nuttx/net/uip/uip_arp.c

/****************************************************************************
 * net/uip/uip_arp.c
 * Implementation of the ARP Address Resolution Protocol.
 *
 *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
 *
 * Based on uIP which also has a BSD style license:
 *
 *   Author: Adam Dunkels <adam@dunkels.com>
 *   Copyright (c) 2001-2003, Adam Dunkels.
 *   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. 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.
 *
 ****************************************************************************/

/* The Address Resolution Protocol ARP is used for mapping between IP
 * addresses and link level addresses such as the Ethernet MAC
 * addresses. ARP uses broadcast queries to ask for the link level
 * address of a known IP address and the host which is configured with
 * the IP address for which the query was meant, will respond with its
 * link level address.
 *
 * Note: This ARP implementation only supports Ethernet.
 */

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>
#ifdef CONFIG_NET

#include <sys/ioctl.h>
#include <stdint.h>
#include <string.h>
#include <debug.h>

#include <netinet/in.h>
#include <net/ethernet.h>
#include <net/uip/uip-arch.h>
#include <net/uip/uip-arp.h>

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#define ARP_REQUEST 1
#define ARP_REPLY   2

#define ARP_HWTYPE_ETH 1

#define ETHBUF ((struct uip_eth_hdr *)&dev->d_buf[0])
#define ARPBUF ((struct arp_hdr *)&dev->d_buf[UIP_LLH_LEN])
#define IPBUF  ((struct ethip_hdr *)&dev->d_buf[UIP_LLH_LEN])

/****************************************************************************
 * Private Types
 ****************************************************************************/

/* ARP header -- Size 28 bytes */

struct arp_hdr
{
  uint16_t ah_hwtype;        /* 16-bit Hardware type (Ethernet=0x001) */
  uint16_t ah_protocol;      /* 16-bit Protocol type (IP=0x0800) */
  uint8_t  ah_hwlen;         /*  8-bit Hardware address size (6) */
  uint8_t  ah_protolen;      /*  8-bit Procotol address size (4) */
  uint16_t ah_opcode;        /* 16-bit Operation */
  uint8_t  ah_shwaddr[6];    /* 48-bit Sender hardware address */   
  uint16_t ah_sipaddr[2];    /* 32-bit Sender IP adress */
  uint8_t  ah_dhwaddr[6];    /* 48-bit Target hardware address */
  uint16_t ah_dipaddr[2];    /* 32-bit Target IP address */
};

/* IP header -- Size 20 or 24 bytes */

struct ethip_hdr
{
  uint8_t  eh_vhl;           /*  8-bit Version (4) and header length (5 or 6) */
  uint8_t  eh_tos;           /*  8-bit Type of service (e.g., 6=TCP) */
  uint8_t  eh_len[2];        /* 16-bit Total length */
  uint8_t  eh_ipid[2];       /* 16-bit Identification */
  uint8_t  eh_ipoffset[2];   /* 16-bit IP flags + fragment offset */
  uint8_t  eh_ttl;           /*  8-bit Time to Live */
  uint8_t  eh_proto;         /*  8-bit Protocol */
  uint16_t eh_ipchksum;      /* 16-bit Header checksum */
  uint16_t eh_srcipaddr[2];  /* 32-bit Source IP address */
  uint16_t eh_destipaddr[2]; /* 32-bit Destination IP address */
  uint16_t eh_ipoption[2];   /* (optional) */
};

/****************************************************************************
 * Private Data
 ****************************************************************************/

/* Support for broadcast address */

static const struct ether_addr g_broadcast_ethaddr =
  {{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}};
static const uint16_t g_broadcast_ipaddr[2] = {0xffff, 0xffff};

/* Support for IGMP multicast addresses.
 *
 * Well-known ethernet multicast address:
 *
 * ADDRESS           TYPE   USAGE
 * 01-00-0c-cc-cc-cc 0x0802 CDP (Cisco Discovery Protocol), VTP (Virtual Trunking Protocol)
 * 01-00-0c-cc-cc-cd 0x0802 Cisco Shared Spanning Tree Protocol Address
 * 01-80-c2-00-00-00 0x0802 Spanning Tree Protocol (for bridges) IEEE 802.1D
 * 01-80-c2-00-00-02 0x0809 Ethernet OAM Protocol IEEE 802.3ah
 * 01-00-5e-xx-xx-xx 0x0800 IPv4 IGMP Multicast Address
 * 33-33-00-00-00-00 0x86DD IPv6 Neighbor Discovery
 * 33-33-xx-xx-xx-xx 0x86DD IPv6 Multicast Address (RFC3307)
 *
 * The following is the first three octects of the IGMP address:
 */

#if defined(CONFIG_NET_MULTICAST) && !defined(CONFIG_NET_IPv6)
static const uint8_t g_multicast_ethaddr[3] = {0x01, 0x00, 0x5e};
#endif

/****************************************************************************
 * Private Functions
 ****************************************************************************/

#if defined(CONFIG_NET_DUMPARP) && defined(CONFIG_DEBUG)
static void uip_arp_dump(struct arp_hdr *arp)
{
  nlldbg("  HW type: %04x Protocol: %04x\n",
         arp->ah_hwtype, arp->ah_protocol);\
  nlldbg("  HW len: %02x Proto len: %02x Operation: %04x\n",
         arp->ah_hwlen, arp->ah_protolen, arp->ah_opcode);
  nlldbg("  Sender MAC: %02x:%02x:%02x:%02x:%02x:%02x IP: %d.%d.%d.%d\n",
         arp->ah_shwaddr[0], arp->ah_shwaddr[1], arp->ah_shwaddr[2],
         arp->ah_shwaddr[3], arp->ah_shwaddr[4], arp->ah_shwaddr[5],
         arp->ah_sipaddr[0] & 0xff, arp->ah_sipaddr[0] >> 8,
         arp->ah_sipaddr[1] & 0xff, arp->ah_sipaddr[1] >> 8);
  nlldbg("  Dest MAC:   %02x:%02x:%02x:%02x:%02x:%02x IP: %d.%d.%d.%d\n",
         arp->ah_dhwaddr[0], arp->ah_dhwaddr[1], arp->ah_dhwaddr[2],
         arp->ah_dhwaddr[3], arp->ah_dhwaddr[4], arp->ah_dhwaddr[5],
         arp->ah_dipaddr[0] & 0xff, arp->ah_dipaddr[0] >> 8,
         arp->ah_dipaddr[1] & 0xff, arp->ah_dipaddr[1] >> 8);
}
#else
# define uip_arp_dump(arp)
#endif

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/* ARP processing for incoming ARP packets.
 *
 * This function should be called by the device driver when an ARP
 * packet has been received. The function will act differently
 * depending on the ARP packet type: if it is a reply for a request
 * that we previously sent out, the ARP cache will be filled in with
 * the values from the ARP reply. If the incoming ARP packet is an ARP
 * request for our IP address, an ARP reply packet is created and put
 * into the d_buf[] buffer.
 *
 * When the function returns, the value of the field d_len
 * indicates whether the device driver should send out a packet or
 * not. If d_len is zero, no packet should be sent. If d_len is
 * non-zero, it contains the length of the outbound packet that is
 * present in the d_buf[] buffer.
 *
 * This function expects an ARP packet with a prepended Ethernet
 * header in the d_buf[] buffer, and the length of the packet in the
 * global variable d_len.
 */

void uip_arp_arpin(struct uip_driver_s *dev)
{
  struct arp_hdr *parp = ARPBUF;
  in_addr_t ipaddr;

  if (dev->d_len < (sizeof(struct arp_hdr) + UIP_LLH_LEN))
    {
      nlldbg("Too small\n");    
      dev->d_len = 0;
      return;
    }
  dev->d_len = 0;

  ipaddr = uip_ip4addr_conv(parp->ah_dipaddr);
  switch(parp->ah_opcode)
    {
      case HTONS(ARP_REQUEST):
        nllvdbg("ARP request for IP %04lx\n", (long)ipaddr);    

        /* ARP request. If it asked for our address, we send out a reply. */

        if (uip_ipaddr_cmp(ipaddr, dev->d_ipaddr))
          {
            struct uip_eth_hdr *peth = ETHBUF;
 
            /* First, we register the one who made the request in our ARP
             * table, since it is likely that we will do more communication
             * with this host in the future.
             */

            uip_arp_update(parp->ah_sipaddr, parp->ah_shwaddr);

            parp->ah_opcode = HTONS(ARP_REPLY);
            memcpy(parp->ah_dhwaddr, parp->ah_shwaddr, ETHER_ADDR_LEN);
            memcpy(parp->ah_shwaddr, dev->d_mac.ether_addr_octet, ETHER_ADDR_LEN);
            memcpy(peth->src, dev->d_mac.ether_addr_octet, ETHER_ADDR_LEN);
            memcpy(peth->dest, parp->ah_dhwaddr, ETHER_ADDR_LEN);

            parp->ah_dipaddr[0] = parp->ah_sipaddr[0];
            parp->ah_dipaddr[1] = parp->ah_sipaddr[1];
            uiphdr_ipaddr_copy(parp->ah_sipaddr, &dev->d_ipaddr);
            uip_arp_dump(parp);

            peth->type          = HTONS(UIP_ETHTYPE_ARP);
            dev->d_len          = sizeof(struct arp_hdr) + UIP_LLH_LEN;
          }
        break;

      case HTONS(ARP_REPLY):
        nllvdbg("ARP reply for IP %04lx\n", (long)ipaddr);    

        /* ARP reply. We insert or update the ARP table if it was meant
         * for us.
         */

        if (uip_ipaddr_cmp(ipaddr, dev->d_ipaddr))
          {
            uip_arp_update(parp->ah_sipaddr, parp->ah_shwaddr);
          }
        break;
    }
}

/* Prepend Ethernet header to an outbound IP packet and see if we need
 * to send out an ARP request.
 *
 * This function should be called before sending out an IP packet. The
 * function checks the destination IP address of the IP packet to see
 * what Ethernet MAC address that should be used as a destination MAC
 * address on the Ethernet.
 *
 * If the destination IP address is in the local network (determined
 * by logical ANDing of netmask and our IP address), the function
 * checks the ARP cache to see if an entry for the destination IP
 * address is found. If so, an Ethernet header is prepended and the
 * function returns. If no ARP cache entry is found for the
 * destination IP address, the packet in the d_buf[] is replaced by
 * an ARP request packet for the IP address. The IP packet is dropped
 * and it is assumed that they higher level protocols (e.g., TCP)
 * eventually will retransmit the dropped packet.
 *
 * If the destination IP address is not on the local network, the IP
 * address of the default router is used instead.
 *
 * When the function returns, a packet is present in the d_buf[]
 * buffer, and the length of the packet is in the field d_len.
 */

void uip_arp_out(struct uip_driver_s *dev)
{
  const struct arp_entry *tabptr = NULL;
  struct arp_hdr         *parp   = ARPBUF;
  struct uip_eth_hdr     *peth   = ETHBUF;
  struct ethip_hdr       *pip    = IPBUF;
  in_addr_t               ipaddr;
  in_addr_t               destipaddr;

  /* Find the destination IP address in the ARP table and construct
   * the Ethernet header. If the destination IP addres isn't on the
   * local network, we use the default router's IP address instead.
   *
   * If not ARP table entry is found, we overwrite the original IP
   * packet with an ARP request for the IP address.
   */

  /* First check if destination is a local broadcast. */

  if (uiphdr_ipaddr_cmp(pip->eh_destipaddr, g_broadcast_ipaddr))
    {
      memcpy(peth->dest, g_broadcast_ethaddr.ether_addr_octet, ETHER_ADDR_LEN);
    }
#if defined(CONFIG_NET_MULTICAST) && !defined(CONFIG_NET_IPv6)
  /* Check if the destination address is a multicast address
   *
   * - IPv4: multicast addresses lie in the class D group -- The address range
   *   224.0.0.0 to 239.255.255.255 (224.0.0.0/4)
   *
   * - IPv6 multicast addresses are have the high-order octet of the
   *   addresses=0xff (ff00::/8.)
   */

 else if (pip->eh_destipaddr[0] >= HTONS(0xe000) &&
          pip->eh_destipaddr[0] <= HTONS(0xefff))
   {
     /* Build the well-known IPv4 IGMP ethernet address.  The first
      * three bytes are fixed; the final three variable come from the
      * last three bytes of the IP address.
      */

     const uint8_t *ip = ((uint8_t*)pip->eh_destipaddr) + 1;
     memcpy(peth->dest,  g_multicast_ethaddr, 3);
     memcpy(&peth->dest[3], ip, 3);
   }
#endif
  else
    {
      /* Check if the destination address is on the local network. */

      destipaddr = uip_ip4addr_conv(pip->eh_destipaddr);
      if (!uip_ipaddr_maskcmp(destipaddr, dev->d_ipaddr, dev->d_netmask))
        {
          /* Destination address was not on the local network, so we need to
           * use the default router's IP address instead of the destination
           * address when determining the MAC address.
           */

          uip_ipaddr_copy(ipaddr, dev->d_draddr);
        }
      else
        {
          /* Else, we use the destination IP address. */

          uip_ipaddr_copy(ipaddr, destipaddr);
        }

      /* Check if we already have this destination address in the ARP table */

      tabptr = uip_arp_find(ipaddr);
      if (!tabptr)
        {
           nllvdbg("ARP request for IP %04lx\n", (long)ipaddr);    

          /* The destination address was not in our ARP table, so we
           * overwrite the IP packet with an ARP request.
           */

          memset(peth->dest, 0xff, ETHER_ADDR_LEN);
          memset(parp->ah_dhwaddr, 0x00, ETHER_ADDR_LEN);
          memcpy(peth->src, dev->d_mac.ether_addr_octet, ETHER_ADDR_LEN);
          memcpy(parp->ah_shwaddr, dev->d_mac.ether_addr_octet, ETHER_ADDR_LEN);

          uiphdr_ipaddr_copy(parp->ah_dipaddr, &ipaddr);
          uiphdr_ipaddr_copy(parp->ah_sipaddr, &dev->d_ipaddr);

          parp->ah_opcode   = HTONS(ARP_REQUEST);
          parp->ah_hwtype   = HTONS(ARP_HWTYPE_ETH);
          parp->ah_protocol = HTONS(UIP_ETHTYPE_IP);
          parp->ah_hwlen    = ETHER_ADDR_LEN;
          parp->ah_protolen = 4;
          uip_arp_dump(parp);

          peth->type        = HTONS(UIP_ETHTYPE_ARP);
          dev->d_len        = sizeof(struct arp_hdr) + UIP_LLH_LEN;
          return;
        }

      /* Build an ethernet header. */

      memcpy(peth->dest, tabptr->at_ethaddr.ether_addr_octet, ETHER_ADDR_LEN);
    }

  /* Finish populating the ethernet header */

  memcpy(peth->src, dev->d_mac.ether_addr_octet, ETHER_ADDR_LEN);
  peth->type  = HTONS(UIP_ETHTYPE_IP);
  dev->d_len += UIP_LLH_LEN;
}
#endif /* CONFIG_NET */