Function PassThrough

pkg/agent/proxy/util/util.go:642–732

PassThrough function is used to pass the network traffic to the destination connection. It also closes the destination connection if the function returns an error.

(ctx context.Context, logger *zap.Logger, clientConn net.Conn, dstCfg *models.ConditionalDstCfg, requestBuffer [][]byte)

// PassThrough function is used to pass the network traffic to the destination connection.
// It also closes the destination connection if the function returns an error.
func PassThrough(ctx context.Context, logger *zap.Logger, clientConn net.Conn, dstCfg *models.ConditionalDstCfg, requestBuffer [][]byte) ([]byte, error) {
	logger.Debug("passing through the network traffic to the destination server", zap.Any("Destination Addr", dstCfg.Addr))
	// making destConn
	var destConn net.Conn
	var err error
	if dstCfg.TLSCfg != nil {
		logger.Debug("trying to establish a TLS connection with the destination server", zap.Any("Destination Addr", dstCfg.Addr))

		destConn, err = tls.Dial("tcp", dstCfg.Addr, dstCfg.TLSCfg)
		if err != nil {
			utils.LogError(logger, err, "failed to dial the conn to destination server", zap.Any("server address", dstCfg.Addr), zap.String("next_step", NextStepDialDestination))
			return nil, err
		}
		logger.Debug("TLS connection established with the destination server", zap.Any("Destination Addr", destConn.RemoteAddr().String()))
	} else {
		logger.Debug("trying to establish a connection with the destination server", zap.Any("Destination Addr", dstCfg.Addr))
		destConn, err = net.Dial("tcp", dstCfg.Addr)
		if err != nil {
			utils.LogError(logger, err, "failed to dial the conn to destination server", zap.Any("server address", dstCfg.Addr), zap.String("next_step", NextStepDialDestination))
			return nil, err
		}
		logger.Debug("connection established with the destination server", zap.Any("Destination Addr", destConn.RemoteAddr().String()))
	}

	logger.Debug("trying to forward requests to target", zap.Any("Destination Addr", destConn.RemoteAddr().String()))
	for _, v := range requestBuffer {
		_, err := destConn.Write(v)
		if err != nil {
			utils.LogError(logger, err, "failed to write request message to the destination server", zap.Any("Destination Addr", destConn.RemoteAddr().String()))
			return nil, err
		}
	}

	destBufferChannel := make(chan []byte)
	clientBufferChannel := make(chan []byte)
	errChannel := make(chan error, 2)
	passthroughContext, cancel := context.WithCancel(ctx)
	defer cancel()

	go func() {
		defer Recover(logger, clientConn, nil)
		defer close(destBufferChannel)
		defer func(destConn net.Conn) {
			err := destConn.Close()
			if err != nil {
				utils.LogError(logger, err, "failed to close the destination connection")
			}
		}(destConn)

		ReadBuffConn(passthroughContext, logger, destConn, destBufferChannel, errChannel, false)
	}()

	go func() {
		defer Recover(logger, clientConn, nil)
		defer close(clientBufferChannel)
		ReadBuffConn(passthroughContext, logger, clientConn, clientBufferChannel, errChannel, false)
	}()