#define _GNU_SOURCE
#include <sched.h>

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <linux/capability.h>
#include <sys/mount.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

int child(void *args)
{
    printf("pid as seen in the child: %lu\n", (unsigned long)getpid());

    pid_t p = mount("overlay", "./hatch/mnt", "overlay", 0, "lowerdir=./hatch/lower,upperdir=./hatch/upper,workdir=./hatch/work");
    if (p == -1){
        perror("mount");
        exit(1);
    }

    // Expose the mount to the parent namespace
    p = mount("none", "./hatch/mnt", NULL, MS_SHARED, NULL);
    if (p == -1){
        perror("mount");
        exit(1);
    }

    char *newargv[] = { "/bin/bash", NULL };

    execv("/bin/bash", newargv);
    perror("exec");
    exit(EXIT_FAILURE);

    return 0;
}
int main()
{
    pid_t p = clone(child, malloc(4096) + 4096, CLONE_NEWNS | CLONE_NEWUSER | SIGCHLD, NULL);
    if (p == -1) {
        perror("clone");
        exit(1);
    }

    printf("child pid: %lu\n", (unsigned long)p);
    waitpid(p, NULL, 0);
    return 0;
}