/*  $OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $ */

/*

 * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>

 * Copyright 2007-2012 Niels Provos and Nick Mathewson

 *

 * 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.

 * 3. The name of the author may not be used to endorse or promote products

 *    derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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 "event2/event-config.h"

#include "evconfig-private.h"

#ifdef _WIN32

#define WIN32_LEAN_AND_MEAN

#include <winsock2.h>

#include <windows.h>

#undef WIN32_LEAN_AND_MEAN

#endif

#include <sys/types.h>

#ifdef EVENT__HAVE_SYS_TIME_H

#include <sys/time.h>

#endif

#include <sys/queue.h>

#ifdef EVENT__HAVE_SYS_SOCKET_H

#include <sys/socket.h>

#endif

#include <signal.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#ifdef EVENT__HAVE_UNISTD_H

#include <unistd.h>

#endif

#include <errno.h>

#ifdef EVENT__HAVE_FCNTL_H

#include <fcntl.h>

#endif

#include "event2/event.h"

#include "event2/event_struct.h"

#include "event-internal.h"

#include "event2/util.h"

#include "evsignal-internal.h"

#include "log-internal.h"

#include "evmap-internal.h"

#include "evthread-internal.h"

/*

  signal.c

  This is the signal-handling implementation we use for backends that don't

  have a better way to do signal handling.  It uses sigaction() or signal()

  to set a signal handler, and a socket pair to tell the event base when

  Note that I said "the event base" : only one event base can be set up to use

  this at a time.  For historical reasons and backward compatibility, if you

  add an event for a signal to event_base A, then add an event for a signal

  (any signal!) to event_base B, event_base B will get informed about the

  signal, but event_base A won't.

  It would be neat to change this behavior in some future version of Libevent.

  kqueue already does something far more sensible.  We can make all backends

  on Linux do a reasonable thing using signalfd.

*/

#ifndef _WIN32

/* Windows wants us to call our signal handlers as __cdecl.  Nobody else

 * expects you to do anything crazy like this. */

#ifndef __cdecl

#define __cdecl

#endif

#endif

static int evsig_add(struct event_base *, evutil_socket_t, short, short, void *);

static int evsig_del(struct event_base *, evutil_socket_t, short, short, void *);

static const struct eventop evsigops = {

  "signal",

  NULL,

  evsig_add,

  evsig_del,

  NULL,

  NULL,

  0, 0, 0

};

#ifndef EVENT__DISABLE_THREAD_SUPPORT

/* Lock for evsig_base and evsig_base_n_signals_added fields. */

static void *evsig_base_lock = NULL;

#endif

/* The event base that's currently getting informed about signals. */

static struct event_base *evsig_base = NULL;

/* A copy of evsig_base->sigev_n_signals_added. */

static int evsig_base_n_signals_added = 0;

static evutil_socket_t evsig_base_fd = -1;

static void __cdecl evsig_handler(int sig);

#define EVSIGBASE_LOCK() EVLOCK_LOCK(evsig_base_lock, 0)

#define EVSIGBASE_UNLOCK() EVLOCK_UNLOCK(evsig_base_lock, 0)

void

evsig_set_base_(struct event_base *base)

{

  EVSIGBASE_LOCK();

  evsig_base = base;

  evsig_base_n_signals_added = base->sig.ev_n_signals_added;

  evsig_base_fd = base->sig.ev_signal_pair[1];

  EVSIGBASE_UNLOCK();

}

/* Callback for when the signal handler write a byte to our signaling socket */

static void

evsig_cb(evutil_socket_t fd, short what, void *arg)

{

  static char signals[1024];

  ev_ssize_t n;

  int i;

  int ncaught[NSIG];

  struct event_base *base;

  base = arg;

  memset(&ncaught, 0, sizeof(ncaught));

  while (1) {

#ifdef _WIN32

    n = recv(fd, signals, sizeof(signals), 0);

#else

    n = read(fd, signals, sizeof(signals));

#endif

    if (n == -1) {

      int err = evutil_socket_geterror(fd);

      if (! EVUTIL_ERR_RW_RETRIABLE(err))

        event_sock_err(1, fd, "%s: recv", __func__);

      break;

    } else if (n == 0) {

      /* XXX warn? */

      break;

    }

    for (i = 0; i < n; ++i) {

      ev_uint8_t sig = signals[i];

      if (sig < NSIG)

        ncaught[sig]++;

    }

  }

  EVBASE_ACQUIRE_LOCK(base, th_base_lock);

  for (i = 0; i < NSIG; ++i) {

    if (ncaught[i])

      evmap_signal_active_(base, i, ncaught[i]);

  }

  EVBASE_RELEASE_LOCK(base, th_base_lock);

}

int

evsig_init_(struct event_base *base)

{

  /*

   * Our signal handler is going to write to one end of the socket

   * pair to wake up our event loop.  The event loop then scans for

   * signals that got delivered.

   */

  if (evutil_make_internal_pipe_(base->sig.ev_signal_pair) == -1) {

#ifdef _WIN32

    /* Make this nonfatal on win32, where sometimes people

       have localhost firewalled. */

    event_sock_warn(-1, "%s: socketpair", __func__);

#else

    event_sock_err(1, -1, "%s: socketpair", __func__);

#endif

    return -1;

  }

  if (base->sig.sh_old) {

    mm_free(base->sig.sh_old);

  }

  base->sig.sh_old = NULL;

  base->sig.sh_old_max = 0;

  event_assign(&base->sig.ev_signal, base, base->sig.ev_signal_pair[0],

    EV_READ | EV_PERSIST, evsig_cb, base);

  base->sig.ev_signal.ev_flags |= EVLIST_INTERNAL;

  event_priority_set(&base->sig.ev_signal, 0);

  base->evsigsel = &evsigops;

  return 0;

}

/* Helper: resize saved signal handler array up to the highest signal

   number. A dynamic array is used to keep footprint on the low side. */

int

evsig_ensure_saved_(struct evsig_info *sig, int evsignal)

{

  if (evsignal >= sig->sh_old_max) {

    void *p;

    int new_max = evsignal + 1;

    event_debug(("%s: evsignal (%d) >= sh_old_max (%d), resizing",

          __func__, evsignal, sig->sh_old_max));

    p = mm_realloc(sig->sh_old, new_max * sizeof(*sig->sh_old));

    if (p == NULL) {

      event_warn("realloc");

      return (-1);

    }

    memset((char *)p + sig->sh_old_max * sizeof(*sig->sh_old),

        0, (new_max - sig->sh_old_max) * sizeof(*sig->sh_old));

    sig->sh_old_max = new_max;

    sig->sh_old = p;

  }

  return 0;

}

/* Helper: set the signal handler for evsignal to handler in base, so that

 * we can restore the original handler when we clear the current one. */

int

evsig_set_handler_(struct event_base *base,

    int evsignal, void (__cdecl *handler)(int))

{

#ifdef EVENT__HAVE_SIGACTION

  struct sigaction sa;

#else

  ev_sighandler_t sh;

#endif

  struct evsig_info *sig = &base->sig;

  /* ensure saved array is large enough */

  if (evsig_ensure_saved_(sig, evsignal) < 0)

    return (-1);

  /* allocate space for previous handler out of dynamic array */

  sig->sh_old[evsignal] = mm_malloc(sizeof *sig->sh_old[evsignal]);

  if (sig->sh_old[evsignal] == NULL) {

    event_warn("malloc");

    return (-1);

  }

  /* save previous handler and setup new handler */

#ifdef EVENT__HAVE_SIGACTION

  memset(&sa, 0, sizeof(sa));

  sa.sa_handler = handler;

#ifdef SA_RESTART

  sa.sa_flags |= SA_RESTART;

#endif

  sigfillset(&sa.sa_mask);

  if (sigaction(evsignal, &sa, sig->sh_old[evsignal]) == -1) {

    event_warn("sigaction");

    mm_free(sig->sh_old[evsignal]);

    sig->sh_old[evsignal] = NULL;

    return (-1);

  }

#else

  if ((sh = signal(evsignal, handler)) == SIG_ERR) {

    event_warn("signal");

    mm_free(sig->sh_old[evsignal]);

    sig->sh_old[evsignal] = NULL;

    return (-1);

  }

  *sig->sh_old[evsignal] = sh;

#endif

  return (0);

}

static int

evsig_add(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)

{

  struct evsig_info *sig = &base->sig;

  (void)p;

  EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);

  /* catch signals if they happen quickly */

  EVSIGBASE_LOCK();

  if (evsig_base != base && evsig_base_n_signals_added) {

    event_warnx("Added a signal to event base %p with signals "

        "already added to event_base %p.  Only one can have "

        "signals at a time with the %s backend.  The base with "

        "the most recently added signal or the most recent "

        "event_base_loop() call gets preference; do "

        "not rely on this behavior in future Libevent versions.",

                   (void *)base, (void *)evsig_base, base->evsel->name);

  }

  evsig_base = base;

  evsig_base_n_signals_added = ++sig->ev_n_signals_added;

  evsig_base_fd = base->sig.ev_signal_pair[1];

  EVSIGBASE_UNLOCK();

  event_debug(("%s: %d: changing signal handler", __func__, (int)evsignal));

  if (evsig_set_handler_(base, (int)evsignal, evsig_handler) == -1) {

    goto err;

  }

  if (!sig->ev_signal_added) {

    if (event_add_nolock_(&sig->ev_signal, NULL, 0))

      goto err;

    sig->ev_signal_added = 1;

  }

  return (0);

err:

  EVSIGBASE_LOCK();

  --evsig_base_n_signals_added;

  --sig->ev_n_signals_added;

  EVSIGBASE_UNLOCK();

  return (-1);

}

int

evsig_restore_handler_(struct event_base *base, int evsignal)

{

  int ret = 0;

  struct evsig_info *sig = &base->sig;

#ifdef EVENT__HAVE_SIGACTION

  struct sigaction *sh;

#else

  ev_sighandler_t *sh;

#endif

  if (evsignal >= sig->sh_old_max) {

    /* Can't actually restore. */

    /* XXXX.*/

    return 0;

  }

  /* restore previous handler */

  sh = sig->sh_old[evsignal];

  sig->sh_old[evsignal] = NULL;

#ifdef EVENT__HAVE_SIGACTION

  if (sigaction(evsignal, sh, NULL) == -1) {

    event_warn("sigaction");

    ret = -1;

  }

#else

  if (signal(evsignal, *sh) == SIG_ERR) {

    event_warn("signal");

    ret = -1;

  }

#endif

  mm_free(sh);

  return ret;

}

static int

evsig_del(struct event_base *base, evutil_socket_t evsignal, short old, short events, void *p)

{

  EVUTIL_ASSERT(evsignal >= 0 && evsignal < NSIG);

  event_debug(("%s: "EV_SOCK_FMT": restoring signal handler",

    __func__, EV_SOCK_ARG(evsignal)));

  EVSIGBASE_LOCK();

  --evsig_base_n_signals_added;

  --base->sig.ev_n_signals_added;

  EVSIGBASE_UNLOCK();

  return (evsig_restore_handler_(base, (int)evsignal));

}

static void __cdecl

evsig_handler(int sig)

{

  int save_errno = errno;

#ifdef _WIN32

  int socket_errno = EVUTIL_SOCKET_ERROR();

#endif

  ev_uint8_t msg;

  if (evsig_base == NULL) {

    event_warnx(

      "%s: received signal %d, but have no base configured",

      __func__, sig);

    return;

  }

#ifndef EVENT__HAVE_SIGACTION

  signal(sig, evsig_handler);

#endif

  /* Wake up our notification mechanism */

  msg = sig;

#ifdef _WIN32

  send(evsig_base_fd, (char*)&msg, 1, 0);

#else

  for (;;) {

    /*

     * errno is only set to provide a descriptive message for event_warnx

     * if write returns 0. Not setting it will result in "No error" message

     * because write does not set errno when returning 0.

     *

     * EAGAIN will print "Try again" message. Another idea is to use

     * ENOSPC, but since we use non blocking sockets EAGAIN is preferable.

     *

     * Other than setting this text of the logged warning, the value in

     * errno has no further effect.

     */

    errno = EAGAIN;

    if (0 >= write(evsig_base_fd, &msg, 1)) {

      if (errno == EINTR)

        continue;

      event_warnx("%s: write: %s", __func__, strerror(errno));

    }

    break;

  }

#endif

  errno = save_errno;

#ifdef _WIN32

  EVUTIL_SET_SOCKET_ERROR(socket_errno);

#endif

}

void

evsig_dealloc_(struct event_base *base)

{

  int i = 0;

  if (base->sig.ev_signal_added) {

    event_del(&base->sig.ev_signal);

    base->sig.ev_signal_added = 0;

  }

  /* debug event is created in evsig_init_/event_assign even when

   * ev_signal_added == 0, so unassign is required */

  event_debug_unassign(&base->sig.ev_signal);

  for (i = 0; i < NSIG; ++i) {

    if (i < base->sig.sh_old_max && base->sig.sh_old[i] != NULL)

      evsig_restore_handler_(base, i);

  }

  EVSIGBASE_LOCK();

  if (base == evsig_base) {

    evsig_base = NULL;

    evsig_base_n_signals_added = 0;

    evsig_base_fd = -1;

  }

  EVSIGBASE_UNLOCK();

  if (base->sig.ev_signal_pair[0] != -1) {

    evutil_closesocket(base->sig.ev_signal_pair[0]);

    base->sig.ev_signal_pair[0] = -1;

  }

  if (base->sig.ev_signal_pair[1] != -1) {

    evutil_closesocket(base->sig.ev_signal_pair[1]);

    base->sig.ev_signal_pair[1] = -1;

  }

  base->sig.sh_old_max = 0;

  /* per index frees are handled in evsig_del() */

  if (base->sig.sh_old) {

    mm_free(base->sig.sh_old);

    base->sig.sh_old = NULL;

  }

}

static void

evsig_free_globals_locks(void)

{

#ifndef EVENT__DISABLE_THREAD_SUPPORT

  if (evsig_base_lock != NULL) {

    EVTHREAD_FREE_LOCK(evsig_base_lock, 0);

    evsig_base_lock = NULL;

  }

#endif

  return;

}

void

evsig_free_globals_(void)

{

  evsig_free_globals_locks();

}

#ifndef EVENT__DISABLE_THREAD_SUPPORT

int

evsig_global_setup_locks_(const int enable_locks)

{

  EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0);

  return 0;

}

#endif