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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 1.8 2010/12/14 22:45:22 dak664 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 uint16_t hwtype; 00069 uint16_t protocol; 00070 uint8_t hwlen; 00071 uint8_t protolen; 00072 uint16_t opcode; 00073 struct uip_eth_addr shwaddr; 00074 uip_ipaddr_t sipaddr; 00075 struct uip_eth_addr dhwaddr; 00076 uip_ipaddr_t dipaddr; 00077 }; 00078 00079 struct ethip_hdr { 00080 struct uip_eth_hdr ethhdr; 00081 /* IP header. */ 00082 uint8_t vhl, 00083 tos, 00084 len[2], 00085 ipid[2], 00086 ipoffset[2], 00087 ttl, 00088 proto; 00089 uint16_t ipchksum; 00090 uip_ipaddr_t srcipaddr, destipaddr; 00091 }; 00092 00093 #define ARP_REQUEST 1 00094 #define ARP_REPLY 2 00095 00096 #define ARP_HWTYPE_ETH 1 00097 00098 struct arp_entry { 00099 uip_ipaddr_t ipaddr; 00100 struct uip_eth_addr ethaddr; 00101 uint8_t time; 00102 }; 00103 00104 static const struct uip_eth_addr broadcast_ethaddr = 00105 {{0xff,0xff,0xff,0xff,0xff,0xff}}; 00106 static const uint16_t broadcast_ipaddr[2] = {0xffff,0xffff}; 00107 00108 static struct arp_entry arp_table[UIP_ARPTAB_SIZE]; 00109 static uip_ipaddr_t ipaddr; 00110 static uint8_t i, c; 00111 00112 static uint8_t arptime; 00113 static uint8_t tmpage; 00114 00115 #define BUF ((struct arp_hdr *)&uip_buf[0]) 00116 #define IPBUF ((struct ethip_hdr *)&uip_buf[0]) 00117 00118 #define DEBUG 0 00119 #if DEBUG 00120 #include <stdio.h> 00121 #define PRINTF(...) printf(__VA_ARGS__) 00122 #else 00123 #define PRINTF(...) 00124 #endif 00125 00126 /*-----------------------------------------------------------------------------------*/ 00127 /** 00128 * Initialize the ARP module. 00129 * 00130 */ 00131 /*-----------------------------------------------------------------------------------*/ 00132 void 00133 uip_arp_init(void) 00134 { 00135 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00136 memset(&arp_table[i].ipaddr, 0, 4); 00137 } 00138 } 00139 /*-----------------------------------------------------------------------------------*/ 00140 /** 00141 * Periodic ARP processing function. 00142 * 00143 * This function performs periodic timer processing in the ARP module 00144 * and should be called at regular intervals. The recommended interval 00145 * is 10 seconds between the calls. 00146 * 00147 */ 00148 /*-----------------------------------------------------------------------------------*/ 00149 void 00150 uip_arp_timer(void) 00151 { 00152 struct arp_entry *tabptr; 00153 00154 ++arptime; 00155 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00156 tabptr = &arp_table[i]; 00157 if(uip_ipaddr_cmp(&tabptr->ipaddr, &uip_all_zeroes_addr) && 00158 arptime - tabptr->time >= UIP_ARP_MAXAGE) { 00159 memset(&tabptr->ipaddr, 0, 4); 00160 } 00161 } 00162 00163 } 00164 00165 /*-----------------------------------------------------------------------------------*/ 00166 static void 00167 uip_arp_update(uip_ipaddr_t *ipaddr, struct uip_eth_addr *ethaddr) 00168 { 00169 register struct arp_entry *tabptr = arp_table; 00170 00171 /* Walk through the ARP mapping table and try to find an entry to 00172 update. If none is found, the IP -> MAC address mapping is 00173 inserted in the ARP table. */ 00174 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00175 tabptr = &arp_table[i]; 00176 00177 /* Only check those entries that are actually in use. */ 00178 if(!uip_ipaddr_cmp(&tabptr->ipaddr, &uip_all_zeroes_addr)) { 00179 00180 /* Check if the source IP address of the incoming packet matches 00181 the IP address in this ARP table entry. */ 00182 if(uip_ipaddr_cmp(ipaddr, &tabptr->ipaddr)) { 00183 00184 /* An old entry found, update this and return. */ 00185 memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6); 00186 tabptr->time = arptime; 00187 00188 return; 00189 } 00190 } 00191 tabptr++; 00192 } 00193 00194 /* If we get here, no existing ARP table entry was found, so we 00195 create one. */ 00196 00197 /* First, we try to find an unused entry in the ARP table. */ 00198 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00199 tabptr = &arp_table[i]; 00200 if(uip_ipaddr_cmp(&tabptr->ipaddr, &uip_all_zeroes_addr)) { 00201 break; 00202 } 00203 } 00204 00205 /* If no unused entry is found, we try to find the oldest entry and 00206 throw it away. */ 00207 if(i == UIP_ARPTAB_SIZE) { 00208 tmpage = 0; 00209 c = 0; 00210 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00211 tabptr = &arp_table[i]; 00212 if(arptime - tabptr->time > tmpage) { 00213 tmpage = arptime - tabptr->time; 00214 c = i; 00215 } 00216 } 00217 i = c; 00218 tabptr = &arp_table[i]; 00219 } 00220 00221 /* Now, i is the ARP table entry which we will fill with the new 00222 information. */ 00223 uip_ipaddr_copy(&tabptr->ipaddr, ipaddr); 00224 memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6); 00225 tabptr->time = arptime; 00226 } 00227 /*-----------------------------------------------------------------------------------*/ 00228 /** 00229 * ARP processing for incoming IP packets 00230 * 00231 * This function should be called by the device driver when an IP 00232 * packet has been received. The function will check if the address is 00233 * in the ARP cache, and if so the ARP cache entry will be 00234 * refreshed. If no ARP cache entry was found, a new one is created. 00235 * 00236 * This function expects an IP packet with a prepended Ethernet header 00237 * in the uip_buf[] buffer, and the length of the packet in the global 00238 * variable uip_len. 00239 */ 00240 /*-----------------------------------------------------------------------------------*/ 00241 #if 0 00242 void 00243 uip_arp_ipin(void) 00244 { 00245 uip_len -= sizeof(struct uip_eth_hdr); 00246 00247 /* Only insert/update an entry if the source IP address of the 00248 incoming IP packet comes from a host on the local network. */ 00249 if((IPBUF->srcipaddr[0] & uip_netmask[0]) != 00250 (uip_hostaddr[0] & uip_netmask[0])) { 00251 return; 00252 } 00253 if((IPBUF->srcipaddr[1] & uip_netmask[1]) != 00254 (uip_hostaddr[1] & uip_netmask[1])) { 00255 return; 00256 } 00257 uip_arp_update(IPBUF->srcipaddr, &(IPBUF->ethhdr.src)); 00258 00259 return; 00260 } 00261 #endif /* 0 */ 00262 /*-----------------------------------------------------------------------------------*/ 00263 /** 00264 * ARP processing for incoming ARP packets. 00265 * 00266 * This function should be called by the device driver when an ARP 00267 * packet has been received. The function will act differently 00268 * depending on the ARP packet type: if it is a reply for a request 00269 * that we previously sent out, the ARP cache will be filled in with 00270 * the values from the ARP reply. If the incoming ARP packet is an ARP 00271 * request for our IP address, an ARP reply packet is created and put 00272 * into the uip_buf[] buffer. 00273 * 00274 * When the function returns, the value of the global variable uip_len 00275 * indicates whether the device driver should send out a packet or 00276 * not. If uip_len is zero, no packet should be sent. If uip_len is 00277 * non-zero, it contains the length of the outbound packet that is 00278 * present in the uip_buf[] buffer. 00279 * 00280 * This function expects an ARP packet with a prepended Ethernet 00281 * header in the uip_buf[] buffer, and the length of the packet in the 00282 * global variable uip_len. 00283 */ 00284 /*-----------------------------------------------------------------------------------*/ 00285 void 00286 uip_arp_arpin(void) 00287 { 00288 00289 if(uip_len < sizeof(struct arp_hdr)) { 00290 uip_len = 0; 00291 return; 00292 } 00293 uip_len = 0; 00294 00295 switch(BUF->opcode) { 00296 case UIP_HTONS(ARP_REQUEST): 00297 /* ARP request. If it asked for our address, we send out a 00298 reply. */ 00299 /* if(BUF->dipaddr[0] == uip_hostaddr[0] && 00300 BUF->dipaddr[1] == uip_hostaddr[1]) {*/ 00301 PRINTF("uip_arp_arpin: request for %d.%d.%d.%d (we are %d.%d.%d.%d)\n", 00302 BUF->dipaddr.u8[0], BUF->dipaddr.u8[1], 00303 BUF->dipaddr.u8[2], BUF->dipaddr.u8[3], 00304 uip_hostaddr.u8[0], uip_hostaddr.u8[1], 00305 uip_hostaddr.u8[2], uip_hostaddr.u8[3]); 00306 if(uip_ipaddr_cmp(&BUF->dipaddr, &uip_hostaddr)) { 00307 /* First, we register the one who made the request in our ARP 00308 table, since it is likely that we will do more communication 00309 with this host in the future. */ 00310 uip_arp_update(&BUF->sipaddr, &BUF->shwaddr); 00311 00312 BUF->opcode = UIP_HTONS(ARP_REPLY); 00313 00314 memcpy(BUF->dhwaddr.addr, BUF->shwaddr.addr, 6); 00315 memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6); 00316 memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6); 00317 memcpy(BUF->ethhdr.dest.addr, BUF->dhwaddr.addr, 6); 00318 00319 uip_ipaddr_copy(&BUF->dipaddr, &BUF->sipaddr); 00320 uip_ipaddr_copy(&BUF->sipaddr, &uip_hostaddr); 00321 00322 BUF->ethhdr.type = UIP_HTONS(UIP_ETHTYPE_ARP); 00323 uip_len = sizeof(struct arp_hdr); 00324 } 00325 break; 00326 case UIP_HTONS(ARP_REPLY): 00327 /* ARP reply. We insert or update the ARP table if it was meant 00328 for us. */ 00329 if(uip_ipaddr_cmp(&BUF->dipaddr, &uip_hostaddr)) { 00330 uip_arp_update(&BUF->sipaddr, &BUF->shwaddr); 00331 } 00332 break; 00333 } 00334 00335 return; 00336 } 00337 /*-----------------------------------------------------------------------------------*/ 00338 /** 00339 * Prepend Ethernet header to an outbound IP packet and see if we need 00340 * to send out an ARP request. 00341 * 00342 * This function should be called before sending out an IP packet. The 00343 * function checks the destination IP address of the IP packet to see 00344 * what Ethernet MAC address that should be used as a destination MAC 00345 * address on the Ethernet. 00346 * 00347 * If the destination IP address is in the local network (determined 00348 * by logical ANDing of netmask and our IP address), the function 00349 * checks the ARP cache to see if an entry for the destination IP 00350 * address is found. If so, an Ethernet header is prepended and the 00351 * function returns. If no ARP cache entry is found for the 00352 * destination IP address, the packet in the uip_buf[] is replaced by 00353 * an ARP request packet for the IP address. The IP packet is dropped 00354 * and it is assumed that they higher level protocols (e.g., TCP) 00355 * eventually will retransmit the dropped packet. 00356 * 00357 * If the destination IP address is not on the local network, the IP 00358 * address of the default router is used instead. 00359 * 00360 * When the function returns, a packet is present in the uip_buf[] 00361 * buffer, and the length of the packet is in the global variable 00362 * uip_len. 00363 */ 00364 /*-----------------------------------------------------------------------------------*/ 00365 void 00366 uip_arp_out(void) 00367 { 00368 struct arp_entry *tabptr = arp_table; 00369 00370 /* Find the destination IP address in the ARP table and construct 00371 the Ethernet header. If the destination IP addres isn't on the 00372 local network, we use the default router's IP address instead. 00373 00374 If not ARP table entry is found, we overwrite the original IP 00375 packet with an ARP request for the IP address. */ 00376 00377 /* First check if destination is a local broadcast. */ 00378 if(uip_ipaddr_cmp(&IPBUF->destipaddr, &uip_broadcast_addr)) { 00379 memcpy(IPBUF->ethhdr.dest.addr, broadcast_ethaddr.addr, 6); 00380 } else if(IPBUF->destipaddr.u8[0] == 224) { 00381 /* Multicast. */ 00382 IPBUF->ethhdr.dest.addr[0] = 0x01; 00383 IPBUF->ethhdr.dest.addr[1] = 0x00; 00384 IPBUF->ethhdr.dest.addr[2] = 0x5e; 00385 IPBUF->ethhdr.dest.addr[3] = IPBUF->destipaddr.u8[1]; 00386 IPBUF->ethhdr.dest.addr[4] = IPBUF->destipaddr.u8[2]; 00387 IPBUF->ethhdr.dest.addr[5] = IPBUF->destipaddr.u8[3]; 00388 } else { 00389 /* Check if the destination address is on the local network. */ 00390 if(!uip_ipaddr_maskcmp(&IPBUF->destipaddr, &uip_hostaddr, &uip_netmask)) { 00391 /* Destination address was not on the local network, so we need to 00392 use the default router's IP address instead of the destination 00393 address when determining the MAC address. */ 00394 uip_ipaddr_copy(&ipaddr, &uip_draddr); 00395 } else { 00396 /* Else, we use the destination IP address. */ 00397 uip_ipaddr_copy(&ipaddr, &IPBUF->destipaddr); 00398 } 00399 for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { 00400 if(uip_ipaddr_cmp(&ipaddr, &tabptr->ipaddr)) { 00401 break; 00402 } 00403 tabptr++; 00404 } 00405 00406 if(i == UIP_ARPTAB_SIZE) { 00407 /* The destination address was not in our ARP table, so we 00408 overwrite the IP packet with an ARP request. */ 00409 00410 memset(BUF->ethhdr.dest.addr, 0xff, 6); 00411 memset(BUF->dhwaddr.addr, 0x00, 6); 00412 memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6); 00413 memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6); 00414 00415 uip_ipaddr_copy(&BUF->dipaddr, &ipaddr); 00416 uip_ipaddr_copy(&BUF->sipaddr, &uip_hostaddr); 00417 BUF->opcode = UIP_HTONS(ARP_REQUEST); /* ARP request. */ 00418 BUF->hwtype = UIP_HTONS(ARP_HWTYPE_ETH); 00419 BUF->protocol = UIP_HTONS(UIP_ETHTYPE_IP); 00420 BUF->hwlen = 6; 00421 BUF->protolen = 4; 00422 BUF->ethhdr.type = UIP_HTONS(UIP_ETHTYPE_ARP); 00423 00424 uip_appdata = &uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN]; 00425 00426 uip_len = sizeof(struct arp_hdr); 00427 return; 00428 } 00429 00430 /* Build an ethernet header. */ 00431 memcpy(IPBUF->ethhdr.dest.addr, tabptr->ethaddr.addr, 6); 00432 } 00433 memcpy(IPBUF->ethhdr.src.addr, uip_ethaddr.addr, 6); 00434 00435 IPBUF->ethhdr.type = UIP_HTONS(UIP_ETHTYPE_IP); 00436 00437 uip_len += sizeof(struct uip_eth_hdr); 00438 } 00439 /*-----------------------------------------------------------------------------------*/ 00440 00441 /** @} */ 00442 /** @} */ 00443