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/* SPDX-License-Identifier: GPL-2.0 */
/** \file daemon.c Some helpers for programs that detach from the console. */
#include <string.h>
#include <stdlib.h>
#include <pwd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <grp.h>
#include <assert.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include "gcc-compat.h"
#include "err.h"
#include "log.h"
#include "str.h"
#include "daemon.h"
/**
* Do the usual stuff to become a daemon.
*
* Fork, become session leader, dup fd 0, 1, 2 to /dev/null.
*
* \sa fork(2), setsid(2), dup(2).
*/
int daemon_init(void)
{
pid_t pid;
int null, fd[2];
DSS_INFO_LOG(("daemonizing\n"));
if (pipe(fd) < 0)
goto err;
pid = fork();
if (pid < 0)
goto err;
if (pid) {
/*
* The parent process exits once it has received one byte from
* the reading end of the pipe. If the child exits before it
* was able to complete its setup (acquire the lock on the
* semaphore), the read() below will return zero. In this case
* we let the parent die unsuccessfully.
*/
char c;
int ret;
close(fd[1]);
ret = read(fd[0], &c, 1);
if (ret <= 0) {
DSS_EMERG_LOG(("child terminated unexpectedly\n"));
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
close(fd[0]);
/* become session leader */
if (setsid() < 0)
goto err;
null = open("/dev/null", O_RDWR);
if (null < 0)
goto err;
if (dup2(null, STDIN_FILENO) < 0)
goto err;
if (dup2(null, STDOUT_FILENO) < 0)
goto err;
if (dup2(null, STDERR_FILENO) < 0)
goto err;
close(null);
return fd[1];
err:
DSS_EMERG_LOG(("fatal: %s\n", strerror(errno)));
exit(EXIT_FAILURE);
}
/**
* fopen() the given file in append mode.
*
* \param logfile_name The name of the file to open.
*
* \return Either calls exit() or returns a valid file handle.
*/
FILE *open_log(const char *logfile_name)
{
FILE *logfile;
assert(logfile_name);
logfile = fopen(logfile_name, "a");
if (!logfile) {
DSS_EMERG_LOG(("can not open %s: %s\n", logfile_name,
strerror(errno)));
exit(EXIT_FAILURE);
}
setlinebuf(logfile);
return logfile;
}
/**
* Close the log file of the daemon.
*
* \param logfile The log file handle.
*
* It's OK to call this with logfile == \p NULL.
*/
void close_log(FILE* logfile)
{
if (!logfile)
return;
DSS_INFO_LOG(("closing logfile\n"));
fclose(logfile);
}
/**
* Log the startup message.
*/
void log_welcome(int loglevel)
{
DSS_INFO_LOG(("***** welcome to dss ******\n"));
DSS_DEBUG_LOG(("using loglevel %d\n", loglevel));
}
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