#include <stdlib.h>
#include <stdbool.h>
#include <stdio.h>
#include <fcntl.h>

#define _GNU_SOURCE
#define __USE_GNU
#include <sched.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <pthread.h>
#include <unistd.h>

static void do_unshare(int num, int flags)
{
	int res;

	printf(" %d) unshare(0x%x).\n", num, flags);
	res = unshare(flags);
	if (res != 0) {
		printf("  %d: unshare(0x%x) failed, errno %d.\n", num, flags, errno);
		exit(3);
	}
}

static void set_rmid_forced(char *value)
{
	int fd;
	int i;

	fd=open("/proc/sys/kernel/shm_rmid_forced", O_RDWR);
	if (fd == -1) {
		printf("open shm_rmid_forced failed, errno %d.\n", errno);
		exit (1);
	}
	i = write(fd, value, 2);
	if (i != 2) {
		printf("unexpected result when writing %s to shm_rmid_forced: %d, errno %d.\n", value, i, errno);
		exit (2);
	}
	close(fd);
}

static void *do_shmget(bool map_it)
{
	int seg;
	void *ptr;

	if ((seg = shmget (IPC_PRIVATE, 1, IPC_CREAT| 0600)) == -1) {
		perror("shmget");
		exit(3);
	}
	if (map_it) {
		if ((ptr = shmat (seg, 0, 0)) == (void*)-1) {
			perror ("shmat");
			exit(4);
		}
	} else {
		ptr = NULL;
	}
	return ptr;
}

int main (int argc, char **argv)
{
	pid_t child;

	(void)argv;
	(void)argc;

	printf("shmns4:\n");
	printf("  One process creates and maps shm segments in multiple namespaces.\n");
	printf("  The namespaces are replaced before unmapping the segments.\n");

	do_unshare(1, CLONE_NEWIPC);
	set_rmid_forced("1\n");

	child = fork();
	if (child == -1) {
		perror ("fork");
		exit(5);
	}
	if (child == 0) {
		printf("create a namespace, create 2 shm segments, do not map them.\n");
		do_unshare(2, CLONE_NEWIPC);
		set_rmid_forced("1\n");
		do_shmget(false);
		do_shmget(false);

		do_unshare(2, CLONE_NEWIPC);
		set_rmid_forced("0\n");
		sleep(5); /* namespace destruction is done in a worker, thus wait a bit */

		printf("create a namespace, create 2 shm segments, do not map them, no auto-rm.\n");
		do_shmget(false);
		do_shmget(false);

		do_unshare(2, CLONE_NEWIPC);
		set_rmid_forced("1\n");
		sleep(5); /* namespace destruction is done in a worker, thus wait a bit */

		printf("create a namespace, create 2 shm segments, map them.\n");
		do_shmget(true);
		do_shmget(true);

		do_unshare(2, CLONE_NEWIPC);
		set_rmid_forced("0\n");
		sleep(5); /* namespace destruction is done in a worker, thus wait a bit */

		printf("Once more: Create a namespace, create 2 shm segments, map them, no auto-rm.\n");
		do_shmget(true);
		do_shmget(true);


		printf("Orphan namespace (switch back to parent namespace).\n");
		{
			char path[255];
			int fd;

			sprintf(path, "/proc/%d/ns/ipc", getppid());
			fd = open(path, O_RDONLY);
			if (fd == -1) {
				perror("open ipc ns");
				exit(6);
			}
			if (setns(fd, 0) == -1) {
				perror("setns to parent");
				exit(7);			
			}
		}
		sleep(5); /* namespace destruction is done in a worker, thus wait a bit */

		printf("Before exit of child: 4 mappings exist in 2 namespaces.\n");

		exit(0);
		
	} else {
		int status;
		int ret;

		sleep(1);
		ret = waitpid(child, &status, 0);
		sleep(10);
		printf("parent:waitpid returned %d, status %d.\n", ret, status);
	}
	return 0;
}