1/*
  2 * Copyright © 2019 Alexey Dobriyan <adobriyan@gmail.com>
  3 *
  4 * Permission to use, copy, modify, and distribute this software for any
  5 * purpose with or without fee is hereby granted, provided that the above
  6 * copyright notice and this permission notice appear in all copies.
  7 *
  8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 15 */
 16/*
 17 * Test that setns(CLONE_NEWNET) points to new /proc/net content even
 18 * if old one is in dcache.
 19 *
 20 * FIXME /proc/net/unix is under CONFIG_UNIX which can be disabled.
 21 */
 22#undef NDEBUG
 23#include <assert.h>
 24#include <errno.h>
 25#include <sched.h>
 26#include <signal.h>
 27#include <stdio.h>
 28#include <stdlib.h>
 29#include <string.h>
 30#include <unistd.h>
 31#include <sys/types.h>
 32#include <sys/stat.h>
 33#include <fcntl.h>
 34#include <sys/socket.h>
 35
 36static pid_t pid = -1;
 37
 38static void f(void)
 39{
 40	if (pid > 0) {
 41		kill(pid, SIGTERM);
 42	}
 43}
 44
 45int main(void)
 46{
 47	int fd[2];
 48	char _ = 0;
 49	int nsfd;
 50
 51	atexit(f);
 52
 53	/* Check for priviledges and syscall availability straight away. */
 54	if (unshare(CLONE_NEWNET) == -1) {
 55		if (errno == ENOSYS || errno == EPERM) {
 56			return 4;
 57		}
 58		return 1;
 59	}
 60	/* Distinguisher between two otherwise empty net namespaces. */
 61	if (socket(AF_UNIX, SOCK_STREAM, 0) == -1) {
 62		return 1;
 63	}
 64
 65	if (pipe(fd) == -1) {
 66		return 1;
 67	}
 68
 69	pid = fork();
 70	if (pid == -1) {
 71		return 1;
 72	}
 73
 74	if (pid == 0) {
 75		if (unshare(CLONE_NEWNET) == -1) {
 76			return 1;
 77		}
 78
 79		if (write(fd[1], &_, 1) != 1) {
 80			return 1;
 81		}
 82
 83		pause();
 84
 85		return 0;
 86	}
 87
 88	if (read(fd[0], &_, 1) != 1) {
 89		return 1;
 90	}
 91
 92	{
 93		char buf[64];
 94		snprintf(buf, sizeof(buf), "/proc/%u/ns/net", pid);
 95		nsfd = open(buf, O_RDONLY);
 96		if (nsfd == -1) {
 97			return 1;
 98		}
 99	}
100
101	/* Reliably pin dentry into dcache. */
102	(void)open("/proc/net/unix", O_RDONLY);
103
104	if (setns(nsfd, CLONE_NEWNET) == -1) {
105		return 1;
106	}
107
108	kill(pid, SIGTERM);
109	pid = 0;
110
111	{
112		char buf[4096];
113		ssize_t rv;
114		int fd;
115
116		fd = open("/proc/net/unix", O_RDONLY);
117		if (fd == -1) {
118			return 1;
119		}
120
121#define S "Num       RefCount Protocol Flags    Type St Inode Path\n"
122		rv = read(fd, buf, sizeof(buf));
123
124		assert(rv == strlen(S));
125		assert(memcmp(buf, S, strlen(S)) == 0);
126	}
127
128	return 0;
129}