Vendor main dependencies.

vendor/github.com/miekg/dns/server.go

@@ -0,0 +1,734 @@
+// DNS server implementation.
+
+package dns
+
+import (
+	"bytes"
+	"crypto/tls"
+	"encoding/binary"
+	"io"
+	"net"
+	"sync"
+	"time"
+)
+
+// Maximum number of TCP queries before we close the socket.
+const maxTCPQueries = 128
+
+// Handler is implemented by any value that implements ServeDNS.
+type Handler interface {
+	ServeDNS(w ResponseWriter, r *Msg)
+}
+
+// A ResponseWriter interface is used by an DNS handler to
+// construct an DNS response.
+type ResponseWriter interface {
+	// LocalAddr returns the net.Addr of the server
+	LocalAddr() net.Addr
+	// RemoteAddr returns the net.Addr of the client that sent the current request.
+	RemoteAddr() net.Addr
+	// WriteMsg writes a reply back to the client.
+	WriteMsg(*Msg) error
+	// Write writes a raw buffer back to the client.
+	Write([]byte) (int, error)
+	// Close closes the connection.
+	Close() error
+	// TsigStatus returns the status of the Tsig.
+	TsigStatus() error
+	// TsigTimersOnly sets the tsig timers only boolean.
+	TsigTimersOnly(bool)
+	// Hijack lets the caller take over the connection.
+	// After a call to Hijack(), the DNS package will not do anything with the connection.
+	Hijack()
+}
+
+type response struct {
+	hijacked       bool // connection has been hijacked by handler
+	tsigStatus     error
+	tsigTimersOnly bool
+	tsigRequestMAC string
+	tsigSecret     map[string]string // the tsig secrets
+	udp            *net.UDPConn      // i/o connection if UDP was used
+	tcp            net.Conn          // i/o connection if TCP was used
+	udpSession     *SessionUDP       // oob data to get egress interface right
+	remoteAddr     net.Addr          // address of the client
+	writer         Writer            // writer to output the raw DNS bits
+}
+
+// ServeMux is an DNS request multiplexer. It matches the
+// zone name of each incoming request against a list of
+// registered patterns add calls the handler for the pattern
+// that most closely matches the zone name. ServeMux is DNSSEC aware, meaning
+// that queries for the DS record are redirected to the parent zone (if that
+// is also registered), otherwise the child gets the query.
+// ServeMux is also safe for concurrent access from multiple goroutines.
+type ServeMux struct {
+	z map[string]Handler
+	m *sync.RWMutex
+}
+
+// NewServeMux allocates and returns a new ServeMux.
+func NewServeMux() *ServeMux { return &ServeMux{z: make(map[string]Handler), m: new(sync.RWMutex)} }
+
+// DefaultServeMux is the default ServeMux used by Serve.
+var DefaultServeMux = NewServeMux()
+
+// The HandlerFunc type is an adapter to allow the use of
+// ordinary functions as DNS handlers.  If f is a function
+// with the appropriate signature, HandlerFunc(f) is a
+// Handler object that calls f.
+type HandlerFunc func(ResponseWriter, *Msg)
+
+// ServeDNS calls f(w, r).
+func (f HandlerFunc) ServeDNS(w ResponseWriter, r *Msg) {
+	f(w, r)
+}
+
+// HandleFailed returns a HandlerFunc that returns SERVFAIL for every request it gets.
+func HandleFailed(w ResponseWriter, r *Msg) {
+	m := new(Msg)
+	m.SetRcode(r, RcodeServerFailure)
+	// does not matter if this write fails
+	w.WriteMsg(m)
+}
+
+func failedHandler() Handler { return HandlerFunc(HandleFailed) }
+
+// ListenAndServe Starts a server on address and network specified Invoke handler
+// for incoming queries.
+func ListenAndServe(addr string, network string, handler Handler) error {
+	server := &Server{Addr: addr, Net: network, Handler: handler}
+	return server.ListenAndServe()
+}
+
+// ListenAndServeTLS acts like http.ListenAndServeTLS, more information in
+// http://golang.org/pkg/net/http/#ListenAndServeTLS
+func ListenAndServeTLS(addr, certFile, keyFile string, handler Handler) error {
+	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
+	if err != nil {
+		return err
+	}
+
+	config := tls.Config{
+		Certificates: []tls.Certificate{cert},
+	}
+
+	server := &Server{
+		Addr:      addr,
+		Net:       "tcp-tls",
+		TLSConfig: &config,
+		Handler:   handler,
+	}
+
+	return server.ListenAndServe()
+}
+
+// ActivateAndServe activates a server with a listener from systemd,
+// l and p should not both be non-nil.
+// If both l and p are not nil only p will be used.
+// Invoke handler for incoming queries.
+func ActivateAndServe(l net.Listener, p net.PacketConn, handler Handler) error {
+	server := &Server{Listener: l, PacketConn: p, Handler: handler}
+	return server.ActivateAndServe()
+}
+
+func (mux *ServeMux) match(q string, t uint16) Handler {
+	mux.m.RLock()
+	defer mux.m.RUnlock()
+	var handler Handler
+	b := make([]byte, len(q)) // worst case, one label of length q
+	off := 0
+	end := false
+	for {
+		l := len(q[off:])
+		for i := 0; i < l; i++ {
+			b[i] = q[off+i]
+			if b[i] >= 'A' && b[i] <= 'Z' {
+				b[i] |= ('a' - 'A')
+			}
+		}
+		if h, ok := mux.z[string(b[:l])]; ok { // causes garbage, might want to change the map key
+			if t != TypeDS {
+				return h
+			}
+			// Continue for DS to see if we have a parent too, if so delegeate to the parent
+			handler = h
+		}
+		off, end = NextLabel(q, off)
+		if end {
+			break
+		}
+	}
+	// Wildcard match, if we have found nothing try the root zone as a last resort.
+	if h, ok := mux.z["."]; ok {
+		return h
+	}
+	return handler
+}
+
+// Handle adds a handler to the ServeMux for pattern.
+func (mux *ServeMux) Handle(pattern string, handler Handler) {
+	if pattern == "" {
+		panic("dns: invalid pattern " + pattern)
+	}
+	mux.m.Lock()
+	mux.z[Fqdn(pattern)] = handler
+	mux.m.Unlock()
+}
+
+// HandleFunc adds a handler function to the ServeMux for pattern.
+func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Msg)) {
+	mux.Handle(pattern, HandlerFunc(handler))
+}
+
+// HandleRemove deregistrars the handler specific for pattern from the ServeMux.
+func (mux *ServeMux) HandleRemove(pattern string) {
+	if pattern == "" {
+		panic("dns: invalid pattern " + pattern)
+	}
+	mux.m.Lock()
+	delete(mux.z, Fqdn(pattern))
+	mux.m.Unlock()
+}
+
+// ServeDNS dispatches the request to the handler whose
+// pattern most closely matches the request message. If DefaultServeMux
+// is used the correct thing for DS queries is done: a possible parent
+// is sought.
+// If no handler is found a standard SERVFAIL message is returned
+// If the request message does not have exactly one question in the
+// question section a SERVFAIL is returned, unlesss Unsafe is true.
+func (mux *ServeMux) ServeDNS(w ResponseWriter, request *Msg) {
+	var h Handler
+	if len(request.Question) < 1 { // allow more than one question
+		h = failedHandler()
+	} else {
+		if h = mux.match(request.Question[0].Name, request.Question[0].Qtype); h == nil {
+			h = failedHandler()
+		}
+	}
+	h.ServeDNS(w, request)
+}
+
+// Handle registers the handler with the given pattern
+// in the DefaultServeMux. The documentation for
+// ServeMux explains how patterns are matched.
+func Handle(pattern string, handler Handler) { DefaultServeMux.Handle(pattern, handler) }
+
+// HandleRemove deregisters the handle with the given pattern
+// in the DefaultServeMux.
+func HandleRemove(pattern string) { DefaultServeMux.HandleRemove(pattern) }
+
+// HandleFunc registers the handler function with the given pattern
+// in the DefaultServeMux.
+func HandleFunc(pattern string, handler func(ResponseWriter, *Msg)) {
+	DefaultServeMux.HandleFunc(pattern, handler)
+}
+
+// Writer writes raw DNS messages; each call to Write should send an entire message.
+type Writer interface {
+	io.Writer
+}
+
+// Reader reads raw DNS messages; each call to ReadTCP or ReadUDP should return an entire message.
+type Reader interface {
+	// ReadTCP reads a raw message from a TCP connection. Implementations may alter
+	// connection properties, for example the read-deadline.
+	ReadTCP(conn net.Conn, timeout time.Duration) ([]byte, error)
+	// ReadUDP reads a raw message from a UDP connection. Implementations may alter
+	// connection properties, for example the read-deadline.
+	ReadUDP(conn *net.UDPConn, timeout time.Duration) ([]byte, *SessionUDP, error)
+}
+
+// defaultReader is an adapter for the Server struct that implements the Reader interface
+// using the readTCP and readUDP func of the embedded Server.
+type defaultReader struct {
+	*Server
+}
+
+func (dr *defaultReader) ReadTCP(conn net.Conn, timeout time.Duration) ([]byte, error) {
+	return dr.readTCP(conn, timeout)
+}
+
+func (dr *defaultReader) ReadUDP(conn *net.UDPConn, timeout time.Duration) ([]byte, *SessionUDP, error) {
+	return dr.readUDP(conn, timeout)
+}
+
+// DecorateReader is a decorator hook for extending or supplanting the functionality of a Reader.
+// Implementations should never return a nil Reader.
+type DecorateReader func(Reader) Reader
+
+// DecorateWriter is a decorator hook for extending or supplanting the functionality of a Writer.
+// Implementations should never return a nil Writer.
+type DecorateWriter func(Writer) Writer
+
+// A Server defines parameters for running an DNS server.
+type Server struct {
+	// Address to listen on, ":dns" if empty.
+	Addr string
+	// if "tcp" or "tcp-tls" (DNS over TLS) it will invoke a TCP listener, otherwise an UDP one
+	Net string
+	// TCP Listener to use, this is to aid in systemd's socket activation.
+	Listener net.Listener
+	// TLS connection configuration
+	TLSConfig *tls.Config
+	// UDP "Listener" to use, this is to aid in systemd's socket activation.
+	PacketConn net.PacketConn
+	// Handler to invoke, dns.DefaultServeMux if nil.
+	Handler Handler
+	// Default buffer size to use to read incoming UDP messages. If not set
+	// it defaults to MinMsgSize (512 B).
+	UDPSize int
+	// The net.Conn.SetReadTimeout value for new connections, defaults to 2 * time.Second.
+	ReadTimeout time.Duration
+	// The net.Conn.SetWriteTimeout value for new connections, defaults to 2 * time.Second.
+	WriteTimeout time.Duration
+	// TCP idle timeout for multiple queries, if nil, defaults to 8 * time.Second (RFC 5966).
+	IdleTimeout func() time.Duration
+	// Secret(s) for Tsig map[<zonename>]<base64 secret>.
+	TsigSecret map[string]string
+	// Unsafe instructs the server to disregard any sanity checks and directly hand the message to
+	// the handler. It will specifically not check if the query has the QR bit not set.
+	Unsafe bool
+	// If NotifyStartedFunc is set it is called once the server has started listening.
+	NotifyStartedFunc func()
+	// DecorateReader is optional, allows customization of the process that reads raw DNS messages.
+	DecorateReader DecorateReader
+	// DecorateWriter is optional, allows customization of the process that writes raw DNS messages.
+	DecorateWriter DecorateWriter
+
+	// Graceful shutdown handling
+
+	inFlight sync.WaitGroup
+
+	lock    sync.RWMutex
+	started bool
+}
+
+// ListenAndServe starts a nameserver on the configured address in *Server.
+func (srv *Server) ListenAndServe() error {
+	srv.lock.Lock()
+	defer srv.lock.Unlock()
+	if srv.started {
+		return &Error{err: "server already started"}
+	}
+	addr := srv.Addr
+	if addr == "" {
+		addr = ":domain"
+	}
+	if srv.UDPSize == 0 {
+		srv.UDPSize = MinMsgSize
+	}
+	switch srv.Net {
+	case "tcp", "tcp4", "tcp6":
+		a, err := net.ResolveTCPAddr(srv.Net, addr)
+		if err != nil {
+			return err
+		}
+		l, err := net.ListenTCP(srv.Net, a)
+		if err != nil {
+			return err
+		}
+		srv.Listener = l
+		srv.started = true
+		srv.lock.Unlock()
+		err = srv.serveTCP(l)
+		srv.lock.Lock() // to satisfy the defer at the top
+		return err
+	case "tcp-tls", "tcp4-tls", "tcp6-tls":
+		network := "tcp"
+		if srv.Net == "tcp4-tls" {
+			network = "tcp4"
+		} else if srv.Net == "tcp6-tls" {
+			network = "tcp6"
+		}
+
+		l, err := tls.Listen(network, addr, srv.TLSConfig)
+		if err != nil {
+			return err
+		}
+		srv.Listener = l
+		srv.started = true
+		srv.lock.Unlock()
+		err = srv.serveTCP(l)
+		srv.lock.Lock() // to satisfy the defer at the top
+		return err
+	case "udp", "udp4", "udp6":
+		a, err := net.ResolveUDPAddr(srv.Net, addr)
+		if err != nil {
+			return err
+		}
+		l, err := net.ListenUDP(srv.Net, a)
+		if err != nil {
+			return err
+		}
+		if e := setUDPSocketOptions(l); e != nil {
+			return e
+		}
+		srv.PacketConn = l
+		srv.started = true
+		srv.lock.Unlock()
+		err = srv.serveUDP(l)
+		srv.lock.Lock() // to satisfy the defer at the top
+		return err
+	}
+	return &Error{err: "bad network"}
+}
+
+// ActivateAndServe starts a nameserver with the PacketConn or Listener
+// configured in *Server. Its main use is to start a server from systemd.
+func (srv *Server) ActivateAndServe() error {
+	srv.lock.Lock()
+	defer srv.lock.Unlock()
+	if srv.started {
+		return &Error{err: "server already started"}
+	}
+	pConn := srv.PacketConn
+	l := srv.Listener
+	if pConn != nil {
+		if srv.UDPSize == 0 {
+			srv.UDPSize = MinMsgSize
+		}
+		// Check PacketConn interface's type is valid and value
+		// is not nil
+		if t, ok := pConn.(*net.UDPConn); ok && t != nil {
+			if e := setUDPSocketOptions(t); e != nil {
+				return e
+			}
+			srv.started = true
+			srv.lock.Unlock()
+			e := srv.serveUDP(t)
+			srv.lock.Lock() // to satisfy the defer at the top
+			return e
+		}
+	}
+	if l != nil {
+		srv.started = true
+		srv.lock.Unlock()
+		e := srv.serveTCP(l)
+		srv.lock.Lock() // to satisfy the defer at the top
+		return e
+	}
+	return &Error{err: "bad listeners"}
+}
+
+// Shutdown gracefully shuts down a server. After a call to Shutdown, ListenAndServe and
+// ActivateAndServe will return. All in progress queries are completed before the server
+// is taken down. If the Shutdown is taking longer than the reading timeout an error
+// is returned.
+func (srv *Server) Shutdown() error {
+	srv.lock.Lock()
+	if !srv.started {
+		srv.lock.Unlock()
+		return &Error{err: "server not started"}
+	}
+	srv.started = false
+	srv.lock.Unlock()
+
+	if srv.PacketConn != nil {
+		srv.PacketConn.Close()
+	}
+	if srv.Listener != nil {
+		srv.Listener.Close()
+	}
+
+	fin := make(chan bool)
+	go func() {
+		srv.inFlight.Wait()
+		fin <- true
+	}()
+
+	select {
+	case <-time.After(srv.getReadTimeout()):
+		return &Error{err: "server shutdown is pending"}
+	case <-fin:
+		return nil
+	}
+}
+
+// getReadTimeout is a helper func to use system timeout if server did not intend to change it.
+func (srv *Server) getReadTimeout() time.Duration {
+	rtimeout := dnsTimeout
+	if srv.ReadTimeout != 0 {
+		rtimeout = srv.ReadTimeout
+	}
+	return rtimeout
+}
+
+// serveTCP starts a TCP listener for the server.
+// Each request is handled in a separate goroutine.
+func (srv *Server) serveTCP(l net.Listener) error {
+	defer l.Close()
+
+	if srv.NotifyStartedFunc != nil {
+		srv.NotifyStartedFunc()
+	}
+
+	reader := Reader(&defaultReader{srv})
+	if srv.DecorateReader != nil {
+		reader = srv.DecorateReader(reader)
+	}
+
+	handler := srv.Handler
+	if handler == nil {
+		handler = DefaultServeMux
+	}
+	rtimeout := srv.getReadTimeout()
+	// deadline is not used here
+	for {
+		rw, err := l.Accept()
+		if err != nil {
+			if neterr, ok := err.(net.Error); ok && neterr.Temporary() {
+				continue
+			}
+			return err
+		}
+		m, err := reader.ReadTCP(rw, rtimeout)
+		srv.lock.RLock()
+		if !srv.started {
+			srv.lock.RUnlock()
+			return nil
+		}
+		srv.lock.RUnlock()
+		if err != nil {
+			continue
+		}
+		srv.inFlight.Add(1)
+		go srv.serve(rw.RemoteAddr(), handler, m, nil, nil, rw)
+	}
+}
+
+// serveUDP starts a UDP listener for the server.
+// Each request is handled in a separate goroutine.
+func (srv *Server) serveUDP(l *net.UDPConn) error {
+	defer l.Close()
+
+	if srv.NotifyStartedFunc != nil {
+		srv.NotifyStartedFunc()
+	}
+
+	reader := Reader(&defaultReader{srv})
+	if srv.DecorateReader != nil {
+		reader = srv.DecorateReader(reader)
+	}
+
+	handler := srv.Handler
+	if handler == nil {
+		handler = DefaultServeMux
+	}
+	rtimeout := srv.getReadTimeout()
+	// deadline is not used here
+	for {
+		m, s, err := reader.ReadUDP(l, rtimeout)
+		srv.lock.RLock()
+		if !srv.started {
+			srv.lock.RUnlock()
+			return nil
+		}
+		srv.lock.RUnlock()
+		if err != nil {
+			continue
+		}
+		srv.inFlight.Add(1)
+		go srv.serve(s.RemoteAddr(), handler, m, l, s, nil)
+	}
+}
+
+// Serve a new connection.
+func (srv *Server) serve(a net.Addr, h Handler, m []byte, u *net.UDPConn, s *SessionUDP, t net.Conn) {
+	defer srv.inFlight.Done()
+
+	w := &response{tsigSecret: srv.TsigSecret, udp: u, tcp: t, remoteAddr: a, udpSession: s}
+	if srv.DecorateWriter != nil {
+		w.writer = srv.DecorateWriter(w)
+	} else {
+		w.writer = w
+	}
+
+	q := 0 // counter for the amount of TCP queries we get
+
+	reader := Reader(&defaultReader{srv})
+	if srv.DecorateReader != nil {
+		reader = srv.DecorateReader(reader)
+	}
+Redo:
+	req := new(Msg)
+	err := req.Unpack(m)
+	if err != nil { // Send a FormatError back
+		x := new(Msg)
+		x.SetRcodeFormatError(req)
+		w.WriteMsg(x)
+		goto Exit
+	}
+	if !srv.Unsafe && req.Response {
+		goto Exit
+	}
+
+	w.tsigStatus = nil
+	if w.tsigSecret != nil {
+		if t := req.IsTsig(); t != nil {
+			secret := t.Hdr.Name
+			if _, ok := w.tsigSecret[secret]; !ok {
+				w.tsigStatus = ErrKeyAlg
+			}
+			w.tsigStatus = TsigVerify(m, w.tsigSecret[secret], "", false)
+			w.tsigTimersOnly = false
+			w.tsigRequestMAC = req.Extra[len(req.Extra)-1].(*TSIG).MAC
+		}
+	}
+	h.ServeDNS(w, req) // Writes back to the client
+
+Exit:
+	if w.tcp == nil {
+		return
+	}
+	// TODO(miek): make this number configurable?
+	if q > maxTCPQueries { // close socket after this many queries
+		w.Close()
+		return
+	}
+
+	if w.hijacked {
+		return // client calls Close()
+	}
+	if u != nil { // UDP, "close" and return
+		w.Close()
+		return
+	}
+	idleTimeout := tcpIdleTimeout
+	if srv.IdleTimeout != nil {
+		idleTimeout = srv.IdleTimeout()
+	}
+	m, err = reader.ReadTCP(w.tcp, idleTimeout)
+	if err == nil {
+		q++
+		goto Redo
+	}
+	w.Close()
+	return
+}
+
+func (srv *Server) readTCP(conn net.Conn, timeout time.Duration) ([]byte, error) {
+	conn.SetReadDeadline(time.Now().Add(timeout))
+	l := make([]byte, 2)
+	n, err := conn.Read(l)
+	if err != nil || n != 2 {
+		if err != nil {
+			return nil, err
+		}
+		return nil, ErrShortRead
+	}
+	length := binary.BigEndian.Uint16(l)
+	if length == 0 {
+		return nil, ErrShortRead
+	}
+	m := make([]byte, int(length))
+	n, err = conn.Read(m[:int(length)])
+	if err != nil || n == 0 {
+		if err != nil {
+			return nil, err
+		}
+		return nil, ErrShortRead
+	}
+	i := n
+	for i < int(length) {
+		j, err := conn.Read(m[i:int(length)])
+		if err != nil {
+			return nil, err
+		}
+		i += j
+	}
+	n = i
+	m = m[:n]
+	return m, nil
+}
+
+func (srv *Server) readUDP(conn *net.UDPConn, timeout time.Duration) ([]byte, *SessionUDP, error) {
+	conn.SetReadDeadline(time.Now().Add(timeout))
+	m := make([]byte, srv.UDPSize)
+	n, s, err := ReadFromSessionUDP(conn, m)
+	if err != nil || n == 0 {
+		if err != nil {
+			return nil, nil, err
+		}
+		return nil, nil, ErrShortRead
+	}
+	m = m[:n]
+	return m, s, nil
+}
+
+// WriteMsg implements the ResponseWriter.WriteMsg method.
+func (w *response) WriteMsg(m *Msg) (err error) {
+	var data []byte
+	if w.tsigSecret != nil { // if no secrets, dont check for the tsig (which is a longer check)
+		if t := m.IsTsig(); t != nil {
+			data, w.tsigRequestMAC, err = TsigGenerate(m, w.tsigSecret[t.Hdr.Name], w.tsigRequestMAC, w.tsigTimersOnly)
+			if err != nil {
+				return err
+			}
+			_, err = w.writer.Write(data)
+			return err
+		}
+	}
+	data, err = m.Pack()
+	if err != nil {
+		return err
+	}
+	_, err = w.writer.Write(data)
+	return err
+}
+
+// Write implements the ResponseWriter.Write method.
+func (w *response) Write(m []byte) (int, error) {
+	switch {
+	case w.udp != nil:
+		n, err := WriteToSessionUDP(w.udp, m, w.udpSession)
+		return n, err
+	case w.tcp != nil:
+		lm := len(m)
+		if lm < 2 {
+			return 0, io.ErrShortBuffer
+		}
+		if lm > MaxMsgSize {
+			return 0, &Error{err: "message too large"}
+		}
+		l := make([]byte, 2, 2+lm)
+		binary.BigEndian.PutUint16(l, uint16(lm))
+		m = append(l, m...)
+
+		n, err := io.Copy(w.tcp, bytes.NewReader(m))
+		return int(n), err
+	}
+	panic("not reached")
+}
+
+// LocalAddr implements the ResponseWriter.LocalAddr method.
+func (w *response) LocalAddr() net.Addr {
+	if w.tcp != nil {
+		return w.tcp.LocalAddr()
+	}
+	return w.udp.LocalAddr()
+}
+
+// RemoteAddr implements the ResponseWriter.RemoteAddr method.
+func (w *response) RemoteAddr() net.Addr { return w.remoteAddr }
+
+// TsigStatus implements the ResponseWriter.TsigStatus method.
+func (w *response) TsigStatus() error { return w.tsigStatus }
+
+// TsigTimersOnly implements the ResponseWriter.TsigTimersOnly method.
+func (w *response) TsigTimersOnly(b bool) { w.tsigTimersOnly = b }
+
+// Hijack implements the ResponseWriter.Hijack method.
+func (w *response) Hijack() { w.hijacked = true }
+
+// Close implements the ResponseWriter.Close method
+func (w *response) Close() error {
+	// Can't close the udp conn, as that is actually the listener.
+	if w.tcp != nil {
+		e := w.tcp.Close()
+		w.tcp = nil
+		return e
+	}
+	return nil
+}