C51 COMPILER V7.07   ARP                                                                   11/25/2003 15:47:43 PAGE 1   


C51 COMPILER V7.07, COMPILATION OF MODULE ARP
OBJECT MODULE PLACED IN ARP.OBJ
COMPILER INVOKED BY: D:\KEIL707\C51\BIN\C51.EXE ARP.C OPTIMIZE(9,SPEED) BROWSE DEBUG OBJECTEXTEND

stmt level    source

   1          //-----------------------------------------------------------------------------
   2          // Copyright (c) 2002 Jim Brady
   3          // Do not use commercially without author's permission
   4          // Last revised August 2002
   5          // Net ARP.C
   6          //
   7          // This module handles ARP messages and ARP resolution and manages
   8          // the ARP cache. Refer to RFC 826 and RFC 1122
   9          //-----------------------------------------------------------------------------
  10          #include <string.h>
  11          #include <stdlib.h>
  12          #include <stdio.h>
  13          #include "C8051f.h"
  14          #include "net.h"
  15          #include "eth.h"
  16          #include "serial.h"
  17          #include "ip.h"
  18          #include "arp.h"
  19          
  20          
  21          
  22          extern WAIT xdata wait;
  23          extern UCHAR code my_hwaddr[];
  24          extern UCHAR code broadcast_hwaddr[]; 
  25          extern ULONG code my_ipaddr;
  26          extern ULONG code my_subnet;
  27          extern ULONG code gateway_ipaddr;
  28          extern UCHAR idata debug;
  29          ARP_CACHE xdata arp_cache[CACHESIZE];
  30          UCHAR waiting_for_arp;
  31          
  32          
  33          
  34          void init_arp(void)
  35          {
  36   1              memset(arp_cache, 0, sizeof(arp_cache)); 
  37   1              memset(&wait, 0, sizeof(wait));
  38   1              waiting_for_arp = FALSE;
  39   1      }
  40          
  41          
  42          
  43          
  44          //------------------------------------------------------------------------
  45          //      This is called every 60 seconds to age the ARP cache
  46          // If an entry times out then it is deleted from the cache
  47          // See "TCP/IP Illustrated, Volume 1" Sect 4.3
  48          //------------------------------------------------------------------------
  49          void age_arp_cache(void)
  50          {
  51   1              UCHAR i;
  52   1              
  53   1         for (i=0; i < CACHESIZE; i++)
  54   1         {
  55   2            if ((arp_cache[i].ipaddr != 0) && (arp_cache[i].timer))
C51 COMPILER V7.07   ARP                                                                   11/25/2003 15:47:43 PAGE 2   

  56   2            {
  57   3               arp_cache[i].timer--;
  58   3                              if (arp_cache[i].timer == 0)
  59   3               {
  60   4                                      // Timed out so clear out cache entry
  61   4                                      // Do not need to zero hwaddr
  62   4                                      arp_cache[i].ipaddr = 0;
  63   4                  if (debug) serial_send("ARP: Aged out a cache entry\r");
  64   4                              }
  65   3                      }
  66   2         }
  67   1      }
  68          
  69          
  70          
  71          
  72          //------------------------------------------------------------------------
  73          // This allocates memory for the entire outgoing message,
  74          // including eth and ip headers, then builds an outgoing
  75          // ARP response message
  76          // See "TCP/IP Illustrated, Volume 1" Sect 4.4
  77          //------------------------------------------------------------------------
  78          void arp_send(UCHAR * hwaddr, ULONG ipaddr, UCHAR msg_type)
  79          {
  80   1              UCHAR xdata * outbuf;
  81   1              ARP_HEADER xdata * arp;
  82   1               
  83   1         
  84   1         // Allocate memory for entire outgoing message including
  85   1         // eth header. Always 42 bytes
  86   1         outbuf = (UCHAR xdata *)malloc(42);
  87   1         if (outbuf == NULL)
  88   1         {
  89   2            if (debug) serial_send("ARP: Oops, out of memory\r");
  90   2            return;
  91   2         }      
  92   1           
  93   1         // Allow 14 bytes for the ethernet header
  94   1         arp = (ARP_HEADER xdata *)(outbuf + 14);
  95   1              
  96   1              arp->hardware_type = DIX_ETHERNET; 
  97   1         arp->protocol_type = IP_PACKET;
  98   1         arp->hwaddr_len = 6;
  99   1              arp->ipaddr_len = 4;               
 100   1         arp->message_type = (UINT)msg_type;
 101   1         
 102   1         // My hardware address and IP addresses 
 103   1         memcpy(arp->source_hwaddr, my_hwaddr, 6);
 104   1         arp->source_ipaddr = my_ipaddr;
 105   1      
 106   1         // Destination hwaddr and dest IP addr
 107   1         if (msg_type == ARP_REQUEST) memset(arp->dest_hwaddr, 0, 6);
 108   1         else memcpy(arp->dest_hwaddr, hwaddr, 6);
 109   1         
 110   1         arp->dest_ipaddr = ipaddr;
 111   1            
 112   1         // If request then the message is a brodcast, if a response then
 113   1         // send to specified hwaddr
 114   1         // ARP payload size is always 28 bytes
 115   1              if (msg_type == ARP_REQUEST) eth_send(outbuf, broadcast_hwaddr, ARP_PACKET, 28);
 116   1         else eth_send(outbuf, hwaddr, ARP_PACKET, 28);
 117   1      }
C51 COMPILER V7.07   ARP                                                                   11/25/2003 15:47:43 PAGE 3   

 118          
 119          
 120          
 121          //------------------------------------------------------------------------
 122          // This re-sends an ARP request if there was no response to
 123          // the first one.        It is called every 0.5 seconds.  If there
 124          // is no response after 2 re-tries, the datagram that IP was 
 125          // trying to send is deleted
 126          //-----------------------------------------------------------------------
 127          void arp_retransmit(void)
 128          {
 129   1              static UCHAR idata retries = 0; 
 130   1              
 131   1              if ((waiting_for_arp) && (wait.timer))
 132   1              {
 133   2                      wait.timer--;
 134   2                      if (wait.timer == 0)
 135   2                      {
 136   3                              retries++;
 137   3                              if (retries <= 2)
 138   3                              {
 139   4                                      if (debug) serial_send("ARP: Re-sending ARP broadcast\r");
 140   4                                      arp_send(NULL, wait.ipaddr, ARP_REQUEST);
 141   4                                      wait.timer = ARP_TIMEOUT;
 142   4                              }
 143   3                              else
 144   3                              {       
 145   4                                      if (debug) serial_send("ARP: Gave up waiting for response\r");
 146   4                                      wait.timer = 0;
 147   4                                      waiting_for_arp = 0;
 148   4                                      free(wait.buf);
 149   4                              }
 150   3                      }
 151   2              }
 152   1      }
 153          
 154          
 155          
 156          
 157          //------------------------------------------------------------------------
 158          // Find the ethernet hardware address for the given ip address
 159          // If destination IP is on my subnet then we want the eth