LXR linux/tools/testing/selftests/proc/setns-dcache.c

   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}
 130