125 lines
3.5 KiB
C
125 lines
3.5 KiB
C
/*-
|
|
* Copyright (c) 2009 Robert N. M. Watson
|
|
* All rights reserved.
|
|
*
|
|
* This software was developed at the University of Cambridge Computer
|
|
* Laboratory with support from a grant from Google, Inc.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*
|
|
* $FreeBSD$
|
|
*/
|
|
|
|
/*
|
|
* When a multi-threaded application calls fork(2) from one thread while
|
|
* another thread is blocked in accept(2), we prefer that the file descriptor
|
|
* to be returned by accept(2) not appear in the child process. Test this by
|
|
* creating a thread blocked in accept(2), then forking a child and seeing if
|
|
* the fd it would have returned is defined in the child or not.
|
|
*/
|
|
|
|
#include <sys/socket.h>
|
|
#include <sys/wait.h>
|
|
|
|
#include <netinet/in.h>
|
|
|
|
#include <err.h>
|
|
#include <errno.h>
|
|
#include <pthread.h>
|
|
#include <signal.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <unistd.h>
|
|
|
|
#ifndef PORT
|
|
#define PORT 9000
|
|
#endif
|
|
|
|
static int listen_fd;
|
|
|
|
static void *
|
|
do_accept(__unused void *arg)
|
|
{
|
|
int accept_fd;
|
|
|
|
accept_fd = accept(listen_fd, NULL, NULL);
|
|
if (accept_fd < 0)
|
|
err(1, "accept");
|
|
|
|
close(accept_fd);
|
|
return (NULL);
|
|
}
|
|
|
|
static void
|
|
do_fork(void)
|
|
{
|
|
int pid;
|
|
|
|
pid = fork();
|
|
if (pid < 0)
|
|
err(1, "fork");
|
|
if (pid > 0) {
|
|
waitpid(pid, NULL, 0);
|
|
exit(0);
|
|
}
|
|
|
|
/*
|
|
* We will call ftruncate(2) on the next available file descriptor,
|
|
* listen_fd+1, and get back EBADF if it's not a valid descriptor,
|
|
* and EINVAL if it is. This (currently) works fine in practice.
|
|
*/
|
|
if (ftruncate(listen_fd + 1, 0) < 0) {
|
|
if (errno == EBADF)
|
|
exit(0);
|
|
else if (errno == EINVAL)
|
|
errx(1, "file descriptor still open in child");
|
|
else
|
|
err(1, "unexpected error");
|
|
} else
|
|
errx(1, "ftruncate succeeded");
|
|
}
|
|
|
|
int
|
|
main(void)
|
|
{
|
|
struct sockaddr_in sin;
|
|
pthread_t accept_thread;
|
|
|
|
listen_fd = socket(PF_INET, SOCK_STREAM, 0);
|
|
if (listen_fd < 0)
|
|
err(1, "socket");
|
|
bzero(&sin, sizeof(sin));
|
|
sin.sin_family = AF_INET;
|
|
sin.sin_len = sizeof(sin);
|
|
sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
|
|
sin.sin_port = htons(PORT);
|
|
if (bind(listen_fd, (struct sockaddr *)&sin, sizeof(sin)) < 0)
|
|
err(1, "bind");
|
|
if (listen(listen_fd, -1) <0)
|
|
err(1, "listen");
|
|
if (pthread_create(&accept_thread, NULL, do_accept, NULL) != 0)
|
|
err(1, "pthread_create");
|
|
sleep(1); /* Easier than using a CV. */
|
|
do_fork();
|
|
exit(0);
|
|
}
|