mirror of
https://github.com/itzg/mc-router.git
synced 2024-06-30 11:15:32 +02:00
291 lines
8.1 KiB
Go
291 lines
8.1 KiB
Go
package server
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import (
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"bytes"
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"context"
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"github.com/go-kit/kit/metrics"
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"github.com/itzg/mc-router/mcproto"
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"github.com/juju/ratelimit"
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"github.com/pires/go-proxyproto"
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"github.com/sirupsen/logrus"
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"io"
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"net"
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"strconv"
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"time"
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)
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const (
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handshakeTimeout = 5 * time.Second
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)
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var noDeadline time.Time
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type Connector interface {
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StartAcceptingConnections(ctx context.Context, listenAddress string, connRateLimit int) error
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}
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type ConnectorMetrics struct {
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Errors metrics.Counter
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BytesTransmitted metrics.Counter
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Connections metrics.Counter
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ActiveConnections metrics.Gauge
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}
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func NewConnector(metrics *ConnectorMetrics, sendProxyProto bool) Connector {
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return &connectorImpl{
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metrics: metrics,
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sendProxyProto: sendProxyProto,
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}
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}
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type connectorImpl struct {
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state mcproto.State
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metrics *ConnectorMetrics
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sendProxyProto bool
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}
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func (c *connectorImpl) StartAcceptingConnections(ctx context.Context, listenAddress string, connRateLimit int) error {
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ln, err := net.Listen("tcp", listenAddress)
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if err != nil {
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logrus.WithError(err).Fatal("Unable to start listening")
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return err
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}
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logrus.WithField("listenAddress", listenAddress).Info("Listening for Minecraft client connections")
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go c.acceptConnections(ctx, ln, connRateLimit)
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return nil
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}
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func (c *connectorImpl) acceptConnections(ctx context.Context, ln net.Listener, connRateLimit int) {
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//noinspection GoUnhandledErrorResult
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defer ln.Close()
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bucket := ratelimit.NewBucketWithRate(float64(connRateLimit), int64(connRateLimit*2))
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for {
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select {
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case <-ctx.Done():
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return
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case <-time.After(bucket.Take(1)):
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conn, err := ln.Accept()
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if err != nil {
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logrus.WithError(err).Error("Failed to accept connection")
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} else {
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go c.HandleConnection(ctx, conn)
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}
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}
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}
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}
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func (c *connectorImpl) HandleConnection(ctx context.Context, frontendConn net.Conn) {
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c.metrics.Connections.With("side", "frontend").Add(1)
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//noinspection GoUnhandledErrorResult
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defer frontendConn.Close()
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clientAddr := frontendConn.RemoteAddr()
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logrus.
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WithField("client", clientAddr).
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Info("Got connection")
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defer logrus.WithField("client", clientAddr).Debug("Closing frontend connection")
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inspectionBuffer := new(bytes.Buffer)
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inspectionReader := io.TeeReader(frontendConn, inspectionBuffer)
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if err := frontendConn.SetReadDeadline(time.Now().Add(handshakeTimeout)); err != nil {
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logrus.
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WithError(err).
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WithField("client", clientAddr).
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Error("Failed to set read deadline")
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c.metrics.Errors.With("type", "read_deadline").Add(1)
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return
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}
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packet, err := mcproto.ReadPacket(inspectionReader, clientAddr, c.state)
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if err != nil {
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logrus.WithError(err).WithField("clientAddr", clientAddr).Error("Failed to read packet")
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c.metrics.Errors.With("type", "read").Add(1)
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return
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}
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logrus.
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WithField("client", clientAddr).
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WithField("length", packet.Length).
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WithField("packetID", packet.PacketID).
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Debug("Got packet")
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if packet.PacketID == mcproto.PacketIdHandshake {
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handshake, err := mcproto.ReadHandshake(packet.Data)
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if err != nil {
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logrus.WithError(err).WithField("clientAddr", clientAddr).
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Error("Failed to read handshake")
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c.metrics.Errors.With("type", "read").Add(1)
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return
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}
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logrus.
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WithField("client", clientAddr).
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WithField("handshake", handshake).
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Debug("Got handshake")
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serverAddress := handshake.ServerAddress
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c.findAndConnectBackend(ctx, frontendConn, clientAddr, inspectionBuffer, serverAddress)
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} else if packet.PacketID == mcproto.PacketIdLegacyServerListPing {
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handshake, ok := packet.Data.(*mcproto.LegacyServerListPing)
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if !ok {
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logrus.
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WithField("client", clientAddr).
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WithField("packet", packet).
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Warn("Unexpected data type for PacketIdLegacyServerListPing")
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c.metrics.Errors.With("type", "unexpected_content").Add(1)
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return
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}
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logrus.
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WithField("client", clientAddr).
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WithField("handshake", handshake).
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Debug("Got legacy server list ping")
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serverAddress := handshake.ServerAddress
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c.findAndConnectBackend(ctx, frontendConn, clientAddr, inspectionBuffer, serverAddress)
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} else {
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logrus.
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WithField("client", clientAddr).
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WithField("packetID", packet.PacketID).
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Error("Unexpected packetID, expected handshake")
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c.metrics.Errors.With("type", "unexpected_content").Add(1)
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return
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}
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}
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func (c *connectorImpl) findAndConnectBackend(ctx context.Context, frontendConn net.Conn,
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clientAddr net.Addr, preReadContent io.Reader, serverAddress string) {
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backendHostPort, resolvedHost := Routes.FindBackendForServerAddress(serverAddress)
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if backendHostPort == "" {
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logrus.WithField("serverAddress", serverAddress).Warn("Unable to find registered backend")
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c.metrics.Errors.With("type", "missing_backend").Add(1)
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return
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}
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logrus.
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WithField("client", clientAddr).
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WithField("server", serverAddress).
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WithField("backendHostPort", backendHostPort).
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Info("Connecting to backend")
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backendConn, err := net.Dial("tcp", backendHostPort)
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if err != nil {
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logrus.
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WithError(err).
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WithField("client", clientAddr).
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WithField("serverAddress", serverAddress).
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WithField("backend", backendHostPort).
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Warn("Unable to connect to backend")
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c.metrics.Errors.With("type", "backend_failed").Add(1)
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return
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}
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c.metrics.Connections.With("side", "backend", "host", resolvedHost).Add(1)
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c.metrics.ActiveConnections.Add(1)
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defer c.metrics.ActiveConnections.Add(-1)
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// PROXY protocol implementation
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if c.sendProxyProto {
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remoteHostStr, _, _ := net.SplitHostPort(backendHostPort)
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sourceAddrStr, sourcePortStr, _ := net.SplitHostPort(clientAddr.String())
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sourcePort, _ := strconv.Atoi(sourcePortStr)
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header := &proxyproto.Header{
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Version: 2,
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Command: proxyproto.PROXY,
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TransportProtocol: proxyproto.TCPv4,
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SourceAddr: &net.TCPAddr{
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IP: net.ParseIP(sourceAddrStr),
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Port: sourcePort,
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},
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DestinationAddr: &net.TCPAddr{
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IP: net.ParseIP(remoteHostStr),
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},
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}
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_, err = header.WriteTo(backendConn)
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if err != nil {
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logrus.
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WithError(err).
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WithField("clientAddr", header.SourceAddr).
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WithField("destAddr", header.DestinationAddr).
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Error("Failed to write PROXY header")
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c.metrics.Errors.With("type", "proxy_write").Add(1)
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_ = backendConn.Close()
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return
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}
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}
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amount, err := io.Copy(backendConn, preReadContent)
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if err != nil {
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logrus.WithError(err).Error("Failed to write handshake to backend connection")
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c.metrics.Errors.With("type", "backend_failed").Add(1)
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return
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}
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logrus.WithField("amount", amount).Debug("Relayed handshake to backend")
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if err = frontendConn.SetReadDeadline(noDeadline); err != nil {
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logrus.
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WithError(err).
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WithField("client", clientAddr).
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Error("Failed to clear read deadline")
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c.metrics.Errors.With("type", "read_deadline").Add(1)
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return
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}
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c.pumpConnections(ctx, frontendConn, backendConn)
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return
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}
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func (c *connectorImpl) pumpConnections(ctx context.Context, frontendConn, backendConn net.Conn) {
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//noinspection GoUnhandledErrorResult
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defer backendConn.Close()
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clientAddr := frontendConn.RemoteAddr()
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defer logrus.WithField("client", clientAddr).Debug("Closing backend connection")
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errors := make(chan error, 2)
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go c.pumpFrames(backendConn, frontendConn, errors, "backend", "frontend", clientAddr)
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go c.pumpFrames(frontendConn, backendConn, errors, "frontend", "backend", clientAddr)
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select {
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case err := <-errors:
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if err != io.EOF {
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logrus.WithError(err).
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WithField("client", clientAddr).
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Error("Error observed on connection relay")
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c.metrics.Errors.With("type", "relay").Add(1)
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}
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case <-ctx.Done():
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logrus.Debug("Observed context cancellation")
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}
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}
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func (c *connectorImpl) pumpFrames(incoming io.Reader, outgoing io.Writer, errors chan<- error, from, to string, clientAddr net.Addr) {
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amount, err := io.Copy(outgoing, incoming)
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logrus.
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WithField("client", clientAddr).
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WithField("amount", amount).
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Infof("Finished relay %s->%s", from, to)
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c.metrics.BytesTransmitted.Add(float64(amount))
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if err != nil {
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errors <- err
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} else {
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// successful io.Copy return nil error, not EOF...to simulate that to trigger outer handling
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errors <- io.EOF
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}
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}
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