00001 /** 00002 * \addtogroup uip 00003 * @{ 00004 */ 00005 00006 /** 00007 * \defgroup uiparp uIP Address Resolution Protocol 00008 * @{ 00009 * 00010 * The Address Resolution Protocol ARP is used for mapping between IP 00011 * addresses and link level addresses such as the Ethernet MAC 00012 * addresses. ARP uses broadcast queries to ask for the link level 00013 * address of a known IP address and the host which is configured with 00014 * the IP address for which the query was meant, will respond with its 00015 * link level address. 00016 * 00017 * \note This ARP implementation only supports Ethernet. 00018 */ 00019 00020 /** 00021 * \file 00022 * Implementation of the ARP Address Resolution Protocol. 00023 * \author Adam Dunkels <adam@dunkels.com> 00024 * 00025 */ 00026 00027 /* 00028 * Copyright (c) 2001-2003, Adam Dunkels. 00029 * All rights reserved. 00030 * 00031 * Redistribution and use in source and binary forms, with or without 00032 * modification, are permitted provided that the following conditions 00033 * are met: 00034 * 1. Redistributions of source code must retain the above copyright 00035 * notice, this list of conditions and the following disclaimer. 00036 * 2. Redistributions in binary form must reproduce the above copyright 00037 * notice, this list of conditions and the following disclaimer in the 00038 * documentation and/or other materials provided with the distribution. 00039 * 3. The name of the author may not be used to endorse or promote 00040 * products derived from this software without specific prior 00041 * written permission. 00042 * 00043 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 00044 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 00045 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 00046 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 00047 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 00048 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE 00049 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 00050 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 00051 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 00052 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 00053 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 00054 * 00055 * This file is part of the uIP TCP/IP stack. 00056 * 00057 * $Id: uip_arp.c,v 1.1 2006/06/17 22:41:19 adamdunkels Exp $ 00058 * 00059 */ 00060 00061 00062 #include "net/uip_arp.h" 00063 00064 #include <string.h> 00065 00066 struct arp_hdr { 00067 struct uip_eth_hdr ethhdr; 00068 u16_t hwtype; 00069 u16_t protocol; 00070 u8_t hwlen; 00071 u8_t protolen; 00072 u16_t opcode; 00073 struct uip_eth_addr shwaddr; 00074 u16_t sipaddr[2]; 00075 struct uip_eth_addr dhwaddr; 00076 u16_t dipaddr[2]; 00077 }; 00078 00079 struct ethip_hdr { 00080 struct uip_eth_hdr ethhdr; 00081 /* IP header. */ 00082 u8_t vhl, 00083 tos, 00084 len[2], 00085 ipid[2], 00086 ipoffset[2], 00087 ttl, 00088 proto; 00089 u16_t ipchksum; 00090 u16_t srcipaddr[2], 00091 destipaddr[2]; 00092 }; 00093 00094 #define ARP_REQUEST 1 00095 #define ARP_REPLY 2 00096 00097 #define ARP_HWTYPE_ETH 1 00098 00099 struct arp_entry { 00100 u16_t ipaddr[2]; 00101 struct uip_eth_addr ethaddr; 00102 u8_t time; 00103 }; 00104 00105 static const struct uip_eth_addr broadcast_ethaddr = 00106 {{0xff,0xff,0xff,0xff,0xff,0xff}}; 00107 static const u16_t broadcast_ipaddr[2] = {0xffff,0xffff}; 00108 00109 static struct arp_entry arp_table[UIP_ARPTAB_SIZE]; 00110 static u16_t ipaddr[2]; 00111 static u8_t i, c; 00112 00113 static u8_t arptime; 00114 static u8_t tmpage; 00115 00116 #define BUF ((struct arp_hdr *)&uip_buf[0]) 00117 #define IPBUF ((struct ethip_hdr *)&uip_buf[0]) 00118 /*-----------------------------------------------------------------------------------*/ 00119 /** 00120 * Initialize the ARP module. 00121 * 00122 */ 00123 /*-----------------------------------------------------------------------------------*/ 00124 void 00125 uip_arp_init(void) 00126 { 00127 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00128 memset(arp_table[i].ipaddr, 0, 4); 00129 } 00130 } 00131 /*-----------------------------------------------------------------------------------*/ 00132 /** 00133 * Periodic ARP processing function. 00134 * 00135 * This function performs periodic timer processing in the ARP module 00136 * and should be called at regular intervals. The recommended interval 00137 * is 10 seconds between the calls. 00138 * 00139 */ 00140 /*-----------------------------------------------------------------------------------*/ 00141 void 00142 uip_arp_timer(void) 00143 { 00144 struct arp_entry *tabptr; 00145 00146 ++arptime; 00147 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00148 tabptr = &arp_table[i]; 00149 if((tabptr->ipaddr[0] | tabptr->ipaddr[1]) != 0 && 00150 arptime - tabptr->time >= UIP_ARP_MAXAGE) { 00151 memset(tabptr->ipaddr, 0, 4); 00152 } 00153 } 00154 00155 } 00156 /*-----------------------------------------------------------------------------------*/ 00157 static void 00158 uip_arp_update(u16_t *ipaddr, struct uip_eth_addr *ethaddr) 00159 { 00160 register struct arp_entry *tabptr; 00161 /* Walk through the ARP mapping table and try to find an entry to 00162 update. If none is found, the IP -> MAC address mapping is 00163 inserted in the ARP table. */ 00164 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00165 00166 tabptr = &arp_table[i]; 00167 /* Only check those entries that are actually in use. */ 00168 if(tabptr->ipaddr[0] != 0 && 00169 tabptr->ipaddr[1] != 0) { 00170 00171 /* Check if the source IP address of the incoming packet matches 00172 the IP address in this ARP table entry. */ 00173 if(ipaddr[0] == tabptr->ipaddr[0] && 00174 ipaddr[1] == tabptr->ipaddr[1]) { 00175 00176 /* An old entry found, update this and return. */ 00177 memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6); 00178 tabptr->time = arptime; 00179 00180 return; 00181 } 00182 } 00183 } 00184 00185 /* If we get here, no existing ARP table entry was found, so we 00186 create one. */ 00187 00188 /* First, we try to find an unused entry in the ARP table. */ 00189 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00190 tabptr = &arp_table[i]; 00191 if(tabptr->ipaddr[0] == 0 && 00192 tabptr->ipaddr[1] == 0) { 00193 break; 00194 } 00195 } 00196 00197 /* If no unused entry is found, we try to find the oldest entry and 00198 throw it away. */ 00199 if(i == UIP_ARPTAB_SIZE) { 00200 tmpage = 0; 00201 c = 0; 00202 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00203 tabptr = &arp_table[i]; 00204 if(arptime - tabptr->time > tmpage) { 00205 tmpage = arptime - tabptr->time; 00206 c = i; 00207 } 00208 } 00209 i = c; 00210 tabptr = &arp_table[i]; 00211 } 00212 00213 /* Now, i is the ARP table entry which we will fill with the new 00214 information. */ 00215 memcpy(tabptr->ipaddr, ipaddr, 4); 00216 memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6); 00217 tabptr->time = arptime; 00218 } 00219 /*-----------------------------------------------------------------------------------*/ 00220 /** 00221 * ARP processing for incoming IP packets 00222 * 00223 * This function should be called by the device driver when an IP 00224 * packet has been received. The function will check if the address is 00225 * in the ARP cache, and if so the ARP cache entry will be 00226 * refreshed. If no ARP cache entry was found, a new one is created. 00227 * 00228 * This function expects an IP packet with a prepended Ethernet header 00229 * in the uip_buf[] buffer, and the length of the packet in the global 00230 * variable uip_len. 00231 */ 00232 /*-----------------------------------------------------------------------------------*/ 00233 #if 0 00234 void 00235 uip_arp_ipin(void) 00236 { 00237 uip_len -= sizeof(struct uip_eth_hdr); 00238 00239 /* Only insert/update an entry if the source IP address of the 00240 incoming IP packet comes from a host on the local network. */ 00241 if((IPBUF->srcipaddr[0] & uip_netmask[0]) != 00242 (uip_hostaddr[0] & uip_netmask[0])) { 00243 return; 00244 } 00245 if((IPBUF->srcipaddr[1] & uip_netmask[1]) != 00246 (uip_hostaddr[1] & uip_netmask[1])) { 00247 return; 00248 } 00249 uip_arp_update(IPBUF->srcipaddr, &(IPBUF->ethhdr.src)); 00250 00251 return; 00252 } 00253 #endif /* 0 */ 00254 /*-----------------------------------------------------------------------------------*/ 00255 /** 00256 * ARP processing for incoming ARP packets. 00257 * 00258 * This function should be called by the device driver when an ARP 00259 * packet has been received. The function will act differently 00260 * depending on the ARP packet type: if it is a reply for a request 00261 * that we previously sent out, the ARP cache will be filled in with 00262 * the values from the ARP reply. If the incoming ARP packet is an ARP 00263 * request for our IP address, an ARP reply packet is created and put 00264 * into the uip_buf[] buffer. 00265 * 00266 * When the function returns, the value of the global variable uip_len 00267 * indicates whether the device driver should send out a packet or 00268 * not. If uip_len is zero, no packet should be sent. If uip_len is 00269 * non-zero, it contains the length of the outbound packet that is 00270 * present in the uip_buf[] buffer. 00271 * 00272 * This function expects an ARP packet with a prepended Ethernet 00273 * header in the uip_buf[] buffer, and the length of the packet in the 00274 * global variable uip_len. 00275 */ 00276 /*-----------------------------------------------------------------------------------*/ 00277 void 00278 uip_arp_arpin(void) 00279 { 00280 00281 if(uip_len < sizeof(struct arp_hdr)) { 00282 uip_len = 0; 00283 return; 00284 } 00285 uip_len = 0; 00286 00287 switch(BUF->opcode) { 00288 case HTONS(ARP_REQUEST): 00289 /* ARP request. If it asked for our address, we send out a 00290 reply. */ 00291 /* if(BUF->dipaddr[0] == uip_hostaddr[0] && 00292 BUF->dipaddr[1] == uip_hostaddr[1]) {*/ 00293 if(uip_ipaddr_cmp(BUF->dipaddr, uip_hostaddr)) { 00294 /* First, we register the one who made the request in our ARP 00295 table, since it is likely that we will do more communication 00296 with this host in the future. */ 00297 uip_arp_update(BUF->sipaddr, &BUF->shwaddr); 00298 00299 /* The reply opcode is 2. */ 00300 BUF->opcode = HTONS(2); 00301 00302 memcpy(BUF->dhwaddr.addr, BUF->shwaddr.addr, 6); 00303 memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6); 00304 memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6); 00305 memcpy(BUF->ethhdr.dest.addr, BUF->dhwaddr.addr, 6); 00306 00307 BUF->dipaddr[0] = BUF->sipaddr[0]; 00308 BUF->dipaddr[1] = BUF->sipaddr[1]; 00309 BUF->sipaddr[0] = uip_hostaddr[0]; 00310 BUF->sipaddr[1] = uip_hostaddr[1]; 00311 00312 BUF->ethhdr.type = HTONS(UIP_ETHTYPE_ARP); 00313 uip_len = sizeof(struct arp_hdr); 00314 } 00315 break; 00316 case HTONS(ARP_REPLY): 00317 /* ARP reply. We insert or update the ARP table if it was meant 00318 for us. */ 00319 /* if(BUF->dipaddr[0] == uip_hostaddr[0] && 00320 BUF->dipaddr[1] == uip_hostaddr[1]) {*/ 00321 if(uip_ipaddr_cmp(BUF->dipaddr, uip_hostaddr)) { 00322 uip_arp_update(BUF->sipaddr, &BUF->shwaddr); 00323 } 00324 break; 00325 } 00326 00327 return; 00328 } 00329 /*-----------------------------------------------------------------------------------*/ 00330 /** 00331 * Prepend Ethernet header to an outbound IP packet and see if we need 00332 * to send out an ARP request. 00333 * 00334 * This function should be called before sending out an IP packet. The 00335 * function checks the destination IP address of the IP packet to see 00336 * what Ethernet MAC address that should be used as a destination MAC 00337 * address on the Ethernet. 00338 * 00339 * If the destination IP address is in the local network (determined 00340 * by logical ANDing of netmask and our IP address), the function 00341 * checks the ARP cache to see if an entry for the destination IP 00342 * address is found. If so, an Ethernet header is prepended and the 00343 * function returns. If no ARP cache entry is found for the 00344 * destination IP address, the packet in the uip_buf[] is replaced by 00345 * an ARP request packet for the IP address. The IP packet is dropped 00346 * and it is assumed that they higher level protocols (e.g., TCP) 00347 * eventually will retransmit the dropped packet. 00348 * 00349 * If the destination IP address is not on the local network, the IP 00350 * address of the default router is used instead. 00351 * 00352 * When the function returns, a packet is present in the uip_buf[] 00353 * buffer, and the length of the packet is in the global variable 00354 * uip_len. 00355 */ 00356 /*-----------------------------------------------------------------------------------*/ 00357 void 00358 uip_arp_out(void) 00359 { 00360 struct arp_entry *tabptr; 00361 00362 /* Find the destination IP address in the ARP table and construct 00363 the Ethernet header. If the destination IP addres isn't on the 00364 local network, we use the default router's IP address instead. 00365 00366 If not ARP table entry is found, we overwrite the original IP 00367 packet with an ARP request for the IP address. */ 00368 00369 /* First check if destination is a local broadcast. */ 00370 if(uip_ipaddr_cmp(IPBUF->destipaddr, broadcast_ipaddr)) { 00371 memcpy(IPBUF->ethhdr.dest.addr, broadcast_ethaddr.addr, 6); 00372 } else { 00373 /* Check if the destination address is on the local network. */ 00374 if(!uip_ipaddr_maskcmp(IPBUF->destipaddr, uip_hostaddr, uip_netmask)) { 00375 /* Destination address was not on the local network, so we need to 00376 use the default router's IP address instead of the destination 00377 address when determining the MAC address. */ 00378 uip_ipaddr_copy(ipaddr, uip_draddr); 00379 } else { 00380 /* Else, we use the destination IP address. */ 00381 uip_ipaddr_copy(ipaddr, IPBUF->destipaddr); 00382 } 00383 00384 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00385 tabptr = &arp_table[i]; 00386 if(uip_ipaddr_cmp(ipaddr, tabptr->ipaddr)) { 00387 break; 00388 } 00389 } 00390 00391 if(i == UIP_ARPTAB_SIZE) { 00392 /* The destination address was not in our ARP table, so we 00393 overwrite the IP packet with an ARP request. */ 00394 00395 memset(BUF->ethhdr.dest.addr, 0xff, 6); 00396 memset(BUF->dhwaddr.addr, 0x00, 6); 00397 memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6); 00398 memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6); 00399 00400 uip_ipaddr_copy(BUF->dipaddr, ipaddr); 00401 uip_ipaddr_copy(BUF->sipaddr, uip_hostaddr); 00402 BUF->opcode = HTONS(ARP_REQUEST); /* ARP request. */ 00403 BUF->hwtype = HTONS(ARP_HWTYPE_ETH); 00404 BUF->protocol = HTONS(UIP_ETHTYPE_IP); 00405 BUF->hwlen = 6; 00406 BUF->protolen = 4; 00407 BUF->ethhdr.type = HTONS(UIP_ETHTYPE_ARP); 00408 00409 uip_appdata = &uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN]; 00410 00411 uip_len = sizeof(struct arp_hdr); 00412 return; 00413 } 00414 00415 /* Build an ethernet header. */ 00416 memcpy(IPBUF->ethhdr.dest.addr, tabptr->ethaddr.addr, 6); 00417 } 00418 memcpy(IPBUF->ethhdr.src.addr, uip_ethaddr.addr, 6); 00419 00420 IPBUF->ethhdr.type = HTONS(UIP_ETHTYPE_IP); 00421 00422 uip_len += sizeof(struct uip_eth_hdr); 00423 } 00424 /*-----------------------------------------------------------------------------------*/ 00425 00426 /** @} */ 00427 /** @} */