Rev Author Line No. Line
3328 povik 1 /**
2 * \addtogroup uip
3 * @{
4 */
5  
6 /**
7 * \defgroup uiparp uIP Address Resolution Protocol
8 * @{
9 *
10 * The Address Resolution Protocol ARP is used for mapping between IP
11 * addresses and link level addresses such as the Ethernet MAC
12 * addresses. ARP uses broadcast queries to ask for the link level
13 * address of a known IP address and the host which is configured with
14 * the IP address for which the query was meant, will respond with its
15 * link level address.
16 *
17 * \note This ARP implementation only supports Ethernet.
18 */
19  
20 /**
21 * \file
22 * Implementation of the ARP Address Resolution Protocol.
23 * \author Adam Dunkels <adam@dunkels.com>
24 *
25 */
26  
27 /*
28 * Copyright (c) 2001-2003, Adam Dunkels.
29 * All rights reserved.
30 *
31 * Redistribution and use in source and binary forms, with or without
32 * modification, are permitted provided that the following conditions
33 * are met:
34 * 1. Redistributions of source code must retain the above copyright
35 * notice, this list of conditions and the following disclaimer.
36 * 2. Redistributions in binary form must reproduce the above copyright
37 * notice, this list of conditions and the following disclaimer in the
38 * documentation and/or other materials provided with the distribution.
39 * 3. The name of the author may not be used to endorse or promote
40 * products derived from this software without specific prior
41 * written permission.
42 *
43 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
44 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
45 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
46 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
47 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
48 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
49 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
50 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
51 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
52 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
53 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
54 *
55 * This file is part of the uIP TCP/IP stack.
56 *
57 * $Id: uip_arp.c,v 1.7.2.3 2003/10/06 22:42:30 adam Exp $
58 *
59 */
60  
61  
62 #include "uip_arp.h"
63  
64 #include <string.h>
65  
66 struct arp_hdr {
67 struct uip_eth_hdr ethhdr;
68 u16_t hwtype;
69 u16_t protocol;
70 u8_t hwlen;
71 u8_t protolen;
72 u16_t opcode;
73 struct uip_eth_addr shwaddr;
74 u16_t sipaddr[2];
75 struct uip_eth_addr dhwaddr;
76 u16_t dipaddr[2];
77 };
78  
79 struct ethip_hdr {
80 struct uip_eth_hdr ethhdr;
81 /* IP header. */
82 u8_t vhl,
83 tos,
84 len[2],
85 ipid[2],
86 ipoffset[2],
87 ttl,
88 proto;
89 u16_t ipchksum;
90 u16_t srcipaddr[2],
91 destipaddr[2];
92 };
93  
94 #define ARP_REQUEST 1
95 #define ARP_REPLY 2
96  
97 #define ARP_HWTYPE_ETH 1
98  
99 struct arp_entry {
100 u16_t ipaddr[2];
101 struct uip_eth_addr ethaddr;
102 u8_t time;
103 };
104  
105 struct uip_eth_addr uip_ethaddr = {{UIP_ETHADDR0,
106 UIP_ETHADDR1,
107 UIP_ETHADDR2,
108 UIP_ETHADDR3,
109 UIP_ETHADDR4,
110 UIP_ETHADDR5}};
111  
112 static struct arp_entry arp_table[UIP_ARPTAB_SIZE];
113 static u16_t ipaddr[2];
114 static u8_t i, c;
115  
116 static u8_t arptime;
117 static u8_t tmpage;
118  
119 #define BUF ((struct arp_hdr *)&uip_buf[0])
120 #define IPBUF ((struct ethip_hdr *)&uip_buf[0])
121 /*-----------------------------------------------------------------------------------*/
122 /**
123 * Initialize the ARP module.
124 *
125 */
126 /*-----------------------------------------------------------------------------------*/
127 void
128 uip_arp_init(void)
129 {
130 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
131 memset(arp_table[i].ipaddr, 0, 4);
132 }
133 }
134 /*-----------------------------------------------------------------------------------*/
135 /**
136 * Periodic ARP processing function.
137 *
138 * This function performs periodic timer processing in the ARP module
139 * and should be called at regular intervals. The recommended interval
140 * is 10 seconds between the calls.
141 *
142 */
143 /*-----------------------------------------------------------------------------------*/
144 void
145 uip_arp_timer(void)
146 {
147 struct arp_entry *tabptr;
148  
149 ++arptime;
150 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
151 tabptr = &arp_table[i];
152 if((tabptr->ipaddr[0] | tabptr->ipaddr[1]) != 0 &&
153 arptime - tabptr->time >= UIP_ARP_MAXAGE) {
154 memset(tabptr->ipaddr, 0, 4);
155 }
156 }
157  
158 }
159 /*-----------------------------------------------------------------------------------*/
160 static void
161 uip_arp_update(u16_t *ipaddr, struct uip_eth_addr *ethaddr)
162 {
163 register struct arp_entry *tabptr;
164 /* Walk through the ARP mapping table and try to find an entry to
165 update. If none is found, the IP -> MAC address mapping is
166 inserted in the ARP table. */
167 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
168  
169 tabptr = &arp_table[i];
170 /* Only check those entries that are actually in use. */
171 if(tabptr->ipaddr[0] != 0 &&
172 tabptr->ipaddr[1] != 0) {
173  
174 /* Check if the source IP address of the incoming packet matches
175 the IP address in this ARP table entry. */
176 if(ipaddr[0] == tabptr->ipaddr[0] &&
177 ipaddr[1] == tabptr->ipaddr[1]) {
178  
179 /* An old entry found, update this and return. */
180 memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6);
181 tabptr->time = arptime;
182  
183 return;
184 }
185 }
186 }
187  
188 /* If we get here, no existing ARP table entry was found, so we
189 create one. */
190  
191 /* First, we try to find an unused entry in the ARP table. */
192 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
193 tabptr = &arp_table[i];
194 if(tabptr->ipaddr[0] == 0 &&
195 tabptr->ipaddr[1] == 0) {
196 break;
197 }
198 }
199  
200 /* If no unused entry is found, we try to find the oldest entry and
201 throw it away. */
202 if(i == UIP_ARPTAB_SIZE) {
203 tmpage = 0;
204 c = 0;
205 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
206 tabptr = &arp_table[i];
207 if(arptime - tabptr->time > tmpage) {
208 tmpage = arptime - tabptr->time;
209 c = i;
210 }
211 }
212 i = c;
213 }
214  
215 /* Now, i is the ARP table entry which we will fill with the new
216 information. */
217 memcpy(tabptr->ipaddr, ipaddr, 4);
218 memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6);
219 tabptr->time = arptime;
220 }
221 /*-----------------------------------------------------------------------------------*/
222 /**
223 * ARP processing for incoming IP packets
224 *
225 * This function should be called by the device driver when an IP
226 * packet has been received. The function will check if the address is
227 * in the ARP cache, and if so the ARP cache entry will be
228 * refreshed. If no ARP cache entry was found, a new one is created.
229 *
230 * This function expects an IP packet with a prepended Ethernet header
231 * in the uip_buf[] buffer, and the length of the packet in the global
232 * variable uip_len.
233 */
234 /*-----------------------------------------------------------------------------------*/
235 void
236 uip_arp_ipin(void)
237 {
238 uip_len -= sizeof(struct uip_eth_hdr);
239  
240 /* Only insert/update an entry if the source IP address of the
241 incoming IP packet comes from a host on the local network. */
242 if((IPBUF->srcipaddr[0] & uip_arp_netmask[0]) !=
243 (uip_hostaddr[0] & uip_arp_netmask[0])) {
244 return;
245 }
246 if((IPBUF->srcipaddr[1] & uip_arp_netmask[1]) !=
247 (uip_hostaddr[1] & uip_arp_netmask[1])) {
248 return;
249 }
250 uip_arp_update(IPBUF->srcipaddr, &(IPBUF->ethhdr.src));
251  
252 return;
253 }
254 /*-----------------------------------------------------------------------------------*/
255 /**
256 * ARP processing for incoming ARP packets.
257 *
258 * This function should be called by the device driver when an ARP
259 * packet has been received. The function will act differently
260 * depending on the ARP packet type: if it is a reply for a request
261 * that we previously sent out, the ARP cache will be filled in with
262 * the values from the ARP reply. If the incoming ARP packet is an ARP
263 * request for our IP address, an ARP reply packet is created and put
264 * into the uip_buf[] buffer.
265 *
266 * When the function returns, the value of the global variable uip_len
267 * indicates whether the device driver should send out a packet or
268 * not. If uip_len is zero, no packet should be sent. If uip_len is
269 * non-zero, it contains the length of the outbound packet that is
270 * present in the uip_buf[] buffer.
271 *
272 * This function expects an ARP packet with a prepended Ethernet
273 * header in the uip_buf[] buffer, and the length of the packet in the
274 * global variable uip_len.
275 */
276 /*-----------------------------------------------------------------------------------*/
277 typedef struct arp_hdr aht;
278  
279 void
280 uip_arp_arpin(void)
281 {
282 int ul;
283  
284 if(uip_len < sizeof(struct arp_hdr)) {
285 uip_len = 0;
286 return;
287 }
288  
289 uip_len = 0;
290  
291 switch(BUF->opcode) {
292 case HTONS(ARP_REQUEST):
293 /* ARP request. If it asked for our address, we send out a
294 reply. */
295 if(BUF->dipaddr[0] == uip_hostaddr[0] &&
296 BUF->dipaddr[1] == uip_hostaddr[1]) {
297 /* The reply opcode is 2. */
298 BUF->opcode = HTONS(2);
299  
300 memcpy(BUF->dhwaddr.addr, BUF->shwaddr.addr, 6);
301 memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6);
302 memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6);
303 memcpy(BUF->ethhdr.dest.addr, BUF->dhwaddr.addr, 6);
304  
305 BUF->dipaddr[0] = BUF->sipaddr[0];
306 BUF->dipaddr[1] = BUF->sipaddr[1];
307 BUF->sipaddr[0] = uip_hostaddr[0];
308 BUF->sipaddr[1] = uip_hostaddr[1];
309  
310 ul = BUF->hwlen;
311 BUF->ethhdr.type = HTONS(UIP_ETHTYPE_ARP);
312 uip_len = sizeof(struct arp_hdr);
313 }
314 break;
315 case HTONS(ARP_REPLY):
316 /* ARP reply. We insert or update the ARP table if it was meant
317 for us. */
318 if(BUF->dipaddr[0] == uip_hostaddr[0] &&
319 BUF->dipaddr[1] == uip_hostaddr[1]) {
320  
321 uip_arp_update(BUF->sipaddr, &BUF->shwaddr);
322 }
323 break;
324 }
325  
326 ( void ) ul;
327  
328 return;
329 }
330 /*-----------------------------------------------------------------------------------*/
331 /**
332 * Prepend Ethernet header to an outbound IP packet and see if we need
333 * to send out an ARP request.
334 *
335 * This function should be called before sending out an IP packet. The
336 * function checks the destination IP address of the IP packet to see
337 * what Ethernet MAC address that should be used as a destination MAC
338 * address on the Ethernet.
339 *
340 * If the destination IP address is in the local network (determined
341 * by logical ANDing of netmask and our IP address), the function
342 * checks the ARP cache to see if an entry for the destination IP
343 * address is found. If so, an Ethernet header is prepended and the
344 * function returns. If no ARP cache entry is found for the
345 * destination IP address, the packet in the uip_buf[] is replaced by
346 * an ARP request packet for the IP address. The IP packet is dropped
347 * and it is assumed that they higher level protocols (e.g., TCP)
348 * eventually will retransmit the dropped packet.
349 *
350 * If the destination IP address is not on the local network, the IP
351 * address of the default router is used instead.
352 *
353 * When the function returns, a packet is present in the uip_buf[]
354 * buffer, and the length of the packet is in the global variable
355 * uip_len.
356 */
357 /*-----------------------------------------------------------------------------------*/
358 void
359 uip_arp_out(void)
360 {
361 struct arp_entry *tabptr;
362 /* Find the destination IP address in the ARP table and construct
363 the Ethernet header. If the destination IP addres isn't on the
364 local network, we use the default router's IP address instead.
365  
366 If not ARP table entry is found, we overwrite the original IP
367 packet with an ARP request for the IP address. */
368  
369 /* Check if the destination address is on the local network. */
370 if((IPBUF->destipaddr[0] & uip_arp_netmask[0]) !=
371 (uip_hostaddr[0] & uip_arp_netmask[0]) ||
372 (IPBUF->destipaddr[1] & uip_arp_netmask[1]) !=
373 (uip_hostaddr[1] & uip_arp_netmask[1])) {
374 /* Destination address was not on the local network, so we need to
375 use the default router's IP address instead of the destination
376 address when determining the MAC address. */
377 ipaddr[0] = uip_arp_draddr[0];
378 ipaddr[1] = uip_arp_draddr[1];
379 } else {
380 /* Else, we use the destination IP address. */
381 ipaddr[0] = IPBUF->destipaddr[0];
382 ipaddr[1] = IPBUF->destipaddr[1];
383 }
384  
385 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
386 tabptr = &arp_table[i];
387 if(ipaddr[0] == tabptr->ipaddr[0] &&
388 ipaddr[1] == tabptr->ipaddr[1])
389 break;
390 }
391  
392 if(i == UIP_ARPTAB_SIZE) {
393 /* The destination address was not in our ARP table, so we
394 overwrite the IP packet with an ARP request. */
395  
396 memset(BUF->ethhdr.dest.addr, 0xff, 6);
397 memset(BUF->dhwaddr.addr, 0x00, 6);
398 memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6);
399 memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6);
400  
401 BUF->dipaddr[0] = ipaddr[0];
402 BUF->dipaddr[1] = ipaddr[1];
403 BUF->sipaddr[0] = uip_hostaddr[0];
404 BUF->sipaddr[1] = uip_hostaddr[1];
405 BUF->opcode = HTONS(ARP_REQUEST); /* ARP request. */
406 BUF->hwtype = HTONS(ARP_HWTYPE_ETH);
407 BUF->protocol = HTONS(UIP_ETHTYPE_IP);
408 BUF->hwlen = 6;
409 BUF->protolen = 4;
410 BUF->ethhdr.type = HTONS(UIP_ETHTYPE_ARP);
411  
412 uip_appdata = &uip_buf[40 + UIP_LLH_LEN];
413  
414 uip_len = sizeof(struct arp_hdr);
415 return;
416 }
417  
418 /* Build an ethernet header. */
419 memcpy(IPBUF->ethhdr.dest.addr, tabptr->ethaddr.addr, 6);
420 memcpy(IPBUF->ethhdr.src.addr, uip_ethaddr.addr, 6);
421  
422 IPBUF->ethhdr.type = HTONS(UIP_ETHTYPE_IP);
423  
424 uip_len += sizeof(struct uip_eth_hdr);
425 }
426 /*-----------------------------------------------------------------------------------*/
427  
428 /** @} */
429 /** @} */