Change algorithm of TCP relaying

internal/cli/run_proxy.go

@@ -183,7 +183,6 @@ func runProxy(conf *config.Config, version string) error {
 		Secret:             conf.Secret,
 		BufferSize:         conf.TCPBuffer.Get(mtglib.DefaultBufferSize),
 		DomainFrontingPort: conf.DomainFrontingPort.Get(mtglib.DefaultDomainFrontingPort),
-		IdleTimeout:        conf.Network.Timeout.Idle.Get(mtglib.DefaultIdleTimeout),
 		PreferIP:           conf.PreferIP.Get(mtglib.DefaultPreferIP),
 	}
 
@@ -192,7 +191,7 @@ func runProxy(conf *config.Config, version string) error {
 		return fmt.Errorf("cannot create a proxy: %w", err)
 	}
 
-	listener, err := net.Listen("tcp", conf.BindTo.Get(""))
+	listener, err := utils.NewListener(conf.BindTo.Get(""), int(opts.BufferSize))
 	if err != nil {
 		return fmt.Errorf("cannot start proxy: %w", err)
 	}

internal/utils/net_listener.go

@@ -0,0 +1,41 @@
+package utils
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/9seconds/mtg/v2/network"
+)
+
+type Listener struct {
+	net.Listener
+
+	bufferSize int
+}
+
+func (l Listener) Accept() (net.Conn, error) {
+	conn, err := l.Listener.Accept()
+	if err != nil {
+		return nil, err // nolint: wrapcheck
+	}
+
+	if err := network.SetClientSocketOptions(conn, l.bufferSize); err != nil {
+		conn.Close()
+
+		return nil, fmt.Errorf("cannot set TCP options: %w", err)
+	}
+
+	return conn, nil
+}
+
+func NewListener(bindTo string, bufferSize int) (net.Listener, error) {
+	base, err := net.Listen("tcp", bindTo)
+	if err != nil {
+		return nil, fmt.Errorf("cannot build a base listener: %w", err)
+	}
+
+	return Listener{
+		Listener:   base,
+		bufferSize: bufferSize,
+	}, nil
+}

mtglib/init.go

@@ -69,6 +69,9 @@ const (
 
 	// DefaultIdleTimeout is a default timeout for closing a connection
 	// in case of idling.
+	//
+	// Deprecated: no longer in use because of changed TCP relay
+	// algorithm.
 	DefaultIdleTimeout = time.Minute
 
 	// DefaultTolerateTimeSkewness is a default timeout for time
@@ -83,9 +86,14 @@ const (
 	// by Telegram and a proxy.
 	SecretKeyLength = 16
 
-	// ConnectionIDBytesLength defines a count of random bytes
+	// ConnectionIDBytesLength defines a count of random bytes used to generate
-	// used to generate a stream/connection ids.
+	// a stream/connection ids.
 	ConnectionIDBytesLength = 16
+
+	// TCPRelayReadTimeout defines a max time period between two consecuitive
+	// reads from Telegram after which connection will be terminated. This is
+	// required to abort stale connections.
+	TCPRelayReadTimeout = 20 * time.Second
 )
 
 // Network defines a knowledge how to work with a network. It may sound

mtglib/internal/faketls/conn.go

@@ -46,7 +46,11 @@ func (c *Conn) Write(p []byte) (int, error) {
 
 	rec.Type = record.TypeApplicationData
 	rec.Version = record.Version12
-	written := 0
+
+	sendBuffer := acquireBytesBuffer()
+	defer releaseBytesBuffer(sendBuffer)
+
+	lenP := len(p)
 
 	for len(p) > 0 {
 		chunkSize := rand.Intn(record.TLSMaxRecordSize)
@@ -56,14 +60,14 @@ func (c *Conn) Write(p []byte) (int, error) {
 
 		rec.Payload.Reset()
 		rec.Payload.Write(p[:chunkSize])
+		rec.Dump(sendBuffer) // nolint: errcheck
 
-		if err := rec.Dump(c.Conn); err != nil {
-			return written, err // nolint: wrapcheck
-		}
-
-		written += chunkSize
 		p = p[chunkSize:]
 	}
 
-	return written, nil
+	if _, err := c.Conn.Write(sendBuffer.Bytes()); err != nil {
+		return 0, err // nolint: wrapcheck
+	}
+
+	return lenP, nil
 }

mtglib/internal/relay/conn.go

@@ -1,35 +1,19 @@
 package relay
 
 import (
-	"context"
+	"fmt"
-	"io"
+	"net"
+	"time"
 )
 
 type conn struct {
-	io.ReadWriteCloser
+	net.Conn
-
-	ctx         context.Context
-	tickChannel chan struct{}
 }
 
 func (c conn) Read(p []byte) (int, error) {
-	n, err := c.ReadWriteCloser.Read(p)
+	if err := c.SetReadDeadline(time.Now().Add(getTimeout())); err != nil {
-
+		return 0, fmt.Errorf("cannot set read deadline: %w", err)
-	select {
-	case <-c.ctx.Done():
-	case c.tickChannel <- struct{}{}:
 	}
 
-	return n, err // nolint: wrapcheck
+	return c.Conn.Read(p) // nolint: wrapcheck
-}
-
-func (c conn) Write(p []byte) (int, error) {
-	n, err := c.ReadWriteCloser.Write(p)
-
-	select {
-	case <-c.ctx.Done():
-	case c.tickChannel <- struct{}{}:
-	}
-
-	return n, err // nolint: wrapcheck
 }

mtglib/internal/relay/conn_internal_test.go

@@ -1,125 +0,0 @@
-package relay
-
-import (
-	"context"
-	"errors"
-	"io"
-	"testing"
-
-	"github.com/9seconds/mtg/v2/internal/testlib"
-	"github.com/stretchr/testify/mock"
-	"github.com/stretchr/testify/suite"
-)
-
-type ConnTestSuite struct {
-	suite.Suite
-
-	ctxCancel   context.CancelFunc
-	connMock    *testlib.NetConnMock
-	tickChannel chan struct{}
-	buf         []byte
-	c           conn
-}
-
-func (suite *ConnTestSuite) SetupTest() {
-	ctx, cancel := context.WithCancel(context.Background())
-
-	suite.tickChannel = make(chan struct{}, 1)
-	suite.connMock = &testlib.NetConnMock{}
-	suite.ctxCancel = cancel
-	suite.buf = make([]byte, 5)
-
-	suite.c = conn{
-		ReadWriteCloser: suite.connMock,
-		ctx:             ctx,
-		tickChannel:     suite.tickChannel,
-	}
-}
-
-func (suite *ConnTestSuite) TestReadOk() {
-	suite.connMock.On("Read", mock.Anything).Once().Return(len(suite.buf), nil)
-
-	n, err := suite.c.Read(suite.buf)
-	suite.NoError(err)
-	suite.Equal(len(suite.buf), n)
-
-	select {
-	case <-suite.tickChannel:
-	default:
-		suite.FailNow("cannot find a tick event")
-	}
-}
-
-func (suite *ConnTestSuite) TestReadErr() {
-	suite.connMock.On("Read", mock.Anything).Once().Return(0, io.EOF)
-
-	_, err := suite.c.Read(suite.buf)
-	suite.True(errors.Is(err, io.EOF))
-
-	select {
-	case <-suite.tickChannel:
-	default:
-		suite.FailNow("cannot find a tick event")
-	}
-}
-
-func (suite *ConnTestSuite) TestReadContextDone() {
-	suite.connMock.On("Read", mock.Anything).Once().Return(len(suite.buf), nil)
-	suite.ctxCancel()
-
-	suite.tickChannel <- struct{}{}
-
-	suite.c.Read(suite.buf) // nolint: errcheck
-}
-
-func (suite *ConnTestSuite) TestWriteOk() {
-	suite.connMock.On("Write", mock.Anything).Once().Return(len(suite.buf), nil)
-
-	n, err := suite.c.Write(suite.buf)
-	suite.NoError(err)
-	suite.Equal(len(suite.buf), n)
-
-	select {
-	case <-suite.tickChannel:
-	default:
-		suite.FailNow("cannot find a tick event")
-	}
-}
-
-func (suite *ConnTestSuite) TestWriteErr() {
-	suite.connMock.On("Write", mock.Anything).Once().Return(0, io.EOF)
-
-	_, err := suite.c.Write(suite.buf)
-	suite.True(errors.Is(err, io.EOF))
-
-	select {
-	case <-suite.tickChannel:
-	default:
-		suite.FailNow("cannot find a tick event")
-	}
-}
-
-func (suite *ConnTestSuite) TestWriteContextDone() {
-	suite.connMock.On("Write", mock.Anything).Once().Return(len(suite.buf), nil)
-	suite.ctxCancel()
-
-	suite.tickChannel <- struct{}{}
-
-	suite.c.Write(suite.buf) // nolint: errcheck
-}
-
-func (suite *ConnTestSuite) TearDownTest() {
-	select {
-	case <-suite.tickChannel:
-	default:
-	}
-
-	close(suite.tickChannel)
-
-	suite.connMock.AssertExpectations(suite.T())
-}
-
-func TestConn(t *testing.T) {
-	t.Parallel()
-	suite.Run(t, &ConnTestSuite{})
-}

mtglib/internal/relay/init.go

@@ -1,5 +1,14 @@
 package relay
 
+import "time"
+
+const (
+	ConnectionTimeToLiveMin = 2 * time.Minute
+	ConnectionTimeToLiveMax = 10 * time.Minute
+	TimeoutMin              = 20 * time.Second
+	TimeoutMax              = time.Minute
+)
+
 type Logger interface {
 	Printf(msg string, args ...interface{})
 }

mtglib/internal/relay/init_test.go

@@ -1,49 +1,5 @@
 package relay_test
 
-import (
-	"bytes"
-	"io"
-	"sync"
-)
-
 type loggerMock struct{}
 
 func (l loggerMock) Printf(format string, args ...interface{}) {}
-
-type rwcMock struct {
-	bytes.Buffer
-
-	closed bool
-	mutex  sync.Mutex
-}
-
-func (r *rwcMock) Read(p []byte) (int, error) {
-	r.mutex.Lock()
-	defer r.mutex.Unlock()
-
-	if r.closed {
-		return 0, io.EOF
-	}
-
-	return r.Buffer.Read(p) // nolint: wrapcheck
-}
-
-func (r *rwcMock) Write(p []byte) (int, error) {
-	r.mutex.Lock()
-	defer r.mutex.Unlock()
-
-	if r.closed {
-		return 0, io.EOF
-	}
-
-	return r.Buffer.Write(p) // nolint: wrapcheck
-}
-
-func (r *rwcMock) Close() error {
-	r.mutex.Lock()
-	defer r.mutex.Unlock()
-
-	r.closed = true
-
-	return nil
-}

mtglib/internal/relay/pools.go

@@ -1,45 +1,32 @@
 package relay
 
-import (
+import "sync"
-	"context"
-	"sync"
-	"time"
-)
 
-var relayPool = sync.Pool{
+type eastWest struct {
+	east []byte
+	west []byte
+}
+
+var eastWestPool = sync.Pool{
 	New: func() interface{} {
-		return &Relay{
+		return &eastWest{}
-			tickChannel:  make(chan struct{}),
-			errorChannel: make(chan error, 1),
-		}
 	},
 }
 
-func AcquireRelay(ctx context.Context, logger Logger, bufferSize int, idleTimeout time.Duration) *Relay {
+func acquireEastWest(bufferSize int) *eastWest {
-	ctx, cancel := context.WithCancel(ctx)
+	wanted := eastWestPool.Get().(*eastWest) // nolint: forcetypeassert
 
-	r, ok := relayPool.Get().(*Relay)
+	if len(wanted.east) != bufferSize {
-	if !ok {
+		wanted.east = make([]byte, bufferSize)
-		panic("Relay pool has no relay!")
 	}
 
-	r.ctx = ctx
+	if len(wanted.west) != bufferSize {
-	r.ctxCancel = cancel
+		wanted.west = make([]byte, bufferSize)
-	r.logger = logger
-	r.tickTimeout = idleTimeout
-
-	if len(r.eastBuffer) != bufferSize {
-		r.eastBuffer = make([]byte, bufferSize)
 	}
 
-	if len(r.westBuffer) != bufferSize {
+	return wanted
-		r.westBuffer = make([]byte, bufferSize)
-	}
-
-	return r
 }
 
-func ReleaseRelay(r *Relay) {
+func releaseEastWest(ew *eastWest) {
-	r.Reset()
+	eastWestPool.Put(ew)
-	relayPool.Put(r)
 }

mtglib/internal/relay/relay.go

@@ -3,127 +3,48 @@ package relay
 import (
 	"context"
 	"io"
+	"net"
 	"sync"
-	"time"
 )
 
-type Relay struct {
+func Relay(ctx context.Context, log Logger, bufferSize int,
-	ctx          context.Context
+	telegramConn net.Conn, clientConn io.ReadWriteCloser) {
-	ctxCancel    context.CancelFunc
+	defer telegramConn.Close()
-	logger       Logger
+	defer clientConn.Close()
-	processMutex sync.Mutex
-	eastBuffer   []byte
-	westBuffer   []byte
-	tickChannel  chan struct{}
-	errorChannel chan error
-	tickTimeout  time.Duration
-}
 
-func (r *Relay) Reset() {
+	ctx, cancel := context.WithTimeout(ctx, getConnectionTimeToLive())
-	r.processMutex.Lock()
+	defer cancel()
-	defer r.processMutex.Unlock()
 
-	if r.ctxCancel != nil {
+	go func() {
-		r.ctxCancel()
+		<-ctx.Done()
-	}
+		telegramConn.Close()
+		clientConn.Close()
+	}()
 
-	r.ctx = nil
+	buffers := acquireEastWest(bufferSize)
-	r.ctxCancel = nil
+	defer releaseEastWest(buffers)
-	r.logger = nil
-}
 
-func (r *Relay) Process(eastConn, westConn io.ReadWriteCloser) error {
+	telegramConn = conn{
-	r.processMutex.Lock()
+		Conn: telegramConn,
-	defer r.processMutex.Unlock()
-
-	eastConn = conn{
-		ReadWriteCloser: eastConn,
-		ctx:             r.ctx,
-		tickChannel:     r.tickChannel,
-	}
-	westConn = conn{
-		ReadWriteCloser: westConn,
-		ctx:             r.ctx,
-		tickChannel:     r.tickChannel,
 	}
 
 	wg := &sync.WaitGroup{}
-	wg.Add(3) // nolint: gomnd
+	wg.Add(2) // nolint: gomnd
 
-	go r.runObserver(eastConn, westConn, wg)
+	go pump(log, telegramConn, clientConn, wg, buffers.east, "east -> west")
 
-	go r.transmit(eastConn, westConn, r.westBuffer, "west", wg)
+	pump(log, clientConn, telegramConn, wg, buffers.west, "west -> east")
-
-	r.transmit(westConn, eastConn, r.eastBuffer, "east", wg)
 
 	wg.Wait()
-
-	select {
-	case err := <-r.errorChannel:
-		return err
-	default:
-		return nil
-	}
 }
 
-func (r *Relay) transmit(src io.ReadCloser, dst io.WriteCloser,
+func pump(log Logger, src io.ReadCloser, dst io.WriteCloser, wg *sync.WaitGroup,
-	buffer []byte, direction string, wg *sync.WaitGroup) {
+	buf []byte, direction string) {
 	defer wg.Done()
+	defer src.Close()
+	defer dst.Close()
 
-	defer func() {
+	if n, err := io.CopyBuffer(dst, src, buf); err != nil {
-		r.ctxCancel()
+		log.Printf("cannot pump %s (written %d bytes): %w", direction, n, err)
-		src.Close()
-		dst.Close()
-	}()
-
-	if _, err := io.CopyBuffer(dst, src, buffer); err != nil {
-		r.logger.Printf("error '%v' happened on direction %s", err, direction)
-
-		select {
-		case <-r.ctx.Done():
-			err = r.ctx.Err()
-		default:
-		}
-
-		select {
-		case r.errorChannel <- err:
-		default:
-		}
-	}
-}
-
-func (r *Relay) runObserver(one, another io.Closer, wg *sync.WaitGroup) {
-	defer wg.Done()
-
-	ticker := time.NewTicker(time.Second)
-
-	defer func() {
-		one.Close()
-		another.Close()
-
-		ticker.Stop()
-
-		select {
-		case <-ticker.C:
-		default:
-		}
-	}()
-
-	lastTickAt := time.Now()
-
-	for {
-		select {
-		case <-r.ctx.Done():
-			return
-		case <-r.tickChannel:
-			lastTickAt = time.Now()
-		case <-ticker.C:
-			if time.Since(lastTickAt) > r.tickTimeout {
-				r.logger.Printf("exit due to a timeout")
-				r.ctxCancel()
-
-				return
-			}
-		}
 	}
 }

mtglib/internal/relay/relay_test.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"io"
 	"testing"
-	"time"
 
 	"github.com/9seconds/mtg/v2/internal/testlib"
 	"github.com/9seconds/mtg/v2/mtglib/internal/relay"
@@ -15,60 +14,40 @@ import (
 type RelayTestSuite struct {
 	suite.Suite
 
-	ctx       context.Context
+	loggerMock       relay.Logger
-	ctxCancel context.CancelFunc
+	ctx              context.Context
-	r         *relay.Relay
+	ctxCancel        context.CancelFunc
+	telegramConnMock *testlib.NetConnMock
+	clientConnMock   *testlib.NetConnMock
 }
 
 func (suite *RelayTestSuite) SetupTest() {
-	suite.ctx, suite.ctxCancel = context.WithCancel(context.Background())
+	ctx, cancel := context.WithCancel(context.Background())
-	suite.r = relay.AcquireRelay(suite.ctx, loggerMock{}, 4096, time.Second)
+	suite.ctx = ctx
+	suite.ctxCancel = cancel
+	suite.loggerMock = &loggerMock{}
+	suite.telegramConnMock = &testlib.NetConnMock{}
+	suite.clientConnMock = &testlib.NetConnMock{}
 }
 
 func (suite *RelayTestSuite) TearDownTest() {
 	suite.ctxCancel()
-	relay.ReleaseRelay(suite.r)
+	suite.telegramConnMock.AssertExpectations(suite.T())
-	suite.r = nil
+	suite.clientConnMock.AssertExpectations(suite.T())
 }
 
-func (suite *RelayTestSuite) TestCancelled() {
+func (suite *RelayTestSuite) TestExit() {
-	suite.ctxCancel()
+	suite.telegramConnMock.On("SetReadDeadline", mock.Anything).Return(nil)
+	suite.telegramConnMock.On("Close").Return(nil)
+	suite.telegramConnMock.On("Read", mock.Anything).Return(10, io.EOF).Once()
+	suite.telegramConnMock.On("Write", mock.Anything).Return(10, io.EOF).Maybe()
 
-	eastConn := &rwcMock{}
+	suite.clientConnMock.On("Read", mock.Anything).Return(0, io.EOF).Once()
-	eastConn.Write([]byte{1, 2, 3, 4, 5}) // nolint: errcheck
+	suite.clientConnMock.On("Write", mock.Anything).Return(10, io.EOF).Maybe()
+	suite.clientConnMock.On("Close").Return(nil)
 
-	westConn := &rwcMock{}
+	relay.Relay(suite.ctx, suite.loggerMock, 1024,
-	westConn.Write([]byte{100, 101, 102}) // nolint: errcheck
+		suite.telegramConnMock, suite.clientConnMock)
-
-	suite.Nil(suite.r.Process(eastConn, westConn))
-}
-
-func (suite *RelayTestSuite) TestCopyFine() {
-	eastConn := &rwcMock{}
-	eastConn.Write([]byte{1, 2, 3, 4, 5}) // nolint: errcheck
-
-	westConn := &rwcMock{}
-	westConn.Write([]byte{100, 101, 102}) // nolint: errcheck
-
-	// yes, this test is not good enough. but apparently, if it hangs,
-	// we can debug most of possible issues.
-	_ = suite.r.Process(eastConn, westConn)
-}
-
-func (suite *RelayTestSuite) TestTimeout() {
-	eastConn := &rwcMock{}
-	eastConn.Write([]byte{1, 2, 3, 4, 5}) // nolint: errcheck
-
-	westConn := &testlib.NetConnMock{}
-	westConn.On("Close").Return(nil)
-	westConn.On("Read", mock.Anything).Return(0, io.EOF).Run(func(_ mock.Arguments) {
-		time.Sleep(2 * time.Second)
-	})
-	westConn.On("Write", mock.Anything).Return(0, io.EOF).Run(func(_ mock.Arguments) {
-		time.Sleep(2 * time.Second)
-	})
-
-	suite.Error(suite.r.Process(eastConn, westConn))
 }
 
 func TestRelay(t *testing.T) {

mtglib/internal/relay/timeouts.go

@@ -0,0 +1,26 @@
+package relay
+
+import (
+	"math"
+	"math/rand"
+	"time"
+)
+
+func getConnectionTimeToLive() time.Duration {
+	return getTime(ConnectionTimeToLiveMin, ConnectionTimeToLiveMax)
+}
+
+func getTimeout() time.Duration {
+	return getTime(TimeoutMin, TimeoutMax)
+}
+
+func getTime(minDuration, maxDuration time.Duration) time.Duration {
+	minDurationInSeconds := minDuration.Seconds()
+	maxDurationInSeconds := maxDuration.Seconds()
+	middle := minDurationInSeconds + (maxDurationInSeconds-minDurationInSeconds)/2 // nolint: gomnd
+
+	number := minDurationInSeconds + rand.ExpFloat64()*middle
+	number = math.Round(math.Min(maxDurationInSeconds, number))
+
+	return time.Duration(number) * time.Second
+}

mtglib/internal/relay/timeouts_internal_test.go

@@ -0,0 +1,37 @@
+package relay
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+)
+
+type TimeoutsTestSuite struct {
+	suite.Suite
+}
+
+func (suite *TimeoutsTestSuite) TestGetConnectionTimeToLive() {
+	for i := 0; i < 100; i++ {
+		value := getConnectionTimeToLive()
+		message := fmt.Sprintf("generated value is %v", value)
+
+		suite.GreaterOrEqual(value, ConnectionTimeToLiveMin, message)
+		suite.LessOrEqual(value, ConnectionTimeToLiveMax, message)
+	}
+}
+
+func (suite *TimeoutsTestSuite) TestGetTimeout() {
+	for i := 0; i < 100; i++ {
+		value := getTimeout()
+		message := fmt.Sprintf("generated value is %v", value)
+
+		suite.GreaterOrEqual(value, TimeoutMin, message)
+		suite.LessOrEqual(value, TimeoutMax, message)
+	}
+}
+
+func TestTimeouts(t *testing.T) {
+	t.Parallel()
+	suite.Run(t, &TimeoutsTestSuite{})
+}

mtglib/proxy.go

@@ -23,7 +23,6 @@ type Proxy struct {
 	ctxCancel       context.CancelFunc
 	streamWaitGroup sync.WaitGroup
 
-	idleTimeout          time.Duration
 	tolerateTimeSkewness time.Duration
 	bufferSize           int
 	domainFrontingPort   int
@@ -81,13 +80,13 @@ func (p *Proxy) ServeConn(conn net.Conn) {
 		return
 	}
 
-	rel := relay.AcquireRelay(ctx,
+	relay.Relay(
-		p.logger.Named("relay"), p.bufferSize, p.idleTimeout)
+		ctx,
-	defer relay.ReleaseRelay(rel)
+		ctx.logger.Named("relay"),
-
+		p.bufferSize,
-	if err := rel.Process(ctx.clientConn, ctx.telegramConn); err != nil {
+		ctx.telegramConn,
-		p.logger.DebugError("relay has been finished", err)
+		ctx.clientConn,
-	}
+	)
 }
 
 // Serve starts a proxy on a given listener.
@@ -255,13 +254,13 @@ func (p *Proxy) doDomainFronting(ctx *streamContext, conn *connRewind) {
 		stream:   p.eventStream,
 	}
 
-	rel := relay.AcquireRelay(ctx,
+	relay.Relay(
-		p.logger.Named("domain-fronting"), p.bufferSize, p.idleTimeout)
+		ctx,
-	defer relay.ReleaseRelay(rel)
+		ctx.logger.Named("domain-fronting"),
-
+		p.bufferSize,
-	if err := rel.Process(conn, frontConn); err != nil {
+		frontConn,
-		p.logger.DebugError("domain fronting relay has been finished", err)
+		conn,
-	}
+	)
 }
 
 // NewProxy makes a new proxy instance.
@@ -287,7 +286,6 @@ func NewProxy(opts ProxyOpts) (*Proxy, error) {
 		logger:               opts.getLogger("proxy"),
 		domainFrontingPort:   opts.getDomainFrontingPort(),
 		tolerateTimeSkewness: opts.getTolerateTimeSkewness(),
-		idleTimeout:          opts.getIdleTimeout(),
 		bufferSize:           opts.getBufferSize(),
 		telegram:             tg,
 	}

mtglib/proxy_opts.go

@@ -143,14 +143,6 @@ func (p ProxyOpts) getDomainFrontingPort() int {
 	return int(p.DomainFrontingPort)
 }
 
-func (p ProxyOpts) getIdleTimeout() time.Duration {
-	if p.IdleTimeout == 0 {
-		return DefaultIdleTimeout
-	}
-
-	return p.IdleTimeout
-}
-
 func (p ProxyOpts) getTolerateTimeSkewness() time.Duration {
 	if p.TolerateTimeSkewness == 0 {
 		return DefaultTolerateTimeSkewness

network/default.go

@@ -5,8 +5,6 @@ import (
 	"fmt"
 	"net"
 	"time"
-
-	"github.com/libp2p/go-reuseport"
 )
 
 type defaultDialer struct {
@@ -31,36 +29,14 @@ func (d *defaultDialer) DialContext(ctx context.Context, network, address string
 		return nil, fmt.Errorf("cannot dial to %s: %w", address, err)
 	}
 
-	tcpConn, ok := conn.(*net.TCPConn)
+	// we do not need to call to end user. End users call us.
-	if !ok {
+	if err := SetServerSocketOptions(conn, d.bufferSize); err != nil {
-		panic("conn type is not tcp")
-	}
-
-	if err := tcpConn.SetNoDelay(true); err != nil {
 		conn.Close()
 
-		return nil, fmt.Errorf("cannot set TCP_NO_DELAY: %w", err)
+		return nil, fmt.Errorf("cannot set socket options: %w", err)
 	}
 
-	if err := tcpConn.SetReadBuffer(d.bufferSize); err != nil {
+	return conn, nil
-		tcpConn.Close()
-
-		return nil, fmt.Errorf("cannot set read buffer size: %w", err)
-	}
-
-	if err := tcpConn.SetWriteBuffer(d.bufferSize); err != nil {
-		tcpConn.Close()
-
-		return nil, fmt.Errorf("cannot set write buffer size: %w", err)
-	}
-
-	if err := tcpConn.SetKeepAlive(true); err != nil {
-		tcpConn.Close()
-
-		return nil, fmt.Errorf("cannot enable keep-alive: %w", err)
-	}
-
-	return tcpConn, nil
 }
 
 // NewDefaultDialer build a new dialer which dials bypassing proxies
@@ -87,7 +63,6 @@ func NewDefaultDialer(timeout time.Duration, bufferSize int) (Dialer, error) {
 	return &defaultDialer{
 		Dialer: net.Dialer{
 			Timeout: timeout,
-			Control: reuseport.Control,
 		},
 		bufferSize: bufferSize,
 	}, nil

network/init.go

@@ -70,6 +70,10 @@ const (
 
 	// DNSTimeout defines a timeout for DNS queries.
 	DNSTimeout = 5 * time.Second
+
+	// tcpLingerTimeout defines a number of seconds to wait for sending
+	// unacknowledged data.
+	tcpLingerTimeout = 1
 )
 
 var (

network/sockopts.go

@@ -0,0 +1,71 @@
+package network
+
+import (
+	"fmt"
+	"net"
+
+	"golang.org/x/sys/unix"
+)
+
+// SetClientSocketOptions tunes a TCP socket that represents a connection to
+// end user (not Telegram service or fronting domain).
+func SetClientSocketOptions(conn net.Conn, bufferSize int) error {
+	tcpConn := conn.(*net.TCPConn) // nolint: forcetypeassert
+
+	if err := tcpConn.SetNoDelay(false); err != nil {
+		return fmt.Errorf("cannot disable TCP_NO_DELAY: %w", err)
+	}
+
+	return setCommonSocketOptions(tcpConn, bufferSize)
+}
+
+// SetServerSocketOptions tunes a TCP socket that represents a connection to
+// remote server like Telegram or fronting domain (but not end user).
+func SetServerSocketOptions(conn net.Conn, bufferSize int) error {
+	tcpConn := conn.(*net.TCPConn) // nolint: forcetypeassert
+
+	if err := tcpConn.SetNoDelay(true); err != nil {
+		return fmt.Errorf("cannot enable TCP_NO_DELAY: %w", err)
+	}
+
+	return setCommonSocketOptions(tcpConn, bufferSize)
+}
+
+func setCommonSocketOptions(conn *net.TCPConn, bufferSize int) error {
+	if err := conn.SetReadBuffer(bufferSize); err != nil {
+		return fmt.Errorf("cannot set read buffer size: %w", err)
+	}
+
+	if err := conn.SetWriteBuffer(bufferSize); err != nil {
+		return fmt.Errorf("cannot set write buffer size: %w", err)
+	}
+
+	if err := conn.SetKeepAlive(false); err != nil {
+		return fmt.Errorf("cannot disable TCP keepalive probes: %w", err)
+	}
+
+	if err := conn.SetLinger(tcpLingerTimeout); err != nil {
+		return fmt.Errorf("cannot set TCP linger timeout: %w", err)
+	}
+
+	rawConn, err := conn.SyscallConn()
+	if err != nil {
+		return fmt.Errorf("cannot get underlying raw connection")
+	}
+
+	rawConn.Control(func(fd uintptr) { // nolint: errcheck
+		err = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEADDR, 1)
+		if err != nil {
+			err = fmt.Errorf("cannot set SO_REUSEADDR: %w", err)
+
+			return
+		}
+
+		err = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEPORT, 1)
+		if err != nil {
+			err = fmt.Errorf("cannot set SO_REUSEPORT: %w", err)
+		}
+	})
+
+	return nil
+}