//-----------------------------------------------------------------------------
// Copyright (c) 2002 Jim Brady
// Do not use commercially without author's permission
// Last revised August 2002
// Net ARP.C
//
// This module handles ARP messages and ARP resolution and manages
// the ARP cache. Refer to RFC 826 and RFC 1122
//-----------------------------------------------------------------------------
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include "C8051f.h"
#include "net.h"
#include "eth.h"
#include "serial.h"
#include "ip.h"
#include "arp.h"
extern WAIT xdata wait;
extern UCHAR code my_hwaddr[];
extern UCHAR code broadcast_hwaddr[];
extern ULONG code my_ipaddr;
extern ULONG code my_subnet;
extern ULONG code gateway_ipaddr;
extern UCHAR idata debug;
ARP_CACHE xdata arp_cache[CACHESIZE];
UCHAR waiting_for_arp;
void init_arp(void)
{
memset(arp_cache, 0, sizeof(arp_cache));
memset(&wait, 0, sizeof(wait));
waiting_for_arp = FALSE;
}
//------------------------------------------------------------------------
// This is called every 60 seconds to age the ARP cache
// If an entry times out then it is deleted from the cache
// See "TCP/IP Illustrated, Volume 1" Sect 4.3
//------------------------------------------------------------------------
void age_arp_cache(void)
{
UCHAR i;
for (i=0; i < CACHESIZE; i++)
{
if ((arp_cache[i].ipaddr != 0) && (arp_cache[i].timer))
{
arp_cache[i].timer--;
if (arp_cache[i].timer == 0)
{
// Timed out so clear out cache entry
// Do not need to zero hwaddr
arp_cache[i].ipaddr = 0;
if (debug) serial_send("ARP: Aged out a cache entry\r");
}
}
}
}
//------------------------------------------------------------------------
// This allocates memory for the entire outgoing message,
// including eth and ip headers, then builds an outgoing
// ARP response message
// See "TCP/IP Illustrated, Volume 1" Sect 4.4
//------------------------------------------------------------------------
void arp_send(UCHAR * hwaddr, ULONG ipaddr, UCHAR msg_type)
{
UCHAR xdata * outbuf;
ARP_HEADER xdata * arp;
// Allocate memory for entire outgoing message including
// eth header. Always 42 bytes
outbuf = (UCHAR xdata *)malloc(42);
if (outbuf == NULL)
{
if (debug) serial_send("ARP: Oops, out of memory\r");
return;
}
// Allow 14 bytes for the ethernet header
arp = (ARP_HEADER xdata *)(outbuf + 14);
arp->hardware_type = DIX_ETHERNET;
arp->protocol_type = IP_PACKET;
arp->hwaddr_len = 6;
arp->ipaddr_len = 4;
arp->message_type = (UINT)msg_type;
// My hardware address and IP addresses
memcpy(arp->source_hwaddr, my_hwaddr, 6);
arp->source_ipaddr = my_ipaddr;
// Destination hwaddr and dest IP addr
if (msg_type == ARP_REQUEST) memset(arp->dest_hwaddr, 0, 6);
else memcpy(arp->dest_hwaddr, hwaddr, 6);
arp->dest_ipaddr = ipaddr;
// If request then the message is a brodcast, if a response then
// send to specified hwaddr
// ARP payload size is always 28 bytes
if (msg_type == ARP_REQUEST) eth_send(outbuf, broadcast_hwaddr, ARP_PACKET, 28);
else eth_send(outbuf, hwaddr, ARP_PACKET, 28);
}
//------------------------------------------------------------------------
// This re-sends an ARP request if there was no response to
// the first one. It is called every 0.5 seconds. If there
// is no response after 2 re-tries, the datagram that IP was
// trying to send is deleted
//-----------------------------------------------------------------------
void arp_retransmit(void)
{
static UCHAR idata retries = 0;
if ((waiting_for_arp) && (wait.timer))
{
wait.timer--;
if (wait.timer == 0)
{
retries++;
if (retries <= 2)
{
if (debug) serial_send("ARP: Re-sending ARP broadcast\r");
arp_send(NULL, wait.ipaddr, ARP_REQUEST);
wait.timer = ARP_TIMEOUT;
}
else
{
if (debug) serial_send("ARP: Gave up waiting for response\r");
wait.timer = 0;
waiting_for_arp = 0;
free(wait.buf);
}
}
}
}
//------------------------------------------------------------------------
// Find the ethernet hardware address for the given ip address
// If destination IP is on my subnet then we want the eth
// address of destination, otherwise we want eth addr of gateway.
// Look in ARP cache first. If not found there, send ARP request.
// Return pointer to the hardware address or NULL if not found
// See "TCP/IP Illustrated, Volume 1" Sect 4.5
//------------------------------------------------------------------------
UCHAR xdata * arp_resolve(ULONG dest_ipaddr)
{
UCHAR i;
// If destination IP is not on my subnet then we really want eth addr
// of gateway, not destination IP
if ((dest_ipaddr ^ my_ipaddr) & my_subnet)
{
if (gateway_ipaddr == 0)
{
if (debug) serial_send("ARP: Error, gateway addr not set\r");
return (NULL);
}
else dest_ipaddr = gateway_ipaddr;
}
// See if IP addr of interest is in ARP cache
for (i=0; i < CACHESIZE; i++)
{
if (arp_cache[i].ipaddr == dest_ipaddr)
return (&arp_cache[i].hwaddr[0]);
}
if (debug) serial_send("ARP: IP addr not found in cache\r");
if (debug) serial_send("ARP: Sending an ARP broadcast\r");
// Not in cache so broadcast ARP request
arp_send(NULL, dest_ipaddr, ARP_REQUEST);
// Set a flag to indicate that an IP datagram is waiting
// to be sent
waiting_for_arp = TRUE;
// Null means that we have sent an ARP request
return (NULL);
}
//------------------------------------------------------------------------
// This handles incoming ARP messages
// See "TCP/IP Illustrated, Volume 1" Sect 4.4
// Todo: Resolve problem of trying to add to a full cache
//------------------------------------------------------------------------
void arp_rcve(UCHAR xdata * inbuf)
{
UCHAR idata i, cached, oldest;
UINT idata minimum;
ARP_HEADER xdata * arp;
arp = (ARP_HEADER xdata *)(inbuf + 14);
cached = FALSE;
// Print message
if (debug)
{
if (arp->message_type == ARP_REQUEST)
serial_send("ARP: Request rcvd\r");
else serial_send("ARP: Response rcvd\r");
}
// Validate incoming frame
if ((arp->hardware_type != DIX_ETHERNET) ||
(arp->protocol_type != IP_PACKET)) return;
// Search ARP cache for senders IP address
// If found, update entry and restart timer
for (i=0; i < CACHESIZE; i++)
{
if (arp_cache[i].ipaddr == arp->source_ipaddr)
{
memcpy(&arp_cache[i].hwaddr[0], &arp->source_hwaddr[0], 6);
arp_cache[i].timer = CACHETIME;
cached = TRUE;
if (debug) serial_send("ARP: Cache entry updated\r");
break;
}
}
if (arp->dest_ipaddr != my_ipaddr) return;
// At this point we know the the frame is addressed to me
// If not already in cache then add entry and start timer
if (cached == FALSE)
{
// Find first blank space and add entry
// Blank entries are indicated by ip addr = 0
for (i=0; i < CACHESIZE; i++)
{
if (arp_cache[i].ipaddr == 0)
{
arp_cache[i].ipaddr = arp->source_ipaddr;
memcpy(&arp_cache[i].hwaddr[0], &arp->source_hwaddr[0], 6);
arp_cache[i].timer = CACHETIME;
if (debug) serial_send("ARP: New cache entry added\r");
break;
}
}
// If no blank entries in arp cache then sort cache
// to find oldest entry and replace it
if (i == CACHESIZE)
{
// Oldest entry is the one with lowest tim
