mirror of
https://github.com/itzg/mc-router.git
synced 2024-12-22 16:17:38 +01:00
396 lines
11 KiB
Go
396 lines
11 KiB
Go
package server
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import (
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"bytes"
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"context"
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"io"
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"net"
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"sync"
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"sync/atomic"
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"time"
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"golang.ngrok.com/ngrok"
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"golang.ngrok.com/ngrok/config"
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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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)
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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 ConnectorMetrics struct {
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Errors metrics.Counter
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BytesTransmitted metrics.Counter
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ConnectionsFrontend metrics.Counter
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ConnectionsBackend metrics.Counter
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ActiveConnections metrics.Gauge
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}
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func NewConnector(metrics *ConnectorMetrics, sendProxyProto bool, receiveProxyProto bool, trustedProxyNets []*net.IPNet) *Connector {
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return &Connector{
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metrics: metrics,
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sendProxyProto: sendProxyProto,
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connectionsCond: sync.NewCond(&sync.Mutex{}),
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receiveProxyProto: receiveProxyProto,
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trustedProxyNets: trustedProxyNets,
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}
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}
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type Connector struct {
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state mcproto.State
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metrics *ConnectorMetrics
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sendProxyProto bool
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receiveProxyProto bool
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trustedProxyNets []*net.IPNet
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activeConnections int32
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connectionsCond *sync.Cond
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ngrokToken string
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}
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func (c *Connector) StartAcceptingConnections(ctx context.Context, listenAddress string, connRateLimit int) error {
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ln, err := c.createListener(ctx, listenAddress)
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if err != nil {
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return err
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}
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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 *Connector) createListener(ctx context.Context, listenAddress string) (net.Listener, error) {
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if c.ngrokToken != "" {
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ngrokTun, err := ngrok.Listen(ctx,
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config.TCPEndpoint(),
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ngrok.WithAuthtoken(c.ngrokToken),
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)
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if err != nil {
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logrus.WithError(err).Fatal("Unable to start ngrok tunnel")
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return nil, err
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}
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logrus.WithField("ngrokUrl", ngrokTun.URL()).Info("Listening for Minecraft client connections via ngrok tunnel")
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return ngrokTun, nil
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}
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listener, 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 nil, err
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}
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logrus.WithField("listenAddress", listenAddress).Info("Listening for Minecraft client connections")
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if c.receiveProxyProto {
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proxyListener := &proxyproto.Listener{
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Listener: listener,
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Policy: c.createProxyProtoPolicy(),
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}
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logrus.Info("Using PROXY protocol listener")
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return proxyListener, nil
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}
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return listener, nil
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}
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func (c *Connector) createProxyProtoPolicy() func(upstream net.Addr) (proxyproto.Policy, error) {
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return func(upstream net.Addr) (proxyproto.Policy, error) {
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trustedIpNets := c.trustedProxyNets
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if len(trustedIpNets) == 0 {
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logrus.Debug("No trusted proxy networks configured, using the PROXY header by default")
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return proxyproto.USE, nil
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}
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upstreamIP := upstream.(*net.TCPAddr).IP
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for _, ipNet := range trustedIpNets {
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if ipNet.Contains(upstreamIP) {
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logrus.WithField("upstream", upstream).Debug("IP is in trusted proxies, using the PROXY header")
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return proxyproto.USE, nil
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}
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}
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logrus.WithField("upstream", upstream).Debug("IP is not in trusted proxies, discarding PROXY header")
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return proxyproto.IGNORE, nil
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}
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}
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func (c *Connector) WaitForConnections() {
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c.connectionsCond.L.Lock()
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defer c.connectionsCond.L.Unlock()
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for {
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count := atomic.LoadInt32(&c.activeConnections)
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if count > 0 {
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logrus.Infof("Waiting on %d connection(s)", count)
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c.connectionsCond.Wait()
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} else {
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break
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}
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}
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}
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func (c *Connector) 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 *Connector) HandleConnection(ctx context.Context, frontendConn net.Conn) {
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c.metrics.ConnectionsFrontend.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 *Connector) 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, waker := Routes.FindBackendForServerAddress(ctx, serverAddress)
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if waker != nil {
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if err := waker(ctx); err != nil {
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logrus.WithFields(logrus.Fields{"serverAddress": serverAddress}).WithError(err).Error("failed to wake up backend")
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c.metrics.Errors.With("type", "wakeup_failed").Add(1)
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return
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}
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}
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if backendHostPort == "" {
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logrus.
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WithField("serverAddress", serverAddress).
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WithField("resolvedHost", resolvedHost).
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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.ConnectionsBackend.With("host", resolvedHost).Add(1)
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c.metrics.ActiveConnections.Set(float64(
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atomic.AddInt32(&c.activeConnections, 1)))
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defer func() {
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c.metrics.ActiveConnections.Set(float64(
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atomic.AddInt32(&c.activeConnections, -1)))
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c.connectionsCond.Signal()
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}()
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// PROXY protocol implementation
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if c.sendProxyProto {
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// Determine transport protocol for the PROXY header by "analyzing" the frontend connection's address
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transportProtocol := proxyproto.TCPv4
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ourHostIpPart, _, err := net.SplitHostPort(frontendConn.LocalAddr().String())
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if err != nil {
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logrus.
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WithError(err).
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WithField("localAddr", frontendConn.LocalAddr()).
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Error("Failed to extract host part of our address")
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_ = backendConn.Close()
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return
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}
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ourFrontendIp := net.ParseIP(ourHostIpPart)
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if ourFrontendIp.To4() == nil {
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transportProtocol = proxyproto.TCPv6
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}
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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: transportProtocol,
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SourceAddr: clientAddr,
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DestinationAddr: frontendConn.LocalAddr(), // our end of the client's connection
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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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}
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func (c *Connector) 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 *Connector) 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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func (c *Connector) UseNgrok(token string) {
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c.ngrokToken = token
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}
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