[cdc_rsync] Use any available server port (#94)

Instead of calling netstat on the remote device to detect available
ports, simply call bind with port 0 to bind to any available port.
Since the port is not yet known when cdc_rsync_server.exe is called,
port forwarding needs to be started AFTER the server reports its port.

.github/workflows/create_release.yml

@@ -63,7 +63,6 @@ jobs:
                      --test_output=errors --local_test_jobs=1  \
                      -- //... -//third_party/... -//cdc_rsync_server:file_finder_test
 
-      # The artifact collector doesn't like the fact that bazel-bin is a symlink.
       - name: Copy artifacts
         run: |
           mkdir artifacts
@@ -152,7 +151,6 @@ jobs:
             //manifest/... `
             //metrics/...
 
-      # The artifact collector doesn't like the fact that bazel-bin is a symlink.
       - name: Copy artifacts
         run: |
           mkdir artifacts

.github/workflows/lint.yml

@@ -3,7 +3,7 @@ name: Lint
 on:
   push:
     branches:
-      - master
+      - main
   pull_request:
 
 jobs:

cdc_rsync/cdc_rsync_client.cc

@@ -118,7 +118,7 @@ CdcRsyncClient::CdcRsyncClient(const Options& options,
   port_manager_ = std::make_unique<PortManager>(
       "cdc_rsync_ports_f77bcdfe-368c-4c45-9f01-230c5e7e2132",
       options.forward_port_first, options.forward_port_last, &process_factory_,
-      remote_util_.get());
+      nullptr /* never reserve remote ports */);
 }
 
 CdcRsyncClient::~CdcRsyncClient() {
@@ -127,19 +127,15 @@ CdcRsyncClient::~CdcRsyncClient() {
 }
 
 absl::Status CdcRsyncClient::Run() {
-  // If |remote_util_| is not set, it's a local sync. Otherwise, guess the
+  // For local syncs, cdc_rsync_server runs on this machine. For remote syncs,
-  // architecture of the device that runs cdc_rsync_server from the destination
+  // guess the architecture of the device that runs cdc_rsync_server from the
-  // path, e.g. "C:\path\to\dest" strongly indicates Windows.
+  // destination path, e.g. "C:\path\to\dest" strongly indicates Windows.
-  ServerArch server_arch = !remote_util_
+  ServerArch server_arch = IsRemoteConnection()
-                               ? ServerArch::DetectFromLocalDevice()
+                               ? ServerArch::GuessFromDestination(destination_)
-                               : ServerArch::GuessFromDestination(destination_);
+                               : ServerArch::DetectFromLocalDevice();
-
-  int port;
-  ASSIGN_OR_RETURN(port, FindAvailablePort(&server_arch),
-                   "Failed to find available port");
 
   // Start the server process.
-  absl::Status status = StartServer(port, server_arch);
+  absl::Status status = StartServer(server_arch);
   if (HasTag(status, Tag::kDeployServer) && server_arch.IsGuess() &&
       server_exit_code_ != kServerExitCodeOutOfDate) {
     // Server couldn't be run, e.g. not found or failed to start.
@@ -155,7 +151,7 @@ absl::Status CdcRsyncClient::Run() {
     if (server_arch.GetType() != old_type) {
       LOG_DEBUG("Guessed server arch type wrong, guessed %s, actual %s.",
                 GetArchTypeStr(old_type), server_arch.GetTypeStr());
-      status = StartServer(port, server_arch);
+      status = StartServer(server_arch);
     }
   }
 
@@ -166,7 +162,7 @@ absl::Status CdcRsyncClient::Run() {
       return WrapStatus(status, "Failed to deploy server");
     }
 
-    status = StartServer(port, server_arch);
+    status = StartServer(server_arch);
   }
   if (!status.ok()) {
     return WrapStatus(status, "Failed to start server");
@@ -198,47 +194,7 @@ absl::Status CdcRsyncClient::Run() {
   return status;
 }
 
-absl::StatusOr<int> CdcRsyncClient::FindAvailablePort(ServerArch* server_arch) {
+absl::Status CdcRsyncClient::StartServer(const ServerArch& arch) {
-  // Find available local and remote ports for port forwarding.
-  // If only one port is in the given range, try that without checking.
-  if (options_.forward_port_first >= options_.forward_port_last) {
-    return options_.forward_port_first;
-  }
-
-  assert(server_arch);
-  absl::StatusOr<int> port = port_manager_->ReservePort(
-      options_.connection_timeout_sec, server_arch->GetType());
-
-  if (absl::IsDeadlineExceeded(port.status())) {
-    // Server didn't respond in time.
-    return SetTag(port.status(), Tag::kConnectionTimeout);
-  }
-  if (absl::IsResourceExhausted(port.status())) {
-    // Port in use.
-    return SetTag(port.status(), Tag::kAddressInUse);
-  }
-
-  // If |server_arch| was guessed, calling netstat might have failed because
-  // the arch was wrong. Properly detect it and try again if it changed.
-  if (!port.ok() && server_arch->IsGuess()) {
-    const ArchType old_type = server_arch->GetType();
-    LOG_DEBUG(
-        "Failed to reserve port, retrying after detecting remote arch: %s",
-        port.status().ToString());
-    ASSIGN_OR_RETURN(*server_arch,
-                     ServerArch::DetectFromRemoteDevice(remote_util_.get()));
-    assert(!server_arch->IsGuess());
-    if (server_arch->GetType() != old_type) {
-      LOG_DEBUG("Guessed server arch type wrong, guessed %s, actual %s.",
-                GetArchTypeStr(old_type), server_arch->GetTypeStr());
-      return FindAvailablePort(server_arch);
-    }
-  }
-
-  return port;
-}
-
-absl::Status CdcRsyncClient::StartServer(int port, const ServerArch& arch) {
   assert(!server_process_);
 
   // Components are expected to reside in the same dir as the executable.
@@ -262,20 +218,20 @@ absl::Status CdcRsyncClient::StartServer(int port, const ServerArch& arch) {
   ProcessStartInfo start_info;
   start_info.name = "cdc_rsync_server";
 
-  if (remote_util_) {
+  if (IsRemoteConnection()) {
     // Run cdc_rsync_server on the remote instance.
-    std::string remote_command = arch.GetStartServerCommand(
+    std::string remote_command =
-        kExitCodeNotFound, absl::StrFormat("%i %s", port, component_args));
+        arch.GetStartServerCommand(kExitCodeNotFound, component_args);
-    start_info = remote_util_->BuildProcessStartInfoForSshPortForwardAndCommand(
+    assert(remote_util_);
-        port, port, /*reverse=*/false, remote_command, arch.GetType());
+    start_info = remote_util_->BuildProcessStartInfoForSsh(remote_command,
+                                                           arch.GetType());
   } else {
     // Run cdc_rsync_server locally.
     std::string exe_dir;
     RETURN_IF_ERROR(path::GetExeDir(&exe_dir), "Failed to get exe directory");
 
     std::string server_path = path::Join(exe_dir, arch.CdcServerFilename());
-    start_info.command =
+    start_info.command = absl::StrFormat("%s %s", server_path, component_args);
-        absl::StrFormat("%s %i %s", server_path, port, component_args);
   }
 
   // Capture stdout, but forward to stdout for debugging purposes.
@@ -283,8 +239,8 @@ absl::Status CdcRsyncClient::StartServer(int port, const ServerArch& arch) {
     return HandleServerOutput(data);
   };
 
-  std::unique_ptr<Process> process = process_factory_.Create(start_info);
+  std::unique_ptr<Process> srv_process = process_factory_.Create(start_info);
-  status = process->Start();
+  status = srv_process->Start();
   if (!status.ok()) {
     return WrapStatus(status, "Failed to start cdc_rsync_server process");
   }
@@ -292,13 +248,13 @@ absl::Status CdcRsyncClient::StartServer(int port, const ServerArch& arch) {
   // Wait until the server process is listening.
   Stopwatch timeout_timer;
   bool is_timeout = false;
-  auto detect_listening_or_timeout = [is_listening = &is_server_listening_,
+  auto detect_listening_or_timeout = [port = &server_listen_port_,
                                       timeout = options_.connection_timeout_sec,
                                       &timeout_timer, &is_timeout]() -> bool {
     is_timeout = timeout_timer.ElapsedSeconds() > timeout;
-    return *is_listening || is_timeout;
+    return *port != 0 || is_timeout;
   };
-  status = process->RunUntil(detect_listening_or_timeout);
+  status = srv_process->RunUntil(detect_listening_or_timeout);
   if (!status.ok()) {
     // Some internal process error. Note that this does NOT mean that
     // cdc_rsync_server does not exist. In that case, the ssh process exits with
@@ -310,10 +266,10 @@ absl::Status CdcRsyncClient::StartServer(int port, const ServerArch& arch) {
                   Tag::kConnectionTimeout);
   }
 
-  if (process->HasExited()) {
+  if (srv_process->HasExited()) {
     // Don't re-deploy for code > kServerExitCodeOutOfDate, which means that the
     // out-of-date check already passed on the server.
-    server_exit_code_ = process->ExitCode();
+    server_exit_code_ = srv_process->ExitCode();
     if (server_exit_code_ > kServerExitCodeOutOfDate &&
         server_exit_code_ <= kServerExitCodeMax) {
       return GetServerExitStatus(server_exit_code_, server_error_);
@@ -321,7 +277,7 @@ absl::Status CdcRsyncClient::StartServer(int port, const ServerArch& arch) {
 
     // Don't re-deploy if we're not copying to a remote device. We can start
     // cdc_rsync_server from the original location directly.
-    if (!remote_util_) {
+    if (!IsRemoteConnection()) {
       return GetServerExitStatus(server_exit_code_, server_error_);
     }
 
@@ -332,19 +288,58 @@ absl::Status CdcRsyncClient::StartServer(int port, const ServerArch& arch) {
     return SetTag(MakeStatus("Redeploy server"), Tag::kDeployServer);
   }
 
+  // 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(
+        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);
+    start_info.forward_output_to_log = true;
+    fwd_process = process_factory_.Create(start_info);
+    RETURN_IF_ERROR(fwd_process->Start(),
+                    "Failed to start cdc_rsync_server process");
+  }
+
+  // Connect to the socket with port |local_port|.
   status = Socket::Initialize();
   if (!status.ok()) {
     return WrapStatus(status, "Failed to initialize sockets");
   }
   socket_finalizer_ = std::make_unique<SocketFinalizer>();
 
-  assert(is_server_listening_);
+  // Poll until the port forwarding connection is set up.
-  status = socket_.Connect(port);
+  timeout_timer.Reset();
-  if (!status.ok()) {
+  for (;;) {
-    return WrapStatus(status, "Failed to initialize connection");
+    assert(local_port != 0);
+    status = socket_.Connect(local_port);
+    if (status.ok()) {
+      break;
     }
 
-  server_process_ = std::move(process);
+    if (timeout_timer.ElapsedSeconds() > options_.connection_timeout_sec) {
+      return SetTag(
+          absl::DeadlineExceededError("Timeout while connecting to server"),
+          Tag::kConnectionTimeout);
+    }
+
+    Util::Sleep(10);
+  }
+
+  server_process_ = std::move(srv_process);
+  port_forwarding_process_ = std::move(fwd_process);
   message_pump_.StartMessagePump();
   return absl::OkStatus();
 }
@@ -365,6 +360,7 @@ absl::Status CdcRsyncClient::StopServer() {
 
   server_exit_code_ = server_process_->ExitCode();
   server_process_.reset();
+  port_forwarding_process_.reset();
   return absl::OkStatus();
 }
 
@@ -396,10 +392,29 @@ absl::Status CdcRsyncClient::HandleServerOutput(const char* data) {
   }
 
   printer_.Print(stdout_data, false, Util::GetConsoleWidth());
-  if (!is_server_listening_) {
+  if (server_listen_port_ == 0) {
     server_output_.append(stdout_data);
-    is_server_listening_ =
+
-        server_output_.find("Server is listening") != std::string::npos;
+    // Parse port from "Port <n>: Server is listening".
+    size_t listening_pos = server_output_.find("Server is listening");
+    if (listening_pos != std::string::npos) {
+      // Search backwards until we find "Port ".
+      constexpr char port_key[] = "Port ";
+      size_t port_pos = server_output_.rfind(port_key, listening_pos);
+      if (port_pos == std::string::npos) {
+        return MakeStatus("Failed to find 'Port' marker in server output '%s'",
+                          server_output_);
+      }
+      assert(listening_pos > port_pos);
+      server_listen_port_ = atoi(
+          server_output_
+              .substr(port_pos + strlen(port_key), listening_pos - port_pos)
+              .c_str());
+      if (server_listen_port_ == 0) {
+        return MakeStatus("Failed to parse port from server output '%s'",
+                          server_output_);
+      }
+    }
   }
 
   return absl::OkStatus();
@@ -466,6 +481,7 @@ absl::Status CdcRsyncClient::Sync() {
 absl::Status CdcRsyncClient::DeployServer(const ServerArch& arch) {
   assert(!server_process_);
   assert(remote_util_);
+  assert(IsRemoteConnection());
 
   std::string exe_dir;
   absl::Status status = path::GetExeDir(&exe_dir);

cdc_rsync/cdc_rsync_client.h

@@ -78,14 +78,9 @@ class CdcRsyncClient {
   absl::Status Run();
 
  private:
-  // Finds available local and remote ports for port forwarding.
-  // May update |server_arch| by properly detecting the architecture and retry
-  // if the architecture was guessed, i.e. if |server_arch|->IsGuess() is true.
-  absl::StatusOr<int> FindAvailablePort(ServerArch* server_arch);
-
   // Starts the server process. If the method returns a status with tag
   // |kTagDeployServer|, Run() calls DeployServer() and tries again.
-  absl::Status StartServer(int port, const ServerArch& arch);
+  absl::Status StartServer(const ServerArch& arch);
 
   // Stops the server process.
   absl::Status StopServer();
@@ -129,6 +124,9 @@ class CdcRsyncClient {
   // Stops the zstd compression stream.
   absl::Status StopCompressionStream();
 
+  // Returns true if the target is a remote target.
+  bool IsRemoteConnection() const { return remote_util_ != nullptr; }
+
   Options options_;
   std::vector<std::string> sources_;
   const std::string destination_;
@@ -143,10 +141,11 @@ class CdcRsyncClient {
   std::unique_ptr<ZstdStream> compression_stream_;
 
   std::unique_ptr<Process> server_process_;
+  std::unique_ptr<Process> port_forwarding_process_;
   std::string server_output_;  // Written in a background thread. Do not access
   std::string server_error_;   // while the server process is active.
   int server_exit_code_ = 0;
-  std::atomic_bool is_server_listening_{false};
+  std::atomic_int server_listen_port_{0};
   bool is_server_error_ = false;
 
   // All source files found on the client.

cdc_rsync/client_socket.cc

@@ -68,11 +68,10 @@ absl::Status ClientSocket::Connect(int port) {
   int count = 0;
   for (addrinfo* curr = addr_infos; curr; curr = curr->ai_next, count++) {
     socket_info_->socket =
-        socket(addr_infos->ai_family, addr_infos->ai_socktype,
+        socket(curr->ai_family, curr->ai_socktype, curr->ai_protocol);
-               addr_infos->ai_protocol);
     if (socket_info_->socket == INVALID_SOCKET) {
       LOG_DEBUG("socket() failed for addr_info %i: %s", count,
-                Util::GetWin32Error(WSAGetLastError()).c_str());
+                Util::GetWin32Error(WSAGetLastError()));
       continue;
     }
 
@@ -80,7 +79,8 @@ absl::Status ClientSocket::Connect(int port) {
     result = connect(socket_info_->socket, curr->ai_addr,
                      static_cast<int>(curr->ai_addrlen));
     if (result == SOCKET_ERROR) {
-      LOG_DEBUG("connect() failed for addr_info %i: %i", count, result);
+      LOG_DEBUG("connect() failed for addr_info %i: %s", count,
+                Util::GetWin32Error(WSAGetLastError()));
       closesocket(socket_info_->socket);
       socket_info_->socket = INVALID_SOCKET;
       continue;

cdc_rsync_server/cdc_rsync_server.cc

@@ -288,7 +288,7 @@ bool CdcRsyncServer::CheckComponents(
   return true;
 }
 
-absl::Status CdcRsyncServer::Run(int port) {
+absl::Status CdcRsyncServer::Run() {
   absl::Status status = Socket::Initialize();
   if (!status.ok()) {
     return WrapStatus(status, "Failed to initialize sockets");
@@ -296,15 +296,15 @@ absl::Status CdcRsyncServer::Run(int port) {
   socket_finalizer_ = std::make_unique<SocketFinalizer>();
 
   socket_ = std::make_unique<ServerSocket>();
-  int new_port;
+  int port;
-  ASSIGN_OR_RETURN(new_port, socket_->StartListening(port),
+  ASSIGN_OR_RETURN(port, socket_->StartListening(0),
-                   "Failed to start listening on port %i", port);
+                   "Failed to start listening for connections");
-  assert(port != 0);
-  assert(port == new_port);
   LOG_INFO("cdc_rsync_server listening on port %i", port);
 
   // This is the marker for the client, so it knows it can connect.
-  printf("Server is listening\n");
+  // Print port first so the client can easily parse it when it sees "Server is
+  // listening" without dealing with half-transmitted data.
+  printf("Port %i: Server is listening\n", port);
   fflush(stdout);
 
   status = socket_->WaitForConnection();
@@ -607,7 +607,7 @@ absl::Status CdcRsyncServer::CreateMissingDirs() {
 template <typename T>
 absl::Status CdcRsyncServer::SendFileIndices(const char* file_type,
                                              const std::vector<T>& files) {
-  LOG_INFO("Sending indices of missing files to client");
+  LOG_INFO("Sending indices of %s files to client", file_type);
   constexpr char error_fmt[] = "Failed to send indices of %s files.";
 
   AddFileIndicesResponse response;

cdc_rsync_server/cdc_rsync_server.h

@@ -43,9 +43,10 @@ class CdcRsyncServer {
   // up-to-date by checking their sizes and timestamps.
   bool CheckComponents(const std::vector<GameletComponent>& components);
 
-  // Listens to |port|, accepts a connection from the client and runs the rsync
+  // Listens to any available port, accepts a connection from the client and
-  // procedure.
+  // runs the rsync procedure. Prints "Port <n>: Server is listening" to stdout,
-  absl::Status Run(int port);
+  // so the client can retrieve the selected port.
+  absl::Status Run();
 
   // Returns the verbosity sent from the client. 0 by default.
   int GetVerbosity() const { return verbosity_; }

cdc_rsync_server/main.cc

@@ -62,29 +62,22 @@ ServerExitCode GetExitCode(const absl::Status& status) {
 
 int main(int argc, const char** argv) {
   if (argc < 5) {
-    printf("cdc_rsync_server - Remote component of cdc_rsync. Version: %s\n\n",
+    printf(R"("cdc_rsync_server - Remote component of cdc_rsync. Version: %s
-           BUILD_VERSION);
+
-    printf(
+Usage: cdc_rsync_server <build_version> cdc_rsync_server <size> <modified_time>
-        "Usage: cdc_rsync_server <port> <build_version> cdc_rsync_server "
+       <build_version>            build version embedded in the component
-        "<size> <time> \n");
+       <size>                     file size of the component
-    printf("       where <size> is the file size, <time> is the  modified\n");
+       <modified_time>            timestamp (Unix epoch) of the component)",
-    printf(
+           BUILD_VERSION);
-        "       timestamp (Unix epoch) and <build_version> is the build "
-        "version of the server.\n");
-    return cdc_ft::kServerExitCodeGenericStartup;
-  }
 
-  int port = atoi(argv[1]);
-  if (port == 0) {
-    SendErrorMessage(absl::StrFormat("Invalid port '%s'", argv[1]).c_str());
     return cdc_ft::kServerExitCodeGenericStartup;
   }
 
   // The rest is expected to be sets of gamelet component info consisting of
-  // (filename, filesize, modified_time). This is used check whether the
+  // (version, filename, size, modified_time). This is used check whether the
   // components are up-to-date.
   std::vector<cdc_ft::GameletComponent> components =
-      cdc_ft::GameletComponent::FromCommandLineArgs(argc - 2, argv + 2);
+      cdc_ft::GameletComponent::FromCommandLineArgs(argc - 1, argv + 1);
 
   cdc_ft::Log::Initialize(
       std::make_unique<cdc_ft::ConsoleLog>(cdc_ft::LogLevel::kWarning));
@@ -94,7 +87,7 @@ int main(int argc, const char** argv) {
     return cdc_ft::kServerExitCodeOutOfDate;
   }
 
-  absl::Status status = server.Run(port);
+  absl::Status status = server.Run();
   if (status.ok()) {
     return 0;
   }

common/port_manager_test.cc

@@ -118,9 +118,8 @@ TEST_F(PortManagerTest, ReservePortLocalNetstatFails) {
   absl::StatusOr<int> port =
       port_manager_.ReservePort(kTimeoutSec, ArchType::kLinux_x86_64);
   EXPECT_NOT_OK(port);
-  EXPECT_TRUE(
+  EXPECT_TRUE(absl::StrContains(port.status().message(),
-      absl::StrContains(port.status().message(),
+                                "Failed to find available local ports"));
-                        "Failed to find available ports on workstation"));
 }
 
 TEST_F(PortManagerTest, ReservePortRemoteNetstatFails) {
@@ -131,7 +130,7 @@ TEST_F(PortManagerTest, ReservePortRemoteNetstatFails) {
       port_manager_.ReservePort(kTimeoutSec, ArchType::kLinux_x86_64);
   EXPECT_NOT_OK(port);
   EXPECT_TRUE(absl::StrContains(port.status().message(),
-                                "Failed to find available ports on instance"));
+                                "Failed to find available remote ports"));
 }
 
 TEST_F(PortManagerTest, ReservePortRemoteNetstatTimesOut) {

common/port_manager_win.cc

@@ -168,7 +168,7 @@ absl::StatusOr<int> PortManager::ReservePort(int remote_timeout_sec,
       local_ports,
       FindAvailableLocalPorts(first_port_, last_port_,
                               ArchType::kWindows_x86_64, process_factory_),
-      "Failed to find available ports on workstation");
+      "Failed to find available local ports");
 
   // Find available port on remote instance.
   std::unordered_set<int> remote_ports = local_ports;
@@ -178,7 +178,7 @@ absl::StatusOr<int> PortManager::ReservePort(int remote_timeout_sec,
         FindAvailableRemotePorts(first_port_, last_port_, remote_arch_type,
                                  process_factory_, remote_util_,
                                  remote_timeout_sec, steady_clock_),
-        "Failed to find available ports on instance");
+        "Failed to find available remote ports");
   }
 
   // Fetch shared memory.
@@ -209,9 +209,9 @@ absl::StatusOr<int> PortManager::ReservePort(int remote_timeout_sec,
       LOG_DEBUG("Trying to reserve port %i", port);
 
       // We have reserved this port. Double-check that it's actually not in use
-      // on both the workstation and the server.
+      // on both the local and the remote device
       if (local_ports.find(port) == local_ports.end()) {
-        LOG_DEBUG("Port %i not available on workstation", port);
+        LOG_DEBUG("Local port %i not available", port);
         InterlockedCompareExchange64(ts_ptr, now, port_timestamp);
         continue;
       }
@@ -221,7 +221,7 @@ absl::StatusOr<int> PortManager::ReservePort(int remote_timeout_sec,
         continue;
       }
 
-      LOG_DEBUG("Port %i is available on workstation and instance", port);
+      LOG_DEBUG("Port %i is available", port);
       reserved_ports_.insert(port);
       return port;
     }
@@ -269,7 +269,7 @@ absl::StatusOr<std::unordered_set<int>> PortManager::FindAvailableLocalPorts(
     return WrapStatus(status, "Failed to run netstat:\n%s", errors);
   }
 
-  LOG_DEBUG("netstat (workstation) output:\n%s", output);
+  LOG_DEBUG("netstat (local) output:\n%s", output);
   return FindAvailablePorts(first_port, last_port, output, arch_type);
 }
 
@@ -316,7 +316,7 @@ absl::StatusOr<std::unordered_set<int>> PortManager::FindAvailableRemotePorts(
                       errors);
   }
 
-  LOG_DEBUG("netstat (instance) output:\n%s", output);
+  LOG_DEBUG("netstat (remote) output:\n%s", output);
   return FindAvailablePorts(first_port, last_port, output, arch_type);
 }