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 
36 static pid_t pid = -1;
37 
f(void)38 static void f(void)
39 {
40 	if (pid > 0) {
41 		kill(pid, SIGTERM);
42 	}
43 }
44 
main(void)45 int 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