newfileops_on_fork_test.c revision 319301 
1/*-
2 * Copyright (c) 2009 Robert N. M. Watson
3 * All rights reserved.
4 *
5 * This software was developed at the University of Cambridge Computer
6 * Laboratory with support from a grant from Google, Inc.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * $FreeBSD: stable/10/tests/sys/file/newfileops_on_fork_test.c 319301 2017-05-31 08:36:47Z ngie $
30 */
31
32/*
33 * When a multi-threaded application calls fork(2) from one thread while
34 * another thread is blocked in accept(2), we prefer that the file descriptor
35 * to be returned by accept(2) not appear in the child process.  Test this by
36 * creating a thread blocked in accept(2), then forking a child and seeing if
37 * the fd it would have returned is defined in the child or not.
38 */
39
40#include <sys/socket.h>
41#include <sys/wait.h>
42
43#include <netinet/in.h>
44
45#include <err.h>
46#include <errno.h>
47#include <pthread.h>
48#include <signal.h>
49#include <stdlib.h>
50#include <string.h>
51#include <unistd.h>
52
53#define	PORT	9000
54
55static int listen_fd;
56
57static void *
58do_accept(__unused void *arg)
59{
60	int accept_fd;
61
62	accept_fd = accept(listen_fd, NULL, NULL);
63	if (accept_fd < 0)
64		err(1, "accept");
65
66	close(accept_fd);
67	return (NULL);
68}
69
70static void
71do_fork(void)
72{
73	int pid;
74
75	pid = fork();
76	if (pid < 0)
77		err(1, "fork");
78	if (pid > 0) {
79		waitpid(pid, NULL, 0);
80		exit(0);
81	}
82
83	/*
84	 * We will call ftruncate(2) on the next available file descriptor,
85	 * listen_fd+1, and get back EBADF if it's not a valid descriptor,
86	 * and EINVAL if it is.  This (currently) works fine in practice.
87	 */
88	if (ftruncate(listen_fd + 1, 0) < 0) {
89		if (errno == EBADF)
90			exit(0);
91		else if (errno == EINVAL)
92			errx(1, "file descriptor still open in child");
93		else
94			err(1, "unexpected error");
95	} else
96		errx(1, "ftruncate succeeded");
97}
98
99int
100main(void)
101{
102	struct sockaddr_in sin;
103	pthread_t accept_thread;
104
105	listen_fd = socket(PF_INET, SOCK_STREAM, 0);
106	if (listen_fd < 0)
107		err(1, "socket");
108	bzero(&sin, sizeof(sin));
109	sin.sin_family = AF_INET;
110	sin.sin_len = sizeof(sin);
111	sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
112	sin.sin_port = htons(PORT);
113	if (bind(listen_fd, (struct sockaddr *)&sin, sizeof(sin)) < 0)
114		err(1, "bind");
115	if (listen(listen_fd, -1) <0)
116		err(1, "listen");
117	if (pthread_create(&accept_thread, NULL, do_accept, NULL) != 0)
118		err(1, "pthread_create");
119	sleep(1);	/* Easier than using a CV. */
120	do_fork();
121	exit(0);
122}
123