/*      $OpenBSD: kqueue-flock.c,v 1.4 2016/09/20 23:05:27 bluhm Exp $  */
/*
 *      Written by Philip Guenther <guenther@openbsd.org> 2012 Public Domain
 */

#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#include <sys/wait.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "main.h"

#define FILE "lock.test"

static void
check_lock(int fd, const char *msg)
{
        pid_t pid = fork();
        int status;

        if (pid == -1)
                err(1, "fork");
        if (pid == 0) {
                struct flock fl;

                memset(&fl, 0, sizeof fl);
                fl.l_type = F_WRLCK;
                if (fcntl(fd, F_SETLK, &fl) == 0) {
                        printf("lock succeeded %s\n", msg);
                        _exit(1);
                }
                if (errno != EAGAIN)
                        err(1, "fcntl(SETLK)");
                if (fcntl(fd, F_GETLK, &fl))
                        err(1, "fcntl(GETLK)");
                if (fl.l_type != F_WRLCK) {
                        printf("lock not found %s\n", msg);
                        _exit(1);
                }
                close(fd);
                _exit(0);
        }

        waitpid(pid, &status, 0);
        if (! WIFEXITED(status) || WEXITSTATUS(status) != 0)
                exit(1);
}

int
do_flock(void)
{
        int fd, kq;
        struct kevent kev;
        struct flock fl;

        fd = open(FILE, O_CREAT|O_RDWR, 0666);
        if (fd < 0)
                err(1, "open");
        memset(&fl, 0, sizeof fl);
        fl.l_type = F_WRLCK;
        if (fcntl(fd, F_SETLK, &fl))
                err(1, "fcntl(SETLK)");

        check_lock(fd, "before");

        kq = kqueue();
        EV_SET(&kev, fd, EVFILT_VNODE, EV_ADD, NOTE_LINK, 0, NULL);
        if (kevent(kq, &kev, 1, NULL, 0, NULL))
                err(1, "kevent");

        check_lock(fd, "after add");

        EV_SET(&kev, fd, EVFILT_VNODE, EV_DELETE, NOTE_LINK, 0, NULL);
        if (kevent(kq, &kev, 1, NULL, 0, NULL))
                err(1, "kevent");

        check_lock(fd, "after delete");

        close(kq);

        check_lock(fd, "after kq close");

        close(fd);
        unlink(FILE);
        return (0);
}