Updating server dependancies. (#9498)

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

@@ -4,10 +4,13 @@ package dns
 
 import (
 	"bytes"
+	"context"
 	"crypto/tls"
 	"encoding/binary"
+	"errors"
 	"io"
 	"net"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -16,11 +19,22 @@ import (
 // Default maximum number of TCP queries before we close the socket.
 const maxTCPQueries = 128
 
-// Interval for stop worker if no load
+// The maximum number of idle workers.
+//
+// This controls the maximum number of workers that are allowed to stay
+// idle waiting for incoming requests before being torn down.
+//
+// If this limit is reached, the server will just keep spawning new
+// workers (goroutines) for each incoming request. In this case, each
+// worker will only be used for a single request.
+const maxIdleWorkersCount = 10000
+
+// The maximum length of time a worker may idle for before being destroyed.
 const idleWorkerTimeout = 10 * time.Second
 
-// Maximum number of workers
-const maxWorkersCount = 10000
+// aLongTimeAgo is a non-zero time, far in the past, used for
+// immediate cancelation of network operations.
+var aLongTimeAgo = time.Unix(1, 0)
 
 // Handler is implemented by any value that implements ServeDNS.
 type Handler interface {
@@ -49,6 +63,12 @@ type ResponseWriter interface {
 	Hijack()
 }
 
+// A ConnectionStater interface is used by a DNS Handler to access TLS connection state
+// when available.
+type ConnectionStater interface {
+	ConnectionState() *tls.ConnectionState
+}
+
 type response struct {
 	msg            []byte
 	hijacked       bool // connection has been hijacked by handler
@@ -60,6 +80,7 @@ type response struct {
 	tcp            net.Conn          // i/o connection if TCP was used
 	udpSession     *SessionUDP       // oob data to get egress interface right
 	writer         Writer            // writer to output the raw DNS bits
+	wg             *sync.WaitGroup   // for gracefull shutdown
 }
 
 // ServeMux is an DNS request multiplexer. It matches the
@@ -151,7 +172,7 @@ func (mux *ServeMux) match(q string, t uint16) Handler {
 		for i := 0; i < l; i++ {
 			b[i] = q[off+i]
 			if b[i] >= 'A' && b[i] <= 'Z' {
-				b[i] |= ('a' - 'A')
+				b[i] |= 'a' - 'A'
 			}
 		}
 		if h, ok := mux.z[string(b[:l])]; ok { // causes garbage, might want to change the map key
@@ -305,14 +326,30 @@ type Server struct {
 	DecorateWriter DecorateWriter
 	// Maximum number of TCP queries before we close the socket. Default is maxTCPQueries (unlimited if -1).
 	MaxTCPQueries int
+	// Whether to set the SO_REUSEPORT socket option, allowing multiple listeners to be bound to a single address.
+	// It is only supported on go1.11+ and when using ListenAndServe.
+	ReusePort bool
 
 	// UDP packet or TCP connection queue
 	queue chan *response
 	// Workers count
 	workersCount int32
+
 	// Shutdown handling
-	lock    sync.RWMutex
-	started bool
+	lock     sync.RWMutex
+	started  bool
+	shutdown chan struct{}
+	conns    map[net.Conn]struct{}
+
+	// A pool for UDP message buffers.
+	udpPool sync.Pool
+}
+
+func (srv *Server) isStarted() bool {
+	srv.lock.RLock()
+	started := srv.started
+	srv.lock.RUnlock()
+	return started
 }
 
 func (srv *Server) worker(w *response) {
@@ -320,7 +357,7 @@ func (srv *Server) worker(w *response) {
 
 	for {
 		count := atomic.LoadInt32(&srv.workersCount)
-		if count > maxWorkersCount {
+		if count > maxIdleWorkersCount {
 			return
 		}
 		if atomic.CompareAndSwapInt32(&srv.workersCount, count, count+1) {
@@ -360,10 +397,36 @@ func (srv *Server) spawnWorker(w *response) {
 	}
 }
 
+func makeUDPBuffer(size int) func() interface{} {
+	return func() interface{} {
+		return make([]byte, size)
+	}
+}
+
+func (srv *Server) init() {
+	srv.queue = make(chan *response)
+
+	srv.shutdown = make(chan struct{})
+	srv.conns = make(map[net.Conn]struct{})
+
+	if srv.UDPSize == 0 {
+		srv.UDPSize = MinMsgSize
+	}
+
+	srv.udpPool.New = makeUDPBuffer(srv.UDPSize)
+}
+
+func unlockOnce(l sync.Locker) func() {
+	var once sync.Once
+	return func() { once.Do(l.Unlock) }
+}
+
 // ListenAndServe starts a nameserver on the configured address in *Server.
 func (srv *Server) ListenAndServe() error {
+	unlock := unlockOnce(&srv.lock)
 	srv.lock.Lock()
-	defer srv.lock.Unlock()
+	defer unlock()
+
 	if srv.started {
 		return &Error{err: "server already started"}
 	}
@@ -372,63 +435,47 @@ func (srv *Server) ListenAndServe() error {
 	if addr == "" {
 		addr = ":domain"
 	}
-	if srv.UDPSize == 0 {
-		srv.UDPSize = MinMsgSize
-	}
-	srv.queue = make(chan *response)
+
+	srv.init()
 	defer close(srv.queue)
+
 	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)
+		l, err := listenTCP(srv.Net, addr, srv.ReusePort)
 		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
+		unlock()
+		return srv.serveTCP(l)
 	case "tcp-tls", "tcp4-tls", "tcp6-tls":
-		network := "tcp"
-		if srv.Net == "tcp4-tls" {
-			network = "tcp4"
-		} else if srv.Net == "tcp6-tls" {
-			network = "tcp6"
+		if srv.TLSConfig == nil || (len(srv.TLSConfig.Certificates) == 0 && srv.TLSConfig.GetCertificate == nil) {
+			return errors.New("dns: neither Certificates nor GetCertificate set in Config")
 		}
-
-		l, err := tls.Listen(network, addr, srv.TLSConfig)
+		network := strings.TrimSuffix(srv.Net, "-tls")
+		l, err := listenTCP(network, addr, srv.ReusePort)
 		if err != nil {
 			return err
 		}
+		l = tls.NewListener(l, srv.TLSConfig)
 		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
+		unlock()
+		return srv.serveTCP(l)
 	case "udp", "udp4", "udp6":
-		a, err := net.ResolveUDPAddr(srv.Net, addr)
+		l, err := listenUDP(srv.Net, addr, srv.ReusePort)
 		if err != nil {
 			return err
 		}
-		l, err := net.ListenUDP(srv.Net, a)
-		if err != nil {
-			return err
-		}
-		if e := setUDPSocketOptions(l); e != nil {
+		u := l.(*net.UDPConn)
+		if e := setUDPSocketOptions(u); 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
+		unlock()
+		return srv.serveUDP(u)
 	}
 	return &Error{err: "bad network"}
 }
@@ -436,20 +483,20 @@ func (srv *Server) ListenAndServe() error {
 // 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 {
+	unlock := unlockOnce(&srv.lock)
 	srv.lock.Lock()
-	defer srv.lock.Unlock()
+	defer unlock()
+
 	if srv.started {
 		return &Error{err: "server already started"}
 	}
 
+	srv.init()
+	defer close(srv.queue)
+
 	pConn := srv.PacketConn
 	l := srv.Listener
-	srv.queue = make(chan *response)
-	defer close(srv.queue)
 	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 {
@@ -457,18 +504,14 @@ func (srv *Server) ActivateAndServe() error {
 				return e
 			}
 			srv.started = true
-			srv.lock.Unlock()
-			e := srv.serveUDP(t)
-			srv.lock.Lock() // to satisfy the defer at the top
-			return e
+			unlock()
+			return srv.serveUDP(t)
 		}
 	}
 	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
+		unlock()
+		return srv.serveTCP(l)
 	}
 	return &Error{err: "bad listeners"}
 }
@@ -476,23 +519,58 @@ func (srv *Server) ActivateAndServe() error {
 // Shutdown shuts down a server. After a call to Shutdown, ListenAndServe and
 // ActivateAndServe will return.
 func (srv *Server) Shutdown() error {
+	return srv.ShutdownContext(context.Background())
+}
+
+// ShutdownContext shuts down a server. After a call to ShutdownContext,
+// ListenAndServe and ActivateAndServe will return.
+//
+// A context.Context may be passed to limit how long to wait for connections
+// to terminate.
+func (srv *Server) ShutdownContext(ctx context.Context) error {
 	srv.lock.Lock()
-	if !srv.started {
-		srv.lock.Unlock()
-		return &Error{err: "server not started"}
-	}
+	started := srv.started
 	srv.started = false
 	srv.lock.Unlock()
 
+	if !started {
+		return &Error{err: "server not started"}
+	}
+
+	if srv.PacketConn != nil {
+		srv.PacketConn.SetReadDeadline(aLongTimeAgo) // Unblock reads
+	}
+
+	if srv.Listener != nil {
+		srv.Listener.Close()
+	}
+
+	srv.lock.Lock()
+	for rw := range srv.conns {
+		rw.SetReadDeadline(aLongTimeAgo) // Unblock reads
+	}
+	srv.lock.Unlock()
+
+	if testShutdownNotify != nil {
+		testShutdownNotify.Broadcast()
+	}
+
+	var ctxErr error
+	select {
+	case <-srv.shutdown:
+	case <-ctx.Done():
+		ctxErr = ctx.Err()
+	}
+
 	if srv.PacketConn != nil {
 		srv.PacketConn.Close()
 	}
-	if srv.Listener != nil {
-		srv.Listener.Close()
-	}
-	return nil
+
+	return ctxErr
 }
 
+var testShutdownNotify *sync.Cond
+
 // 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
@@ -510,22 +588,36 @@ func (srv *Server) serveTCP(l net.Listener) error {
 		srv.NotifyStartedFunc()
 	}
 
-	for {
+	var wg sync.WaitGroup
+	defer func() {
+		wg.Wait()
+		close(srv.shutdown)
+	}()
+
+	for srv.isStarted() {
 		rw, err := l.Accept()
-		srv.lock.RLock()
-		if !srv.started {
-			srv.lock.RUnlock()
-			return nil
-		}
-		srv.lock.RUnlock()
 		if err != nil {
+			if !srv.isStarted() {
+				return nil
+			}
 			if neterr, ok := err.(net.Error); ok && neterr.Temporary() {
 				continue
 			}
 			return err
 		}
-		srv.spawnWorker(&response{tsigSecret: srv.TsigSecret, tcp: rw})
+		srv.lock.Lock()
+		// Track the connection to allow unblocking reads on shutdown.
+		srv.conns[rw] = struct{}{}
+		srv.lock.Unlock()
+		wg.Add(1)
+		srv.spawnWorker(&response{
+			tsigSecret: srv.TsigSecret,
+			tcp:        rw,
+			wg:         &wg,
+		})
 	}
+
+	return nil
 }
 
 // serveUDP starts a UDP listener for the server.
@@ -541,27 +633,42 @@ func (srv *Server) serveUDP(l *net.UDPConn) error {
 		reader = srv.DecorateReader(reader)
 	}
 
+	var wg sync.WaitGroup
+	defer func() {
+		wg.Wait()
+		close(srv.shutdown)
+	}()
+
 	rtimeout := srv.getReadTimeout()
 	// deadline is not used here
-	for {
+	for srv.isStarted() {
 		m, s, err := reader.ReadUDP(l, rtimeout)
-		srv.lock.RLock()
-		if !srv.started {
-			srv.lock.RUnlock()
-			return nil
-		}
-		srv.lock.RUnlock()
 		if err != nil {
+			if !srv.isStarted() {
+				return nil
+			}
 			if netErr, ok := err.(net.Error); ok && netErr.Temporary() {
 				continue
 			}
 			return err
 		}
 		if len(m) < headerSize {
+			if cap(m) == srv.UDPSize {
+				srv.udpPool.Put(m[:srv.UDPSize])
+			}
 			continue
 		}
-		srv.spawnWorker(&response{msg: m, tsigSecret: srv.TsigSecret, udp: l, udpSession: s})
+		wg.Add(1)
+		srv.spawnWorker(&response{
+			msg:        m,
+			tsigSecret: srv.TsigSecret,
+			udp:        l,
+			udpSession: s,
+			wg:         &wg,
+		})
 	}
+
+	return nil
 }
 
 func (srv *Server) serve(w *response) {
@@ -574,20 +681,28 @@ func (srv *Server) serve(w *response) {
 	if w.udp != nil {
 		// serve UDP
 		srv.serveDNS(w)
-		return
-	}
 
-	reader := Reader(&defaultReader{srv})
-	if srv.DecorateReader != nil {
-		reader = srv.DecorateReader(reader)
+		w.wg.Done()
+		return
 	}
 
 	defer func() {
 		if !w.hijacked {
 			w.Close()
 		}
+
+		srv.lock.Lock()
+		delete(srv.conns, w.tcp)
+		srv.lock.Unlock()
+
+		w.wg.Done()
 	}()
 
+	reader := Reader(&defaultReader{srv})
+	if srv.DecorateReader != nil {
+		reader = srv.DecorateReader(reader)
+	}
+
 	idleTimeout := tcpIdleTimeout
 	if srv.IdleTimeout != nil {
 		idleTimeout = srv.IdleTimeout()
@@ -600,7 +715,7 @@ func (srv *Server) serve(w *response) {
 		limit = maxTCPQueries
 	}
 
-	for q := 0; q < limit || limit == -1; q++ {
+	for q := 0; (q < limit || limit == -1) && srv.isStarted(); q++ {
 		var err error
 		w.msg, err = reader.ReadTCP(w.tcp, timeout)
 		if err != nil {
@@ -623,6 +738,10 @@ func (srv *Server) serve(w *response) {
 func (srv *Server) serveDNS(w *response) {
 	req := new(Msg)
 	err := req.Unpack(w.msg)
+	if w.udp != nil && cap(w.msg) == srv.UDPSize {
+		srv.udpPool.Put(w.msg[:srv.UDPSize])
+	}
+	w.msg = nil
 	if err != nil { // Send a FormatError back
 		x := new(Msg)
 		x.SetRcodeFormatError(req)
@@ -691,9 +810,10 @@ func (srv *Server) readTCP(conn net.Conn, timeout time.Duration) ([]byte, error)
 
 func (srv *Server) readUDP(conn *net.UDPConn, timeout time.Duration) ([]byte, *SessionUDP, error) {
 	conn.SetReadDeadline(time.Now().Add(timeout))
-	m := make([]byte, srv.UDPSize)
+	m := srv.udpPool.Get().([]byte)
 	n, s, err := ReadFromSessionUDP(conn, m)
 	if err != nil {
+		srv.udpPool.Put(m)
 		return nil, nil, err
 	}
 	m = m[:n]
@@ -780,3 +900,15 @@ func (w *response) Close() error {
 	}
 	return nil
 }
+
+// ConnectionState() implements the ConnectionStater.ConnectionState() interface.
+func (w *response) ConnectionState() *tls.ConnectionState {
+	type tlsConnectionStater interface {
+		ConnectionState() tls.ConnectionState
+	}
+	if v, ok := w.tcp.(tlsConnectionStater); ok {
+		t := v.ConnectionState()
+		return &t
+	}
+	return nil
+}