arp.lst

用c8051f340基于51单片机上网

 153   2              }
 154   1      }
 155          
 156          
 157          
 158          
 159          //------------------------------------------------------------------------
 160          // Find the ethernet hardware address for the given ip address
 161          // If destination IP is on my subnet then we want the eth
 162          // address      of destination, otherwise we want eth addr of gateway. 
 163          // Look in ARP cache first.  If not found there, send ARP request.
 164          // Return pointer to the hardware address or NULL if not found
 165          // See "TCP/IP Illustrated, Volume 1" Sect 4.5
 166          //------------------------------------------------------------------------
 167          UCHAR xdata * arp_resolve(ULONG dest_ipaddr)
 168          {
 169   1         UCHAR i;
 170   1            
 171   1         // If destination IP is not on my subnet then we really want eth addr
 172   1              // of gateway, not destination IP
 173   1              if ((dest_ipaddr ^ my_ipaddr) & my_subnet)
 174   1              {
 175   2                      if (gateway_ipaddr == 0)
 176   2                      {
C51 COMPILER V8.08   ARP                                                                   11/04/2008 18:45:33 PAGE 4   

 177   3                              return (NULL);  
 178   3                      }
 179   2                      else dest_ipaddr = gateway_ipaddr;
 180   2              }
 181   1              
 182   1                 
 183   1         // See if IP addr of interest is in ARP cache
 184   1         for (i=0; i < CACHESIZE; i++)
 185   1         {
 186   2            if (arp_cache[i].ipaddr == dest_ipaddr)
 187   2               return (&arp_cache[i].hwaddr[0]);
 188   2         }
 189   1      
 190   1              // Not in cache so broadcast ARP request
 191   1              arp_send(NULL, dest_ipaddr, ARP_REQUEST);
 192   1                 
 193   1         // Set a flag to indicate that an IP datagram is waiting
 194   1         // to be sent
 195   1         waiting_for_arp = TRUE;
 196   1                                            
 197   1         // Null means that we have sent an ARP request
 198   1         return (NULL); 
 199   1      }
 200          
 201          
 202          
 203          
 204          
 205          //------------------------------------------------------------------------
 206          // This handles incoming ARP messages
 207          // See "TCP/IP Illustrated, Volume 1" Sect 4.4
 208          // Todo:  Resolve problem of trying to add to a full cache
 209          //------------------------------------------------------------------------
 210          void arp_rcve(UCHAR xdata * inbuf)
 211          {
 212   1         UCHAR idata i, cached, oldest;
 213   1         UINT idata minimum;
 214   1         ARP_HEADER xdata * arp;
 215   1            
 216   1         arp = (ARP_HEADER xdata *)(inbuf + 14);
 217   1         cached = FALSE;
 218   1         
 219   1         // Print message
 220   1               
 221   1         // Validate incoming frame
 222   1         if ((arp->hardware_type != DIX_ETHERNET) ||
 223   1             (arp->protocol_type != IP_PACKET)) return;
 224   1      
 225   1         // Search ARP cache for senders IP address
 226   1         // If found, update entry and restart timer
 227   1         for (i=0; i < CACHESIZE; i++)
 228   1         {
 229   2            if (arp_cache[i].ipaddr == arp->source_ipaddr)
 230   2            {
 231   3               memcpy(&arp_cache[i].hwaddr[0], &arp->source_hwaddr[0], 6);
 232   3               arp_cache[i].timer = CACHETIME;                
 233   3               cached = TRUE;
 234   3                        
 235   3               break;  
 236   3            }
 237   2         }
 238   1         
C51 COMPILER V8.08   ARP                                                                   11/04/2008 18:45:33 PAGE 5   

 239   1         if (arp->dest_ipaddr != my_ipaddr) return;
 240   1         
 241   1         // At this point we know the the frame is addressed to me
 242   1         // If not already in cache then add entry and start timer
 243   1         if (cached == FALSE)
 244   1         {
 245   2            // Find first blank space and add entry
 246   2                      // Blank entries are indicated by ip addr = 0
 247   2            for (i=0; i < CACHESIZE; i++)
 248   2            {
 249   3               if (arp_cache[i].ipaddr == 0) 
 250   3               {
 251   4                  arp_cache[i].ipaddr = arp->source_ipaddr;
 252   4                  memcpy(&arp_cache[i].hwaddr[0], &arp->source_hwaddr[0], 6);   
 253   4                  arp_cache[i].timer = CACHETIME;
 254   4                      break;
 255   4               }
 256   3            }
 257   2      
 258   2                      // If no blank entries in arp cache     then sort cache
 259   2                      // to find oldest entry and replace it
 260   2                      if (i == CACHESIZE)
 261   2                      {
 262   3                              // Oldest entry is the one with lowest timer value                      
 263   3                              minimum = 0xFFFF;
 264   3                              for (i=0; i < CACHESIZE; i++)
 265   3              {
 266   4                                      if (arp_cache[i].timer < minimum) 
 267   4                                      {
 268   5                                              minimum = arp_cache[i].timer;
 269   5                                              oldest = i;
 270   5                                      }
 271   4                              }
 272   3              
 273   3                              // "oldest" is now index of oldest entry, so replace it
 274   3                              arp_cache[oldest].ipaddr = arp->source_ipaddr;
 275   3               memcpy(&arp_cache[oldest].hwaddr[0], &arp->source_hwaddr[0], 6);   
 276   3               arp_cache[oldest].timer = CACHETIME;
 277   3              }
 278   2              }
 279   1      
 280   1         
 281   1         // If we are waiting for an arp response and the arp response
 282   1              // that just came in is addressed to me and is from the host
 283   1              // we are waiting for, then send        the message-in-waiting
 284   1         if (arp->message_type == ARP_RESPONSE)
 285   1         {
 286   2              if ((waiting_for_arp) && (wait.ipaddr == arp->source_ipaddr))
 287   2              {
 288   3                      waiting_for_arp = FALSE;
 289   3                              ip_send(wait.buf, wait.ipaddr, wait.proto_id, wait.len);
 290   3                      }
 291   2              }
 292   1              else if (arp->message_type == ARP_REQUEST)
 293   1         {
 294   2              // Send ARP response 
 295   2              arp_send(arp->source_hwaddr, arp->source_ipaddr, ARP_RESPONSE);
 296   2              }
 297   1      }
 298          
 299          

C51 COMPILER V8.08   ARP                                                                   11/04/2008 18:45:33 PAGE 6   


MODULE INFORMATION:   STATIC OVERLAYABLE
   CODE SIZE        =   1449    ----
   CONSTANT SIZE    =   ----    ----
   XDATA SIZE       =    110    ----
   PDATA SIZE       =   ----    ----
   DATA SIZE        =      1      20
   IDATA SIZE       =      1       5
   BIT SIZE         =   ----    ----
END OF MODULE INFORMATION.


C51 COMPILATION COMPLETE.  2 WARNING(S),  0 ERROR(S)