📄 arp.lst
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159 // Return pointer to the hardware address or NULL if not found
160 // See "TCP/IP Illustrated, Volume 1" Sect 4.5
161 //------------------------------------------------------------------------
162 UCHAR xdata * arp_resolve(ULONG dest_ipaddr)
163 {
164 1 UCHAR i;
165 1
166 1 // If destination IP is not on my subnet then we really want eth addr
167 1 // of gateway, not destination IP
168 1 if ((dest_ipaddr ^ my_ipaddr) & my_subnet)
169 1 {
170 2 if (gateway_ipaddr == 0)
171 2 {
172 3 if (debug) printf("ARP: Error, gateway addr not set\n");
173 3 return (NULL);
174 3 }
175 2 else dest_ipaddr = gateway_ipaddr;
176 2 }
177 1
178 1
179 1 // See if IP addr of interest is in ARP cache
C51 COMPILER V7.06 ARP 05/21/2004 23:09:31 PAGE 4
180 1 for (i=0; i < CACHESIZE; i++)
181 1 {
182 2 if (arp_cache[i].ipaddr == dest_ipaddr)
183 2 return (&arp_cache[i].hwaddr[0]);
184 2 }
185 1
186 1 if (debug) printf("ARP: IP addr not found in cache\n");
187 1 if (debug) printf("ARP: Sending an ARP broadcast\n");
188 1 // Not in cache so broadcast ARP request
189 1 arp_send(NULL, dest_ipaddr, ARP_REQUEST);
190 1
191 1 // Set a flag to indicate that an IP datagram is waiting
192 1 // to be sent
193 1 waiting_for_arp = TRUE;
194 1
195 1 // Null means that we have sent an ARP request
196 1 return (NULL);
197 1 }
198
199
200
201
202
203 //------------------------------------------------------------------------
204 // This handles incoming ARP messages
205 // See "TCP/IP Illustrated, Volume 1" Sect 4.4
206 // Todo: Resolve problem of trying to add to a full cache
207 //------------------------------------------------------------------------
208 void arp_rcve(UCHAR xdata * inbuf)
209 {
210 1 UCHAR idata i, cached, oldest;
211 1 UINT idata minimum;
212 1 ARP_HEADER xdata * arp;
213 1
214 1 arp = (ARP_HEADER xdata *)(inbuf + 14);
215 1 cached = FALSE;
216 1
217 1 // Print message
218 1 if (debug)
219 1 {
220 2 if (arp->message_type == ARP_REQUEST)
221 2 printf("ARP: Request rcvd\n");
222 2 else printf("ARP: Response rcvd\n");
223 2 }
224 1
225 1 // Validate incoming frame
226 1 if ((arp->hardware_type != DIX_ETHERNET) ||
227 1 (arp->protocol_type != IP_PACKET)) return;
228 1
229 1 // Search ARP cache for senders IP address
230 1 // If found, update entry and restart timer
231 1 for (i=0; i < CACHESIZE; i++)
232 1 {
233 2 if (arp_cache[i].ipaddr == arp->source_ipaddr)
234 2 {
235 3 memcpy(&arp_cache[i].hwaddr[0], &arp->source_hwaddr[0], 6);
236 3 arp_cache[i].timer = CACHETIME;
237 3 cached = TRUE;
238 3 if (debug) printf("ARP: Cache entry updated\n");
239 3
240 3 break;
241 3 }
C51 COMPILER V7.06 ARP 05/21/2004 23:09:31 PAGE 5
242 2 }
243 1
244 1 if (arp->dest_ipaddr != my_ipaddr) return;
245 1
246 1 // At this point we know the the frame is addressed to me
247 1 // If not already in cache then add entry and start timer
248 1 if (cached == FALSE)
249 1 {
250 2 // Find first blank space and add entry
251 2 // Blank entries are indicated by ip addr = 0
252 2 for (i=0; i < CACHESIZE; i++)
253 2 {
254 3 if (arp_cache[i].ipaddr == 0)
255 3 {
256 4 arp_cache[i].ipaddr = arp->source_ipaddr;
257 4 memcpy(&arp_cache[i].hwaddr[0], &arp->source_hwaddr[0], 6);
258 4 arp_cache[i].timer = CACHETIME;
259 4 if (debug) printf("ARP: New cache entry added\n");
260 4 break;
261 4 }
262 3 }
263 2
264 2 // If no blank entries in arp cache then sort cache
265 2 // to find oldest entry and replace it
266 2 if (i == CACHESIZE)
267 2 {
268 3 // Oldest entry is the one with lowest timer value
269 3 minimum = 0xFFFF;
270 3 for (i=0; i < CACHESIZE; i++)
271 3 {
272 4 if (arp_cache[i].timer < minimum)
273 4 {
274 5 minimum = arp_cache[i].timer;
275 5 oldest = i;
276 5 }
277 4 }
278 3
279 3 // "oldest" is now index of oldest entry, so replace it
280 3 arp_cache[oldest].ipaddr = arp->source_ipaddr;
281 3 memcpy(&arp_cache[oldest].hwaddr[0], &arp->source_hwaddr[0], 6);
282 3 arp_cache[oldest].timer = CACHETIME;
283 3 if (debug) printf("ARP: Cache full, so replaced oldest\n");
284 3 }
285 2 }
286 1
287 1
288 1 // If we are waiting for an arp response and the arp response
289 1 // that just came in is addressed to me and is from the host
290 1 // we are waiting for, then send the message-in-waiting
291 1 if (arp->message_type == ARP_RESPONSE)
292 1 {
293 2 if ((waiting_for_arp) && (wait.ipaddr == arp->source_ipaddr))
294 2 {
295 3 waiting_for_arp = FALSE;
296 3 ip_send(wait.buf, wait.ipaddr, wait.proto_id, wait.len);
297 3 }
298 2 }
299 1 else if (arp->message_type == ARP_REQUEST)
300 1 {
301 2 // Send ARP response
302 2 if (debug) printf("ARP: Sending response\n");
303 2 arp_send(arp->source_hwaddr, arp->source_ipaddr, ARP_RESPONSE);
C51 COMPILER V7.06 ARP 05/21/2004 23:09:31 PAGE 6
304 2 }
305 1 }
306
307
MODULE INFORMATION: STATIC OVERLAYABLE
CODE SIZE = 1822 ----
CONSTANT SIZE = 372 ----
XDATA SIZE = 111 20
PDATA SIZE = ---- ----
DATA SIZE = ---- ----
IDATA SIZE = 1 5
BIT SIZE = ---- ----
END OF MODULE INFORMATION.
C51 COMPILATION COMPLETE. 0 WARNING(S), 0 ERROR(S)
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