autoip.c

00001 /**
00002  * @file
00003  * AutoIP Automatic LinkLocal IP Configuration
00004  *
00005  */
00006 
00007 /*
00008  *
00009  * Copyright (c) 2007 Dominik Spies <kontakt@dspies.de>
00010  * All rights reserved.
00011  *
00012  * Redistribution and use in source and binary forms, with or without modification,
00013  * are permitted provided that the following conditions are met:
00014  *
00015  * 1. Redistributions of source code must retain the above copyright notice,
00016  *    this list of conditions and the following disclaimer.
00017  * 2. Redistributions in binary form must reproduce the above copyright notice,
00018  *    this list of conditions and the following disclaimer in the documentation
00019  *    and/or other materials provided with the distribution.
00020  * 3. The name of the author may not be used to endorse or promote products
00021  *    derived from this software without specific prior written permission.
00022  *
00023  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
00024  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
00025  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
00026  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00027  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
00028  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00029  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
00030  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
00031  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
00032  * OF SUCH DAMAGE.
00033  *
00034  * Author: Dominik Spies <kontakt@dspies.de>
00035  *
00036  * This is a AutoIP implementation for the lwIP TCP/IP stack. It aims to conform
00037  * with RFC 3927.
00038  *
00039  *
00040  * Please coordinate changes and requests with Dominik Spies
00041  * <kontakt@dspies.de>
00042  */
00043 
00044 /*******************************************************************************
00045  * USAGE:
00046  * 
00047  * define LWIP_AUTOIP 1  in your lwipopts.h
00048  * 
00049  * If you don't use tcpip.c (so, don't call, you don't call tcpip_init):
00050  * - First, call autoip_init().
00051  * - call autoip_tmr() all AUTOIP_TMR_INTERVAL msces,
00052  *   that should be defined in autoip.h.
00053  *   I recommend a value of 100. The value must divide 1000 with a remainder almost 0.
00054  *   Possible values are 1000, 500, 333, 250, 200, 166, 142, 125, 111, 100 ....
00055  *
00056  * Without DHCP:
00057  * - Call autoip_start() after netif_add().
00058  * 
00059  * With DHCP:
00060  * - define LWIP_DHCP_AUTOIP_COOP 1 in your lwipopts.h.
00061  * - Configure your DHCP Client.
00062  *
00063  */
00064 
00065 #include "lwip/opt.h"
00066 
00067 #if LWIP_AUTOIP /* don't build if not configured for use in lwipopts.h */
00068 
00069 #include "lwip/mem.h"
00070 #include "lwip/udp.h"
00071 #include "lwip/ip_addr.h"
00072 #include "lwip/netif.h"
00073 #include "lwip/autoip.h"
00074 #include "netif/etharp.h"
00075 
00076 #include <stdlib.h>
00077 #include <string.h>
00078 
00079 /* 169.254.0.0 */
00080 #define AUTOIP_NET         0xA9FE0000
00081 /* 169.254.1.0 */
00082 #define AUTOIP_RANGE_START (AUTOIP_NET | 0x0100)
00083 /* 169.254.254.255 */
00084 #define AUTOIP_RANGE_END   (AUTOIP_NET | 0xFEFF)
00085 
00086 
00087 /** Pseudo random macro based on netif informations.
00088  * You could use "rand()" from the C Library if you define LWIP_AUTOIP_RAND in lwipopts.h */
00089 #ifndef LWIP_AUTOIP_RAND
00090 #define LWIP_AUTOIP_RAND(netif) ( (((u32_t)((netif->hwaddr[5]) & 0xff) << 24) | \
00091                                    ((u32_t)((netif->hwaddr[3]) & 0xff) << 16) | \
00092                                    ((u32_t)((netif->hwaddr[2]) & 0xff) << 8) | \
00093                                    ((u32_t)((netif->hwaddr[4]) & 0xff))) + \
00094                                    (netif->autoip?netif->autoip->tried_llipaddr:0))
00095 #endif /* LWIP_AUTOIP_RAND */
00096 
00097 /**
00098  * Macro that generates the initial IP address to be tried by AUTOIP.
00099  * If you want to override this, define it to something else in lwipopts.h.
00100  */
00101 #ifndef LWIP_AUTOIP_CREATE_SEED_ADDR
00102 #define LWIP_AUTOIP_CREATE_SEED_ADDR(netif) \
00103   htonl(AUTOIP_RANGE_START + ((u32_t)(((u8_t)(netif->hwaddr[4])) | \
00104                  ((u32_t)((u8_t)(netif->hwaddr[5]))) << 8)))
00105 #endif /* LWIP_AUTOIP_CREATE_SEED_ADDR */
00106 
00107 /* static functions */
00108 static void autoip_handle_arp_conflict(struct netif *netif);
00109 
00110 /* creates a pseudo random LL IP-Address for a network interface */
00111 static void autoip_create_addr(struct netif *netif, ip_addr_t *ipaddr);
00112 
00113 /* sends an ARP probe */
00114 static err_t autoip_arp_probe(struct netif *netif);
00115 
00116 /* sends an ARP announce */
00117 static err_t autoip_arp_announce(struct netif *netif);
00118 
00119 /* configure interface for use with current LL IP-Address */
00120 static err_t autoip_bind(struct netif *netif);
00121 
00122 /* start sending probes for llipaddr */
00123 static void autoip_start_probing(struct netif *netif);
00124 
00125 /**
00126  * Initialize this module
00127  */
00128 void
00129 autoip_init(void)
00130 {
00131   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_init()\n"));
00132 }
00133 
00134 /** Set a statically allocated struct autoip to work with.
00135  * Using this prevents autoip_start to allocate it using mem_malloc.
00136  *
00137  * @param netif the netif for which to set the struct autoip
00138  * @param dhcp (uninitialised) dhcp struct allocated by the application
00139  */
00140 void
00141 autoip_set_struct(struct netif *netif, struct autoip *autoip)
00142 {
00143   LWIP_ASSERT("netif != NULL", netif != NULL);
00144   LWIP_ASSERT("autoip != NULL", autoip != NULL);
00145   LWIP_ASSERT("netif already has a struct autoip set", netif->autoip == NULL);
00146 
00147   /* clear data structure */
00148   memset(autoip, 0, sizeof(struct autoip));
00149   /* autoip->state = AUTOIP_STATE_OFF; */
00150   netif->autoip = autoip;
00151 }
00152 
00153 /** Restart AutoIP client and check the next address (conflict detected)
00154  *
00155  * @param netif The netif under AutoIP control
00156  */
00157 static void
00158 autoip_restart(struct netif *netif)
00159 {
00160   netif->autoip->tried_llipaddr++;
00161   autoip_start(netif);
00162 }
00163 
00164 /**
00165  * Handle a IP address conflict after an ARP conflict detection
00166  */
00167 static void
00168 autoip_handle_arp_conflict(struct netif *netif)
00169 {
00170   /* Somehow detect if we are defending or retreating */
00171   unsigned char defend = 1; /* tbd */
00172 
00173   if(defend) {
00174     if(netif->autoip->lastconflict > 0) {
00175       /* retreat, there was a conflicting ARP in the last
00176        * DEFEND_INTERVAL seconds
00177        */
00178       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
00179         ("autoip_handle_arp_conflict(): we are defending, but in DEFEND_INTERVAL, retreating\n"));
00180 
00181       /* TODO: close all TCP sessions */
00182       autoip_restart(netif);
00183     } else {
00184       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
00185         ("autoip_handle_arp_conflict(): we are defend, send ARP Announce\n"));
00186       autoip_arp_announce(netif);
00187       netif->autoip->lastconflict = DEFEND_INTERVAL * AUTOIP_TICKS_PER_SECOND;
00188     }
00189   } else {
00190     LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
00191       ("autoip_handle_arp_conflict(): we do not defend, retreating\n"));
00192     /* TODO: close all TCP sessions */
00193     autoip_restart(netif);
00194   }
00195 }
00196 
00197 /**
00198  * Create an IP-Address out of range 169.254.1.0 to 169.254.254.255
00199  *
00200  * @param netif network interface on which create the IP-Address
00201  * @param ipaddr ip address to initialize
00202  */
00203 static void
00204 autoip_create_addr(struct netif *netif, ip_addr_t *ipaddr)
00205 {
00206   /* Here we create an IP-Address out of range 169.254.1.0 to 169.254.254.255
00207    * compliant to RFC 3927 Section 2.1
00208    * We have 254 * 256 possibilities */
00209 
00210   u32_t addr = ntohl(LWIP_AUTOIP_CREATE_SEED_ADDR(netif));
00211   addr += netif->autoip->tried_llipaddr;
00212   addr = AUTOIP_NET | (addr & 0xffff);
00213   /* Now, 169.254.0.0 <= addr <= 169.254.255.255 */ 
00214 
00215   if (addr < AUTOIP_RANGE_START) {
00216     addr += AUTOIP_RANGE_END - AUTOIP_RANGE_START + 1;
00217   }
00218   if (addr > AUTOIP_RANGE_END) {
00219     addr -= AUTOIP_RANGE_END - AUTOIP_RANGE_START + 1;
00220   }
00221   LWIP_ASSERT("AUTOIP address not in range", (addr >= AUTOIP_RANGE_START) &&
00222     (addr <= AUTOIP_RANGE_END));
00223   ip4_addr_set_u32(ipaddr, htonl(addr));
00224   
00225   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
00226     ("autoip_create_addr(): tried_llipaddr=%"U16_F", %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00227     (u16_t)(netif->autoip->tried_llipaddr), ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr),
00228     ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr)));
00229 }
00230 
00231 /**
00232  * Sends an ARP probe from a network interface
00233  *
00234  * @param netif network interface used to send the probe
00235  */
00236 static err_t
00237 autoip_arp_probe(struct netif *netif)
00238 {
00239   return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
00240     (struct eth_addr *)netif->hwaddr, IP_ADDR_ANY, &ethzero,
00241     &netif->autoip->llipaddr, ARP_REQUEST);
00242 }
00243 
00244 /**
00245  * Sends an ARP announce from a network interface
00246  *
00247  * @param netif network interface used to send the announce
00248  */
00249 static err_t
00250 autoip_arp_announce(struct netif *netif)
00251 {
00252   return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
00253     (struct eth_addr *)netif->hwaddr, &netif->autoip->llipaddr, &ethzero,
00254     &netif->autoip->llipaddr, ARP_REQUEST);
00255 }
00256 
00257 /**
00258  * Configure interface for use with current LL IP-Address
00259  *
00260  * @param netif network interface to configure with current LL IP-Address
00261  */
00262 static err_t
00263 autoip_bind(struct netif *netif)
00264 {
00265   struct autoip *autoip = netif->autoip;
00266   ip_addr_t sn_mask, gw_addr;
00267 
00268   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
00269     ("autoip_bind(netif=%p) %c%c%"U16_F" %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00270     (void*)netif, netif->name[0], netif->name[1], (u16_t)netif->num,
00271     ip4_addr1_16(&autoip->llipaddr), ip4_addr2_16(&autoip->llipaddr),
00272     ip4_addr3_16(&autoip->llipaddr), ip4_addr4_16(&autoip->llipaddr)));
00273 
00274   IP4_ADDR(&sn_mask, 255, 255, 0, 0);
00275   IP4_ADDR(&gw_addr, 0, 0, 0, 0);
00276 
00277   netif_set_ipaddr(netif, &autoip->llipaddr);
00278   netif_set_netmask(netif, &sn_mask);
00279   netif_set_gw(netif, &gw_addr);  
00280 
00281   /* bring the interface up */
00282   netif_set_up(netif);
00283 
00284   return ERR_OK;
00285 }
00286 
00287 /**
00288  * Start AutoIP client
00289  *
00290  * @param netif network interface on which start the AutoIP client
00291  */
00292 err_t
00293 autoip_start(struct netif *netif)
00294 {
00295   struct autoip *autoip = netif->autoip;
00296   err_t result = ERR_OK;
00297 
00298   if(netif_is_up(netif)) {
00299     netif_set_down(netif);
00300   }
00301 
00302   /* Set IP-Address, Netmask and Gateway to 0 to make sure that
00303    * ARP Packets are formed correctly
00304    */
00305   ip_addr_set_zero(&netif->ip_addr);
00306   ip_addr_set_zero(&netif->netmask);
00307   ip_addr_set_zero(&netif->gw);
00308 
00309   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
00310     ("autoip_start(netif=%p) %c%c%"U16_F"\n", (void*)netif, netif->name[0],
00311     netif->name[1], (u16_t)netif->num));
00312   if(autoip == NULL) {
00313     /* no AutoIP client attached yet? */
00314     LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
00315       ("autoip_start(): starting new AUTOIP client\n"));
00316     autoip = (struct autoip *)mem_malloc(sizeof(struct autoip));
00317     if(autoip == NULL) {
00318       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
00319         ("autoip_start(): could not allocate autoip\n"));
00320       return ERR_MEM;
00321     }
00322     memset(autoip, 0, sizeof(struct autoip));
00323     /* store this AutoIP client in the netif */
00324     netif->autoip = autoip;
00325     LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_start(): allocated autoip"));
00326   } else {
00327     autoip->state = AUTOIP_STATE_OFF;
00328     autoip->ttw = 0;
00329     autoip->sent_num = 0;
00330     ip_addr_set_zero(&autoip->llipaddr);
00331     autoip->lastconflict = 0;
00332   }
00333 
00334   autoip_create_addr(netif, &(autoip->llipaddr));
00335   autoip_start_probing(netif);
00336 
00337   return result;
00338 }
00339 
00340 static void
00341 autoip_start_probing(struct netif *netif)
00342 {
00343   struct autoip *autoip = netif->autoip;
00344 
00345   autoip->state = AUTOIP_STATE_PROBING;
00346   autoip->sent_num = 0;
00347   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
00348      ("autoip_start_probing(): changing state to PROBING: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00349       ip4_addr1_16(&netif->autoip->llipaddr), ip4_addr2_16(&netif->autoip->llipaddr),
00350       ip4_addr3_16(&netif->autoip->llipaddr), ip4_addr4_16(&netif->autoip->llipaddr)));
00351 
00352   /* time to wait to first probe, this is randomly
00353    * choosen out of 0 to PROBE_WAIT seconds.
00354    * compliant to RFC 3927 Section 2.2.1
00355    */
00356   autoip->ttw = (u16_t)(LWIP_AUTOIP_RAND(netif) % (PROBE_WAIT * AUTOIP_TICKS_PER_SECOND));
00357 
00358   /*
00359    * if we tried more then MAX_CONFLICTS we must limit our rate for
00360    * accquiring and probing address
00361    * compliant to RFC 3927 Section 2.2.1
00362    */
00363   if(autoip->tried_llipaddr > MAX_CONFLICTS) {
00364     autoip->ttw = RATE_LIMIT_INTERVAL * AUTOIP_TICKS_PER_SECOND;
00365   }
00366 }
00367 
00368 /**
00369  * Handle a possible change in the network configuration.
00370  *
00371  * If there is an AutoIP address configured, take the interface down
00372  * and begin probing with the same address.
00373  */
00374 void
00375 autoip_network_changed(struct netif *netif)
00376 {
00377   if (netif->autoip && netif->autoip->state != AUTOIP_STATE_OFF) {
00378     netif_set_down(netif);
00379     autoip_start_probing(netif);
00380   }
00381 }
00382 
00383 /**
00384  * Stop AutoIP client
00385  *
00386  * @param netif network interface on which stop the AutoIP client
00387  */
00388 err_t
00389 autoip_stop(struct netif *netif)
00390 {
00391   netif->autoip->state = AUTOIP_STATE_OFF;
00392   netif_set_down(netif);
00393   return ERR_OK;
00394 }
00395 
00396 /**
00397  * Has to be called in loop every AUTOIP_TMR_INTERVAL milliseconds
00398  */
00399 void
00400 autoip_tmr()
00401 {
00402   struct netif *netif = netif_list;
00403   /* loop through netif's */
00404   while (netif != NULL) {
00405     /* only act on AutoIP configured interfaces */
00406     if (netif->autoip != NULL) {
00407       if(netif->autoip->lastconflict > 0) {
00408         netif->autoip->lastconflict--;
00409       }
00410 
00411       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
00412         ("autoip_tmr() AutoIP-State: %"U16_F", ttw=%"U16_F"\n",
00413         (u16_t)(netif->autoip->state), netif->autoip->ttw));
00414 
00415       switch(netif->autoip->state) {
00416         case AUTOIP_STATE_PROBING:
00417           if(netif->autoip->ttw > 0) {
00418             netif->autoip->ttw--;
00419           } else {
00420             if(netif->autoip->sent_num >= PROBE_NUM) {
00421               netif->autoip->state = AUTOIP_STATE_ANNOUNCING;
00422               netif->autoip->sent_num = 0;
00423               netif->autoip->ttw = ANNOUNCE_WAIT * AUTOIP_TICKS_PER_SECOND;
00424               LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
00425                  ("autoip_tmr(): changing state to ANNOUNCING: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00426                   ip4_addr1_16(&netif->autoip->llipaddr), ip4_addr2_16(&netif->autoip->llipaddr),
00427                   ip4_addr3_16(&netif->autoip->llipaddr), ip4_addr4_16(&netif->autoip->llipaddr)));
00428             } else {
00429               autoip_arp_probe(netif);
00430               LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
00431                 ("autoip_tmr() PROBING Sent Probe\n"));
00432               netif->autoip->sent_num++;
00433               /* calculate time to wait to next probe */
00434               netif->autoip->ttw = (u16_t)((LWIP_AUTOIP_RAND(netif) %
00435                 ((PROBE_MAX - PROBE_MIN) * AUTOIP_TICKS_PER_SECOND) ) +
00436                 PROBE_MIN * AUTOIP_TICKS_PER_SECOND);
00437             }
00438           }
00439           break;
00440 
00441         case AUTOIP_STATE_ANNOUNCING:
00442           if(netif->autoip->ttw > 0) {
00443             netif->autoip->ttw--;
00444           } else {
00445             if(netif->autoip->sent_num == 0) {
00446              /* We are here the first time, so we waited ANNOUNCE_WAIT seconds
00447               * Now we can bind to an IP address and use it.
00448               *
00449               * autoip_bind calls netif_set_up. This triggers a gratuitous ARP
00450               * which counts as an announcement.
00451               */
00452               autoip_bind(netif);
00453             } else {
00454               autoip_arp_announce(netif);
00455               LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
00456                 ("autoip_tmr() ANNOUNCING Sent Announce\n"));
00457             }
00458             netif->autoip->ttw = ANNOUNCE_INTERVAL * AUTOIP_TICKS_PER_SECOND;
00459             netif->autoip->sent_num++;
00460 
00461             if(netif->autoip->sent_num >= ANNOUNCE_NUM) {
00462                 netif->autoip->state = AUTOIP_STATE_BOUND;
00463                 netif->autoip->sent_num = 0;
00464                 netif->autoip->ttw = 0;
00465                  LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
00466                     ("autoip_tmr(): changing state to BOUND: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00467                      ip4_addr1_16(&netif->autoip->llipaddr), ip4_addr2_16(&netif->autoip->llipaddr),
00468                      ip4_addr3_16(&netif->autoip->llipaddr), ip4_addr4_16(&netif->autoip->llipaddr)));
00469             }
00470           }
00471           break;
00472       }
00473     }
00474     /* proceed to next network interface */
00475     netif = netif->next;
00476   }
00477 }
00478 
00479 /**
00480  * Handles every incoming ARP Packet, called by etharp_arp_input.
00481  *
00482  * @param netif network interface to use for autoip processing
00483  * @param hdr Incoming ARP packet
00484  */
00485 void
00486 autoip_arp_reply(struct netif *netif, struct etharp_hdr *hdr)
00487 {
00488   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_arp_reply()\n"));
00489   if ((netif->autoip != NULL) && (netif->autoip->state != AUTOIP_STATE_OFF)) {
00490    /* when ip.src == llipaddr && hw.src != netif->hwaddr
00491     *
00492     * when probing  ip.dst == llipaddr && hw.src != netif->hwaddr
00493     * we have a conflict and must solve it
00494     */
00495     ip_addr_t sipaddr, dipaddr;
00496     struct eth_addr netifaddr;
00497     netifaddr.addr[0] = netif->hwaddr[0];
00498     netifaddr.addr[1] = netif->hwaddr[1];
00499     netifaddr.addr[2] = netif->hwaddr[2];
00500     netifaddr.addr[3] = netif->hwaddr[3];
00501     netifaddr.addr[4] = netif->hwaddr[4];
00502     netifaddr.addr[5] = netif->hwaddr[5];
00503 
00504     /* Copy struct ip_addr2 to aligned ip_addr, to support compilers without
00505      * structure packing (not using structure copy which breaks strict-aliasing rules).
00506      */
00507     IPADDR2_COPY(&sipaddr, &hdr->sipaddr);
00508     IPADDR2_COPY(&dipaddr, &hdr->dipaddr);
00509       
00510     if ((netif->autoip->state == AUTOIP_STATE_PROBING) ||
00511         ((netif->autoip->state == AUTOIP_STATE_ANNOUNCING) &&
00512          (netif->autoip->sent_num == 0))) {
00513      /* RFC 3927 Section 2.2.1:
00514       * from beginning to after ANNOUNCE_WAIT
00515       * seconds we have a conflict if
00516       * ip.src == llipaddr OR
00517       * ip.dst == llipaddr && hw.src != own hwaddr
00518       */
00519       if ((ip_addr_cmp(&sipaddr, &netif->autoip->llipaddr)) ||
00520           (ip_addr_cmp(&dipaddr, &netif->autoip->llipaddr) &&
00521            !eth_addr_cmp(&netifaddr, &hdr->shwaddr))) {
00522         LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | LWIP_DBG_LEVEL_WARNING,
00523           ("autoip_arp_reply(): Probe Conflict detected\n"));
00524         autoip_restart(netif);
00525       }
00526     } else {
00527      /* RFC 3927 Section 2.5:
00528       * in any state we have a conflict if
00529       * ip.src == llipaddr && hw.src != own hwaddr
00530       */
00531       if (ip_addr_cmp(&sipaddr, &netif->autoip->llipaddr) &&
00532           !eth_addr_cmp(&netifaddr, &hdr->shwaddr)) {
00533         LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | LWIP_DBG_LEVEL_WARNING,
00534           ("autoip_arp_reply(): Conflicting ARP-Packet detected\n"));
00535         autoip_handle_arp_conflict(netif);
00536       }
00537     }
00538   }
00539 }
00540 
00541 #endif /* LWIP_AUTOIP */