1 files changed, 256 insertions, 0 deletions
diff --git a/tools/android/forwarder2/daemon.cc b/tools/android/forwarder2/daemon.cc
new file mode 100644
index 0000000..c056460
--- /dev/null
+++ b/tools/android/forwarder2/daemon.cc
@@ -0,0 +1,256 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "tools/android/forwarder2/daemon.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/eintr_wrapper.h"
+#include "base/file_path.h"
+#include "base/file_util.h"
+#include "base/logging.h"
+#include "base/safe_strerror_posix.h"
+#include "base/string_number_conversions.h"
+#include "base/stringprintf.h"
+#include "tools/android/forwarder2/common.h"
+
+namespace forwarder2 {
+namespace {
+
+const char kLogFilePath[] = "/tmp/host_forwarder_log";
+
+class FileDescriptorAutoCloser {
+ public:
+  explicit FileDescriptorAutoCloser(int fd) : fd_(fd) {
+    DCHECK(fd_ >= 0);
+  }
+
+  ~FileDescriptorAutoCloser() {
+    if (fd_ > -1)
+      CloseFD(fd_);
+  }
+
+  int Release() {
+    const int fd = fd_;
+    fd_ = -1;
+    return fd;
+  }
+
+ private:
+  int fd_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileDescriptorAutoCloser);
+};
+
+// Handles creation and destruction of the PID file.
+class PIDFile {
+ public:
+  static scoped_ptr<PIDFile> Create(const std::string& path) {
+    scoped_ptr<PIDFile> pid_file;
+    const int pid_file_fd = HANDLE_EINTR(
+        open(path.c_str(), O_CREAT | O_WRONLY, 0600));
+    if (pid_file_fd < 0) {
+      PError("open()");
+      return pid_file.Pass();
+    }
+    FileDescriptorAutoCloser fd_closer(pid_file_fd);
+    struct flock lock_info = {};
+    lock_info.l_type = F_WRLCK;
+    lock_info.l_whence = SEEK_CUR;
+    if (HANDLE_EINTR(fcntl(pid_file_fd, F_SETLK, &lock_info)) < 0) {
+      if (errno == EAGAIN || errno == EACCES) {
+        LOG(ERROR) << "Daemon already running (PID file already locked)";
+        return pid_file.Pass();
+      }
+      PError("lockf()");
+      return pid_file.Pass();
+    }
+    const std::string pid_string = base::StringPrintf("%d\n", getpid());
+    CHECK(HANDLE_EINTR(write(pid_file_fd, pid_string.c_str(),
+                             pid_string.length())));
+    pid_file.reset(new PIDFile(fd_closer.Release(), path));
+    return pid_file.Pass();
+  }
+
+  ~PIDFile() {
+    CloseFD(fd_);  // This also releases the lock.
+    if (remove(path_.c_str()) < 0)
+      PError("remove");
+  }
+
+ private:
+  PIDFile(int fd, const std::string& path) : fd_(fd), path_(path) {
+    DCHECK(fd_ >= 0);
+  }
+
+  const int fd_;
+  const std::string path_;
+
+  DISALLOW_COPY_AND_ASSIGN(PIDFile);
+};
+
+// Takes ownership of |data|.
+void ReleaseDaemonResourcesAtExit(void* data) {
+  DCHECK(data);
+  delete reinterpret_cast<PIDFile*>(data);
+}
+
+void InitLogging(const char* log_file) {
+  CHECK(
+      logging::InitLogging(
+          log_file,
+          logging::LOG_ONLY_TO_FILE,
+          logging::DONT_LOCK_LOG_FILE,
+          logging::APPEND_TO_OLD_LOG_FILE,
+          logging::ENABLE_DCHECK_FOR_NON_OFFICIAL_RELEASE_BUILDS));
+}
+
+void SigChildHandler(int signal_number) {
+  DCHECK_EQ(signal_number, SIGCHLD);
+  // The daemon should not terminate while its parent is still running.
+  int status;
+  pid_t child_pid = waitpid(-1 /* any child */, &status, WNOHANG);
+  if (child_pid < 0) {
+    PError("waitpid");
+    return;
+  }
+  if (child_pid == 0)
+    return;
+  // Avoid using StringAppendF() since it's unsafe in a signal handler due to
+  // its use of LOG().
+  FixedSizeStringBuilder<256> string_builder;
+  string_builder.Append("Daemon (pid=%d) died unexpectedly with ", child_pid);
+  if (WIFEXITED(status))
+    string_builder.Append("status %d.", WEXITSTATUS(status));
+  else if (WIFSIGNALED(status))
+    string_builder.Append("signal %d.", WTERMSIG(status));
+  else
+    string_builder.Append("unknown reason.");
+  SIGNAL_SAFE_LOG(ERROR, string_builder.buffer());
+}
+
+// Note that 0 is written to |lock_owner_pid| in case the file is not locked.
+bool GetFileLockOwnerPid(int fd, pid_t* lock_owner_pid) {
+  struct flock lock_info = {};
+  lock_info.l_type = F_WRLCK;
+  lock_info.l_whence = SEEK_CUR;
+  const int ret = HANDLE_EINTR(fcntl(fd, F_GETLK, &lock_info));
+  if (ret < 0) {
+    if (errno == EBADF) {
+      // Assume that the provided file descriptor corresponding to the PID file
+      // was valid until the daemon removed this file.
+      *lock_owner_pid = 0;
+      return true;
+    }
+    PError("fcntl");
+    return false;
+  }
+  if (lock_info.l_type == F_UNLCK) {
+    *lock_owner_pid = 0;
+    return true;
+  }
+  CHECK_EQ(F_WRLCK /* exclusive lock */, lock_info.l_type);
+  *lock_owner_pid = lock_info.l_pid;
+  return true;
+}
+
+}  // namespace
+
+Daemon::Daemon(const std::string& pid_file_path)
+    : pid_file_path_(pid_file_path) {
+}
+
+bool Daemon::Spawn(bool* is_daemon) {
+  switch (fork()) {
+    case -1:
+      *is_daemon = false;
+      PError("fork()");
+      return false;
+    case 0: {  // Child.
+      *is_daemon = true;
+      scoped_ptr<PIDFile> pid_file = PIDFile::Create(pid_file_path_);
+      if (!pid_file)
+        return false;
+      base::AtExitManager::RegisterCallback(
+          &ReleaseDaemonResourcesAtExit, pid_file.release());
+      if (setsid() < 0) {  // Detach the child process from its parent.
+        PError("setsid");
+        return false;
+      }
+      CloseFD(STDOUT_FILENO);
+      CloseFD(STDERR_FILENO);
+      InitLogging(kLogFilePath);
+      break;
+    }
+    default:  // Parent.
+      *is_daemon = false;
+      signal(SIGCHLD, SigChildHandler);
+  }
+  return true;
+}
+
+bool Daemon::Kill() {
+  int pid_file_fd = HANDLE_EINTR(open(pid_file_path_.c_str(), O_WRONLY));
+  if (pid_file_fd < 0) {
+    if (errno == ENOENT)
+      return true;
+    LOG(ERROR) << "Could not open " << pid_file_path_ << " in write mode: "
+               << safe_strerror(errno);
+    return false;
+  }
+  const FileDescriptorAutoCloser fd_closer(pid_file_fd);
+  pid_t lock_owner_pid;
+  if (!GetFileLockOwnerPid(pid_file_fd, &lock_owner_pid))
+    return false;
+  if (lock_owner_pid == 0)
+    // No daemon running.
+    return true;
+  if (kill(lock_owner_pid, SIGTERM) < 0) {
+    if (errno == ESRCH /* invalid PID */)
+      // The daemon exited for some reason (e.g. kill by a process other than
+      // us) right before the call to kill() above.
+      return true;
+    PError("kill");
+    return false;
+  }
+  // Wait until the daemon exits. Rely on the fact that the daemon releases the
+  // lock on the PID file when it exits.
+  // TODO(pliard): Consider using a mutex + condition in shared memory to avoid
+  // polling.
+  const int kTries = 20;
+  const int kIdleTimeMS = 50;
+  for (int i = 0; i < kTries; ++i) {
+    pid_t current_lock_owner_pid;
+    if (!GetFileLockOwnerPid(pid_file_fd, &current_lock_owner_pid))
+      return false;
+    if (current_lock_owner_pid == 0)
+      // The daemon released the PID file's lock.
+      return true;
+    // Since we are polling we might not see the 'daemon exited' event if
+    // another daemon was spawned during our idle period.
+    if (current_lock_owner_pid != lock_owner_pid) {
+      LOG(WARNING) << "Daemon (pid=" << lock_owner_pid
+                   << ") was successfully killed but a new daemon (pid="
+                   << current_lock_owner_pid << ") seems to be running now.";
+      return true;
+    }
+    usleep(kIdleTimeMS * 1000);
+  }
+  LOG(ERROR) << "Timed out while killing daemon. "
+                "It might still be tearing down.";
+  return false;
+}
+
+}  // namespace forwarder2