/* serverpacket.c
 *
 * Construct and send DHCP server packets
 *
 * Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * 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 <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <time.h>

#include "common.h"
#include "serverpacket.h"
#include "dhcpd.h"
#include "options.h"
#include "static_leases.h"

/* send a packet to giaddr using the kernel ip stack */
static int send_packet_to_relay(struct dhcpMessage *payload)
{
  DEBUG(LOG_INFO, "Forwarding packet to relay");

  return kernel_packet(payload, server_config.server, SERVER_PORT,
      payload->giaddr, SERVER_PORT);
}


/* send a packet to a specific arp address and ip address by creating our own ip packet */
static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
{
  uint8_t *chaddr;
  uint32_t ciaddr;

  if (force_broadcast) {
    DEBUG(LOG_INFO, "broadcasting packet to client (NAK)");
    ciaddr = INADDR_BROADCAST;
    chaddr = MAC_BCAST_ADDR;
  } else if (payload->ciaddr) {
    DEBUG(LOG_INFO, "unicasting packet to client ciaddr");
    ciaddr = payload->ciaddr;
    chaddr = payload->chaddr;
  } else if (ntohs(payload->flags) & BROADCAST_FLAG) {
    DEBUG(LOG_INFO, "broadcasting packet to client (requested)");
    ciaddr = INADDR_BROADCAST;
    chaddr = MAC_BCAST_ADDR;
  } else {
    DEBUG(LOG_INFO, "unicasting packet to client yiaddr");
    ciaddr = payload->yiaddr;
    chaddr = payload->chaddr;
  }
  return raw_packet(payload, server_config.server, SERVER_PORT,
      ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
}


/* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
static int send_packet(struct dhcpMessage *payload, int force_broadcast)
{
  int ret;

  if (payload->giaddr)
    ret = send_packet_to_relay(payload);
  else ret = send_packet_to_client(payload, force_broadcast);
  return ret;
}


static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
{
  init_header(packet, type);
  packet->xid = oldpacket->xid;
  memcpy(packet->chaddr, oldpacket->chaddr, 16);
  packet->flags = oldpacket->flags;
  packet->giaddr = oldpacket->giaddr;
  packet->ciaddr = oldpacket->ciaddr;
  add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
}


/* add in the bootp options */
static void add_bootp_options(struct dhcpMessage *packet)
{
  packet->siaddr = server_config.siaddr;
  if (server_config.sname)
    strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
  if (server_config.boot_file)
    strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
}


/* send a DHCP OFFER to a DHCP DISCOVER */
int sendOffer(struct dhcpMessage *oldpacket)
{
  struct dhcpMessage packet;
  struct dhcpOfferedAddr *lease = NULL;
  uint32_t req_align, lease_time_align = server_config.lease;
  uint8_t *req, *lease_time, *opt_hname;
  struct option_set *curr;
  struct in_addr addr;
  uint8_t opt_len=0;

  uint32_t static_lease_ip;

  opt_hname = get_option(oldpacket, DHCP_HOST_NAME);
  if(opt_hname )
    opt_len = get_option_len(oldpacket, DHCP_HOST_NAME);
  

  init_packet(&packet, oldpacket, DHCPOFFER);
  // Leo Lin 2010/8/12 modify start
  // no need to get static lease here again
        //uci_read_static_leases();  // Bryan add
  // Leo Lin 2010/8/12 modify end

  static_lease_ip = getIpByMac(server_config.static_leases, oldpacket->chaddr);

  /* ADDME: if static, short circuit */
  if(!static_lease_ip)
  {
  /* the client is in our lease/offered table */
  if ((lease = find_lease_by_chaddr(oldpacket->chaddr))) {
    if (!lease_expired(lease))
      lease_time_align = lease->expires - time(0);
    packet.yiaddr = lease->yiaddr;

  /* Or the client has a requested ip */
  } else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&

       /* Don't look here (ugly hackish thing to do) */
       memcpy(&req_align, req, 4) &&

       /* and the ip is in the lease range */
       ntohl(req_align) >= ntohl(server_config.start) &&
       ntohl(req_align) <= ntohl(server_config.end) &&

      !static_lease_ip &&  /* Check that its not a static lease */
      /* and is not already taken/offered */
       ((!(lease = find_lease_by_yiaddr(req_align)) ||

       /* or its taken, but expired */ /* ADDME: or maybe in here */
       lease_expired(lease)))
      // Leo Lin 2010/8/11 modify start
      // add check if request ip is serserved
      && (!reservedIp( server_config.static_leases, req_align) )
      // Leo Lin 2010/8/11 modify end
       ) {
        DEBUG(LOG_INFO, "[%s] accept client requested ip %x", __FUNCTION__, req_align);
        packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */
      /* otherwise, find a free IP */
  } else {
      /* Is it a static lease? (No, because find_address skips static lease) */
    packet.yiaddr = find_address(0);
    /* try for an expired lease */
    if (!packet.yiaddr) packet.yiaddr = find_address(1);
    DEBUG(LOG_INFO, "[%s] find an address ip %x", __FUNCTION__, packet.yiaddr);
  }

  if(!packet.yiaddr) {
    LOG(LOG_WARNING, "no IP addresses to give -- OFFER abandoned");
    return -1;
  }
   
  if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time, opt_hname, opt_len)) {
    LOG(LOG_WARNING, "lease pool is full -- OFFER abandoned");
    return -1;
  }
  

  if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
    memcpy(&lease_time_align, lease_time, 4);
    lease_time_align = ntohl(lease_time_align);
    if (lease_time_align > server_config.lease)
      lease_time_align = server_config.lease;
  }

  /* Make sure we aren't just using the lease time from the previous offer */
  if (lease_time_align < server_config.min_lease)
    lease_time_align = server_config.lease;
  }
  /* ADDME: end of short circuit */
  else
  {
    /* It is a static lease... use it */
    packet.yiaddr = static_lease_ip;
  }

  add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));

  curr = server_config.options;
  while (curr) {
    if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
      add_option_string(packet.options, curr->data);
    curr = curr->next;
  }

  add_bootp_options(&packet);

  addr.s_addr = packet.yiaddr;
  LOG(LOG_INFO, "sending OFFER of %s", inet_ntoa(addr));
  return send_packet(&packet, 0);
}


int sendNAK(struct dhcpMessage *oldpacket)
{
  struct dhcpMessage packet;

  init_packet(&packet, oldpacket, DHCPNAK);

  DEBUG(LOG_INFO, "sending NAK");
  return send_packet(&packet, 1);
}


int sendACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
{
  struct dhcpMessage packet;
  struct option_set *curr;
  uint8_t *lease_time, *opt_hname;
  uint32_t lease_time_align = server_config.lease;
  struct in_addr addr;
    uint8_t opt_len=0;

  opt_hname = get_option(oldpacket, DHCP_HOST_NAME);
  if(opt_hname != NULL)
    opt_len = get_option_len(oldpacket, DHCP_HOST_NAME);
  

  init_packet(&packet, oldpacket, DHCPACK);
  packet.yiaddr = yiaddr;

  if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
    memcpy(&lease_time_align, lease_time, 4);
    lease_time_align = ntohl(lease_time_align);
    if (lease_time_align > server_config.lease)
      lease_time_align = server_config.lease;
    else if (lease_time_align < server_config.min_lease)
      lease_time_align = server_config.lease;
  }

  add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));

  curr = server_config.options;
  while (curr) {
    if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
      add_option_string(packet.options, curr->data);
    curr = curr->next;
  }

  add_bootp_options(&packet);

  addr.s_addr = packet.yiaddr;
  LOG(LOG_INFO, "sending ACK to %s", inet_ntoa(addr));

  if (send_packet(&packet, 0) < 0)
    return -1;

  add_lease(packet.chaddr, packet.yiaddr, lease_time_align, opt_hname, opt_len);

  write_hosts();
  
  return 0;
}


int send_inform(struct dhcpMessage *oldpacket)
{
  struct dhcpMessage packet;
  struct option_set *curr;

  init_packet(&packet, oldpacket, DHCPACK);

  curr = server_config.options;
  while (curr) {
    if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
      add_option_string(packet.options, curr->data);
    curr = curr->next;
  }

  add_bootp_options(&packet);

  return send_packet(&packet, 0);
}
