Releasing the former Stadia file transfer tools

The tools allow efficient and fast synchronization of large directory
trees from a Windows workstation to a Linux target machine.

cdc_rsync* support efficient copy of files by using content-defined
chunking (CDC) to identify chunks within files that can be reused.

asset_stream_manager + cdc_fuse_fs support efficient streaming of a
local directory to a remote virtual file system based on FUSE. It also
employs CDC to identify and reuse unchanged data chunks.

common/port_manager.h

@@ -0,0 +1,113 @@
+/*
+ * Copyright 2022 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef COMMON_PORT_MANAGER_H_
+#define COMMON_PORT_MANAGER_H_
+
+#include <absl/status/statusor.h>
+
+#include <memory>
+#include <string>
+#include <unordered_set>
+
+#include "common/clock.h"
+
+namespace cdc_ft {
+
+class ProcessFactory;
+class RemoteUtil;
+class SharedMemory;
+
+// Class for reserving ports globally. Use if there can be multiple processes
+// of the same type that might request ports at the same time, e.g. multiple
+// cdc_rsync.exe processes running concurrently.
+class PortManager {
+ public:
+  // |unique_name| is a globally unique name used for shared memory to
+  // synchronize port reservation. The range of possible ports managed by this
+  // instance is [|first_port|, |last_port|]. |process_factory| is a valid
+  // pointer to a ProcessFactory instance to run processes locally.
+  // |remote_util| is a valid pointer to a RemoteUtil instance to run processes
+  // remotely.
+  PortManager(std::string unique_name, int first_port, int last_port,
+              ProcessFactory* process_factory, RemoteUtil* remote_util,
+              SystemClock* system_clock = DefaultSystemClock::GetInstance(),
+              SteadyClock* steady_clock = DefaultSteadyClock::GetInstance());
+  ~PortManager();
+
+  // Reserves a port in the range passed to the constructor. The port is
+  // released automatically upon destruction if ReleasePort() is not called
+  // explicitly.
+  // |timeout_sec| is the timeout for finding available ports on the gamelet
+  // instance. Returns a DeadlineExceeded error if the timeout is exceeded.
+  // Returns a ResourceExhausted error if no ports are available.
+  absl::StatusOr<int> ReservePort(int timeout_sec);
+
+  // Releases a reserved port.
+  absl::Status ReleasePort(int port);
+
+  //
+  // Lower-level interface for finding available ports directly.
+  //
+
+  // Finds available ports in the range [first_port, last_port] for port
+  // forwarding on the local workstation.
+  // |ip| is the IP address to filter by.
+  // |process_factory| is used to create a netstat process.
+  // |forward_output_to_log| determines whether the stderr of netstat is
+  // forwarded to the logs. Returns ResourceExhaustedError if no port is
+  // available.
+  static absl::StatusOr<std::unordered_set<int>> FindAvailableLocalPorts(
+      int first_port, int last_port, const char* ip,
+      ProcessFactory* process_factory, bool forward_output_to_log);
+
+  // Finds available ports in the range [first_port, last_port] for port
+  // forwarding on the instance.
+  // |ip| is the IP address to filter by.
+  // |process_factory| is used to create a netstat process.
+  // |remote_util| is used to connect to the instance.
+  // |timeout_sec| is the connection timeout in seconds.
+  // |forward_output_to_log| determines whether the stderr of netstat is
+  // forwarded to the logs. Returns a DeadlineExceeded error if the timeout is
+  // exceeded. Returns ResourceExhaustedError if no port is available.
+  static absl::StatusOr<std::unordered_set<int>> FindAvailableRemotePorts(
+      int first_port, int last_port, const char* ip,
+      ProcessFactory* process_factory, RemoteUtil* remote_util, int timeout_sec,
+      bool forward_output_to_log,
+      SteadyClock* steady_clock = DefaultSteadyClock::GetInstance());
+
+ private:
+  // Returns a list of available ports in the range [|first_port|, |last_port|]
+  // from the given |netstat_output|. |ip| is the IP address to look for, e.g.
+  // "127.0.0.1".
+  // Returns ResourceExhaustedError if no port is available.
+  static absl::StatusOr<std::unordered_set<int>> FindAvailablePorts(
+      int first_port, int last_port, const std::string& netstat_output,
+      const char* ip);
+
+  int first_port_;
+  int last_port_;
+  ProcessFactory* process_factory_;
+  RemoteUtil* remote_util_;
+  SystemClock* system_clock_;
+  SteadyClock* steady_clock_;
+  std::unique_ptr<SharedMemory> shared_mem_;
+  std::unordered_set<int> reserved_ports_;
+};
+
+}  // namespace cdc_ft
+
+#endif  // COMMON_PORT_MANAGER_H_