/* tinyproxy - A fast light-weight HTTP proxy
 * Copyright (C) 2000 Robert James Kaes <rjkaes@users.sourceforge.net>
 *
 * 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.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/* Handles the creation/destruction of the various children required for
 * processing incoming connections.
 */

#include "tinyproxy.h"

#include "child.h"
#include "daemon.h"
#include "filter.h"
#include "heap.h"
#include "log.h"
#include "reqs.h"
#include "sock.h"
#include "utils.h"

static int listenfd;
static socklen_t addrlen;

/*
 * Stores the internal data needed for each child (connection)
 */
enum child_status_t
{ T_EMPTY, T_WAITING, T_CONNECTED };
struct child_s
{
  pid_t tid;
  unsigned int connects;
  enum child_status_t status;
};

/*
 * A pointer to an array of children. A certain number of children are
 * created when the program is started.
 */
static struct child_s *child_ptr;

static struct child_config_s
{
  int maxclients, maxrequestsperchild;
  int maxspareservers, minspareservers, startservers;
} child_config;

static unsigned int *servers_waiting;	/* servers waiting for a connection */

/*
 * Lock/Unlock the "servers_waiting" variable so that two children cannot
 * modify it at the same time.
 */
#define SERVER_COUNT_LOCK()   _child_lock_wait()
#define SERVER_COUNT_UNLOCK() _child_lock_release()

/* START OF LOCKING SECTION */

/*
 * These variables are required for the locking mechanism.  Also included
 * are the "private" functions for locking/unlocking.
 */
static struct flock lock_it, unlock_it;
static int lock_fd = -1;

static void
_child_lock_init (void)
{
  char lock_file[] = "/tmp/tinyproxy.servers.lock.XXXXXX";

  /* Only allow u+rw bits. This may be required for some versions
   * of glibc so that mkstemp() doesn't make us vulnerable.
   */
  umask (0177);

  lock_fd = mkstemp (lock_file);
  unlink (lock_file);

  lock_it.l_type = F_WRLCK;
  lock_it.l_whence = SEEK_SET;
  lock_it.l_start = 0;
  lock_it.l_len = 0;

  unlock_it.l_type = F_UNLCK;
  unlock_it.l_whence = SEEK_SET;
  unlock_it.l_start = 0;
  unlock_it.l_len = 0;
}

static void
_child_lock_wait (void)
{
  int rc;

  while ((rc = fcntl (lock_fd, F_SETLKW, &lock_it)) < 0)
    {
      if (errno == EINTR)
	continue;
      else
	return;
    }
}

static void
_child_lock_release (void)
{
  if (fcntl (lock_fd, F_SETLKW, &unlock_it) < 0)
    return;
}

/* END OF LOCKING SECTION */

#define SERVER_INC() do { \
    SERVER_COUNT_LOCK(); \
    ++(*servers_waiting); \
    DEBUG2("INC: servers_waiting: %d", *servers_waiting); \
    SERVER_COUNT_UNLOCK(); \
} while (0)

#define SERVER_DEC() do { \
    SERVER_COUNT_LOCK(); \
    assert(*servers_waiting > 0); \
    --(*servers_waiting); \
    DEBUG2("DEC: servers_waiting: %d", *servers_waiting); \
    SERVER_COUNT_UNLOCK(); \
} while (0)

/*
 * Set the configuration values for the various child related settings.
 */
short int
child_configure (child_config_t type, int val)
{
  switch (type)
    {
    case CHILD_MAXCLIENTS:
      child_config.maxclients = val;
      break;
    case CHILD_MAXSPARESERVERS:
      child_config.maxspareservers = val;
      break;
    case CHILD_MINSPARESERVERS:
      child_config.minspareservers = val;
      break;
    case CHILD_STARTSERVERS:
      child_config.startservers = val;
      break;
    case CHILD_MAXREQUESTSPERCHILD:
      child_config.maxrequestsperchild = val;
      break;
    default:
      DEBUG2 ("Invalid type (%d)", type);
      return -1;
    }

  return 0;
}

/*
 * This is the main (per child) loop.
 */
static void
child_main (struct child_s *ptr)
{
  int connfd;
  struct sockaddr *cliaddr;
  socklen_t clilen;

  cliaddr = safemalloc (addrlen);
  if (!cliaddr)
    {
      log_message (LOG_CRIT, "Could not allocate memory for child address.");
      exit (0);
    }

  ptr->connects = 0;

  while (!config.quit)
    {
      ptr->status = T_WAITING;

      clilen = addrlen;

      connfd = accept (listenfd, cliaddr, &clilen);

#ifndef NDEBUG
      /*
       * Enable the TINYPROXY_DEBUG environment variable if you
       * want to use the GDB debugger.
       */
      if (getenv ("TINYPROXY_DEBUG"))
	{
	  /* Pause for 10 seconds to allow us to connect debugger */
	  fprintf (stderr,
		   "Process has accepted connection: %ld\n",
		   (long int) ptr->tid);
	  sleep (10);
	  fprintf (stderr, "Continuing process: %ld\n", (long int) ptr->tid);
	}
#endif

      /*
       * Make sure no error occurred...
       */
      if (connfd < 0)
	{
	  log_message (LOG_ERR,
		       "Accept returned an error (%s) ... retrying.",
		       strerror (errno));
	  continue;
	}

      ptr->status = T_CONNECTED;

      SERVER_DEC ();

      handle_connection (connfd);
      ptr->connects++;

      if (child_config.maxrequestsperchild != 0)
	{
	  DEBUG2 ("%u connections so far...", ptr->connects);

	  if (ptr->connects == child_config.maxrequestsperchild)
	    {
	      log_message (LOG_NOTICE,
			   "Child has reached MaxRequestsPerChild (%u). Killing child.",
			   ptr->connects);
	      break;
	    }
	}

      SERVER_COUNT_LOCK ();
      if (*servers_waiting > child_config.maxspareservers)
	{
	  /*
	   * There are too many spare children, kill ourself
	   * off.
	   */
	  log_message (LOG_NOTICE,
		       "Waiting servers (%d) exceeds MaxSpareServers (%d). Killing child.",
		       *servers_waiting, child_config.maxspareservers);
	  SERVER_COUNT_UNLOCK ();

	  break;
	}
      else
	{
	  SERVER_COUNT_UNLOCK ();
	}

      SERVER_INC ();
    }

  ptr->status = T_EMPTY;

  safefree (cliaddr);
  exit (0);
}

/*
 * Fork a child "child" (or in our case a process) and then start up the
 * child_main() function.
 */
static pid_t
child_make (struct child_s *ptr)
{
  pid_t pid;

  if ((pid = fork ()) > 0)
    return pid;			/* parent */

  /*
   * Reset the SIGNALS so that the child can be reaped.
   */
  set_signal_handler (SIGCHLD, SIG_DFL);
  set_signal_handler (SIGTERM, SIG_DFL);
  set_signal_handler (SIGHUP, SIG_DFL);

  child_main (ptr);		/* never returns */
  return -1;
}

/*
 * Create a pool of children to handle incoming connections
 */
short int
child_pool_create (void)
{
  unsigned int i;

  /*
   * Make sure the number of MaxClients is not zero, since this
   * variable determines the size of the array created for children
   * later on.
   */
  if (child_config.maxclients == 0)
    {
      log_message (LOG_ERR,
		   "child_pool_create: \"MaxClients\" must be greater than zero.");
      return -1;
    }
  if (child_config.startservers == 0)
    {
      log_message (LOG_ERR,
		   "child_pool_create: \"StartServers\" must be greater than zero.");
      return -1;
    }

  child_ptr = calloc_shared_memory (child_config.maxclients,
				    sizeof (struct child_s));
  if (!child_ptr)
    {
      log_message (LOG_ERR, "Could not allocate memory for children.");
      return -1;
    }

  servers_waiting = malloc_shared_memory (sizeof (unsigned int));
  if (servers_waiting == MAP_FAILED)
    {
      log_message (LOG_ERR, "Could not allocate memory for child counting.");
      return -1;
    }
  *servers_waiting = 0;

  /*
   * Create a "locking" file for use around the servers_waiting
   * variable.
   */
  _child_lock_init ();

  if (child_config.startservers > child_config.maxclients)
    {
      log_message (LOG_WARNING,
		   "Can not start more than \"MaxClients\" servers. Starting %u servers instead.",
		   child_config.maxclients);
      child_config.startservers = child_config.maxclients;
    }

  for (i = 0; i != child_config.maxclients; i++)
    {
      child_ptr[i].status = T_EMPTY;
      child_ptr[i].connects = 0;
    }

  for (i = 0; i != child_config.startservers; i++)
    {
      DEBUG2 ("Trying to create child %d of %d", i + 1,
	      child_config.startservers);
      child_ptr[i].status = T_WAITING;
      child_ptr[i].tid = child_make (&child_ptr[i]);

      if (child_ptr[i].tid < 0)
	{
	  log_message (LOG_WARNING,
		       "Could not create child number %d of %d",
		       i, child_config.startservers);
	  return -1;
	}
      else
	{
	  log_message (LOG_INFO,
		       "Creating child number %d of %d ...",
		       i + 1, child_config.startservers);

	  SERVER_INC ();
	}
    }

  log_message (LOG_INFO, "Finished creating all children.");

  return 0;
}

/*
 * Keep the proper number of servers running. This is the birth of the
 * servers. It monitors this at least once a second.
 */
void
child_main_loop (void)
{
  unsigned int i;

  while (1)
    {
      if (config.quit)
	return;

      /* If there are not enough spare servers, create more */
      SERVER_COUNT_LOCK ();
      if (*servers_waiting < child_config.minspareservers)
	{
	  log_message (LOG_NOTICE,
		       "Waiting servers (%d) is less than MinSpareServers (%d). Creating new child.",
		       *servers_waiting, child_config.minspareservers);

	  SERVER_COUNT_UNLOCK ();

	  for (i = 0; i != child_config.maxclients; i++)
	    {
	      if (child_ptr[i].status == T_EMPTY)
		{
		  child_ptr[i].status = T_WAITING;
		  child_ptr[i].tid = child_make (&child_ptr[i]);
		  if (child_ptr[i].tid < 0)
		    {
		      log_message (LOG_NOTICE, "Could not create child");

		      child_ptr[i].status = T_EMPTY;
		      break;
		    }

		  SERVER_INC ();

		  break;
		}
	    }
	}
      else
	{
	  SERVER_COUNT_UNLOCK ();
	}

      sleep (5);

      /* Handle log rotation if it was requested */
      if (received_sighup)
	{
	  truncate_log_file ();

#ifdef FILTER_ENABLE
	  if (config.filter)
	    {
	      filter_destroy ();
	      filter_init ();
	    }
	  log_message (LOG_NOTICE, "Re-reading filter file.");
#endif /* FILTER_ENABLE */

	  received_sighup = FALSE;
	}
    }
}

/*
 * Go through all the non-empty children and cancel them.
 */
void
child_kill_children (void)
{
  unsigned int i;

  for (i = 0; i != child_config.maxclients; i++)
    {
      if (child_ptr[i].status != T_EMPTY)
	kill (child_ptr[i].tid, SIGTERM);
    }
}

int
child_listening_sock (uint16_t port)
{
  listenfd = listen_sock (port, &addrlen);
  return listenfd;
}

void
child_close_sock (void)
{
  close (listenfd);
}