/* Starts a subprocess with the arguments in the null-terminated argv[] array.
* argv[0] is used as the name of the process. Searches the PATH environment
* variable to find the program to execute.
*
* All file descriptors are closed before executing the subprocess, except for
* fds 0, 1, and 2 and the 'n_keep_fds' fds listed in 'keep_fds'. Also, any of
* the 'n_null_fds' fds listed in 'null_fds' are replaced by /dev/null.
*
* Returns 0 if successful, otherwise a positive errno value indicating the
* error. If successful, '*pp' is assigned a new struct process that may be
* used to query the process's status. On failure, '*pp' is set to NULL. */
int
process_start(char **argv,
const int keep_fds[], size_t n_keep_fds,
const int null_fds[], size_t n_null_fds,
struct process **pp)
{
sigset_t oldsigs;
pid_t pid;
int error;
*pp = NULL;
COVERAGE_INC(process_start);
error = process_prestart(argv);
if (error) {
return error;
}
block_sigchld(&oldsigs);
pid = fork();
if (pid < 0) {
unblock_sigchld(&oldsigs);
VLOG_WARN("fork failed: %s", strerror(errno));
return errno;
} else if (pid) {
/* Running in parent process. */
*pp = process_register(argv[0], pid);
unblock_sigchld(&oldsigs);
return 0;
} else {
/* Running in child process. */
int fd_max = get_max_fds();
int fd;
fatal_signal_fork();
unblock_sigchld(&oldsigs);
for (fd = 0; fd < fd_max; fd++) {
if (is_member(fd, null_fds, n_null_fds)) {
/* We can't use get_null_fd() here because we might have
* already closed its fd. */
int nullfd = open("/dev/null", O_RDWR);
dup2(nullfd, fd);
close(nullfd);
} else if (fd >= 3 && !is_member(fd, keep_fds, n_keep_fds)) {
close(fd);
}
}
execvp(argv[0], argv);
fprintf(stderr, "execvp(\"%s\") failed: %s\n",
argv[0], strerror(errno));
_exit(1);
}
}
/* Calls fork() and on success returns its return value. On failure, logs an
* error and exits unsuccessfully.
*
* Post-fork, but before returning, this function calls a few other functions
* that are generally useful if the child isn't planning to exec a new
* process. */
static pid_t
fork_and_clean_up(void)
{
pid_t pid = xfork();
if (pid > 0) {
/* Running in parent process. */
fatal_signal_fork();
} else if (!pid) {
/* Running in child process. */
lockfile_postfork();
}
return pid;
}
static pid_t
fork_and_wait_for_startup(int *fdp)
{
int fds[2];
pid_t pid;
if (pipe(fds) < 0) {
ovs_fatal(errno, "pipe failed");
}
pid = fork();
if (pid > 0) {
/* Running in parent process. */
char c;
close(fds[1]);
fatal_signal_fork();
if (read(fds[0], &c, 1) != 1) {
int retval;
int status;
do {
retval = waitpid(pid, &status, 0);
} while (retval == -1 && errno == EINTR);
if (retval == pid
&& WIFEXITED(status)
&& WEXITSTATUS(status)) {
/* Child exited with an error. Convey the same error to
* our parent process as a courtesy. */
exit(WEXITSTATUS(status));
}
ovs_fatal(errno, "fork child failed to signal startup");
}
close(fds[0]);
*fdp = -1;
} else if (!pid) {
/* Running in child process. */
close(fds[0]);
time_postfork();
lockfile_postfork();
*fdp = fds[1];
} else {
ovs_fatal(errno, "could not fork");
}
return pid;
}
static pid_t
fork_and_wait_for_startup(int *fdp)
{
int fds[2];
pid_t pid;
xpipe(fds);
pid = fork();
if (pid > 0) {
/* Running in parent process. */
size_t bytes_read;
char c;
close(fds[1]);
fatal_signal_fork();
if (read_fully(fds[0], &c, 1, &bytes_read) != 0) {
int retval;
int status;
do {
retval = waitpid(pid, &status, 0);
} while (retval == -1 && errno == EINTR);
if (retval == pid
&& WIFEXITED(status)
&& WEXITSTATUS(status)) {
/* Child exited with an error. Convey the same error to
* our parent process as a courtesy. */
exit(WEXITSTATUS(status));
}
VLOG_FATAL("fork child failed to signal startup (%s)",
strerror(errno));
}
close(fds[0]);
*fdp = -1;
} else if (!pid) {
/* Running in child process. */
close(fds[0]);
time_postfork();
lockfile_postfork();
*fdp = fds[1];
} else {
VLOG_FATAL("fork failed (%s)", strerror(errno));
}
return pid;
}
/* Calls fork() and on success returns its return value. On failure, logs an
* error and exits unsuccessfully.
*
* Post-fork, but before returning, this function calls a few other functions
* that are generally useful if the child isn't planning to exec a new
* process. */
pid_t
fork_and_clean_up(void)
{
pid_t pid;
pid = fork();
if (pid > 0) {
/* Running in parent process. */
fatal_signal_fork();
} else if (!pid) {
/* Running in child process. */
time_postfork();
lockfile_postfork();
} else {
VLOG_FATAL("fork failed (%s)", strerror(errno));
}
return pid;
}
/* If configured with set_pidfile() or set_detach(), creates the pid file and
* detaches from the foreground session. */
void
daemonize(void)
{
if (detach) {
char c = 0;
int fds[2];
if (pipe(fds) < 0) {
ofp_fatal(errno, "pipe failed");
}
switch (fork()) {
default:
/* Parent process: wait for child to create pidfile, then exit. */
close(fds[1]);
fatal_signal_fork();
if (read(fds[0], &c, 1) != 1) {
ofp_fatal(errno, "daemon child failed to signal startup");
}
exit(0);
case 0:
/* Child process. */
close(fds[0]);
make_pidfile();
write(fds[1], &c, 1);
close(fds[1]);
setsid();
chdir("/");
break;
case -1:
/* Error. */
ofp_fatal(errno, "could not fork");
break;
}
} else {
make_pidfile();
}
}
/* Starts the process whose arguments are given in the null-terminated array
* 'argv' and waits for it to exit. On success returns 0 and stores the
* process exit value (suitable for passing to process_status_msg()) in
* '*status'. On failure, returns a positive errno value and stores 0 in
* '*status'.
*
* If 'stdout_log' is nonnull, then the subprocess's output to stdout (up to a
* limit of PROCESS_MAX_CAPTURE bytes) is captured in a memory buffer, which
* when this function returns 0 is stored as a null-terminated string in
* '*stdout_log'. The caller is responsible for freeing '*stdout_log' (by
* passing it to free()). When this function returns an error, '*stdout_log'
* is set to NULL.
*
* If 'stderr_log' is nonnull, then it is treated like 'stdout_log' except
* that it captures the subprocess's output to stderr. */
int
process_run_capture(char **argv, char **stdout_log, char **stderr_log,
int *status)
{
struct stream s_stdout, s_stderr;
sigset_t oldsigs;
pid_t pid;
int error;
COVERAGE_INC(process_run_capture);
if (stdout_log) {
*stdout_log = NULL;
}
if (stderr_log) {
*stderr_log = NULL;
}
*status = 0;
error = process_prestart(argv);
if (error) {
return error;
}
error = stream_open(&s_stdout);
if (error) {
return error;
}
error = stream_open(&s_stderr);
if (error) {
stream_close(&s_stdout);
return error;
}
block_sigchld(&oldsigs);
pid = fork();
if (pid < 0) {
int error = errno;
unblock_sigchld(&oldsigs);
VLOG_WARN("fork failed: %s", strerror(error));
stream_close(&s_stdout);
stream_close(&s_stderr);
*status = 0;
return error;
} else if (pid) {
/* Running in parent process. */
struct process *p;
p = process_register(argv[0], pid);
unblock_sigchld(&oldsigs);
close(s_stdout.fds[1]);
close(s_stderr.fds[1]);
while (!process_exited(p)) {
stream_read(&s_stdout);
stream_read(&s_stderr);
stream_wait(&s_stdout);
stream_wait(&s_stderr);
process_wait(p);
poll_block();
}
stream_read(&s_stdout);
stream_read(&s_stderr);
if (stdout_log) {
*stdout_log = ds_steal_cstr(&s_stdout.log);
}
if (stderr_log) {
*stderr_log = ds_steal_cstr(&s_stderr.log);
}
stream_close(&s_stdout);
stream_close(&s_stderr);
*status = process_status(p);
process_destroy(p);
return 0;
} else {
/* Running in child process. */
int max_fds;
int i;
fatal_signal_fork();
unblock_sigchld(&oldsigs);
dup2(get_null_fd(), 0);
dup2(s_stdout.fds[1], 1);
dup2(s_stderr.fds[1], 2);
max_fds = get_max_fds();
for (i = 3; i < max_fds; i++) {
close(i);
}
execvp(argv[0], argv);
fprintf(stderr, "execvp(\"%s\") failed: %s\n",
argv[0], strerror(errno));
exit(EXIT_FAILURE);
}
}
