7 * \defgroup uiparp uIP Address Resolution Protocol
\r
10 * The Address Resolution Protocol ARP is used for mapping between IP
\r
11 * addresses and link level addresses such as the Ethernet MAC
\r
12 * addresses. ARP uses broadcast queries to ask for the link level
\r
13 * address of a known IP address and the host which is configured with
\r
14 * the IP address for which the query was meant, will respond with its
\r
15 * link level address.
\r
17 * \note This ARP implementation only supports Ethernet.
\r
22 * Implementation of the ARP Address Resolution Protocol.
\r
23 * \author Adam Dunkels <adam@dunkels.com>
\r
28 * Copyright (c) 2001-2003, Adam Dunkels.
\r
29 * All rights reserved.
\r
31 * Redistribution and use in source and binary forms, with or without
\r
32 * modification, are permitted provided that the following conditions
\r
34 * 1. Redistributions of source code must retain the above copyright
\r
35 * notice, this list of conditions and the following disclaimer.
\r
36 * 2. Redistributions in binary form must reproduce the above copyright
\r
37 * notice, this list of conditions and the following disclaimer in the
\r
38 * documentation and/or other materials provided with the distribution.
\r
39 * 3. The name of the author may not be used to endorse or promote
\r
40 * products derived from this software without specific prior
\r
41 * written permission.
\r
43 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
\r
44 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
\r
45 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
\r
46 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
\r
47 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
\r
48 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
\r
49 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
\r
50 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
\r
51 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
\r
52 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
\r
53 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
\r
55 * This file is part of the uIP TCP/IP stack.
\r
57 * $Id: uip_arp.c,v 1.8 2006/06/02 23:36:21 adam Exp $
\r
60 #include "uip_arp.h"
\r
69 struct uip_eth_hdr ethhdr;
\r
75 struct uip_eth_addr shwaddr;
\r
77 struct uip_eth_addr dhwaddr;
\r
89 struct uip_eth_hdr ethhdr;
\r
92 u8_t vhl, tos, len[2], ipid[2], ipoffset[2], ttl, proto;
\r
94 u16_t srcipaddr[2], destipaddr[2];
\r
100 #define ARP_REQUEST 1
\r
101 #define ARP_REPLY 2
\r
103 #define ARP_HWTYPE_ETH 1
\r
108 struct uip_eth_addr ethaddr;
\r
112 static const struct uip_eth_addr broadcast_ethaddr = { { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff } };
\r
113 static const u16_t broadcast_ipaddr[2] = { 0xffff, 0xffff };
\r
115 static struct arp_entry arp_table[UIP_ARPTAB_SIZE];
\r
116 static u16_t ipaddr[2];
\r
119 static u8_t arptime;
\r
120 static u8_t tmpage;
\r
122 #define BUF ( ( struct arp_hdr * ) &uip_buf[0] )
\r
123 #define IPBUF ( ( struct ethip_hdr * ) &uip_buf[0] )
\r
125 /*-----------------------------------------------------------------------------------*/
\r
128 * Initialize the ARP module.
\r
132 /*-----------------------------------------------------------------------------------*/
\r
133 void uip_arp_init( void )
\r
135 for( i = 0; i < UIP_ARPTAB_SIZE; ++i )
\r
137 memset( arp_table[i].ipaddr, 0, 4 );
\r
141 /*-----------------------------------------------------------------------------------*/
\r
144 * Periodic ARP processing function.
\r
146 * This function performs periodic timer processing in the ARP module
\r
147 * and should be called at regular intervals. The recommended interval
\r
148 * is 10 seconds between the calls.
\r
152 /*-----------------------------------------------------------------------------------*/
\r
153 void uip_arp_timer( void )
\r
155 struct arp_entry *tabptr;
\r
158 for( i = 0; i < UIP_ARPTAB_SIZE; ++i )
\r
160 tabptr = &arp_table[i];
\r
161 if( (tabptr->ipaddr[0] | tabptr->ipaddr[1]) != 0 && arptime - tabptr->time >= UIP_ARP_MAXAGE )
\r
163 memset( tabptr->ipaddr, 0, 4 );
\r
168 /*-----------------------------------------------------------------------------------*/
\r
169 static void uip_arp_update( u16_t *ipaddr, struct uip_eth_addr *ethaddr )
\r
171 register struct arp_entry *tabptr;
\r
173 /* Walk through the ARP mapping table and try to find an entry to
\r
174 update. If none is found, the IP -> MAC address mapping is
\r
175 inserted in the ARP table. */
\r
176 for( i = 0; i < UIP_ARPTAB_SIZE; ++i )
\r
178 tabptr = &arp_table[i];
\r
180 /* Only check those entries that are actually in use. */
\r
181 if( tabptr->ipaddr[0] != 0 && tabptr->ipaddr[1] != 0 )
\r
183 /* Check if the source IP address of the incoming packet matches
\r
184 the IP address in this ARP table entry. */
\r
185 if( ipaddr[0] == tabptr->ipaddr[0] && ipaddr[1] == tabptr->ipaddr[1] )
\r
187 /* An old entry found, update this and return. */
\r
188 memcpy( tabptr->ethaddr.addr, ethaddr->addr, 6 );
\r
189 tabptr->time = arptime;
\r
196 /* If we get here, no existing ARP table entry was found, so we
\r
199 /* First, we try to find an unused entry in the ARP table. */
\r
200 for( i = 0; i < UIP_ARPTAB_SIZE; ++i )
\r
202 tabptr = &arp_table[i];
\r
203 if( tabptr->ipaddr[0] == 0 && tabptr->ipaddr[1] == 0 )
\r
209 /* If no unused entry is found, we try to find the oldest entry and
\r
211 if( i == UIP_ARPTAB_SIZE )
\r
215 for( i = 0; i < UIP_ARPTAB_SIZE; ++i )
\r
217 tabptr = &arp_table[i];
\r
218 if( arptime - tabptr->time > tmpage )
\r
220 tmpage = arptime - tabptr->time;
\r
226 tabptr = &arp_table[i];
\r
229 /* Now, i is the ARP table entry which we will fill with the new
\r
231 memcpy( tabptr->ipaddr, ipaddr, 4 );
\r
232 memcpy( tabptr->ethaddr.addr, ethaddr->addr, 6 );
\r
233 tabptr->time = arptime;
\r
236 /*-----------------------------------------------------------------------------------*/
\r
239 * ARP processing for incoming IP packets
\r
241 * This function should be called by the device driver when an IP
\r
242 * packet has been received. The function will check if the address is
\r
243 * in the ARP cache, and if so the ARP cache entry will be
\r
244 * refreshed. If no ARP cache entry was found, a new one is created.
\r
246 * This function expects an IP packet with a prepended Ethernet header
\r
247 * in the uip_buf[] buffer, and the length of the packet in the global
\r
248 * variable uip_len.
\r
251 /*-----------------------------------------------------------------------------------*/
\r
253 void uip_arp_ipin( void )
\r
255 uip_len -= sizeof( struct uip_eth_hdr );
\r
257 /* Only insert/update an entry if the source IP address of the
\r
258 incoming IP packet comes from a host on the local network. */
\r
259 if( (IPBUF->srcipaddr[0] & uip_netmask[0]) != (uip_hostaddr[0] & uip_netmask[0]) )
\r
264 if( (IPBUF->srcipaddr[1] & uip_netmask[1]) != (uip_hostaddr[1] & uip_netmask[1]) )
\r
269 uip_arp_update( IPBUF->srcipaddr, &(IPBUF->ethhdr.src) );
\r
276 /*-----------------------------------------------------------------------------------*/
\r
279 * ARP processing for incoming ARP packets.
\r
281 * This function should be called by the device driver when an ARP
\r
282 * packet has been received. The function will act differently
\r
283 * depending on the ARP packet type: if it is a reply for a request
\r
284 * that we previously sent out, the ARP cache will be filled in with
\r
285 * the values from the ARP reply. If the incoming ARP packet is an ARP
\r
286 * request for our IP address, an ARP reply packet is created and put
\r
287 * into the uip_buf[] buffer.
\r
289 * When the function returns, the value of the global variable uip_len
\r
290 * indicates whether the device driver should send out a packet or
\r
291 * not. If uip_len is zero, no packet should be sent. If uip_len is
\r
292 * non-zero, it contains the length of the outbound packet that is
\r
293 * present in the uip_buf[] buffer.
\r
295 * This function expects an ARP packet with a prepended Ethernet
\r
296 * header in the uip_buf[] buffer, and the length of the packet in the
\r
297 * global variable uip_len.
\r
300 /*-----------------------------------------------------------------------------------*/
\r
301 void uip_arp_arpin( void )
\r
303 if( uip_len < sizeof(struct arp_hdr) )
\r
311 switch( BUF->opcode )
\r
313 case HTONS( ARP_REQUEST ):
\r
314 /* ARP request. If it asked for our address, we send out a
\r
316 if( uip_ipaddr_cmp(BUF->dipaddr, uip_hostaddr) )
\r
318 /* First, we register the one who made the request in our ARP
\r
319 table, since it is likely that we will do more communication
\r
320 with this host in the future. */
\r
321 uip_arp_update( BUF->sipaddr, &BUF->shwaddr );
\r
323 /* The reply opcode is 2. */
\r
324 BUF->opcode = HTONS( 2 );
\r
326 memcpy( BUF->dhwaddr.addr, BUF->shwaddr.addr, 6 );
\r
327 memcpy( BUF->shwaddr.addr, uip_ethaddr.addr, 6 );
\r
328 memcpy( BUF->ethhdr.src.addr, uip_ethaddr.addr, 6 );
\r
329 memcpy( BUF->ethhdr.dest.addr, BUF->dhwaddr.addr, 6 );
\r
331 BUF->dipaddr[0] = BUF->sipaddr[0];
\r
332 BUF->dipaddr[1] = BUF->sipaddr[1];
\r
333 BUF->sipaddr[0] = uip_hostaddr[0];
\r
334 BUF->sipaddr[1] = uip_hostaddr[1];
\r
336 BUF->ethhdr.type = HTONS( UIP_ETHTYPE_ARP );
\r
337 uip_len = sizeof( struct arp_hdr );
\r
342 case HTONS( ARP_REPLY ):
\r
343 /* ARP reply. We insert or update the ARP table if it was meant
\r
345 if( uip_ipaddr_cmp(BUF->dipaddr, uip_hostaddr) )
\r
347 uip_arp_update( BUF->sipaddr, &BUF->shwaddr );
\r
356 /*-----------------------------------------------------------------------------------*/
\r
359 * Prepend Ethernet header to an outbound IP packet and see if we need
\r
360 * to send out an ARP request.
\r
362 * This function should be called before sending out an IP packet. The
\r
363 * function checks the destination IP address of the IP packet to see
\r
364 * what Ethernet MAC address that should be used as a destination MAC
\r
365 * address on the Ethernet.
\r
367 * If the destination IP address is in the local network (determined
\r
368 * by logical ANDing of netmask and our IP address), the function
\r
369 * checks the ARP cache to see if an entry for the destination IP
\r
370 * address is found. If so, an Ethernet header is prepended and the
\r
371 * function returns. If no ARP cache entry is found for the
\r
372 * destination IP address, the packet in the uip_buf[] is replaced by
\r
373 * an ARP request packet for the IP address. The IP packet is dropped
\r
374 * and it is assumed that they higher level protocols (e.g., TCP)
\r
375 * eventually will retransmit the dropped packet.
\r
377 * If the destination IP address is not on the local network, the IP
\r
378 * address of the default router is used instead.
\r
380 * When the function returns, a packet is present in the uip_buf[]
\r
381 * buffer, and the length of the packet is in the global variable
\r
385 /*-----------------------------------------------------------------------------------*/
\r
386 void uip_arp_out( void )
\r
388 struct arp_entry *tabptr;
\r
390 /* Find the destination IP address in the ARP table and construct
\r
391 the Ethernet header. If the destination IP addres isn't on the
\r
392 local network, we use the default router's IP address instead.
\r
394 If not ARP table entry is found, we overwrite the original IP
\r
395 packet with an ARP request for the IP address. */
\r
397 /* First check if destination is a local broadcast. */
\r
398 if( uip_ipaddr_cmp(IPBUF->destipaddr, broadcast_ipaddr) )
\r
400 memcpy( IPBUF->ethhdr.dest.addr, broadcast_ethaddr.addr, 6 );
\r
404 /* Check if the destination address is on the local network. */
\r
405 if( !uip_ipaddr_maskcmp(IPBUF->destipaddr, uip_hostaddr, uip_netmask) )
\r
407 /* Destination address was not on the local network, so we need to
\r
408 use the default router's IP address instead of the destination
\r
409 address when determining the MAC address. */
\r
410 uip_ipaddr_copy( ipaddr, uip_draddr );
\r
414 /* Else, we use the destination IP address. */
\r
415 uip_ipaddr_copy( ipaddr, IPBUF->destipaddr );
\r
418 for( i = 0; i < UIP_ARPTAB_SIZE; ++i )
\r
420 tabptr = &arp_table[i];
\r
421 if( uip_ipaddr_cmp(ipaddr, tabptr->ipaddr) )
\r
427 if( i == UIP_ARPTAB_SIZE )
\r
429 /* The destination address was not in our ARP table, so we
\r
430 overwrite the IP packet with an ARP request. */
\r
431 memset( BUF->ethhdr.dest.addr, 0xff, 6 );
\r
432 memset( BUF->dhwaddr.addr, 0x00, 6 );
\r
433 memcpy( BUF->ethhdr.src.addr, uip_ethaddr.addr, 6 );
\r
434 memcpy( BUF->shwaddr.addr, uip_ethaddr.addr, 6 );
\r
436 uip_ipaddr_copy( BUF->dipaddr, ipaddr );
\r
437 uip_ipaddr_copy( BUF->sipaddr, uip_hostaddr );
\r
438 BUF->opcode = HTONS( ARP_REQUEST ); /* ARP request. */
\r
439 BUF->hwtype = HTONS( ARP_HWTYPE_ETH );
\r
440 BUF->protocol = HTONS( UIP_ETHTYPE_IP );
\r
443 BUF->ethhdr.type = HTONS( UIP_ETHTYPE_ARP );
\r
445 uip_appdata = &uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN];
\r
447 uip_len = sizeof( struct arp_hdr );
\r
451 /* Build an ethernet header. */
\r
452 memcpy( IPBUF->ethhdr.dest.addr, tabptr->ethaddr.addr, 6 );
\r
455 memcpy( IPBUF->ethhdr.src.addr, uip_ethaddr.addr, 6 );
\r
457 IPBUF->ethhdr.type = HTONS( UIP_ETHTYPE_IP );
\r
459 uip_len += sizeof( struct uip_eth_hdr );
\r
462 /*-----------------------------------------------------------------------------------*/
\r