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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
// Run a function in a forked child, with a timeout.
#pragma once
#include <functional>
#include <signal.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <ostream>
#include "include/ceph_assert.h"
#include "common/errno.h"
static void _fork_function_dummy_sighandler(int sig) {}
// Run a function post-fork, with a timeout. Function can return
// int8_t only due to unix exit code limitations. Returns -ETIMEDOUT
// if timeout is reached.
static inline int fork_function(
int timeout,
std::ostream& errstr,
std::function<int8_t(void)> f)
{
// first fork the forker.
pid_t forker_pid = fork();
if (forker_pid) {
// just wait
int status;
while (waitpid(forker_pid, &status, 0) == -1) {
ceph_assert(errno == EINTR);
}
if (WIFSIGNALED(status)) {
errstr << ": got signal: " << WTERMSIG(status) << "\n";
return 128 + WTERMSIG(status);
}
if (WIFEXITED(status)) {
int8_t r = WEXITSTATUS(status);
errstr << ": exit status: " << (int)r << "\n";
return r;
}
errstr << ": waitpid: unknown status returned\n";
return -1;
}
// we are forker (first child)
// close all fds
int maxfd = sysconf(_SC_OPEN_MAX);
if (maxfd == -1)
maxfd = 16384;
for (int fd = 0; fd <= maxfd; fd++) {
if (fd == STDIN_FILENO)
continue;
if (fd == STDOUT_FILENO)
continue;
if (fd == STDERR_FILENO)
continue;
::close(fd);
}
sigset_t mask, oldmask;
int pid;
// Restore default action for SIGTERM in case the parent process decided
// to ignore it.
if (signal(SIGTERM, SIG_DFL) == SIG_ERR) {
std::cerr << ": signal failed: " << cpp_strerror(errno) << "\n";
goto fail_exit;
}
// Because SIGCHLD is ignored by default, setup dummy handler for it,
// so we can mask it.
if (signal(SIGCHLD, _fork_function_dummy_sighandler) == SIG_ERR) {
std::cerr << ": signal failed: " << cpp_strerror(errno) << "\n";
goto fail_exit;
}
// Setup timeout handler.
if (signal(SIGALRM, timeout_sighandler) == SIG_ERR) {
std::cerr << ": signal failed: " << cpp_strerror(errno) << "\n";
goto fail_exit;
}
// Block interesting signals.
sigemptyset(&mask);
sigaddset(&mask, SIGINT);
sigaddset(&mask, SIGTERM);
sigaddset(&mask, SIGCHLD);
sigaddset(&mask, SIGALRM);
if (sigprocmask(SIG_SETMASK, &mask, &oldmask) == -1) {
std::cerr << ": sigprocmask failed: "
<< cpp_strerror(errno) << "\n";
goto fail_exit;
}
pid = fork();
if (pid == -1) {
std::cerr << ": fork failed: " << cpp_strerror(errno) << "\n";
goto fail_exit;
}
if (pid == 0) { // we are second child
// Restore old sigmask.
if (sigprocmask(SIG_SETMASK, &oldmask, NULL) == -1) {
std::cerr << ": sigprocmask failed: "
<< cpp_strerror(errno) << "\n";
goto fail_exit;
}
(void)setpgid(0, 0); // Become process group leader.
int8_t r = f();
_exit((uint8_t)r);
}
// Parent
(void)alarm(timeout);
for (;;) {
int signo;
if (sigwait(&mask, &signo) == -1) {
std::cerr << ": sigwait failed: " << cpp_strerror(errno) << "\n";
goto fail_exit;
}
switch (signo) {
case SIGCHLD:
int status;
if (waitpid(pid, &status, WNOHANG) == -1) {
std::cerr << ": waitpid failed: " << cpp_strerror(errno) << "\n";
goto fail_exit;
}
if (WIFEXITED(status))
_exit(WEXITSTATUS(status));
if (WIFSIGNALED(status))
_exit(128 + WTERMSIG(status));
std::cerr << ": unknown status returned\n";
goto fail_exit;
case SIGINT:
case SIGTERM:
// Pass SIGINT and SIGTERM, which are usually used to terminate
// a process, to the child.
if (::kill(pid, signo) == -1) {
std::cerr << ": kill failed: " << cpp_strerror(errno) << "\n";
goto fail_exit;
}
continue;
case SIGALRM:
std::cerr << ": timed out (" << timeout << " sec)\n";
if (::killpg(pid, SIGKILL) == -1) {
std::cerr << ": kill failed: " << cpp_strerror(errno) << "\n";
goto fail_exit;
}
_exit(-ETIMEDOUT);
default:
std::cerr << ": sigwait: invalid signal: " << signo << "\n";
goto fail_exit;
}
}
return 0;
fail_exit:
_exit(EXIT_FAILURE);
}
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