#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/prctl.h>
#include "utils.h"

#define ERROR(f_, ...) fprintf(stderr, (f_), ##__VA_ARGS__)
#define UNUSED(x)      (void)(x)
#define ERROR_EXIT(f_, ...) { \
        fprintf(stderr, (f_), ##__VA_ARGS__); \
        return 1; \
    }

volatile sig_atomic_t term_caught = 0;
void onterm(int sig)
{
    printf("sigterm caught\n");
    UNUSED(sig);
    term_caught = 1;
}

int main()
{
    int result;
    int sock_fd, sock_conn;
    int nsfd;

    /* Get current namespace's file descriptor. */
    nsfd = open("/proc/self/ns/mnt", O_RDONLY);
    if (nsfd == -1)
        ERROR_EXIT("error: failed to acquire mount namespace's fd.%s\n",
                   strerror(errno));

    /* Fork. */
    pid_t ppid_before_fork = getpid();
    pid_t pid = fork();
    if (pid == -1)
        ERROR_EXIT("fork: %s\n", strerror(errno));

    if (pid == 0) {
        /* Catch SIGTERM. */
        struct sigaction sa = {0};
        sa.sa_handler = onterm;
        sigaction(SIGTERM, &sa, NULL);

        /* Ignore SIGINT. */
        signal(SIGINT, SIG_IGN);

        /* Set the child to die when parent thread dies. */
        int r = prctl(PR_SET_PDEATHSIG, SIGTERM);
        if (r == -1)
            ERROR_EXIT("prctl: %s\n", strerror(errno));
        if (getppid() != ppid_before_fork)
            ERROR_EXIT("error: parent has died already.\n");

        /* Create unix socket. */
        sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
        if (sock_fd == -1)
            ERROR_EXIT("socket: %s.\n", strerror(errno));

        struct sockaddr_un sock_addr = {0};
        sock_addr.sun_family = AF_UNIX;
        strcpy(&sock_addr.sun_path[1], "/tmp/voidnsrun-test.sock");

        if (bind(sock_fd, (struct sockaddr *)&sock_addr, sizeof(sock_addr)) == -1)
            ERROR_EXIT("bind: %s\n", strerror(errno));

        listen(sock_fd, 1);

        while (!term_caught) {
            sock_conn = accept(sock_fd, NULL, 0);
            if (sock_conn == -1) {
                ERROR("accept: %s\n", strerror(errno));
                continue;
            }
            printf("accepted\n");
            send_fd(sock_conn, nsfd);
        }
        printf("exiting\n");
    } else {
        /* This is parent. Launch a program. */
        char *argv[2] = {"/bin/sh", NULL};

        result = execvp(argv[0], (char *const *)argv);
        if (result == -1)
            ERROR_EXIT("execvp: %s\n", strerror(errno));
    }

    return 0;
}