/* 
 * Shameless taken from udhcp as I think it's a good idea.
 * Signal pipe infrastructure. A reliable way of delivering signals.
 *
 * Russ Dill <Russ.Dill@asu.edu> December 2003
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <sys/socket.h>
#include <sys/select.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>

#include "logger.h"

static int signal_pipe[2];

static void signal_handler (int sig)
{
  if (send (signal_pipe[1], &sig, sizeof (sig), MSG_DONTWAIT) < 0)
    logger (LOG_ERR, "Could not send signal: %s", strerror (errno));
}


/* Call this before doing anything else. Sets up the socket pair
 * and installs the signal handler */
void signal_setup(void)
{
  int i;
  int flags;

  socketpair (AF_UNIX, SOCK_STREAM, 0, signal_pipe);

  /* Stop any scripts from inheriting us */
  for (i = 0; i < 2; i++)
    if ((flags = fcntl (signal_pipe[i], F_GETFD, 0)) < 0 ||
	fcntl (signal_pipe[i], F_SETFD, flags | FD_CLOEXEC) < 0)
      logger (LOG_ERR ,"fcntl: %s", strerror (errno));
  
  signal (SIGHUP, signal_handler);
  signal (SIGALRM, signal_handler);
  signal (SIGTERM, signal_handler);
  signal (SIGINT, signal_handler);
}


/* Quick little function to setup the rfds. Will return the
 * max_fd for use with select. Limited in that you can only pass
 * one extra fd */
int signal_fd_set (fd_set *rfds, int extra_fd)
{
  FD_ZERO (rfds);
  FD_SET (signal_pipe[0], rfds);
  if (extra_fd >= 0)
    FD_SET (extra_fd, rfds);
  return signal_pipe[0] > extra_fd ? signal_pipe[0] : extra_fd;
}


/* Read a signal from the signal pipe. Returns 0 if there is
 * no signal, -1 on error (and sets errno appropriately), and
 * your signal on success */
int signal_read (fd_set *rfds)
{
  int sig;

  if (!FD_ISSET (signal_pipe[0], rfds))
    return 0;

  if (read (signal_pipe[0], &sig, sizeof (sig)) < 0)
    return -1;

  return sig;
}