transmission/daemon/daemon-posix.cc

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/*
* This file Copyright (C) 2015 Mnemosyne LLC
*
* It may be used under the GNU GPL versions 2 or 3
* or any future license endorsed by Mnemosyne LLC.
*
*/
#include <assert.h>
#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <stdlib.h> /* abort(), daemon(), exit() */
#include <fcntl.h> /* open() */
#include <unistd.h> /* fork(), setsid(), chdir(), dup2(), close(), pipe() */
#include <libtransmission/transmission.h>
#include <libtransmission/error.h>
#include <libtransmission/utils.h>
#include "daemon.h"
/***
****
***/
static dtr_callbacks const* callbacks = nullptr;
static void* callback_arg = nullptr;
static int signal_pipe[2];
/***
****
***/
static void set_system_error(tr_error** error, int code, char const* message)
{
tr_error_set(error, code, "%s (%d): %s", message, code, tr_strerror(code));
}
/***
****
***/
static void handle_signal(int sig)
{
switch (sig)
{
case SIGHUP:
callbacks->on_reconfigure(callback_arg);
break;
case SIGINT:
case SIGTERM:
callbacks->on_stop(callback_arg);
break;
default:
assert("Unexpected signal");
}
}
static void send_signal_to_pipe(int sig)
{
int const old_errno = errno;
if (write(signal_pipe[1], &sig, sizeof(sig)) == -1)
{
abort();
}
errno = old_errno;
}
static void* signal_handler_thread_main(void* /*arg*/)
{
int sig;
while (read(signal_pipe[0], &sig, sizeof(sig)) == sizeof(sig) && sig != 0)
{
handle_signal(sig);
}
return nullptr;
}
static bool create_signal_pipe(tr_error** error)
{
if (pipe(signal_pipe) == -1)
{
set_system_error(error, errno, "pipe() failed");
return false;
}
return true;
}
static void destroy_signal_pipe(void)
{
close(signal_pipe[0]);
close(signal_pipe[1]);
}
static bool create_signal_handler_thread(pthread_t* thread, tr_error** error)
{
if (!create_signal_pipe(error))
{
return false;
}
if ((errno = pthread_create(thread, nullptr, &signal_handler_thread_main, nullptr)) != 0)
{
set_system_error(error, errno, "pthread_create() failed");
destroy_signal_pipe();
return false;
}
return true;
}
static void destroy_signal_handler_thread(pthread_t thread)
{
send_signal_to_pipe(0);
pthread_join(thread, nullptr);
destroy_signal_pipe();
}
static bool setup_signal_handler(int sig, tr_error** error)
{
assert(sig != 0);
if (signal(sig, &send_signal_to_pipe) == SIG_ERR)
{
set_system_error(error, errno, "signal() failed");
return false;
}
return true;
}
/***
****
***/
bool dtr_daemon(dtr_callbacks const* cb, void* cb_arg, bool foreground, int* exit_code, tr_error** error)
{
callbacks = cb;
callback_arg = cb_arg;
*exit_code = 1;
if (!foreground)
{
#if defined(HAVE_DAEMON) && !defined(__APPLE__) && !defined(__UCLIBC__)
if (daemon(true, false) == -1)
{
set_system_error(error, errno, "daemon() failed");
return false;
}
#else
/* this is loosely based off of glibc's daemon() implementation
* http://sourceware.org/git/?p=glibc.git;a=blob_plain;f=misc/daemon.c */
switch (fork())
{
case -1:
set_system_error(error, errno, "fork() failed");
return false;
case 0:
break;
default:
*exit_code = 0;
return true;
}
if (setsid() == -1)
{
set_system_error(error, errno, "setsid() failed");
return false;
}
/*
if (chdir("/") == -1)
{
set_system_error(error, errno, "chdir() failed");
return false;
}
*/
{
int const fd = open("/dev/null", O_RDWR, 0);
dup2(fd, STDIN_FILENO);
dup2(fd, STDOUT_FILENO);
dup2(fd, STDERR_FILENO);
close(fd);
}
#endif
}
pthread_t signal_thread;
if (!create_signal_handler_thread(&signal_thread, error))
{
return false;
}
if (!setup_signal_handler(SIGINT, error) || !setup_signal_handler(SIGTERM, error) || !setup_signal_handler(SIGHUP, error))
{
destroy_signal_handler_thread(signal_thread);
return false;
}
*exit_code = cb->on_start(cb_arg, foreground);
destroy_signal_handler_thread(signal_thread);
return true;
}