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selftests/namespaces: third active reference count tests 

Test that a namespace remains active while a process is using it,
even after the creating process exits.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-25-2e6f823ebdc0@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2025-10-29 13:20:38 +01:00
parent 721c7e41b1
commit c6e25d930b
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GPG Key ID: 91C61BC06578DCA2
1 changed files with 124 additions and 0 deletions
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124
tools/testing/selftests/namespaces/ns_active_ref_test.c
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@ -152,4 +152,128 @@ TEST(ns_inactive_after_exit)
ASSERT_TRUE(errno == ENOENT || errno == ESTALE); ASSERT_TRUE(errno == ENOENT || errno == ESTALE);
} }
/*
* Test that a namespace remains active while a process is using it,
* even after the creating process exits.
*/
TEST(ns_active_with_multiple_processes)
{
struct file_handle *handle;
int mount_id;
int ret;
int fd;
int pipefd[2];
int syncpipe[2];
pid_t pid1, pid2;
int status;
char buf[sizeof(*handle) + MAX_HANDLE_SZ];
char sync_byte;
/* Create pipes for communication */
ASSERT_EQ(pipe(pipefd), 0);
ASSERT_EQ(pipe(syncpipe), 0);
pid1 = fork();
ASSERT_GE(pid1, 0);
if (pid1 == 0) {
/* First child - creates namespace */
close(pipefd[0]);
close(syncpipe[1]);
/* Create new network namespace */
ret = unshare(CLONE_NEWNET);
if (ret < 0) {
close(pipefd[1]);
close(syncpipe[0]);
exit(1);
}
/* Open and get handle */
fd = open("/proc/self/ns/net", O_RDONLY);
if (fd < 0) {
close(pipefd[1]);
close(syncpipe[0]);
exit(1);
}
handle = (struct file_handle *)buf;
handle->handle_bytes = MAX_HANDLE_SZ;
ret = name_to_handle_at(fd, "", handle, &mount_id, AT_EMPTY_PATH);
close(fd);
if (ret < 0) {
close(pipefd[1]);
close(syncpipe[0]);
exit(1);
}
/* Send handle to parent */
write(pipefd[1], buf, sizeof(*handle) + handle->handle_bytes);
close(pipefd[1]);
/* Wait for signal before exiting */
read(syncpipe[0], &sync_byte, 1);
close(syncpipe[0]);
exit(0);
}
/* Parent reads handle */
close(pipefd[1]);
ret = read(pipefd[0], buf, sizeof(buf));
close(pipefd[0]);
ASSERT_GT(ret, 0);
handle = (struct file_handle *)buf;
/* Create second child that will keep namespace active */
pid2 = fork();
ASSERT_GE(pid2, 0);
if (pid2 == 0) {
/* Second child - reopens the namespace */
close(syncpipe[0]);
close(syncpipe[1]);
/* Open the namespace via handle */
fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
if (fd < 0) {
exit(1);
}
/* Join the namespace */
ret = setns(fd, CLONE_NEWNET);
close(fd);
if (ret < 0) {
exit(1);
}
/* Sleep to keep namespace active */
sleep(1);
exit(0);
}
/* Let second child enter the namespace */
usleep(100000); /* 100ms */
/* Signal first child to exit */
close(syncpipe[0]);
sync_byte = 'X';
write(syncpipe[1], &sync_byte, 1);
close(syncpipe[1]);
/* Wait for first child */
waitpid(pid1, &status, 0);
ASSERT_TRUE(WIFEXITED(status));
/* Namespace should still be active because second child is using it */
fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
ASSERT_GE(fd, 0);
close(fd);
/* Wait for second child */
waitpid(pid2, &status, 0);
ASSERT_TRUE(WIFEXITED(status));
}
TEST_HARNESS_MAIN TEST_HARNESS_MAIN