[cdc_rsync] Use ephemeral port on client (#96)

Instead of calling netstat locally to find out available ports in a
tight range, call bind() with port zero to find an available ephemeral
port. This is faster and much simpler, and will eventually help
getting rid of PortManager.

Also fixes issues with running SSH commands on Windows when the remote
shell is Powershell (aka Backslash Bingo).

cdc_rsync/BUILD

@@ -71,9 +71,9 @@ cc_library(
         "//common:path",
         "//common:path_filter",
         "//common:platform",
-        "//common:port_manager",
         "//common:process",
         "//common:remote_util",
+        "//common:server_socket",
         "//common:socket",
         "//common:status",
         "//common:status_macros",

cdc_rsync/cdc_rsync_client.cc

@@ -30,9 +30,9 @@
 #include "common/gamelet_component.h"
 #include "common/log.h"
 #include "common/path.h"
-#include "common/port_manager.h"
 #include "common/process.h"
 #include "common/remote_util.h"
+#include "common/server_socket.h"
 #include "common/status.h"
 #include "common/status_macros.h"
 #include "common/stopwatch.h"
@@ -113,12 +113,6 @@ CdcRsyncClient::CdcRsyncClient(const Options& options,
       remote_util_->SetSftpCommand(options_.sftp_command);
     }
   }
-
-  // Note that remote_util_.get() may be null.
-  port_manager_ = std::make_unique<PortManager>(
-      "cdc_rsync_ports_f77bcdfe-368c-4c45-9f01-230c5e7e2132",
-      options.forward_port_first, options.forward_port_last, &process_factory_,
-      nullptr /* never reserve remote ports */);
 }
 
 CdcRsyncClient::~CdcRsyncClient() {
@@ -288,22 +282,15 @@ absl::Status CdcRsyncClient::StartServer(const ServerArch& arch) {
     return SetTag(MakeStatus("Redeploy server"), Tag::kDeployServer);
   }
 
+  // Start up sockets.
+  RETURN_IF_ERROR(Socket::Initialize(), "Failed to initialize sockets");
+  socket_finalizer_ = std::make_unique<SocketFinalizer>();
+
   // Now that we know which port the server is using, set up port forwarding.
   std::unique_ptr<Process> fwd_process;
   int local_port = server_listen_port_;
   if (IsRemoteConnection()) {
-    absl::StatusOr<int> local_port_or = port_manager_->ReservePort(
+    ASSIGN_OR_RETURN(local_port, ServerSocket::FindAvailablePort());
-        options_.connection_timeout_sec, arch.GetType());
-
-    if (absl::IsResourceExhausted(local_port_or.status())) {
-      // Port in use.
-      return SetTag(local_port_or.status(), Tag::kAddressInUse);
-    }
-    if (!local_port_or.ok()) {
-      return local_port_or.status();
-    }
-
-    local_port = *local_port_or;
     ProcessStartInfo start_info =
         remote_util_->BuildProcessStartInfoForSshPortForward(
             local_port, server_listen_port_, /*reverse=*/false);
@@ -313,14 +300,8 @@ absl::Status CdcRsyncClient::StartServer(const ServerArch& arch) {
                     "Failed to start cdc_rsync_server process");
   }
 
-  // Connect to the socket with port |local_port|.
+  // Poll the connection to the socket with port |local_port| until the port
-  status = Socket::Initialize();
+  // forwarding connection is set up.
-  if (!status.ok()) {
-    return WrapStatus(status, "Failed to initialize sockets");
-  }
-  socket_finalizer_ = std::make_unique<SocketFinalizer>();
-
-  // Poll until the port forwarding connection is set up.
   timeout_timer.Reset();
   for (;;) {
     assert(local_port != 0);

cdc_rsync/cdc_rsync_client.h

@@ -30,7 +30,6 @@
 
 namespace cdc_ft {
 
-class PortManager;
 class Process;
 class RemoteUtil;
 class ServerArch;
@@ -53,8 +52,6 @@ class CdcRsyncClient {
     std::string copy_dest;
     int compress_level = 6;
     int connection_timeout_sec = 10;
-    int forward_port_first = 44450;
-    int forward_port_last = 44459;
     std::string ssh_command;
     std::string sftp_command;
     std::string sources_dir;  // Base dir for files loaded for --files-from.
@@ -132,7 +129,6 @@ class CdcRsyncClient {
   const std::string destination_;
   WinProcessFactory process_factory_;
   std::unique_ptr<RemoteUtil> remote_util_;
-  std::unique_ptr<PortManager> port_manager_;
   std::unique_ptr<SocketFinalizer> socket_finalizer_;
   ClientSocket socket_;
   MessagePump message_pump_{&socket_, MessagePump::PacketReceivedDelegate()};

cdc_rsync/params.cc

@@ -80,8 +80,6 @@ Options:
     --sftp-command <cmd>    Path and arguments of sftp command to use, e.g.
                             "C:\path\to\sftp.exe -P 12345 -i id_rsa -oUserKnownHostsFile=known_hosts"
                             Can also be specified by the CDC_SFTP_COMMAND environment variable.
-    --forward-port <port>   TCP port or range used for SSH port forwarding (default: 44450-44459).
-                            If a range is specified, searches for available ports (slower).
 -h, --help                  Help for cdc_rsync
 )";
 
@@ -305,15 +303,9 @@ OptionResult HandleParameter(const std::string& key, const char* value,
   }
 
   if (key == "forward-port") {
-    if (!ValidateValue(key, value)) return OptionResult::kError;
+    // This param is no longer needed. Just print a warning for backwards
-    uint16_t first, last;
+    // compatibility.
-    if (!port_range::Parse(value, &first, &last)) {
+    std::cout << "--forward-port argument no longer needed" << std::endl;
-      PrintError("Failed to parse %s=%s, expected <port> or <port1>-<port2>",
-                 key, value);
-      return OptionResult::kError;
-    }
-    params->options.forward_port_first = first;
-    params->options.forward_port_last = last;
     return OptionResult::kConsumedKeyValue;
   }
 

cdc_rsync/params_test.cc

@@ -585,40 +585,6 @@ TEST_F(ParamsTest, IncludeExcludeMixed_ProperOrder) {
   ExpectNoError();
 }
 
-TEST_F(ParamsTest, ForwardPort_Single) {
-  const char* argv[] = {"cdc_rsync.exe", "--forward-port=65535", kSrc,
-                        kUserHostDst, NULL};
-  EXPECT_TRUE(Parse(static_cast<int>(std::size(argv)) - 1, argv, &parameters_));
-  EXPECT_EQ(parameters_.options.forward_port_first, 65535);
-  EXPECT_EQ(parameters_.options.forward_port_last, 65535);
-  ExpectNoError();
-}
-
-TEST_F(ParamsTest, ForwardPort_Range) {
-  const char* argv[] = {
-      "cdc_rsync.exe", "--forward-port", "1-2", kSrc, kUserHostDst, NULL};
-  EXPECT_TRUE(Parse(static_cast<int>(std::size(argv)) - 1, argv, &parameters_));
-  EXPECT_EQ(parameters_.options.forward_port_first, 1);
-  EXPECT_EQ(parameters_.options.forward_port_last, 2);
-  ExpectNoError();
-}
-
-TEST_F(ParamsTest, ForwardPort_NoValue) {
-  const char* argv[] = {"cdc_rsync.exe", "--forward-port=", kSrc, kUserHostDst,
-                        NULL};
-  EXPECT_FALSE(
-      Parse(static_cast<int>(std::size(argv)) - 1, argv, &parameters_));
-  ExpectError(NeedsValueError("forward-port"));
-}
-
-TEST_F(ParamsTest, ForwardPort_BadValueTooSmall) {
-  const char* argv[] = {"cdc_rsync.exe", "--forward-port=0", kSrc, kUserHostDst,
-                        NULL};
-  EXPECT_FALSE(
-      Parse(static_cast<int>(std::size(argv)) - 1, argv, &parameters_));
-  ExpectError("Failed to parse");
-}
-
 }  // namespace
 }  // namespace params
 }  // namespace cdc_ft

cdc_rsync/server_arch.cc

@@ -147,8 +147,7 @@ absl::StatusOr<ServerArch> ServerArch::DetectFromRemoteDevice(
   // Note: That space after PROCESSOR_ARCHITECTURE is important or else Windows
   //       command magic interprets quotes as part of the string.
   std::string arch_out;
-  std::string windows_cmd =
+  std::string windows_cmd = "\"cmd /C set PROCESSOR_ARCHITECTURE \"";
-      RemoteUtil::QuoteForSsh("cmd /C set PROCESSOR_ARCHITECTURE ");
   status = remote_util->RunWithCapture(windows_cmd,
                                        "set PROCESSOR_ARCHITECTURE", &arch_out,
                                        nullptr, ArchType::kWindows_x86_64);
@@ -223,14 +222,13 @@ std::string ServerArch::GetStartServerCommand(int exit_code_not_found,
     // a minor issue and means we display "Deploying server..." instead of
     // "Server not deployed. Deploying...";
     return RemoteUtil::QuoteForWindows(
-        absl::StrFormat("powershell -Command \" "
+        absl::StrFormat("powershell -Command "
                         "Set-StrictMode -Version 2; "
                         "$ErrorActionPreference = 'Stop'; "
                         "if (-not (Test-Path -Path '%s')) { "
                         "  exit %i; "
                         "} "
-                        "%s %s "
+                        "%s %s",
-                        "\"",
                         server_path, exit_code_not_found, server_path, args));
   }
 

cdc_rsync_server/cdc_rsync_server.cc

@@ -289,10 +289,7 @@ bool CdcRsyncServer::CheckComponents(
 }
 
 absl::Status CdcRsyncServer::Run() {
-  absl::Status status = Socket::Initialize();
+  RETURN_IF_ERROR(Socket::Initialize(), "Failed to initialize sockets");
-  if (!status.ok()) {
-    return WrapStatus(status, "Failed to initialize sockets");
-  }
   socket_finalizer_ = std::make_unique<SocketFinalizer>();
 
   socket_ = std::make_unique<ServerSocket>();
@@ -307,10 +304,8 @@ absl::Status CdcRsyncServer::Run() {
   printf("Port %i: Server is listening\n", port);
   fflush(stdout);
 
-  status = socket_->WaitForConnection();
+  RETURN_IF_ERROR(socket_->WaitForConnection(),
-  if (!status.ok()) {
+                  "Failed to establish a connection");
-    return WrapStatus(status, "Failed to establish a connection");
-  }
 
   message_pump_ = std::make_unique<MessagePump>(
       socket_.get(),
@@ -318,7 +313,7 @@ absl::Status CdcRsyncServer::Run() {
   message_pump_->StartMessagePump();
 
   LOG_INFO("Client connected. Starting to sync.");
-  status = Sync();
+  absl::Status status = Sync();
   if (!status.ok()) {
     socket_->ShutdownSendingEnd().IgnoreError();
     return status;

common/server_socket.cc

@@ -125,6 +125,12 @@ ServerSocket::~ServerSocket() {
   StopListening();
 }
 
+// static
+absl::StatusOr<int> ServerSocket::FindAvailablePort() {
+  ServerSocket socket;
+  return socket.StartListening(0);
+}
+
 absl::StatusOr<int> ServerSocket::StartListening(int port) {
   if (socket_info_->listen_sock != kInvalidSocket) {
     return MakeStatus("Already listening");
@@ -246,7 +252,7 @@ absl::StatusOr<int> ServerSocket::StartListeningInternal(int port,
 
 void ServerSocket::StopListening() {
   Close(&socket_info_->listen_sock);
-  LOG_INFO("Stopped listening.");
+  LOG_DEBUG("Stopped listening.");
 }
 
 absl::Status ServerSocket::WaitForConnection() {
@@ -268,7 +274,7 @@ absl::Status ServerSocket::WaitForConnection() {
 
 void ServerSocket::Disconnect() {
   Close(&socket_info_->conn_sock);
-  LOG_INFO("Disconnected");
+  LOG_DEBUG("Disconnected");
 }
 
 absl::Status ServerSocket::ShutdownSendingEnd() {

common/server_socket.h

@@ -30,6 +30,15 @@ class ServerSocket : public Socket {
   ServerSocket();
   ~ServerSocket();
 
+  // Returns an available ephemeral port that can be used as a listening port.
+  // Note that calling this function, followed by StartListening() or similar,
+  // is slightly racy as another process might use the port in the meantime.
+  // However, the OS usually returns ephemeral ports in a round-robin manner,
+  // and ports remain in TIME_WAIT state for a while, which may block other apps
+  // from reusing the port. Hence, the chances of races are small. Nevertheless,
+  // consider calling StartListening() with zero |port| if possible.
+  static absl::StatusOr<int> FindAvailablePort();
+
   // Starts listening for connections on |port|.
   // Passing 0 as port will bind to any available port.
   // Returns the port that was bound to.

integration_tests/cdc_rsync/connection_test.py

@@ -27,37 +27,19 @@ RETURN_CODE_GENERIC_ERROR = 1
 RETURN_CODE_CONNECTION_TIMEOUT = 2
 RETURN_CODE_ADDRESS_IN_USE = 4
 
-FIRST_PORT = 44450
-LAST_PORT = 44459
-
 
 class ConnectionTest(test_base.CdcRsyncTest):
   """cdc_rsync connection test class."""
 
-  def test_valid_instance(self):
-    """Runs rsync with --instance option for a valid id.
-
-       1) Uploads a file with --instance option instead of --ip --port.
-       2) Checks the file exists on the used instance.
-    """
-    utils.create_test_file(self.local_data_path, 1024)
-    res = utils.run_rsync(self.local_data_path, self.remote_base_dir)
-    self._assert_rsync_success(res)
-    self.assertTrue(utils.does_file_exist_remotely(self.remote_data_path))
-
   def test_invalid_instance(self):
-    """Runs rsync with --instance option for an invalid id.
+    """Runs rsync with an invalid host"""
-
-       1) Uploads a file with --instance option for a non-existing id.
-       2) Checks the error message.
-    """
     bad_host = 'bad_host'
 
     utils.create_test_file(self.local_data_path, 1024)
     res = utils.run_rsync(self.local_data_path,
                           bad_host + ":" + self.remote_base_dir)
     self.assertEqual(res.returncode, RETURN_CODE_GENERIC_ERROR)
-    self.assertIn('Failed to find available ports', str(res.stderr))
+    self.assertIn('Failed to detect remote architecture', str(res.stderr))
 
   def test_contimeout(self):
     """Runs rsync with --contimeout option for an invalid ip.
@@ -89,7 +71,7 @@ class ConnectionTest(test_base.CdcRsyncTest):
 
   def test_multiple_instances(self):
     """Runs multiple instances of rsync at the same time."""
-    num_instances = LAST_PORT - FIRST_PORT + 1
+    num_instances = 10
 
     local_data_paths = []
     for n in range(num_instances):
@@ -106,26 +88,6 @@ class ConnectionTest(test_base.CdcRsyncTest):
       for r in res:
         self._assert_rsync_success(r.result())
 
-  def test_address_in_use(self):
-    """Blocks all ports and checks that rsync fails with the expected error."""
-    sockets = []
-    try:
-      # Occupy all ports.
-      for port in range(FIRST_PORT, LAST_PORT + 1):
-        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        sockets.append(s)
-        s.bind(('127.0.0.1', port))
-        s.listen()
-
-      # rsync shouldn't be able to find an available port now.
-      utils.create_test_file(self.local_data_path, 1024)
-      res = utils.run_rsync(self.local_data_path, self.remote_base_dir)
-      self.assertIn('All ports are already in use', str(res.stderr))
-
-    finally:
-      for s in sockets:
-        s.close()
-
 
 if __name__ == '__main__':
   test_base.test_base.main()