arp.lst

Keil_C51程序,C8051实现的TCP/IP功能源码

 154          // See "TCP/IP Illustrated, Volume 1" Sect 4.5
 155          // arp解析
 156          //------------------------------------------------------------------------
 157          UCHAR xdata * arp_resolve(ULONG dest_ipaddr)
 158          {
 159   1         UCHAR i;
 160   1            
 161   1         // If destination IP is not on my subnet then we really want eth addr
 162   1              // of gateway, not destination IP
 163   1              if ((dest_ipaddr ^ my_ipaddr) & my_subnet)
 164   1              {
 165   2                      if (gateway_ipaddr == 0)
 166   2                      {
 167   3                              if (debug) SendCommString("ARP: Error, gateway addr not set\r");
 168   3                              return (NULL);  
 169   3                      }
 170   2                      else dest_ipaddr = gateway_ipaddr;
 171   2              }
 172   1              
 173   1                 
 174   1         // See if IP addr of interest is in ARP cache
 175   1         for (i=0; i < CACHESIZE; i++)
 176   1         {
 177   2            if (arp_cache[i].ipaddr == dest_ipaddr)
 178   2               return (&arp_cache[i].hwaddr[0]);
 179   2         }
C51 COMPILER V7.20   ARP                                                                   03/07/2006 14:49:08 PAGE 4   

 180   1      
 181   1              if (debug) SendCommString("ARP: IP addr not found in cache\r");
 182   1              if (debug) SendCommString("ARP: Sending an ARP broadcast\r");
 183   1              // Not in cache so broadcast ARP request
 184   1              arp_send(NULL, dest_ipaddr, ARP_REQUEST);
 185   1                 
 186   1         // Set a flag to indicate that an IP datagram is waiting
 187   1         // to be sent
 188   1         waiting_for_arp = TRUE;
 189   1                                            
 190   1         // Null means that we have sent an ARP request
 191   1         return (NULL); 
 192   1      }
 193          
 194          
 195          //------------------------------------------------------------------------
 196          // This handles incoming ARP messages
 197          // See "TCP/IP Illustrated, Volume 1" Sect 4.4
 198          // Todo:  Resolve problem of trying to add to a full cache
 199          //------------------------------------------------------------------------
 200          void arp_rcve(UCHAR xdata * inbuf)
 201          {
 202   1              UCHAR idata i, cached, oldest;
 203   1              UINT idata minimum;
 204   1              ARP_HEADER xdata * arp;
 205   1                    
 206   1              arp = (ARP_HEADER xdata *)(inbuf + 14);
 207   1              cached = FALSE;
 208   1         
 209   1              // Print message
 210   1              if (debug)
 211   1              {
 212   2              if (arp->message_type == ARP_REQUEST)SendCommString("ARP: Request rcvd\r");
 213   2                  else SendCommString("ARP: Response rcvd\r");
 214   2              }
 215   1               
 216   1         // Validate incoming frame
 217   1              if ((arp->hardware_type != DIX_ETHERNET) ||
 218   1             (arp->protocol_type != IP_PACKET)) return;
 219   1      
 220   1         // Search ARP cache for senders IP address
 221   1         // If found, update entry and restart timer
 222   1         for (i=0; i < CACHESIZE; i++)
 223   1         {
 224   2            if (arp_cache[i].ipaddr == arp->source_ipaddr)
 225   2            {
 226   3               memcpy(&arp_cache[i].hwaddr[0], &arp->source_hwaddr[0], 6);
 227   3               arp_cache[i].timer = CACHETIME;                
 228   3               cached = TRUE;
 229   3               if (debug) SendCommString("ARP: Cache entry updated\r");                 
 230   3               break;  
 231   3            }
 232   2         }
 233   1         
 234   1         if (arp->dest_ipaddr != my_ipaddr) return;
 235   1         
 236   1         // At this point we know the the frame is addressed to me
 237   1         // If not already in cache then add entry and start timer
 238   1         if (cached == FALSE)
 239   1         {
 240   2            // Find first blank space and add entry
 241   2                      // Blank entries are indicated by ip addr = 0
C51 COMPILER V7.20   ARP                                                                   03/07/2006 14:49:08 PAGE 5   

 242   2            for (i=0; i < CACHESIZE; i++)
 243   2            {
 244   3               if (arp_cache[i].ipaddr == 0) 
 245   3               {
 246   4                  arp_cache[i].ipaddr = arp->source_ipaddr;
 247   4                  memcpy(&arp_cache[i].hwaddr[0], &arp->source_hwaddr[0], 6);   
 248   4                  arp_cache[i].timer = CACHETIME;
 249   4                      if (debug) SendCommString("ARP: New cache entry added\r");
 250   4                      break;
 251   4               }
 252   3            }
 253   2      
 254   2                      // If no blank entries in arp cache     then sort cache
 255   2                      // to find oldest entry and replace it
 256   2                      if (i == CACHESIZE)
 257   2                      {
 258   3                              // Oldest entry is the one with lowest timer value                      
 259   3                              minimum = 0xFFFF;
 260   3                              for (i=0; i < CACHESIZE; i++)
 261   3                      {
 262   4                                      if (arp_cache[i].timer < minimum) 
 263   4                                      {
 264   5                                              minimum = arp_cache[i].timer;
 265   5                                              oldest = i;
 266   5                                      }
 267   4                              }
 268   3              
 269   3                              // "oldest" is now index of oldest entry, so replace it
 270   3                              arp_cache[oldest].ipaddr = arp->source_ipaddr;
 271   3                      memcpy(&arp_cache[oldest].hwaddr[0], &arp->source_hwaddr[0], 6);   
 272   3                      arp_cache[oldest].timer = CACHETIME;
 273   3                      if (debug) SendCommString("ARP: Cache full, so replaced oldest\r");
 274   3                      }
 275   2              }
 276   1      
 277   1         
 278   1         // If we are waiting for an arp response and the arp response
 279   1              // that just came in is addressed to me and is from the host
 280   1              // we are waiting for, then send        the message-in-waiting
 281   1              if (arp->message_type == ARP_RESPONSE)
 282   1              {
 283   2                      if ((waiting_for_arp) && (wait.ipaddr == arp->source_ipaddr))
 284   2                      {
 285   3                              waiting_for_arp = FALSE;
 286   3                              ip_send(wait.buf, wait.ipaddr, wait.proto_id, wait.len);
 287   3                      }
 288   2              }
 289   1              else if (arp->message_type == ARP_REQUEST)
 290   1              {
 291   2              // Send ARP response 
 292   2              if (debug) SendCommString("ARP: Sending response\r");
 293   2              arp_send(arp->source_hwaddr, arp->source_ipaddr, ARP_RESPONSE);
 294   2              }
 295   1      }
 296          
 297          


MODULE INFORMATION:   STATIC OVERLAYABLE
   CODE SIZE        =   1303    ----
   CONSTANT SIZE    =    372    ----
   XDATA SIZE       =    110    ----
C51 COMPILER V7.20   ARP                                                                   03/07/2006 14:49:08 PAGE 6   

   PDATA SIZE       =   ----    ----
   DATA SIZE        =      1      20
   IDATA SIZE       =      1       5
   BIT SIZE         =   ----    ----
END OF MODULE INFORMATION.


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