 				ns := gost.NameServer{
 					Addr:     ss[0],
 					Protocol: ss[1],
 				}
-				if err := ns.Init(); err == nil {
 				nss = append(nss, ns)
 			}
 		}
-		}
 		return gost.NewResolver(0, nss...)
 	}
 	defer f.Close()

cmd/gost/route.go

@@ -477,6 +477,13 @@ func (r *route) GenRouters() ([]router, error) {
 					QueueSize: node.GetInt("queue"),
 				},
 			)
+		case "dns":
+			ln, err = gost.DNSListener(
+				node.Addr,
+				&gost.DNSOptions{
+					TCPMode: node.GetBool("tcp"),
+				},
+			)
 		default:
 			ln, err = gost.TCPListener(node.Addr)
 		}
@@ -518,6 +525,8 @@ func (r *route) GenRouters() ([]router, error) {
 			handler = gost.TunHandler()
 		case "tap":
 			handler = gost.TapHandler()
+		case "dns", "dot", "doh":
+			handler = gost.DNSHandler(node.Remote)
 		default:
 			// start from 2.5, if remote is not empty, then we assume that it is a forward tunnel.
 			if node.Remote != "" {
@@ -540,10 +549,14 @@ func (r *route) GenRouters() ([]router, error) {
 		}
 
 		node.Bypass = parseBypass(node.Get("bypass"))
-		resolver := parseResolver(node.Get("dns"))
 		hosts := parseHosts(node.Get("hosts"))
 		ips := parseIP(node.Get("ip"), "")
 
+		resolver := parseResolver(node.Get("dns"))
+		if resolver != nil {
+			resolver.Init(gost.ChainResolverOption(chain))
+		}
+
 		handler.Init(
 			gost.AddrHandlerOption(ln.Addr().String()),
 			gost.ChainHandlerOption(chain),

dns.go

@@ -0,0 +1,224 @@
+package gost
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"net"
+	"strconv"
+	"time"
+
+	"github.com/go-log/log"
+	"github.com/miekg/dns"
+)
+
+type dnsHandler struct {
+	options *HandlerOptions
+}
+
+// DNSHandler creates a Handler for DNS server.
+func DNSHandler(raddr string, opts ...HandlerOption) Handler {
+	h := &dnsHandler{}
+
+	for _, opt := range opts {
+		opt(h.options)
+	}
+	return h
+}
+
+func (h *dnsHandler) Init(opts ...HandlerOption) {
+	if h.options == nil {
+		h.options = &HandlerOptions{}
+	}
+
+	for _, opt := range opts {
+		opt(h.options)
+	}
+}
+
+func (h *dnsHandler) Handle(conn net.Conn) {
+	defer conn.Close()
+
+	b := mPool.Get().([]byte)
+	defer mPool.Put(b)
+
+	n, err := conn.Read(b)
+	if err != nil {
+		log.Logf("[dns] %s - %s: %v", conn.RemoteAddr(), conn.LocalAddr(), err)
+	}
+
+	mq := &dns.Msg{}
+	if err = mq.Unpack(b[:n]); err != nil {
+		log.Logf("[dns] %s - %s request unpack: %v", conn.RemoteAddr(), conn.LocalAddr(), err)
+		return
+	}
+	log.Logf("[dns] %s -> %s: %s", conn.RemoteAddr(), conn.LocalAddr(), h.dumpMsgHeader(mq))
+	if Debug {
+		log.Logf("[dns] %s >>> %s: %s", conn.RemoteAddr(), conn.LocalAddr(), mq.String())
+	}
+
+	start := time.Now()
+	reply, err := h.options.Resolver.Exchange(context.Background(), b[:n])
+	if err != nil {
+		log.Logf("[dns] %s - %s exchange: %v", conn.RemoteAddr(), conn.LocalAddr(), err)
+		return
+	}
+
+	rtt := time.Since(start)
+
+	mr := &dns.Msg{}
+	if err = mr.Unpack(reply); err != nil {
+		log.Logf("[dns] %s - %s reply unpack: %v", conn.RemoteAddr(), conn.LocalAddr(), err)
+		return
+	}
+	log.Logf("[dns] %s <- %s: %s [%s]",
+		conn.RemoteAddr(), conn.LocalAddr(), h.dumpMsgHeader(mr), rtt)
+	if Debug {
+		log.Logf("[dns] %s <<< %s: %s", conn.RemoteAddr(), conn.LocalAddr(), mr.String())
+	}
+
+	if _, err = conn.Write(reply); err != nil {
+		log.Logf("[dns] %s - %s reply unpack: %v", conn.RemoteAddr(), conn.LocalAddr(), err)
+	}
+}
+
+func (h *dnsHandler) dumpMsgHeader(m *dns.Msg) string {
+	buf := new(bytes.Buffer)
+	buf.WriteString(m.MsgHdr.String() + " ")
+	buf.WriteString("QUERY: " + strconv.Itoa(len(m.Question)) + ", ")
+	buf.WriteString("ANSWER: " + strconv.Itoa(len(m.Answer)) + ", ")
+	buf.WriteString("AUTHORITY: " + strconv.Itoa(len(m.Ns)) + ", ")
+	buf.WriteString("ADDITIONAL: " + strconv.Itoa(len(m.Extra)))
+	return buf.String()
+}
+
+type DNSOptions struct {
+	TCPMode      bool
+	UDPSize      int
+	ReadTimeout  time.Duration
+	WriteTimeout time.Duration
+}
+
+type dnsListener struct {
+	addr     net.Addr
+	server   *dns.Server
+	connChan chan net.Conn
+	errc     chan error
+}
+
+func DNSListener(addr string, options *DNSOptions) (Listener, error) {
+	if options == nil {
+		options = &DNSOptions{}
+	}
+
+	ln := &dnsListener{
+		connChan: make(chan net.Conn, 128),
+		errc:     make(chan error, 1),
+	}
+
+	var nets string
+	var err error
+
+	if options.TCPMode {
+		nets = "tcp"
+		ln.addr, err = net.ResolveTCPAddr("tcp", addr)
+	} else {
+		nets = "udp"
+		ln.addr, err = net.ResolveUDPAddr("udp", addr)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	ln.server = &dns.Server{
+		Addr: addr,
+		Net:  nets,
+	}
+
+	dns.HandleFunc(".", ln.handleRequest)
+
+	go func() {
+		if err := ln.server.ListenAndServe(); err != nil {
+			ln.errc <- err
+			return
+		}
+	}()
+
+	select {
+	case err := <-ln.errc:
+		return nil, err
+	default:
+	}
+
+	return ln, nil
+}
+
+func (l *dnsListener) handleRequest(w dns.ResponseWriter, m *dns.Msg) {
+	if w == nil || m == nil {
+		return
+	}
+
+	conn := &dnsServerConn{
+		mq:             make(chan []byte, 1),
+		ResponseWriter: w,
+	}
+
+	buf := mPool.Get().([]byte)
+	defer mPool.Put(buf)
+	buf = buf[:0]
+	b, err := m.PackBuffer(buf)
+	if err != nil {
+		log.Logf("[dns] %s: %v", l.addr, err)
+		return
+	}
+	conn.mq <- b
+
+	select {
+	case l.connChan <- conn:
+	default:
+		log.Logf("[dns] %s: connection queue is full", l.addr)
+	}
+}
+
+func (l *dnsListener) Accept() (conn net.Conn, err error) {
+	select {
+	case conn = <-l.connChan:
+	case err = <-l.errc:
+	}
+	return
+}
+
+func (l *dnsListener) Close() error {
+	return l.server.Shutdown()
+}
+
+func (l *dnsListener) Addr() net.Addr {
+	return l.addr
+}
+
+type dnsServerConn struct {
+	mq chan []byte
+	dns.ResponseWriter
+}
+
+func (c *dnsServerConn) Read(b []byte) (n int, err error) {
+	var mb []byte
+	select {
+	case mb = <-c.mq:
+	default:
+	}
+	n = copy(b, mb)
+	return
+}
+
+func (c *dnsServerConn) SetDeadline(t time.Time) error {
+	return &net.OpError{Op: "set", Net: "dns", Source: nil, Addr: nil, Err: errors.New("deadline not supported")}
+}
+
+func (c *dnsServerConn) SetReadDeadline(t time.Time) error {
+	return &net.OpError{Op: "set", Net: "dns", Source: nil, Addr: nil, Err: errors.New("deadline not supported")}
+}
+
+func (c *dnsServerConn) SetWriteDeadline(t time.Time) error {
+	return &net.OpError{Op: "set", Net: "dns", Source: nil, Addr: nil, Err: errors.New("deadline not supported")}
+}

go.mod

@@ -27,7 +27,7 @@ require (
 	github.com/lucas-clemente/aes12 v0.0.0-20171027163421-cd47fb39b79f // indirect
 	github.com/lucas-clemente/quic-go v0.10.0
 	github.com/lucas-clemente/quic-go-certificates v0.0.0-20160823095156-d2f86524cced // indirect
-	github.com/miekg/dns v1.1.3
+	github.com/miekg/dns v1.1.27
 	github.com/milosgajdos83/tenus v0.0.0-20190415114537-1f3ed00ae7d8
 	github.com/onsi/ginkgo v1.7.0 // indirect
 	github.com/onsi/gomega v1.4.3 // indirect
@@ -40,9 +40,8 @@ require (
 	github.com/templexxx/xor v0.0.0-20181023030647-4e92f724b73b // indirect
 	github.com/tjfoc/gmsm v1.0.1 // indirect
 	github.com/xtaci/tcpraw v1.2.25
-	golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2
+	golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550
-	golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3
+	golang.org/x/net v0.0.0-20190923162816-aa69164e4478
-	golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4 // indirect
 	gopkg.in/gorilla/websocket.v1 v1.4.0
 	gopkg.in/xtaci/kcp-go.v4 v4.3.2
 	gopkg.in/xtaci/smux.v1 v1.0.7

go.sum

@@ -58,6 +58,8 @@ github.com/lucas-clemente/quic-go-certificates v0.0.0-20160823095156-d2f86524cce
 github.com/lucas-clemente/quic-go-certificates v0.0.0-20160823095156-d2f86524cced/go.mod h1:NCcRLrOTZbzhZvixZLlERbJtDtYsmMw8Jc4vS8Z0g58=
 github.com/miekg/dns v1.1.3 h1:1g0r1IvskvgL8rR+AcHzUA+oFmGcQlaIm4IqakufeMM=
 github.com/miekg/dns v1.1.3/go.mod h1:W1PPwlIAgtquWBMBEV9nkV9Cazfe8ScdGz/Lj7v3Nrg=
+github.com/miekg/dns v1.1.27 h1:aEH/kqUzUxGJ/UHcEKdJY+ugH6WEzsEBBSPa8zuy1aM=
+github.com/miekg/dns v1.1.27/go.mod h1:KNUDUusw/aVsxyTYZM1oqvCicbwhgbNgztCETuNZ7xM=
 github.com/milosgajdos83/tenus v0.0.0-20190415114537-1f3ed00ae7d8 h1:4WFQEfEJ7zaHYViIVM2Cd6tnQOOhiEHbmQtlcV7aOpc=
 github.com/milosgajdos83/tenus v0.0.0-20190415114537-1f3ed00ae7d8/go.mod h1:G95Wwn625/q6JCCytI4VR/a5VtPwrtI0B+Q1Gi38QLA=
 github.com/onsi/ginkgo v1.6.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
@@ -88,23 +90,35 @@ golang.org/x/crypto v0.0.0-20190130090550-b01c7a725664 h1:YbZJ76lQ1BqNhVe7dKTSB6
 golang.org/x/crypto v0.0.0-20190130090550-b01c7a725664/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2 h1:VklqNMn3ovrHsnt90PveolxSbWFaJdECFbxSq0Mqo2M=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550 h1:ObdrDkeb4kJdCP557AjRjq69pTHfNouLtWZG7j9rPN8=
+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/mod v0.1.1-0.20191105210325-c90efee705ee/go.mod h1:QqPTAvyqsEbceGzBzNggFXnrqF1CaUcvgkdR5Ot7KZg=
 golang.org/x/net v0.0.0-20180906233101-161cd47e91fd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20181011144130-49bb7cea24b1/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190125091013-d26f9f9a57f3 h1:ulvT7fqt0yHWzpJwI57MezWnYDVpCAYBVuYst/L+fAY=
 golang.org/x/net v0.0.0-20190125091013-d26f9f9a57f3/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3 h1:0GoQqolDA55aaLxZyTzK/Y2ePZzZTUrRacwib7cNsYQ=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20190923162816-aa69164e4478 h1:l5EDrHhldLYb3ZRHDUhXF7Om7MvYXnkV9/iQNo1lX6g=
+golang.org/x/net v0.0.0-20190923162816-aa69164e4478/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4 h1:YUO/7uOKsKeq9UokNS62b8FYywz3ker1l1vDZRCRefw=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190228124157-a34e9553db1e h1:ZytStCyV048ZqDsWHiYDdoI2Vd4msMcrDECFxS+tL9c=
 golang.org/x/sys v0.0.0-20190228124157-a34e9553db1e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190405154228-4b34438f7a67 h1:1Fzlr8kkDLQwqMP8GxrhptBLqZG/EDpiATneiZHY998=
 golang.org/x/sys v0.0.0-20190405154228-4b34438f7a67/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190924154521-2837fb4f24fe h1:6fAMxZRR6sl1Uq8U61gxU+kPTs2tR8uOySCbBP7BN/M=
+golang.org/x/sys v0.0.0-20190924154521-2837fb4f24fe/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/tools v0.0.0-20191216052735-49a3e744a425/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
+golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/fsnotify.v1 v1.4.7 h1:xOHLXZwVvI9hhs+cLKq5+I5onOuwQLhQwiu63xxlHs4=

node.go

@@ -84,6 +84,7 @@ func ParseNode(s string) (node Node, err error) {
 	case "ohttp": // obfs-http
 	case "tun", "tap": // tun/tap device
 	case "ftcp": // fake TCP
+	case "dns", "dot", "doh":
 	default:
 		node.Transport = "tcp"
 	}
@@ -97,6 +98,7 @@ func ParseNode(s string) (node Node, err error) {
 	case "redirect": // TCP transparent proxy
 	case "tun", "tap": // tun/tap device
 	case "ftcp": // fake TCP
+	case "dns", "dot", "doh":
 	default:
 		node.Protocol = ""
 	}

resolver.go

@@ -17,7 +17,6 @@ import (
 
 	"github.com/go-log/log"
 	"github.com/miekg/dns"
-	"golang.org/x/net/http2"
 )
 
 var (
@@ -25,18 +24,23 @@ var (
 	DefaultResolverTimeout = 5 * time.Second
 )
 
-// Resolver is a name resolver for domain name.
+type nameServerOptions struct {
-// It contains a list of name servers.
+	timeout time.Duration
-type Resolver interface {
+	chain   *Chain
-	// Resolve returns a slice of that host's IPv4 and IPv6 addresses.
-	Resolve(host string) ([]net.IP, error)
 }
 
-// ReloadResolver is resolover that support live reloading.
+type NameServerOption func(*nameServerOptions)
-type ReloadResolver interface {
+
-	Resolver
+func TimeoutNameServerOption(timeout time.Duration) NameServerOption {
-	Reloader
+	return func(opts *nameServerOptions) {
-	Stoppable
+		opts.timeout = timeout
+	}
+}
+
+func ChainNameServerOption(chain *Chain) NameServerOption {
+	return func(opts *nameServerOptions) {
+		opts.chain = chain
+	}
 }
 
 // NameServer is a name server.
@@ -45,26 +49,23 @@ type NameServer struct {
 	Addr      string
 	Protocol  string
 	Hostname  string // for TLS handshake verification
-	Timeout   time.Duration
 	exchanger Exchanger
+	options   nameServerOptions
 }
 
 // Init initializes the name server.
-func (ns *NameServer) Init() error {
+func (ns *NameServer) Init(opts ...NameServerOption) error {
-	timeout := ns.Timeout
+	for _, opt := range opts {
-	if timeout <= 0 {
+		opt(&ns.options)
-		timeout = DefaultResolverTimeout
 	}
 
 	switch strings.ToLower(ns.Protocol) {
 	case "tcp":
-		ns.exchanger = &dnsExchanger{
+		ns.exchanger = NewDNSTCPExchanger(
-			endpoint: ns.Addr,
+			ns.Addr,
-			client: &dns.Client{
+			TimeoutExchangerOption(ns.options.timeout),
-				Net:     "tcp",
+			ChainExchangerOption(ns.options.chain),
-				Timeout: timeout,
+		)
-			},
-		}
 	case "tls":
 		cfg := &tls.Config{
 			ServerName: ns.Hostname,
@@ -72,51 +73,39 @@ func (ns *NameServer) Init() error {
 		if cfg.ServerName == "" {
 			cfg.InsecureSkipVerify = true
 		}
-
+		ns.exchanger = NewDoTExchanger(
-		ns.exchanger = &dnsExchanger{
+			ns.Addr, cfg,
-			endpoint: ns.Addr,
+			TimeoutExchangerOption(ns.options.timeout),
-			client: &dns.Client{
+			ChainExchangerOption(ns.options.chain),
-				Net:       "tcp-tls",
+		)
-				Timeout:   timeout,
-				TLSConfig: cfg,
-			},
-		}
 	case "https":
 		u, err := url.Parse(ns.Addr)
 		if err != nil {
 			return err
 		}
 		cfg := &tls.Config{ServerName: u.Hostname()}
-		transport := &http.Transport{
+		if cfg.ServerName == "" {
-			TLSClientConfig:    cfg,
+			cfg.InsecureSkipVerify = true
-			DisableCompression: true,
-			MaxIdleConns:       1,
-		}
-		http2.ConfigureTransport(transport)
-
-		ns.exchanger = &dohExchanger{
-			endpoint: u,
-			client: &http.Client{
-				Transport: transport,
-				Timeout:   timeout,
-			},
 		}
+		ns.exchanger = NewDoHExchanger(
+			u, cfg,
+			TimeoutExchangerOption(ns.options.timeout),
+			ChainExchangerOption(ns.options.chain),
+		)
 	case "udp":
 		fallthrough
 	default:
-		ns.exchanger = &dnsExchanger{
+		ns.exchanger = NewDNSExchanger(
-			endpoint: ns.Addr,
+			ns.Addr,
-			client: &dns.Client{
+			TimeoutExchangerOption(ns.options.timeout),
-				Net:     "udp",
+			ChainExchangerOption(ns.options.chain),
-				Timeout: timeout,
+		)
-			},
-		}
 	}
 
 	return nil
 }
 
-func (ns NameServer) String() string {
+func (ns *NameServer) String() string {
 	addr := ns.Addr
 	prot := ns.Protocol
 	if _, port, _ := net.SplitHostPort(addr); port == "" {
@@ -128,15 +117,48 @@ func (ns NameServer) String() string {
 	return fmt.Sprintf("%s/%s", addr, prot)
 }
 
+type resolverOptions struct {
+	chain *Chain
+}
+
+type ResolverOption func(*resolverOptions)
+
+func ChainResolverOption(chain *Chain) ResolverOption {
+	return func(opts *resolverOptions) {
+		opts.chain = chain
+	}
+}
+
+// Resolver is a name resolver for domain name.
+// It contains a list of name servers.
+type Resolver interface {
+	// Init initializes the Resolver instance.
+	Init(opts ...ResolverOption) error
+	// Resolve returns a slice of that host's IPv4 and IPv6 addresses.
+	Resolve(host string) ([]net.IP, error)
+	// Exchange performs a synchronous query,
+	// It sends the message query and waits for a reply.
+	Exchange(ctx context.Context, query []byte) (reply []byte, err error)
+}
+
+// ReloadResolver is resolover that support live reloading.
+type ReloadResolver interface {
+	Resolver
+	Reloader
+	Stoppable
+}
+
 type resolver struct {
 	Servers []NameServer
 	mCache  *sync.Map
 	TTL     time.Duration
+	timeout time.Duration
 	period  time.Duration
 	domain  string
 	stopped chan struct{}
 	mux     sync.RWMutex
 	prefer  string // ipv4 or ipv6
+	options resolverOptions
 }
 
 // NewResolver create a new Resolver with the given name servers and resolution timeout.
@@ -154,6 +176,34 @@ func newResolver(ttl time.Duration, servers ...NameServer) *resolver {
 	}
 }
 
+func (r *resolver) Init(opts ...ResolverOption) error {
+	if r == nil {
+		return nil
+	}
+
+	r.mux.Lock()
+	defer r.mux.Unlock()
+
+	for _, opt := range opts {
+		opt(&r.options)
+	}
+
+	var nss []NameServer
+	for _, ns := range r.Servers {
+		if err := ns.Init( // init all name servers
+			ChainNameServerOption(r.options.chain),
+			TimeoutNameServerOption(r.timeout),
+		); err != nil {
+			continue // ignore invalid name servers
+		}
+		nss = append(nss, ns)
+	}
+
+	r.Servers = nss
+
+	return nil
+}
+
 func (r *resolver) copyServers() []NameServer {
 	var servers []NameServer
 	for i := range r.Servers {
@@ -196,12 +246,12 @@ func (r *resolver) Resolve(host string) (ips []net.IP, err error) {
 	for _, ns := range servers {
 		ips, ttl, err = r.resolve(ns.exchanger, host)
 		if err != nil {
-			log.Logf("[resolver] %s via %s : %s", host, ns, err)
+			log.Logf("[resolver] %s via %s : %s", host, ns.String(), err)
 			continue
 		}
 
 		if Debug {
-			log.Logf("[resolver] %s via %s %v(ttl: %v)", host, ns, ips, ttl)
+			log.Logf("[resolver] %s via %s %v(ttl: %v)", host, ns.String(), ips, ttl)
 		}
 		if len(ips) > 0 {
 			break
@@ -233,10 +283,24 @@ func (r *resolver) resolve(ex Exchanger, host string) (ips []net.IP, ttl time.Du
 }
 
 func (*resolver) resolveIPs(ctx context.Context, ex Exchanger, query *dns.Msg) (ips []net.IP, ttl time.Duration, err error) {
-	mr, err := ex.Exchange(ctx, query)
+	// buf := mPool.Get().([]byte)
+	// defer mPool.Put(buf)
+
+	//	buf = buf[:0]
+	//	mq, err := query.PackBuffer(buf)
+	mq, err := query.Pack()
 	if err != nil {
 		return
 	}
+	reply, err := ex.Exchange(ctx, mq)
+	if err != nil {
+		return
+	}
+	mr := &dns.Msg{}
+	if err = mr.Unpack(reply); err != nil {
+		return
+	}
+
 	for _, ans := range mr.Answer {
 		if ar, _ := ans.(*dns.AAAA); ar != nil {
 			ips = append(ips, ar.AAAA)
@@ -250,6 +314,25 @@ func (*resolver) resolveIPs(ctx context.Context, ex Exchanger, query *dns.Msg) (
 	return
 }
 
+func (r *resolver) Exchange(ctx context.Context, query []byte) (reply []byte, err error) {
+	if r == nil {
+		return
+	}
+
+	var servers []NameServer
+	r.mux.RLock()
+	servers = r.copyServers()
+	r.mux.RUnlock()
+
+	for _, ns := range servers {
+		reply, err = ns.exchanger.Exchange(ctx, query)
+		if err == nil {
+			return
+		}
+	}
+	return
+}
+
 type resolverCacheItem struct {
 	IPs []net.IP
 	ts  int64
@@ -352,13 +435,9 @@ func (r *resolver) Reload(rd io.Reader) error {
 			if strings.HasPrefix(ns.Addr, "https") {
 				ns.Protocol = "https"
 			}
-			ns.Timeout = timeout
-
-			if err := ns.Init(); err == nil {
 			nss = append(nss, ns)
 		}
 	}
-	}
 
 	if err := scanner.Err(); err != nil {
 		return err
@@ -366,12 +445,15 @@ func (r *resolver) Reload(rd io.Reader) error {
 
 	r.mux.Lock()
 	r.TTL = ttl
+	r.timeout = timeout
 	r.domain = domain
 	r.period = period
 	r.prefer = prefer
 	r.Servers = nss
 	r.mux.Unlock()
 
+	r.Init()
+
 	return nil
 }
 
@@ -425,62 +507,270 @@ func (r *resolver) String() string {
 
 // Exchanger is an interface for DNS synchronous query.
 type Exchanger interface {
-	Exchange(ctx context.Context, query *dns.Msg) (*dns.Msg, error)
+	Exchange(ctx context.Context, query []byte) ([]byte, error)
+}
+
+type exchangerOptions struct {
+	chain   *Chain
+	timeout time.Duration
+}
+
+type ExchangerOption func(opts *exchangerOptions)
+
+func ChainExchangerOption(chain *Chain) ExchangerOption {
+	return func(opts *exchangerOptions) {
+		opts.chain = chain
+	}
+}
+
+func TimeoutExchangerOption(timeout time.Duration) ExchangerOption {
+	return func(opts *exchangerOptions) {
+		opts.timeout = timeout
+	}
 }
 
 type dnsExchanger struct {
-	endpoint string
+	addr    string
-	client   *dns.Client
+	options exchangerOptions
 }
 
-func (ex *dnsExchanger) Exchange(ctx context.Context, query *dns.Msg) (*dns.Msg, error) {
+func NewDNSExchanger(addr string, opts ...ExchangerOption) Exchanger {
-	ep := ex.endpoint
+	var options exchangerOptions
-	if _, port, _ := net.SplitHostPort(ep); port == "" {
+	for _, opt := range opts {
-		ep = net.JoinHostPort(ep, "53")
+		opt(&options)
 	}
-	mr, _, err := ex.client.Exchange(query, ep)
+
-	return mr, err
+	if _, port, _ := net.SplitHostPort(addr); port == "" {
+		addr = net.JoinHostPort(addr, "53")
+	}
+
+	return &dnsExchanger{
+		addr:    addr,
+		options: options,
+	}
+}
+
+func (ex *dnsExchanger) dial(ctx context.Context, network, address string) (conn net.Conn, err error) {
+	if ex.options.chain.IsEmpty() {
+		d := &net.Dialer{
+			Timeout: ex.options.timeout,
+		}
+		return d.DialContext(ctx, network, address)
+	}
+
+	raddr, err := net.ResolveUDPAddr(network, address)
+	if err != nil {
+		return
+	}
+	cc, err := getSOCKS5UDPTunnel(ex.options.chain, nil)
+	conn = &udpTunnelConn{Conn: cc, raddr: raddr}
+	return
+}
+
+func (ex *dnsExchanger) Exchange(ctx context.Context, query []byte) ([]byte, error) {
+	c, err := ex.dial(ctx, "udp", ex.addr)
+	if err != nil {
+		return nil, err
+	}
+
+	mq := &dns.Msg{}
+	if err = mq.Unpack(query); err != nil {
+		return nil, err
+	}
+
+	conn := &dns.Conn{
+		Conn: c,
+	}
+
+	if err = conn.WriteMsg(mq); err != nil {
+		return nil, err
+	}
+
+	mr, err := conn.ReadMsg()
+	if err != nil {
+		return nil, err
+	}
+
+	return mr.Pack()
+}
+
+type dnsTCPExchanger struct {
+	addr    string
+	options exchangerOptions
+}
+
+func NewDNSTCPExchanger(addr string, opts ...ExchangerOption) Exchanger {
+	var options exchangerOptions
+	for _, opt := range opts {
+		opt(&options)
+	}
+
+	if _, port, _ := net.SplitHostPort(addr); port == "" {
+		addr = net.JoinHostPort(addr, "53")
+	}
+
+	return &dnsTCPExchanger{
+		addr:    addr,
+		options: options,
+	}
+}
+
+func (ex *dnsTCPExchanger) dial(ctx context.Context, network, address string) (conn net.Conn, err error) {
+	if ex.options.chain.IsEmpty() {
+		d := &net.Dialer{
+			Timeout: ex.options.timeout,
+		}
+		return d.DialContext(ctx, network, address)
+	}
+	return ex.options.chain.Dial(address, TimeoutChainOption(ex.options.timeout))
+}
+
+func (ex *dnsTCPExchanger) Exchange(ctx context.Context, query []byte) ([]byte, error) {
+	c, err := ex.dial(ctx, "tcp", ex.addr)
+	if err != nil {
+		return nil, err
+	}
+
+	conn := &dns.Conn{
+		Conn: c,
+	}
+
+	if _, err = conn.Write(query); err != nil {
+		return nil, err
+	}
+
+	mr, err := conn.ReadMsg()
+	if err != nil {
+		log.Log("[dns] exchange", err)
+		return nil, err
+	}
+
+	return mr.Pack()
+}
+
+type dotExchanger struct {
+	addr      string
+	tlsConfig *tls.Config
+	options   exchangerOptions
+}
+
+func NewDoTExchanger(addr string, tlsConfig *tls.Config, opts ...ExchangerOption) Exchanger {
+	var options exchangerOptions
+	for _, opt := range opts {
+		opt(&options)
+	}
+
+	if _, port, _ := net.SplitHostPort(addr); port == "" {
+		addr = net.JoinHostPort(addr, "53")
+	}
+
+	if tlsConfig == nil {
+		tlsConfig = &tls.Config{
+			InsecureSkipVerify: true,
+		}
+	}
+	return &dotExchanger{
+		addr:      addr,
+		tlsConfig: tlsConfig,
+		options:   options,
+	}
+}
+
+func (ex *dotExchanger) dial(ctx context.Context, network, address string) (conn net.Conn, err error) {
+	if ex.options.chain.IsEmpty() {
+		d := &net.Dialer{
+			Timeout: ex.options.timeout,
+		}
+		conn, err = d.DialContext(ctx, network, address)
+	} else {
+		conn, err = ex.options.chain.Dial(address, TimeoutChainOption(ex.options.timeout))
+	}
+	if err == nil {
+		conn = tls.Client(conn, ex.tlsConfig)
+	}
+	return
+}
+
+func (ex *dotExchanger) Exchange(ctx context.Context, query []byte) ([]byte, error) {
+	c, err := ex.dial(ctx, "tcp", ex.addr)
+	if err != nil {
+		return nil, err
+	}
+
+	conn := &dns.Conn{
+		Conn: c,
+	}
+
+	if _, err = conn.Write(query); err != nil {
+		return nil, err
+	}
+
+	mr, err := conn.ReadMsg()
+	if err != nil {
+		return nil, err
+	}
+
+	return mr.Pack()
 }
 
 type dohExchanger struct {
 	endpoint *url.URL
 	client   *http.Client
+	options  exchangerOptions
 }
 
-// reference: https://github.com/cloudflare/cloudflared/blob/master/tunneldns/https_upstream.go#L54
+func NewDoHExchanger(urlStr *url.URL, tlsConfig *tls.Config, opts ...ExchangerOption) Exchanger {
-func (ex *dohExchanger) Exchange(ctx context.Context, query *dns.Msg) (*dns.Msg, error) {
+	var options exchangerOptions
-	queryBuf, err := query.Pack()
+	for _, opt := range opts {
-	if err != nil {
+		opt(&options)
-		return nil, fmt.Errorf("failed to pack DNS query: %s", err)
+	}
+	ex := &dohExchanger{
+		endpoint: urlStr,
+		options:  options,
 	}
 
-	// No content negotiation for now, use DNS wire format
+	ex.client = &http.Client{
-	buf, backendErr := ex.exchangeWireformat(queryBuf)
+		Timeout: options.timeout,
-	if backendErr == nil {
+		Transport: &http.Transport{
-		response := &dns.Msg{}
+			// Proxy: ProxyFromEnvironment,
-		if err := response.Unpack(buf); err != nil {
+			TLSClientConfig:       tlsConfig,
-			return nil, fmt.Errorf("failed to unpack DNS response from body: %s", err)
+			ForceAttemptHTTP2:     true,
+			MaxIdleConns:          100,
+			IdleConnTimeout:       90 * time.Second,
+			TLSHandshakeTimeout:   options.timeout,
+			ExpectContinueTimeout: 1 * time.Second,
+			DialContext:           ex.dialContext,
+		},
 	}
 
-		response.Id = query.Id
+	return ex
-		return response, nil
-	}
-
-	return nil, backendErr
 }
 
-// Perform message exchange with the default UDP wireformat defined in current draft
+func (ex *dohExchanger) dialContext(ctx context.Context, network, address string) (conn net.Conn, err error) {
-// https://datatracker.ietf.org/doc/draft-ietf-doh-dns-over-https
+	if ex.options.chain.IsEmpty() {
-func (ex *dohExchanger) exchangeWireformat(msg []byte) ([]byte, error) {
+		d := &net.Dialer{
-	req, err := http.NewRequest("POST", ex.endpoint.String(), bytes.NewBuffer(msg))
+			Timeout: ex.options.timeout,
+		}
+		return d.DialContext(ctx, network, address)
+	}
+	return ex.options.chain.Dial(address, TimeoutChainOption(ex.options.timeout))
+}
+
+func (ex *dohExchanger) Exchange(ctx context.Context, query []byte) ([]byte, error) {
+	req, err := http.NewRequestWithContext(ctx, "POST", ex.endpoint.String(), bytes.NewBuffer(query))
 	if err != nil {
 		return nil, fmt.Errorf("failed to create an HTTPS request: %s", err)
 	}
 
-	req.Header.Add("Content-Type", "application/dns-udpwireformat")
+	// req.Header.Add("Content-Type", "application/dns-udpwireformat")
+	req.Header.Add("Content-Type", "application/dns-message")
 	req.Host = ex.endpoint.Hostname()
 
-	resp, err := ex.client.Do(req)
+	client := ex.client
+	if client == nil {
+		client = http.DefaultClient
+	}
+	resp, err := client.Do(req)
 	if err != nil {
 		return nil, fmt.Errorf("failed to perform an HTTPS request: %s", err)
 	}