/* uip-fw.c
 * uIP packet forwarding.
 * Author: Adam Dunkels <adam@sics.se>
 *
 * This file implements a number of simple functions which do packet
 * forwarding over multiple network interfaces with uIP.
 *
 * Copyright (c) 2004, Swedish Institute of Computer Science.
 * 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.
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE 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 INSTITUTE 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 <nuttx/config.h>
#include <debug.h>
#include <net/uip/uip.h>
#include <net/uip/uip-arch.h>

#include "uip-fw.h"

#include <string.h> /* for memcpy() */

/* The list of registered network interfaces. */

static struct uip_fw_netif *netifs = NULL;

/* A pointer to the default network interface. */

static struct uip_fw_netif *defaultnetif = NULL;

struct tcpip_hdr
{
  /* IP header */

  uint8  vhl;
  uint8  tos;
  uint16 len;
  uint16 ipid;
  uint16 ipoffset;
  uint8  ttl;
  uint8  proto;
  uint16 ipchksum;
  in_addr_t srcipaddr;
  in_addr_t destipaddr;

  /* TCP header */

  uint16 srcport;
  uint16 destport;
  uint8  seqno[4];
  uint8  ackno[4];
  uint8  tcpoffset;
  uint8  flags;
  uint8  wnd[2];
  uint16 tcpchksum;
  uint8  urgp[2];
  uint8 optdata[4];
};

struct icmpip_hdr
{
  /* IP header */

  uint8  vhl;
  uint8  tos;
  uint8  len[2];
  uint8  ipid[2];
  uint8  ipoffset[2];
  uint8  ttl;
  uint8  proto;
  uint16 ipchksum;
  in_addr_t srcipaddr;
  in_addr_t destipaddr;

  /* ICMP (echo) header */

  uint8 type, icode;
  uint16 icmpchksum;
  uint16 id, seqno;
  uint8 payload[1];
};

/* ICMP ECHO. */

#define ICMP_ECHO 8

/* ICMP TIME-EXCEEDED. */

#define ICMP_TE 11

/* Pointer to the TCP/IP headers of the packet in the d_buf buffer. */

#define BUF ((struct tcpip_hdr *)&dev->d_buf[UIP_LLH_LEN])

/* Pointer to the ICMP/IP headers of the packet in the d_buf buffer. */

#define ICMPBUF ((struct icmpip_hdr *)&dev->d_buf[UIP_LLH_LEN])

/* Certain fields of an IP packet that are used for identifying
 * duplicate packets.
 */

struct fwcache_entry
{
  uint16 timer;
  in_addr_t srcipaddr;
  in_addr_t destipaddr;
  uint16 ipid;
  uint8 proto;
  uint8 unused;

#if notdef
  uint16 payload[2];
#endif

#if UIP_REASSEMBLY > 0
  uint16 len, offset;
#endif
};

/* The number of packets to remember when looking for duplicates. */
#ifdef CONFIG_NET_FWCACHE_SIZE
# define FWCACHE_SIZE CONFIG_NET_FWCACHE_SIZE
#else
# define FWCACHE_SIZE 2
#endif

/* A cache of packet header fields which are used for
 * identifying duplicate packets.
 */

static struct fwcache_entry fwcache[FWCACHE_SIZE];

/* The time that a packet cache is active. */
#define FW_TIME 20

/* Initialize the uIP packet forwarding module. */

void uip_fw_init(void)
{
  struct uip_fw_netif *t;
  defaultnetif = NULL;
  while(netifs != NULL)
    {
      t       = netifs;
      netifs  = netifs->next;
      t->next = NULL;
    }
}

/* Send out an ICMP TIME-EXCEEDED message.
 *
 * This function replaces the packet in the d_buf buffer with the
 * ICMP packet.
 */

static void time_exceeded(struct uip_driver_s *dev)
{
  in_addr_t tmp_addr;

  /* We don't send out ICMP errors for ICMP messages. */

  if (ICMPBUF->proto == UIP_PROTO_ICMP)
    {
      dev->d_len = 0;
      return;
    }

  /* Copy fields from packet header into payload of this ICMP packet. */

  memcpy(&(ICMPBUF->payload[0]), ICMPBUF, 28);

  /* Set the ICMP type and code. */

  ICMPBUF->type  = ICMP_TE;
  ICMPBUF->icode = 0;

  /* Calculate the ICMP checksum. */

  ICMPBUF->icmpchksum = 0;
  ICMPBUF->icmpchksum = ~uip_chksum((uint16 *)&(ICMPBUF->type), 36);

  /* Set the IP destination address to be the source address of the
   * original packet.
   */

  tmp_addr        = BUF->destipaddr;
  BUF->destipaddr = BUF->srcipaddr;
  BUF->srcipaddr  = tmp_addr;

  /* Set our IP address as the source address. */

  BUF->srcipaddr = dev->d_ipaddr;

  /* The size of the ICMP time exceeded packet is 36 + the size of the
   * IP header (20) = 56.
   */

  dev->d_len      = 56;
  ICMPBUF->len[0] = 0;
  ICMPBUF->len[1] = dev->d_len;

  /* Fill in the other fields in the IP header. */

  ICMPBUF->vhl         = 0x45;
  ICMPBUF->tos         = 0;
  ICMPBUF->ipoffset[0] = ICMPBUF->ipoffset[1] = 0;
  ICMPBUF->ttl         = UIP_TTL;
  ICMPBUF->proto       = UIP_PROTO_ICMP;

  /* Calculate IP checksum. */

  ICMPBUF->ipchksum    = 0;
  ICMPBUF->ipchksum    = ~(uip_ipchksum(dev));
}

/* Register a packet in the forwarding cache so that it won't be
 * forwarded again.
 */

static void fwcache_register(struct uip_driver_s *dev)
{
  struct fwcache_entry *fw;
  int i, oldest;

  oldest = FW_TIME;
  fw     = NULL;

  /* Find the oldest entry in the cache. */

  for (i = 0; i < FWCACHE_SIZE; ++i)
    {
      if (fwcache[i].timer == 0)
        {
          fw = &fwcache[i];
          break;
        }
      else if (fwcache[i].timer <= oldest)
        {
          fw     = &fwcache[i];
          oldest = fwcache[i].timer;
        }
    }

  fw->timer      = FW_TIME;
  fw->ipid       = BUF->ipid;
  fw->srcipaddr  = BUF->srcipaddr;
  fw->destipaddr = BUF->destipaddr;
  fw->proto      = BUF->proto;
#if notdef
  fw->payload[0] = BUF->srcport;
  fw->payload[1] = BUF->destport;
#endif
#if UIP_REASSEMBLY > 0
  fw->len        = BUF->len;
  fw->offset     = BUF->ipoffset;
#endif
}

/* Find a network interface for the IP packet in d_buf. */

static struct uip_fw_netif *find_netif (struct uip_driver_s *dev)
{
  struct uip_fw_netif *netif;

  /* Walk through every network interface to check for a match. */

  for (netif = netifs; netif != NULL; netif = netif->next)
    {
      if (uip_ipaddr_maskcmp(BUF->destipaddr, netif->ipaddr, netif->netmask))
        {
          /* If there was a match, we break the loop. */

          return netif;
        }
    }

  /* If no matching netif was found, we use default netif. */

  return defaultnetif;
}

/* Output an IP packet on the correct network interface.
 *
 * The IP packet should be present in the d_buf buffer and its
 * length in the d_len field.
 *
 * Return: UIP_FW_ZEROLEN Indicates that a zero-length packet
 * transmission was attempted and that no packet was sent.
 *
 * Return: UIP_FW_NOROUTE No suitable network interface could be found
 * for the outbound packet, and the packet was not sent.
 *
 * Return: The return value from the actual network interface output
 * function is passed unmodified as a return value.
 */

uint8 uip_fw_output(struct uip_driver_s *dev)
{
  struct uip_fw_netif *netif;

  if (dev->d_len == 0)
    {
      return UIP_FW_ZEROLEN;
    }

  fwcache_register(dev);

#ifdef CONFIG_NET_BROADCAST
  /* Link local broadcasts go out on all interfaces. */

  if (/*BUF->proto == UIP_PROTO_UDP &&*/
      BUF->destipaddr[0] == 0xffff &&
      BUF->destipaddr[1] == 0xffff)
    {
      if (defaultnetif != NULL)
        {
          defaultnetif->output();
        }
      for (netif = netifs; netif != NULL; netif = netif->next)
        {
          netif->output();
        }
      return UIP_FW_OK;
    }
#endif

  netif = find_netif (dev);
  dbg("netif: %p output: %p len: %d\n", netif, netif->output, dev->d_len);

  if (netif == NULL)
    {
      return UIP_FW_NOROUTE;
    }

  /* If we now have found a suitable network interface, we call its
   * output function to send out the packet.
   */

  return netif->output();
}

/* Forward an IP packet in the d_buf buffer.
 *
 * Return: UIP_FW_FORWARDED if the packet was forwarded, UIP_FW_LOCAL if
 * the packet should be processed locally.
 */

uint8 uip_fw_forward(struct uip_driver_s *dev)
{
  struct fwcache_entry *fw;

  /* First check if the packet is destined for ourselves and return 0
   * to indicate that the packet should be processed locally.
   */

  if (BUF->destipaddr == dev->d_ipaddr)
    {
      return UIP_FW_LOCAL;
    }

  /* If we use ping IP address configuration, and our IP address is
   * not yet configured, we should intercept all ICMP echo packets.
   */

#ifdef CONFIG_NET_PINGADDRCONF
  if (dev->d_ipaddr == 0 && BUF->proto == UIP_PROTO_ICMP && ICMPBUF->type == ICMP_ECHO)
    {
      return UIP_FW_LOCAL;
    }
#endif

  /* Check if the packet is in the forwarding cache already, and if so
     we drop it. */

  for (fw = fwcache; fw < &fwcache[FWCACHE_SIZE]; ++fw)
    {
      if (fw->timer      != 0 &&
#if UIP_REASSEMBLY > 0
          fw->len        == BUF->len &&
          fw->offset     == BUF->ipoffset &&
#endif
          fw->ipid       == BUF->ipid &&
          fw->srcipaddr  == BUF->srcipaddr &&
          fw->destipaddr == BUF->destipaddr &&
#if notdef
          fw->payload[0] == BUF->srcport &&
          fw->payload[1] == BUF->destport &&
#endif
          fw->proto      == BUF->proto)
        {
          /* Drop packet. */
          return UIP_FW_FORWARDED;
        }
    }

  /* If the TTL reaches zero we produce an ICMP time exceeded message
   * in the d_buf buffer and forward that packet back to the sender
   * of the packet.
   */

  if (BUF->ttl <= 1)
    {
      /* No time exceeded for broadcasts and multicasts! */

      if (BUF->destipaddr == 0xffffffff)
        {
          return UIP_FW_LOCAL;
        }
      time_exceeded(dev);
    }

  /* Decrement the TTL (time-to-live) value in the IP header */

  BUF->ttl = BUF->ttl - 1;

  /* Update the IP checksum. */

  if (BUF->ipchksum >= HTONS(0xffff - 0x0100))
    {
      BUF->ipchksum = BUF->ipchksum + HTONS(0x0100) + 1;
    }
  else
    {
      BUF->ipchksum = BUF->ipchksum + HTONS(0x0100);
    }

  if (dev->d_len > 0)
    {
      dev->d_appdata = &dev->d_buf[UIP_LLH_LEN + UIP_TCPIP_HLEN];
      uip_fw_output(dev);
    }

#ifdef CONFIG_NET_BROADCAST
  if (BUF->destipaddr[0] == 0xffff && BUF->destipaddr[1] == 0xffff)
    {
      return UIP_FW_LOCAL;
    }
#endif

  /* Return non-zero to indicate that the packet was forwarded and that no
   * other processing should be made.
   */

  return UIP_FW_FORWARDED;
}

/* Register a network interface with the forwarding module.
 *
 * netif A pointer to the network interface that is to be
 * registered.
 */

void uip_fw_register(struct uip_fw_netif *netif)
{
  netif->next = netifs;
  netifs      = netif;
}

/* Register a default network interface.
 *
 * All packets that don't go out on any of the other interfaces will
 * be routed to the default interface.
 *
 * netif A pointer to the network interface that is to be
 * registered.
 */

void uip_fw_default(struct uip_fw_netif *netif)
{
  defaultnetif = netif;
}

/* Perform periodic processing. */

void uip_fw_periodic(void)
{
  struct fwcache_entry *fw;
  for (fw = fwcache; fw < &fwcache[FWCACHE_SIZE]; ++fw)
    {
      if (fw->timer > 0)
        {
          --fw->timer;
        }
    }
}