/*      $NetBSD: filemon_dev.c,v 1.9 2022/03/04 23:17:16 sjg Exp $      */

/*
* Copyright (c) 2020 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Taylor R. Campbell.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/

#include "filemon.h"

#include <sys/ioctl.h>

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>

#ifdef HAVE_FILEMON_H
# include <filemon.h>
#endif

#ifndef _PATH_FILEMON
#define _PATH_FILEMON   "/dev/filemon"
#endif

#ifndef MAKE_ATTR_UNUSED
#define MAKE_ATTR_UNUSED        __attribute__((__unused__))
#endif

struct filemon {
       int     fd;
};

const char *
filemon_path(void)
{

       return _PATH_FILEMON;
}

struct filemon *
filemon_open(void)
{
       struct filemon *F;
       unsigned i;
       int error;

       /* Allocate and zero a struct filemon object.  */
       F = calloc(1, sizeof *F);
       if (F == NULL)
               return NULL;

       /* Try opening /dev/filemon, up to six times (cargo cult!).  */
       for (i = 0; (F->fd = open(_PATH_FILEMON, O_RDWR|O_CLOEXEC)) == -1; i++) {
               if (i == 5) {
                       error = errno;
                       goto fail0;
               }
       }

       /* Success!  */
       return F;

fail0:  free(F);
       errno = error;
       return NULL;
}

int
filemon_setfd(struct filemon *F, int fd)
{

       /* Point the kernel at this file descriptor.  */
       if (ioctl(F->fd, FILEMON_SET_FD, &fd) == -1)
               return -1;

       /* No need for it in userland any more; close it.  */
       (void)close(fd);

       /* Success!  */
       return 0;
}

void
filemon_setpid_parent(struct filemon *F MAKE_ATTR_UNUSED, pid_t pid MAKE_ATTR_UNUSED)
{
       /* Nothing to do!  */
}

int
filemon_setpid_child(const struct filemon *F, pid_t pid)
{

       /* Just pass it on to the kernel.  */
       return ioctl(F->fd, FILEMON_SET_PID, &pid);
}

int
filemon_close(struct filemon *F)
{
       int error = 0;

       /* Close the filemon device fd.  */
       if (close(F->fd) == -1 && error == 0)
               error = errno;

       /* Free the filemon descriptor.  */
       free(F);

       /* Set errno and return -1 if anything went wrong.  */
       if (error != 0) {
               errno = error;
               return -1;
       }

       /* Success!  */
       return 0;
}

int
filemon_readfd(const struct filemon *F MAKE_ATTR_UNUSED)
{

       return -1;
}

int
filemon_process(struct filemon *F MAKE_ATTR_UNUSED)
{

       return 0;
}