/*
    net.c -- most of the network code
    Copyright (C) 1998-2002 Ivo Timmermans <itimmermans@bigfoot.com>,
                  2000-2002 Guus Sliepen <guus@sliepen.warande.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., 675 Mass Ave, Cambridge, MA 02139, USA.

    $Id: net.c,v 1.35.4.169 2002/04/01 21:28:05 guus Exp $
*/

#include "config.h"

#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <netinet/in.h>
#ifdef HAVE_LINUX
 #include <netinet/ip.h>
 #include <netinet/tcp.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <sys/time.h>
#include <sys/types.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/ioctl.h>
/* SunOS really wants sys/socket.h BEFORE net/if.h,
   and FreeBSD wants these lines below the rest. */
#include <arpa/inet.h>
#include <sys/socket.h>
#include <net/if.h>

#include <openssl/rand.h>

#include <utils.h>
#include <xalloc.h>
#include <avl_tree.h>
#include <list.h>

#include "conf.h"
#include "connection.h"
#include "meta.h"
#include "net.h"
#include "netutl.h"
#include "process.h"
#include "protocol.h"
#include "subnet.h"
#include "graph.h"
#include "process.h"
#include "route.h"
#include "device.h"
#include "event.h"

#include "system.h"

int do_purge = 0;
int sighup = 0;
int sigalrm = 0;

time_t now = 0;

/* Purge edges and subnets of unreachable nodes. Use carefully. */

void purge(void)
{
  avl_node_t *nnode, *nnext, *enode, *enext, *snode, *snext, *cnode;
  node_t *n;
  edge_t *e;
  subnet_t *s;
  connection_t *c;
cp
  if(debug_lvl >= DEBUG_PROTOCOL)
    syslog(LOG_DEBUG, _("Purging unreachable nodes"));

  for(nnode = node_tree->head; nnode; nnode = nnext)
  {
    nnext = nnode->next;
    n = (node_t *)nnode->data;

    if(!n->status.reachable)
    {
      if(debug_lvl >= DEBUG_SCARY_THINGS)
        syslog(LOG_DEBUG, _("Purging node %s (%s)"), n->name, n->hostname);

      for(snode = n->subnet_tree->head; snode; snode = snext)
      {
        snext = snode->next;
        s = (subnet_t *)snode->data;

        for(cnode = connection_tree->head; cnode; cnode = cnode->next)
        {
          c = (connection_t *)cnode->data;
          if(c->status.active)
            send_del_subnet(c, s);
        }

        subnet_del(n, s);
      }

      for(enode = n->edge_tree->head; enode; enode = enext)
      {
        enext = enode->next;
        e = (edge_t *)enode->data;

        for(cnode = connection_tree->head; cnode; cnode = cnode->next)
        {
          c = (connection_t *)cnode->data;
          if(c->status.active)
            send_del_edge(c, e);
        }

        edge_del(e);
      }

      node_del(n);
    }
  }
cp
}

/*
  put all file descriptors in an fd_set array
  While we're at it, purge stuff that needs to be removed.
*/
void build_fdset(fd_set *fs)
{
  avl_node_t *node, *next;
  connection_t *c;
  int i;
cp
  FD_ZERO(fs);

  for(node = connection_tree->head; node; node = next)
    {
      next = node->next;
      c = (connection_t *)node->data;

      if(c->status.remove)
        connection_del(c);
      else
        FD_SET(c->socket, fs);
    }

  if(!connection_tree->head)
    purge();

  for(i = 0; i < listen_sockets; i++)
    {
      FD_SET(listen_socket[i].tcp, fs);
      FD_SET(listen_socket[i].udp, fs);
    }

  FD_SET(device_fd, fs);
cp
}

/*
  Terminate a connection:
  - Close the socket
  - Remove associated edge and tell other connections about it if report = 1
  - Check if we need to retry making an outgoing connection
  - Deactivate the host
*/
void terminate_connection(connection_t *c, int report)
{
  avl_node_t *node;
  connection_t *other;
cp
  if(c->status.remove)
    return;

  if(debug_lvl >= DEBUG_CONNECTIONS)
    syslog(LOG_NOTICE, _("Closing connection with %s (%s)"),
           c->name, c->hostname);

  c->status.remove = 1;
  c->status.active = 0;

  if(c->node)
    c->node->connection = NULL;

  if(c->socket)
    close(c->socket);

  if(c->edge)
    {
      if(report)
        {
          for(node = connection_tree->head; node; node = node->next)
            {
              other = (connection_t *)node->data;
              if(other->status.active && other != c)
                send_del_edge(other, c->edge);
            }
        }

      edge_del(c->edge);

      /* Run MST and SSSP algorithms */

      graph();
    }

  /* Check if this was our outgoing connection */

  if(c->outgoing)
    {
      retry_outgoing(c->outgoing);
      c->outgoing = NULL;
    }
cp
}

/*
  Check if the other end is active.
  If we have sent packets, but didn't receive any,
  then possibly the other end is dead. We send a
  PING request over the meta connection. If the other
  end does not reply in time, we consider them dead
  and close the connection.
*/
void check_dead_connections(void)
{
  avl_node_t *node, *next;
  connection_t *c;
cp
  for(node = connection_tree->head; node; node = next)
    {
      next = node->next;
      c = (connection_t *)node->data;
      if(c->last_ping_time + pingtimeout < now)
        {
          if(c->status.active)
            {
              if(c->status.pinged)
                {
                  if(debug_lvl >= DEBUG_PROTOCOL)
                    syslog(LOG_INFO, _("%s (%s) didn't respond to PING"),
                           c->name, c->hostname);
                  c->status.timeout = 1;
                  terminate_connection(c, 1);
                }
              else
                {
                  send_ping(c);
                }
            }
          else
            {
              if(debug_lvl >= DEBUG_CONNECTIONS)
                syslog(LOG_WARNING, _("Timeout from %s (%s) during authentication"),
                       c->name, c->hostname);
              terminate_connection(c, 0);
            }
        }
    }
cp
}

/*
  check all connections to see if anything
  happened on their sockets
*/
void check_network_activity(fd_set *f)
{
  connection_t *c;
  avl_node_t *node;
  int result, i;
  int len = sizeof(result);
  vpn_packet_t packet;
cp
  if(FD_ISSET(device_fd, f))
    {
      if(!read_packet(&packet))
        route_outgoing(&packet);
    }

  for(node = connection_tree->head; node; node = node->next)
    {
      c = (connection_t *)node->data;

      if(c->status.remove)
        continue;

      if(FD_ISSET(c->socket, f))
        {
          if(c->status.connecting)
            {
              c->status.connecting = 0;
              getsockopt(c->socket, SOL_SOCKET, SO_ERROR, &result, &len);
              if(!result)
                finish_connecting(c);
              else
                {
                  if(debug_lvl >= DEBUG_CONNECTIONS)
                    syslog(LOG_DEBUG, _("Error while connecting to %s (%s): %s"), c->name, c->hostname, strerror(result));
                  close(c->socket);
                  do_outgoing_connection(c);
                  continue;
                }
            }
          if(receive_meta(c) < 0)
            {
              terminate_connection(c, c->status.active);
              continue;
            }
        }
    }

  for(i = 0; i < listen_sockets; i++)
    {
      if(FD_ISSET(listen_socket[i].udp, f))
	handle_incoming_vpn_data(listen_socket[i].udp);
      if(FD_ISSET(listen_socket[i].tcp, f))
	handle_new_meta_connection(listen_socket[i].tcp);
    }
cp
}

/*
  this is where it all happens...
*/
void main_loop(void)
{
  fd_set fset;
  struct timeval tv;
  int r;
  time_t last_ping_check;
  event_t *event;
cp
  last_ping_check = now;

  srand(now);

  for(;;)
    {
      now = time(NULL);

      tv.tv_sec = 1 + (rand() & 7); /* Approx. 5 seconds, randomized to prevent global synchronisation effects */
      tv.tv_usec = 0;

      build_fdset(&fset);

      if((r = select(FD_SETSIZE, &fset, NULL, NULL, &tv)) < 0)
        {
          if(errno != EINTR && errno != EAGAIN)
            {
              syslog(LOG_ERR, _("Error while waiting for input: %s"), strerror(errno));
              cp_trace();
	      dump_connections();
              return;
            }

	  continue;
        }

      check_network_activity(&fset);

      if(do_purge)
        {
          purge();
          do_purge = 0;
        }

      /* Let's check if everybody is still alive */

      if(last_ping_check + pingtimeout < now)
        {
          check_dead_connections();
          last_ping_check = now;

          if(routing_mode== RMODE_SWITCH)
	    age_mac();

          age_past_requests();

          /* Should we regenerate our key? */

          if(keyexpires < now)
            {
              if(debug_lvl >= DEBUG_STATUS)
                syslog(LOG_INFO, _("Regenerating symmetric key"));

              RAND_pseudo_bytes(myself->key, myself->keylength);
              send_key_changed(myself->connection, myself);
              keyexpires = now + keylifetime;
            }
        }


      while((event = get_expired_event()))
        {
          event->handler(event->data);
          free(event);
        }

      if(sigalrm)
        {
          syslog(LOG_INFO, _("Flushing event queue"));

          while(event_tree->head)
            {
              event = (event_t *)event_tree->head->data;
              event->handler(event->data);
              event_del(event);
            }
          sigalrm = 0;
        }

      if(sighup)
        {
          sighup = 0;
          close_network_connections();
          exit_configuration(&config_tree);

          syslog(LOG_INFO, _("Rereading configuration file and restarting in 5 seconds..."));
          sleep(5);

          init_configuration(&config_tree);

          if(read_server_config())
            {
              syslog(LOG_ERR, _("Unable to reread configuration file, exitting."));
              exit(1);
            }

          if(setup_network_connections())
            return;

          continue;
        }
    }
cp
}