path: root/src/customdhcpcd/signal.c

/*
 * dhcpcd - DHCP client daemon
 * Copyright 2006-2008 Roy Marples <roy@marples.name>
 * All rights reserved

 * 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 AUTHOR 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 AUTHOR 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 <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <poll.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>

#include "common.h"
#include "logger.h"
#include "signal.h"

static int signal_pipe[2];
static int signals[5];

static const int handle_sigs[] =
{
  SIGHUP,
  SIGALRM,
  SIGTERM,
  SIGINT
};

static void signal_handler (int sig)
{
  unsigned int i = 0;
  int serrno = errno;

  /* Add a signal to our stack */
  while (signals[i])
    i++;
  if (i > sizeof (signals) / sizeof (signals[0]))
    logger (LOG_ERR, "signal buffer overrun");
  else
    signals[i] = sig;

  if (write (signal_pipe[1], &sig, sizeof (sig)) == -1)
    logger (LOG_ERR, "Could not send signal: %s", strerror (errno));

  /* Restore errno */
  errno = serrno;
}

int signal_fd (void)
{
  return (signal_pipe[0]);
}

/* Check if we have a signal or not */
int signal_exists (const struct pollfd *fd)
{
  if (signals[0] || (fd && fd->revents & POLLIN))
    return (0);
  return (-1);
}

/* 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 (struct pollfd *fd)
{
  int sig = -1;

  /* Pop a signal off the our stack */
  if (signals[0])
    {
      unsigned int i = 0;
      sig = signals[0];
      while (i < (sizeof (signals) / sizeof (signals[0])) - 1)
        {
          signals[i] = signals[i + 1];
          if (! signals[++i])
            break;
        }
    }

  if (fd && fd->revents & POLLIN)
    {
      char buf[16];
      size_t bytes;

      memset (buf, 0, sizeof (buf));
      bytes = read (signal_pipe[0], buf, sizeof (buf));

      if (bytes >= sizeof (sig))
        memcpy (&sig, buf, sizeof (sig));

      /* We need to clear us from rset if nothing left in the buffer
       * in case we are called many times */
      if (bytes == sizeof (sig))
        fd->revents = 0;
    }

  return (sig);
}

/* Call this before doing anything else. Sets up the socket pair
 * and installs the signal handler */
int signal_init (void)
{
  struct sigaction sa;

  if (pipe (signal_pipe) == -1)
    {
      logger (LOG_ERR, "pipe: %s", strerror (errno));
      return (-1);
    }

  /* Stop any scripts from inheriting us */
  close_on_exec (signal_pipe[0]);
  close_on_exec (signal_pipe[1]);

  /* Ignore child signals and don't make zombies.
   * Because we do this, we don't need to be in signal_setup */
  memset (&sa, 0, sizeof (sa));
  sa.sa_handler = SIG_DFL;
  sa.sa_flags = SA_NOCLDSTOP | SA_NOCLDWAIT;
  if (sigaction (SIGCHLD, &sa, NULL) == -1)
    {
      logger (LOG_ERR, "sigaction: %s", strerror (errno));
      return (-1);
    }

  memset (signals, 0, sizeof (signals));
  return (0);
}

int signal_setup (void)
{
  unsigned int i;
  struct sigaction sa;

  memset (&sa, 0, sizeof (sa));
  sa.sa_handler = signal_handler;
  sigemptyset (&sa.sa_mask);

  for (i = 0; i < sizeof (handle_sigs) / sizeof (handle_sigs[0]); i++)
    if (sigaction (handle_sigs[i], &sa, NULL) == -1)
      {
        logger (LOG_ERR, "sigaction: %s", strerror (errno));
        return (-1);
      }

  return (0);
}

int signal_reset (void)
{
  struct sigaction sa;
  unsigned int i;

  memset (&sa, 0, sizeof (sa));
  sa.sa_handler = SIG_DFL;
  sigemptyset (&sa.sa_mask);

  for (i = 0; i < sizeof (handle_sigs) / sizeof (handle_sigs[0]); i++)
    if (sigaction (handle_sigs[i], &sa, NULL) == -1)
      {
        logger (LOG_ERR, "sigaction: %s", strerror (errno));
        return (-1);
      }

  return (0);
}