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/*
* Copyright (c) 2014 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "daemon.h"
#include "daemon-private.h"
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include "util.h"
#include "ovs-thread.h"
#include "openvswitch/vlog.h"
VLOG_DEFINE_THIS_MODULE(daemon);
/* For each of the standard file descriptors, whether to replace it by
* /dev/null (if false) or keep it for the daemon to use (if true). */
static bool save_fds[3];
/* Will daemonize() really detach? */
bool
get_detach(void)
{
return detach;
}
/* If configured with set_pidfile() or set_detach(), creates the pid file and
* detaches from the foreground session. */
void
daemonize(void)
{
daemonize_start(false);
daemonize_complete();
}
/* Sets up a following call to daemonize() to create a pidfile named 'name'.
* If 'name' begins with '/' (or contains ':' in windows), then it is treated
* as an absolute path. Otherwise, it is taken relative to RUNDIR,
* which is $(prefix)/var/run by default.
*
* If 'name' is null, then program_name followed by ".pid" is used. */
void
set_pidfile(const char *name)
{
assert_single_threaded();
free(pidfile);
pidfile = make_pidfile_name(name);
}
/* A daemon doesn't normally have any use for the file descriptors for stdin,
* stdout, and stderr after it detaches. To keep these file descriptors from
* e.g. holding an SSH session open, by default detaching replaces each of
* these file descriptors by /dev/null. But a few daemons expect the user to
* redirect stdout or stderr to a file, in which case it is desirable to keep
* these file descriptors. This function, therefore, disables replacing 'fd'
* by /dev/null when the daemon detaches. */
void
daemon_save_fd(int fd)
{
ovs_assert(fd == STDIN_FILENO ||
fd == STDOUT_FILENO ||
fd == STDERR_FILENO);
save_fds[fd] = true;
}
/* Returns a readable and writable fd for /dev/null, if successful, otherwise
* a negative errno value. The caller must not close the returned fd (because
* the same fd will be handed out to subsequent callers). */
static int
get_null_fd(void)
{
static int null_fd;
#ifndef _WIN32
char *device = "/dev/null";
#else
char *device = "nul";
#endif
if (!null_fd) {
null_fd = open(device, O_RDWR);
if (null_fd < 0) {
int error = errno;
VLOG_ERR("could not open %s: %s", device, ovs_strerror(error));
null_fd = -error;
}
}
return null_fd;
}
/* Close standard file descriptors (except any that the client has requested we
* leave open by calling daemon_save_fd()). If we're started from e.g. an SSH
* session, then this keeps us from holding that session open artificially. */
void
close_standard_fds(void)
{
int null_fd = get_null_fd();
if (null_fd >= 0) {
int fd;
for (fd = 0; fd < 3; fd++) {
if (!save_fds[fd]) {
dup2(null_fd, fd);
}
}
}
/* Disable logging to stderr to avoid wasting CPU time. */
vlog_set_levels(NULL, VLF_CONSOLE, VLL_OFF);
}
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