// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <sched.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/socket.h>

#ifndef SO_NETNS_COOKIE
#define SO_NETNS_COOKIE 71
#endif

#define pr_err(fmt, ...) \
        ({ \
                fprintf(stderr, "%s:%d:" fmt ": %m\n", \
                        __func__, __LINE__, ##__VA_ARGS__); \
                1; \
        })

int main(int argc, char *argvp[])
{
        uint64_t cookie1, cookie2;
        socklen_t vallen;
        int sock1, sock2;

        sock1 = socket(AF_INET, SOCK_STREAM, 0);
        if (sock1 < 0)
                return pr_err("Unable to create TCP socket");

        vallen = sizeof(cookie1);
        if (getsockopt(sock1, SOL_SOCKET, SO_NETNS_COOKIE, &cookie1, &vallen) != 0)
                return pr_err("getsockopt(SOL_SOCKET, SO_NETNS_COOKIE)");

        if (!cookie1)
                return pr_err("SO_NETNS_COOKIE returned zero cookie");

        if (unshare(CLONE_NEWNET))
                return pr_err("unshare");

        sock2 = socket(AF_INET, SOCK_STREAM, 0);
        if (sock2 < 0)
                return pr_err("Unable to create TCP socket");

        vallen = sizeof(cookie2);
        if (getsockopt(sock2, SOL_SOCKET, SO_NETNS_COOKIE, &cookie2, &vallen) != 0)
                return pr_err("getsockopt(SOL_SOCKET, SO_NETNS_COOKIE)");

        if (!cookie2)
                return pr_err("SO_NETNS_COOKIE returned zero cookie");

        if (cookie1 == cookie2)
                return pr_err("SO_NETNS_COOKIE returned identical cookies for distinct ns");

        close(sock1);
        close(sock2);
        return 0;
}