1 files changed, 108 insertions, 0 deletions
diff --git a/src/daemonizer/posix_fork.cpp b/src/daemonizer/posix_fork.cpp
new file mode 100644
index 000000000..c068912ec
--- /dev/null
+++ b/src/daemonizer/posix_fork.cpp
@@ -0,0 +1,108 @@
+// Copyright (c) 2003-2011 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include "daemonizer/posix_fork.h"
+#include "misc_log_ex.h"
+
+#include <cstdlib>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdexcept>
+#include <string>
+#include <sys/stat.h>
+
+namespace posix {
+
+namespace {
+  void quit(std::string const & message)
+  {
+    LOG_ERROR(message);
+    throw std::runtime_error(message);
+  }
+}
+
+void fork()
+{
+  // Fork the process and have the parent exit. If the process was started
+  // from a shell, this returns control to the user. Forking a new process is
+  // also a prerequisite for the subsequent call to setsid().
+  if (pid_t pid = ::fork())
+  {
+    if (pid > 0)
+    {
+      // We're in the parent process and need to exit.
+      //
+      // When the exit() function is used, the program terminates without
+      // invoking local variables' destructors. Only global variables are
+      // destroyed.
+      exit(0);
+    }
+    else
+    {
+      quit("First fork failed");
+    }
+  }
+
+  // Make the process a new session leader. This detaches it from the
+  // terminal.
+  setsid();
+
+  // A process inherits its working directory from its parent. This could be
+  // on a mounted filesystem, which means that the running daemon would
+  // prevent this filesystem from being unmounted. Changing to the root
+  // directory avoids this problem.
+  if (chdir("/") < 0)
+  {
+    quit("Unable to change working directory to root");
+  }
+
+  // The file mode creation mask is also inherited from the parent process.
+  // We don't want to restrict the permissions on files created by the
+  // daemon, so the mask is cleared.
+  umask(0);
+
+  // A second fork ensures the process cannot acquire a controlling terminal.
+  if (pid_t pid = ::fork())
+  {
+    if (pid > 0)
+    {
+      exit(0);
+    }
+    else
+    {
+      quit("Second fork failed");
+    }
+  }
+
+  // Close the standard streams. This decouples the daemon from the terminal
+  // that started it.
+  close(0);
+  close(1);
+  close(2);
+
+  // We don't want the daemon to have any standard input.
+  if (open("/dev/null", O_RDONLY) < 0)
+  {
+    quit("Unable to open /dev/null");
+  }
+
+  // Send standard output to a log file.
+  const char* output = "/tmp/bitmonero.daemon.stdout.stderr";
+  const int flags = O_WRONLY | O_CREAT | O_APPEND;
+  const mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
+  if (open(output, flags, mode) < 0)
+  {
+    quit("Unable to open output file: " + std::string(output));
+  }
+
+  // Also send standard error to the same log file.
+  if (dup(1) < 0)
+  {
+    quit("Unable to dup output descriptor");
+  }
+}
+
+} // namespace posix