/*
 * Copyright © 2019 Alexey Dobriyan <adobriyan@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
/*
 * Test that setns(CLONE_NEWNET) points to new /proc/net content even
 * if old one is in dcache.
 *
 * FIXME /proc/net/unix is under CONFIG_UNIX which can be disabled.
 */
#undef NDEBUG
#include <assert.h>
#include <errno.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/socket.h>

static pid_t pid = -1;

static void f(void)
{
        if (pid > 0) {
                kill(pid, SIGTERM);
        }
}

int main(void)
{
        int fd[2];
        char _ = 0;
        int nsfd;

        atexit(f);

        /* Check for priviledges and syscall availability straight away. */
        if (unshare(CLONE_NEWNET) == -1) {
                if (errno == ENOSYS || errno == EPERM) {
                        return 4;
                }
                return 1;
        }
        /* Distinguisher between two otherwise empty net namespaces. */
        if (socket(AF_UNIX, SOCK_STREAM, 0) == -1) {
                return 1;
        }

        if (pipe(fd) == -1) {
                return 1;
        }

        pid = fork();
        if (pid == -1) {
                return 1;
        }

        if (pid == 0) {
                if (unshare(CLONE_NEWNET) == -1) {
                        return 1;
                }

                if (write(fd[1], &_, 1) != 1) {
                        return 1;
                }

                pause();

                return 0;
        }

        if (read(fd[0], &_, 1) != 1) {
                return 1;
        }

        {
                char buf[64];
                snprintf(buf, sizeof(buf), "/proc/%u/ns/net", pid);
                nsfd = open(buf, O_RDONLY);
                if (nsfd == -1) {
                        return 1;
                }
        }

        /* Reliably pin dentry into dcache. */
        (void)open("/proc/net/unix", O_RDONLY);

        if (setns(nsfd, CLONE_NEWNET) == -1) {
                return 1;
        }

        kill(pid, SIGTERM);
        pid = 0;

        {
                char buf[4096];
                ssize_t rv;
                int fd;

                fd = open("/proc/net/unix", O_RDONLY);
                if (fd == -1) {
                        return 1;
                }

#define S "Num       RefCount Protocol Flags    Type St Inode Path\n"
                rv = read(fd, buf, sizeof(buf));

                assert(rv == strlen(S));
                assert(memcmp(buf, S, strlen(S)) == 0);
        }

        return 0;
}