transmission/daemon/daemon-posix.cc

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// This file Copyright © 2015-2023 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <assert.h>
#include <errno.h>
#include <pthread.h>
#ifdef HAVE_SYS_SIGNALFD_H
#include <sys/signalfd.h>
#endif /* signalfd API */
#include <event2/event.h>
#include <signal.h>
#include <stdlib.h> /* abort(), daemon(), exit() */
#include <fcntl.h> /* open() */
#include <unistd.h> /* fork(), setsid(), chdir(), dup2(), close(), pipe() */
#include <string_view>
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#include <fmt/format.h>
#include "daemon.h"
static void set_system_error(tr_error** error, int code, std::string_view message)
{
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tr_error_set(error, code, fmt::format(FMT_STRING("{:s}: {:s} ({:d}"), message, tr_strerror(code), code));
}
#ifdef HAVE_SYS_SIGNALFD_H
static void handle_signals(evutil_socket_t fd, short /*what*/, void* arg)
{
struct signalfd_siginfo fdsi;
auto* const daemon = static_cast<tr_daemon*>(arg);
if (read(fd, &fdsi, sizeof(fdsi)) != sizeof(fdsi))
assert("Error reading signal descriptor" && 0);
else
{
switch (fdsi.ssi_signo)
{
case SIGHUP:
daemon->reconfigure();
break;
case SIGINT:
case SIGTERM:
daemon->stop();
break;
default:
assert("Unexpected signal" && 0);
}
}
}
bool tr_daemon::setup_signals()
{
sigset_t mask = {};
struct event* sigev = nullptr;
struct event_base* base = ev_base_;
sigemptyset(&mask);
sigaddset(&mask, SIGINT);
sigaddset(&mask, SIGTERM);
sigaddset(&mask, SIGHUP);
if (sigprocmask(SIG_BLOCK, &mask, nullptr) < 0)
return false;
sigfd_ = signalfd(-1, &mask, 0);
if (sigfd_ < 0)
return false;
sigev = event_new(base, sigfd_, EV_READ | EV_PERSIST, handle_signals, this);
if (sigev == nullptr)
{
close(sigfd_);
return false;
}
if (event_add(sigev, nullptr) < 0)
{
event_del(sigev);
close(sigfd_);
return false;
}
return true;
}
#else /* no signalfd API, use evsignal */
static void reconfigureMarshall(evutil_socket_t /*fd*/, short /*events*/, void* arg)
{
static_cast<tr_daemon*>(arg)->reconfigure();
}
static void stopMarshall(evutil_socket_t /*fd*/, short /*events*/, void* arg)
{
static_cast<tr_daemon*>(arg)->stop();
}
static bool setup_signal(struct event_base* base, int sig, void (*callback)(evutil_socket_t, short, void*), void* arg)
{
struct event* sigev = evsignal_new(base, sig, callback, arg);
if (sigev == nullptr)
return false;
if (evsignal_add(sigev, nullptr) < 0)
{
event_free(sigev);
return false;
}
return true;
}
bool tr_daemon::setup_signals()
{
return setup_signal(ev_base_, SIGHUP, reconfigureMarshall, this) && setup_signal(ev_base_, SIGINT, stopMarshall, this) &&
setup_signal(ev_base_, SIGTERM, stopMarshall, this);
}
#endif /* HAVE_SYS_SIGNALFD_H */
bool tr_daemon::spawn(bool foreground, int* exit_code, tr_error** error)
{
*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
* https://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
}
*exit_code = start(foreground);
return true;
}