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/* Copyright (c) 2003, Roger Dingledine
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2020, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file daemon.c
* \brief Run the tor process in the background (unix only)
**/
#include "orconfig.h"
#include "lib/process/daemon.h"
#ifndef _WIN32
#include "lib/fs/files.h"
#include "lib/log/log.h"
#include "lib/thread/threads.h"
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
#include <errno.h>
#include <stdlib.h>
#include <string.h>
/* Based on code contributed by christian grothoff */
/** True iff we've called start_daemon(). */
static int start_daemon_called = 0;
/** True iff we've called finish_daemon(). */
static int finish_daemon_called = 0;
/** Socketpair used to communicate between parent and child process while
* daemonizing. */
static int daemon_filedes[2];
/**
* Return true iff we've called start_daemon() at least once.
*/
bool
start_daemon_has_been_called(void)
{
return start_daemon_called != 0;
}
/** Start putting the process into daemon mode: fork and drop all resources
* except standard fds. The parent process never returns, but stays around
* until finish_daemon is called. (Note: it's safe to call this more
* than once: calls after the first are ignored.) Return true if we actually
* forked and this is the child; false otherwise.
*/
int
start_daemon(void)
{
pid_t pid;
if (start_daemon_called)
return 0;
start_daemon_called = 1;
if (pipe(daemon_filedes)) {
/* LCOV_EXCL_START */
log_err(LD_GENERAL,"pipe failed; exiting. Error was %s", strerror(errno));
exit(1); // exit ok: during daemonize, pipe failed.
/* LCOV_EXCL_STOP */
}
pid = fork();
if (pid < 0) {
/* LCOV_EXCL_START */
log_err(LD_GENERAL,"fork failed. Exiting.");
exit(1); // exit ok: during daemonize, fork failed
/* LCOV_EXCL_STOP */
}
if (pid) { /* Parent */
int ok;
char c;
close(daemon_filedes[1]); /* we only read */
ok = -1;
while (0 < read(daemon_filedes[0], &c, sizeof(char))) {
if (c == '.')
ok = 1;
}
fflush(stdout);
if (ok == 1)
exit(0); // exit ok: during daemonize, daemonizing.
else
exit(1); /* child reported error. exit ok: daemonize failed. */
return 0; // LCOV_EXCL_LINE unreachable
} else { /* Child */
close(daemon_filedes[0]); /* we only write */
(void) setsid(); /* Detach from controlling terminal */
/*
* Fork one more time, so the parent (the session group leader) can exit.
* This means that we, as a non-session group leader, can never regain a
* controlling terminal. This part is recommended by Stevens's
* _Advanced Programming in the Unix Environment_.
*/
if (fork() != 0) {
exit(0); // exit ok: during daemonize, fork failed (2)
}
set_main_thread(); /* We are now the main thread. */
return 1;
}
}
/** Finish putting the process into daemon mode: drop standard fds, and tell
* the parent process to exit. (Note: it's safe to call this more than once:
* calls after the first are ignored. Calls start_daemon first if it hasn't
* been called already.) Return true if we actually did a fork; false if we
* didn't.
*/
int
finish_daemon(const char *desired_cwd)
{
int nullfd;
char c = '.';
if (finish_daemon_called)
return 0;
if (!start_daemon_called)
start_daemon();
finish_daemon_called = 1;
if (!desired_cwd)
desired_cwd = "/";
/* Don't hold the wrong FS mounted */
if (chdir(desired_cwd) < 0) {
log_err(LD_GENERAL,"chdir to \"%s\" failed. Exiting.",desired_cwd);
exit(1); // exit ok: during daemonize, chdir failed.
}
nullfd = tor_open_cloexec("/dev/null", O_RDWR, 0);
if (nullfd < 0) {
/* LCOV_EXCL_START */
log_err(LD_GENERAL,"/dev/null can't be opened. Exiting.");
exit(1); // exit ok: during daemonize, couldn't open /dev/null
/* LCOV_EXCL_STOP */
}
/* close fds linking to invoking terminal, but
* close usual incoming fds, but redirect them somewhere
* useful so the fds don't get reallocated elsewhere.
*/
if (dup2(nullfd,0) < 0 ||
dup2(nullfd,1) < 0 ||
dup2(nullfd,2) < 0) {
/* LCOV_EXCL_START */
log_err(LD_GENERAL,"dup2 failed. Exiting.");
exit(1); // exit ok: during daemonize, dup2 failed.
/* LCOV_EXCL_STOP */
}
if (nullfd > 2)
close(nullfd);
/* signal success */
if (write(daemon_filedes[1], &c, sizeof(char)) != sizeof(char)) {
log_err(LD_GENERAL,"write failed. Exiting.");
}
close(daemon_filedes[1]);
return 0;
}
#else /* defined(_WIN32) */
/* defined(_WIN32) */
int
start_daemon(void)
{
return 0;
}
int
finish_daemon(const char *cp)
{
(void)cp;
return 0;
}
bool
start_daemon_has_been_called(void)
{
return false;
}
#endif /* !defined(_WIN32) */
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