arp.lst

Keil_C51程序,C8051实现的TCP/IP功能源码

C51 COMPILER V7.20   ARP                                                                   03/07/2006 14:49:08 PAGE 1   


C51 COMPILER V7.20, COMPILATION OF MODULE ARP
OBJECT MODULE PLACED IN ARP.OBJ
COMPILER INVOKED BY: C:\Keil\C51\BIN\C51.EXE ARP.C OPTIMIZE(9,SPEED) BROWSE DEBUG OBJECTEXTEND

line level    source

   1          //-----------------------------------------------------------------------------
   2          // Net ARP.C
   3          //
   4          // This module handles ARP messages and ARP resolution and manages
   5          // the ARP cache. Refer to RFC 826 and RFC 1122
   6          //-----------------------------------------------------------------------------
   7          #include <string.h>
   8          #include <stdlib.h>
   9          #include <stdio.h>
  10          #include "reg52.h"
  11          #include "net.h"
  12          #include "eth.h"
  13          #include "serial.h"
  14          #include "ip.h"
  15          #include "arp.h"
  16          
  17          
  18          extern WAIT xdata wait;
  19          extern UCHAR code my_hwaddr[];
  20          extern UCHAR code broadcast_hwaddr[]; 
  21          extern ULONG code my_ipaddr;
  22          extern ULONG code my_subnet;
  23          extern ULONG code gateway_ipaddr;
  24          extern UCHAR idata debug;
  25          ARP_CACHE xdata arp_cache[CACHESIZE];
  26          UCHAR waiting_for_arp;
  27          
  28          //初始化arp内存
  29          void init_arp(void)
  30          {
  31   1              memset(arp_cache, 0, sizeof(arp_cache)); 
  32   1              memset(&wait, 0, sizeof(wait));
  33   1              waiting_for_arp = FALSE;
  34   1      }
  35          
  36          //------------------------------------------------------------------------
  37          //      This is called every 60 seconds to age the ARP cache
  38          // If an entry times out then it is deleted from the cache
  39          // See "TCP/IP Illustrated, Volume 1" Sect 4.3
  40          //每60秒访问一次，如果生存时间超时就将他从ARP缓存中清掉
  41          //------------------------------------------------------------------------
  42          void    age_arp_cache(void)
  43          {
  44   1              UCHAR i;
  45   1              
  46   1              for (i=0; i < CACHESIZE; i++)
  47   1              {
  48   2              if ((arp_cache[i].ipaddr != 0) && (arp_cache[i].timer))
  49   2              {
  50   3                      //不为空且时间不为零时
  51   3                      arp_cache[i].timer--;
  52   3                              if (arp_cache[i].timer == 0)
  53   3                      {
  54   4                                      // Timed out so clear out cache entry
  55   4                                      // Do not need to zero hwaddr
C51 COMPILER V7.20   ARP                                                                   03/07/2006 14:49:08 PAGE 2   

  56   4                                      //超时，就清空记录
  57   4                                      arp_cache[i].ipaddr = 0;
  58   4                      if (debug) SendCommString("ARP: Aged out a cache entry\r");
  59   4                              }
  60   3                      }
  61   2              }
  62   1      }
  63          
  64          //------------------------------------------------------------------------
  65          // This allocates memory for the entire outgoing message,
  66          // including eth and ip headers, then builds an outgoing
  67          // ARP response message
  68          // See "TCP/IP Illustrated, Volume 1" Sect 4.4
  69          // ARP发送，包括MAC和IP地址。
  70          //------------------------------------------------------------------------
  71          void    arp_send(UCHAR * hwaddr, ULONG ipaddr, UCHAR msg_type)
  72          {
  73   1              UCHAR xdata * outbuf;
  74   1              ARP_HEADER xdata * arp;
  75   1               
  76   1         // Allocate memory for entire outgoing message including
  77   1         // eth header. Always 42 bytes
  78   1         outbuf = (UCHAR xdata *)malloc(42);
  79   1         if (outbuf == NULL)
  80   1         {
  81   2            if (debug) SendCommString("ARP: Oops, out of memory\r");
  82   2            return;
  83   2         }      
  84   1           
  85   1         // Allow 14 bytes for the ethernet header
  86   1              arp = (ARP_HEADER xdata *)(outbuf + 14);
  87   1              
  88   1              arp->hardware_type = DIX_ETHERNET; 
  89   1              arp->protocol_type = IP_PACKET;
  90   1              arp->hwaddr_len = 6;
  91   1              arp->ipaddr_len = 4;               
  92   1              arp->message_type = (UINT)msg_type;
  93   1         
  94   1              // My hardware address and IP addresses 
  95   1              memcpy(arp->source_hwaddr, my_hwaddr, 6);
  96   1              arp->source_ipaddr = my_ipaddr;
  97   1      
  98   1              // Destination hwaddr and dest IP addr
  99   1              if (msg_type == ARP_REQUEST) memset(arp->dest_hwaddr, 0, 6);
 100   1              else memcpy(arp->dest_hwaddr, hwaddr, 6);
 101   1         
 102   1              arp->dest_ipaddr = ipaddr;
 103   1            
 104   1              // If request then the message is a brodcast, if a response then
 105   1              // send to specified hwaddr
 106   1              // ARP payload size is always 28 bytes
 107   1              //负载28字符，判断是广播还是回复
 108   1              if (msg_type == ARP_REQUEST) eth_send(outbuf, broadcast_hwaddr, ARP_PACKET, 28);
 109   1              else eth_send(outbuf, hwaddr, ARP_PACKET, 28);
 110   1      }
 111          
 112          //------------------------------------------------------------------------
 113          // This re-sends an ARP request if there was no response to
 114          // the first one.        It is called every 0.5 seconds.  If there
 115          // is no response after 2 re-tries, the datagram that IP was 
 116          // trying to send is deleted
 117          // 如果第一次发没有回信号，ARP就重发。每0.5秒运行一次。
C51 COMPILER V7.20   ARP                                                                   03/07/2006 14:49:08 PAGE 3   

 118          // 重试2次后，如果还是没有数据，就删除需要发的数据。
 119          //-----------------------------------------------------------------------
 120          void    arp_retransmit(void)
 121          {
 122   1              static UCHAR idata retries = 0; 
 123   1              
 124   1              if ((waiting_for_arp) && (wait.timer))
 125   1              {
 126   2                      wait.timer--;
 127   2                      if (wait.timer == 0)
 128   2                      {
 129   3                              retries++;
 130   3                              if (retries <= 2)
 131   3                              {
 132   4                                      if (debug) SendCommString("ARP: Re-sending ARP broadcast\r");
 133   4                                      arp_send(NULL, wait.ipaddr, ARP_REQUEST);
 134   4                                      wait.timer = ARP_TIMEOUT;
 135   4                              }
 136   3                              else
 137   3                              {       
 138   4                                      if (debug) SendCommString("ARP: Gave up waiting for response\r");
 139   4                                      wait.timer = 0;
 140   4                                      waiting_for_arp = 0;
 141   4                                      free(wait.buf);
 142   4                              }
 143   3                      }
 144   2              }
 145   1      }
 146          
 147          
 148          //------------------------------------------------------------------------
 149          // Find the ethernet hardware address for the given ip address
 150          // If destination IP is on my subnet then we want the eth
 151          // address      of destination, otherwise we want eth addr of gateway. 
 152          // Look in ARP cache first.  If not found there, send ARP request.
 153          // Return pointer to the hardware address or NULL if not found