• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 /**
2  * @file
3  * AutoIP Automatic LinkLocal IP Configuration
4  *
5  */
6 
7 /*
8  *
9  * Copyright (c) 2007 Dominik Spies <kontakt@dspies.de>
10  * All rights reserved.
11  *
12  * Redistribution and use in source and binary forms, with or without modification,
13  * are permitted provided that the following conditions are met:
14  *
15  * 1. Redistributions of source code must retain the above copyright notice,
16  *    this list of conditions and the following disclaimer.
17  * 2. Redistributions in binary form must reproduce the above copyright notice,
18  *    this list of conditions and the following disclaimer in the documentation
19  *    and/or other materials provided with the distribution.
20  * 3. The name of the author may not be used to endorse or promote products
21  *    derived from this software without specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
24  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
25  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
26  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
27  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
28  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
29  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
30  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
31  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
32  * OF SUCH DAMAGE.
33  *
34  * Author: Dominik Spies <kontakt@dspies.de>
35  *
36  * This is a AutoIP implementation for the lwIP TCP/IP stack. It aims to conform
37  * with RFC 3927.
38  *
39  *
40  * Please coordinate changes and requests with Dominik Spies
41  * <kontakt@dspies.de>
42  */
43 
44 /*******************************************************************************
45  * USAGE:
46  *
47  * define LWIP_AUTOIP 1  in your lwipopts.h
48  *
49  * If you don't use tcpip.c (so, don't call, you don't call tcpip_init):
50  * - First, call autoip_init().
51  * - call autoip_tmr() all AUTOIP_TMR_INTERVAL msces,
52  *   that should be defined in autoip.h.
53  *   I recommend a value of 100. The value must divide 1000 with a remainder almost 0.
54  *   Possible values are 1000, 500, 333, 250, 200, 166, 142, 125, 111, 100 ....
55  *
56  * Without DHCP:
57  * - Call autoip_start() after netif_add().
58  *
59  * With DHCP:
60  * - define LWIP_DHCP_AUTOIP_COOP 1 in your lwipopts.h.
61  * - Configure your DHCP Client.
62  *
63  */
64 
65 #include "lwip/opt.h"
66 
67 #if LWIP_AUTOIP /* don't build if not configured for use in lwipopts.h */
68 
69 #include "lwip/mem.h"
70 #include "lwip/udp.h"
71 #include "lwip/ip_addr.h"
72 #include "lwip/netif.h"
73 #include "lwip/autoip.h"
74 #include "netif/etharp.h"
75 
76 #include <stdlib.h>
77 #include <string.h>
78 
79 /* 169.254.0.0 */
80 #define AUTOIP_NET         0xA9FE0000
81 /* 169.254.1.0 */
82 #define AUTOIP_RANGE_START (AUTOIP_NET | 0x0100)
83 /* 169.254.254.255 */
84 #define AUTOIP_RANGE_END   (AUTOIP_NET | 0xFEFF)
85 
86 
87 /** Pseudo random macro based on netif informations.
88  * You could use "rand()" from the C Library if you define LWIP_AUTOIP_RAND in lwipopts.h */
89 #ifndef LWIP_AUTOIP_RAND
90 #define LWIP_AUTOIP_RAND(netif) ( (((u32_t)((netif->hwaddr[5]) & 0xff) << 24) | \
91                                    ((u32_t)((netif->hwaddr[3]) & 0xff) << 16) | \
92                                    ((u32_t)((netif->hwaddr[2]) & 0xff) << 8) | \
93                                    ((u32_t)((netif->hwaddr[4]) & 0xff))) + \
94                                    (netif->autoip?netif->autoip->tried_llipaddr:0))
95 #endif /* LWIP_AUTOIP_RAND */
96 
97 /**
98  * Macro that generates the initial IP address to be tried by AUTOIP.
99  * If you want to override this, define it to something else in lwipopts.h.
100  */
101 #ifndef LWIP_AUTOIP_CREATE_SEED_ADDR
102 #define LWIP_AUTOIP_CREATE_SEED_ADDR(netif) \
103   htonl(AUTOIP_RANGE_START + ((u32_t)(((u8_t)(netif->hwaddr[4])) | \
104                  ((u32_t)((u8_t)(netif->hwaddr[5]))) << 8)))
105 #endif /* LWIP_AUTOIP_CREATE_SEED_ADDR */
106 
107 /* static functions */
108 static void autoip_handle_arp_conflict(struct netif *netif);
109 
110 /* creates a pseudo random LL IP-Address for a network interface */
111 static void autoip_create_addr(struct netif *netif, ip_addr_t *ipaddr);
112 
113 /* sends an ARP probe */
114 static err_t autoip_arp_probe(struct netif *netif);
115 
116 /* sends an ARP announce */
117 static err_t autoip_arp_announce(struct netif *netif);
118 
119 /* configure interface for use with current LL IP-Address */
120 static err_t autoip_bind(struct netif *netif);
121 
122 /* start sending probes for llipaddr */
123 static void autoip_start_probing(struct netif *netif);
124 
125 /**
126  * Initialize this module
127  */
128 void
autoip_init(void)129 autoip_init(void)
130 {
131   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_init()\n"));
132 }
133 
134 /** Set a statically allocated struct autoip to work with.
135  * Using this prevents autoip_start to allocate it using mem_malloc.
136  *
137  * @param netif the netif for which to set the struct autoip
138  * @param dhcp (uninitialised) dhcp struct allocated by the application
139  */
140 void
autoip_set_struct(struct netif * netif,struct autoip * autoip)141 autoip_set_struct(struct netif *netif, struct autoip *autoip)
142 {
143   LWIP_ASSERT("netif != NULL", netif != NULL);
144   LWIP_ASSERT("autoip != NULL", autoip != NULL);
145   LWIP_ASSERT("netif already has a struct autoip set", netif->autoip == NULL);
146 
147   /* clear data structure */
148   memset(autoip, 0, sizeof(struct autoip));
149   /* autoip->state = AUTOIP_STATE_OFF; */
150   netif->autoip = autoip;
151 }
152 
153 /** Restart AutoIP client and check the next address (conflict detected)
154  *
155  * @param netif The netif under AutoIP control
156  */
157 static void
autoip_restart(struct netif * netif)158 autoip_restart(struct netif *netif)
159 {
160   netif->autoip->tried_llipaddr++;
161   autoip_start(netif);
162 }
163 
164 /**
165  * Handle a IP address conflict after an ARP conflict detection
166  */
167 static void
autoip_handle_arp_conflict(struct netif * netif)168 autoip_handle_arp_conflict(struct netif *netif)
169 {
170   /* Somehow detect if we are defending or retreating */
171   unsigned char defend = 1; /* tbd */
172 
173   if(defend) {
174     if(netif->autoip->lastconflict > 0) {
175       /* retreat, there was a conflicting ARP in the last
176        * DEFEND_INTERVAL seconds
177        */
178       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
179         ("autoip_handle_arp_conflict(): we are defending, but in DEFEND_INTERVAL, retreating\n"));
180 
181       /* TODO: close all TCP sessions */
182       autoip_restart(netif);
183     } else {
184       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
185         ("autoip_handle_arp_conflict(): we are defend, send ARP Announce\n"));
186       autoip_arp_announce(netif);
187       netif->autoip->lastconflict = DEFEND_INTERVAL * AUTOIP_TICKS_PER_SECOND;
188     }
189   } else {
190     LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
191       ("autoip_handle_arp_conflict(): we do not defend, retreating\n"));
192     /* TODO: close all TCP sessions */
193     autoip_restart(netif);
194   }
195 }
196 
197 /**
198  * Create an IP-Address out of range 169.254.1.0 to 169.254.254.255
199  *
200  * @param netif network interface on which create the IP-Address
201  * @param ipaddr ip address to initialize
202  */
203 static void
autoip_create_addr(struct netif * netif,ip_addr_t * ipaddr)204 autoip_create_addr(struct netif *netif, ip_addr_t *ipaddr)
205 {
206   /* Here we create an IP-Address out of range 169.254.1.0 to 169.254.254.255
207    * compliant to RFC 3927 Section 2.1
208    * We have 254 * 256 possibilities */
209 
210   u32_t addr = ntohl(LWIP_AUTOIP_CREATE_SEED_ADDR(netif));
211   addr += netif->autoip->tried_llipaddr;
212   addr = AUTOIP_NET | (addr & 0xffff);
213   /* Now, 169.254.0.0 <= addr <= 169.254.255.255 */
214 
215   if (addr < AUTOIP_RANGE_START) {
216     addr += AUTOIP_RANGE_END - AUTOIP_RANGE_START + 1;
217   }
218   if (addr > AUTOIP_RANGE_END) {
219     addr -= AUTOIP_RANGE_END - AUTOIP_RANGE_START + 1;
220   }
221   LWIP_ASSERT("AUTOIP address not in range", (addr >= AUTOIP_RANGE_START) &&
222     (addr <= AUTOIP_RANGE_END));
223   ip4_addr_set_u32(ipaddr, htonl(addr));
224 
225   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
226     ("autoip_create_addr(): tried_llipaddr=%"U16_F", %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
227     (u16_t)(netif->autoip->tried_llipaddr), ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr),
228     ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr)));
229 }
230 
231 /**
232  * Sends an ARP probe from a network interface
233  *
234  * @param netif network interface used to send the probe
235  */
236 static err_t
autoip_arp_probe(struct netif * netif)237 autoip_arp_probe(struct netif *netif)
238 {
239   return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
240     (struct eth_addr *)netif->hwaddr, IP_ADDR_ANY, &ethzero,
241     &netif->autoip->llipaddr, ARP_REQUEST);
242 }
243 
244 /**
245  * Sends an ARP announce from a network interface
246  *
247  * @param netif network interface used to send the announce
248  */
249 static err_t
autoip_arp_announce(struct netif * netif)250 autoip_arp_announce(struct netif *netif)
251 {
252   return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
253     (struct eth_addr *)netif->hwaddr, &netif->autoip->llipaddr, &ethzero,
254     &netif->autoip->llipaddr, ARP_REQUEST);
255 }
256 
257 /**
258  * Configure interface for use with current LL IP-Address
259  *
260  * @param netif network interface to configure with current LL IP-Address
261  */
262 static err_t
autoip_bind(struct netif * netif)263 autoip_bind(struct netif *netif)
264 {
265   struct autoip *autoip = netif->autoip;
266   ip_addr_t sn_mask, gw_addr;
267 
268   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
269     ("autoip_bind(netif=%p) %c%c%"U16_F" %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
270     (void*)netif, netif->name[0], netif->name[1], (u16_t)netif->num,
271     ip4_addr1_16(&autoip->llipaddr), ip4_addr2_16(&autoip->llipaddr),
272     ip4_addr3_16(&autoip->llipaddr), ip4_addr4_16(&autoip->llipaddr)));
273 
274   IP4_ADDR(&sn_mask, 255, 255, 0, 0);
275   IP4_ADDR(&gw_addr, 0, 0, 0, 0);
276 
277   netif_set_ipaddr(netif, &autoip->llipaddr);
278   netif_set_netmask(netif, &sn_mask);
279   netif_set_gw(netif, &gw_addr);
280 
281   /* bring the interface up */
282   netif_set_up(netif);
283 
284   return ERR_OK;
285 }
286 
287 /**
288  * Start AutoIP client
289  *
290  * @param netif network interface on which start the AutoIP client
291  */
292 err_t
autoip_start(struct netif * netif)293 autoip_start(struct netif *netif)
294 {
295   struct autoip *autoip = netif->autoip;
296   err_t result = ERR_OK;
297 
298   if(netif_is_up(netif)) {
299     netif_set_down(netif);
300   }
301 
302   /* Set IP-Address, Netmask and Gateway to 0 to make sure that
303    * ARP Packets are formed correctly
304    */
305   ip_addr_set_zero(&netif->ip_addr);
306   ip_addr_set_zero(&netif->netmask);
307   ip_addr_set_zero(&netif->gw);
308 
309   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
310     ("autoip_start(netif=%p) %c%c%"U16_F"\n", (void*)netif, netif->name[0],
311     netif->name[1], (u16_t)netif->num));
312   if(autoip == NULL) {
313     /* no AutoIP client attached yet? */
314     LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
315       ("autoip_start(): starting new AUTOIP client\n"));
316     autoip = (struct autoip *)mem_malloc(sizeof(struct autoip));
317     if(autoip == NULL) {
318       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
319         ("autoip_start(): could not allocate autoip\n"));
320       return ERR_MEM;
321     }
322     memset(autoip, 0, sizeof(struct autoip));
323     /* store this AutoIP client in the netif */
324     netif->autoip = autoip;
325     LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_start(): allocated autoip"));
326   } else {
327     autoip->state = AUTOIP_STATE_OFF;
328     autoip->ttw = 0;
329     autoip->sent_num = 0;
330     ip_addr_set_zero(&autoip->llipaddr);
331     autoip->lastconflict = 0;
332   }
333 
334   autoip_create_addr(netif, &(autoip->llipaddr));
335   autoip_start_probing(netif);
336 
337   return result;
338 }
339 
340 static void
autoip_start_probing(struct netif * netif)341 autoip_start_probing(struct netif *netif)
342 {
343   struct autoip *autoip = netif->autoip;
344 
345   autoip->state = AUTOIP_STATE_PROBING;
346   autoip->sent_num = 0;
347   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
348      ("autoip_start_probing(): changing state to PROBING: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
349       ip4_addr1_16(&netif->autoip->llipaddr), ip4_addr2_16(&netif->autoip->llipaddr),
350       ip4_addr3_16(&netif->autoip->llipaddr), ip4_addr4_16(&netif->autoip->llipaddr)));
351 
352   /* time to wait to first probe, this is randomly
353    * choosen out of 0 to PROBE_WAIT seconds.
354    * compliant to RFC 3927 Section 2.2.1
355    */
356   autoip->ttw = (u16_t)(LWIP_AUTOIP_RAND(netif) % (PROBE_WAIT * AUTOIP_TICKS_PER_SECOND));
357 
358   /*
359    * if we tried more then MAX_CONFLICTS we must limit our rate for
360    * accquiring and probing address
361    * compliant to RFC 3927 Section 2.2.1
362    */
363   if(autoip->tried_llipaddr > MAX_CONFLICTS) {
364     autoip->ttw = RATE_LIMIT_INTERVAL * AUTOIP_TICKS_PER_SECOND;
365   }
366 }
367 
368 /**
369  * Handle a possible change in the network configuration.
370  *
371  * If there is an AutoIP address configured, take the interface down
372  * and begin probing with the same address.
373  */
374 void
autoip_network_changed(struct netif * netif)375 autoip_network_changed(struct netif *netif)
376 {
377   if (netif->autoip && netif->autoip->state != AUTOIP_STATE_OFF) {
378     netif_set_down(netif);
379     autoip_start_probing(netif);
380   }
381 }
382 
383 /**
384  * Stop AutoIP client
385  *
386  * @param netif network interface on which stop the AutoIP client
387  */
388 err_t
autoip_stop(struct netif * netif)389 autoip_stop(struct netif *netif)
390 {
391   netif->autoip->state = AUTOIP_STATE_OFF;
392   netif_set_down(netif);
393   return ERR_OK;
394 }
395 
396 /**
397  * Has to be called in loop every AUTOIP_TMR_INTERVAL milliseconds
398  */
399 void
autoip_tmr()400 autoip_tmr()
401 {
402   struct netif *netif = netif_list;
403   /* loop through netif's */
404   while (netif != NULL) {
405     /* only act on AutoIP configured interfaces */
406     if (netif->autoip != NULL) {
407       if(netif->autoip->lastconflict > 0) {
408         netif->autoip->lastconflict--;
409       }
410 
411       LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
412         ("autoip_tmr() AutoIP-State: %"U16_F", ttw=%"U16_F"\n",
413         (u16_t)(netif->autoip->state), netif->autoip->ttw));
414 
415       switch(netif->autoip->state) {
416         case AUTOIP_STATE_PROBING:
417           if(netif->autoip->ttw > 0) {
418             netif->autoip->ttw--;
419           } else {
420             if(netif->autoip->sent_num >= PROBE_NUM) {
421               netif->autoip->state = AUTOIP_STATE_ANNOUNCING;
422               netif->autoip->sent_num = 0;
423               netif->autoip->ttw = ANNOUNCE_WAIT * AUTOIP_TICKS_PER_SECOND;
424               LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
425                  ("autoip_tmr(): changing state to ANNOUNCING: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
426                   ip4_addr1_16(&netif->autoip->llipaddr), ip4_addr2_16(&netif->autoip->llipaddr),
427                   ip4_addr3_16(&netif->autoip->llipaddr), ip4_addr4_16(&netif->autoip->llipaddr)));
428             } else {
429               autoip_arp_probe(netif);
430               LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
431                 ("autoip_tmr() PROBING Sent Probe\n"));
432               netif->autoip->sent_num++;
433               /* calculate time to wait to next probe */
434               netif->autoip->ttw = (u16_t)((LWIP_AUTOIP_RAND(netif) %
435                 ((PROBE_MAX - PROBE_MIN) * AUTOIP_TICKS_PER_SECOND) ) +
436                 PROBE_MIN * AUTOIP_TICKS_PER_SECOND);
437             }
438           }
439           break;
440 
441         case AUTOIP_STATE_ANNOUNCING:
442           if(netif->autoip->ttw > 0) {
443             netif->autoip->ttw--;
444           } else {
445             if(netif->autoip->sent_num == 0) {
446              /* We are here the first time, so we waited ANNOUNCE_WAIT seconds
447               * Now we can bind to an IP address and use it.
448               *
449               * autoip_bind calls netif_set_up. This triggers a gratuitous ARP
450               * which counts as an announcement.
451               */
452               autoip_bind(netif);
453             } else {
454               autoip_arp_announce(netif);
455               LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
456                 ("autoip_tmr() ANNOUNCING Sent Announce\n"));
457             }
458             netif->autoip->ttw = ANNOUNCE_INTERVAL * AUTOIP_TICKS_PER_SECOND;
459             netif->autoip->sent_num++;
460 
461             if(netif->autoip->sent_num >= ANNOUNCE_NUM) {
462                 netif->autoip->state = AUTOIP_STATE_BOUND;
463                 netif->autoip->sent_num = 0;
464                 netif->autoip->ttw = 0;
465                  LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
466                     ("autoip_tmr(): changing state to BOUND: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
467                      ip4_addr1_16(&netif->autoip->llipaddr), ip4_addr2_16(&netif->autoip->llipaddr),
468                      ip4_addr3_16(&netif->autoip->llipaddr), ip4_addr4_16(&netif->autoip->llipaddr)));
469             }
470           }
471           break;
472       }
473     }
474     /* proceed to next network interface */
475     netif = netif->next;
476   }
477 }
478 
479 /**
480  * Handles every incoming ARP Packet, called by etharp_arp_input.
481  *
482  * @param netif network interface to use for autoip processing
483  * @param hdr Incoming ARP packet
484  */
485 void
autoip_arp_reply(struct netif * netif,struct etharp_hdr * hdr)486 autoip_arp_reply(struct netif *netif, struct etharp_hdr *hdr)
487 {
488   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_arp_reply()\n"));
489   if ((netif->autoip != NULL) && (netif->autoip->state != AUTOIP_STATE_OFF)) {
490    /* when ip.src == llipaddr && hw.src != netif->hwaddr
491     *
492     * when probing  ip.dst == llipaddr && hw.src != netif->hwaddr
493     * we have a conflict and must solve it
494     */
495     ip_addr_t sipaddr, dipaddr;
496     struct eth_addr netifaddr;
497     ETHADDR16_COPY(netifaddr.addr, netif->hwaddr);
498 
499     /* Copy struct ip_addr2 to aligned ip_addr, to support compilers without
500      * structure packing (not using structure copy which breaks strict-aliasing rules).
501      */
502     IPADDR2_COPY(&sipaddr, &hdr->sipaddr);
503     IPADDR2_COPY(&dipaddr, &hdr->dipaddr);
504 
505     if ((netif->autoip->state == AUTOIP_STATE_PROBING) ||
506         ((netif->autoip->state == AUTOIP_STATE_ANNOUNCING) &&
507          (netif->autoip->sent_num == 0))) {
508      /* RFC 3927 Section 2.2.1:
509       * from beginning to after ANNOUNCE_WAIT
510       * seconds we have a conflict if
511       * ip.src == llipaddr OR
512       * ip.dst == llipaddr && hw.src != own hwaddr
513       */
514       if ((ip_addr_cmp(&sipaddr, &netif->autoip->llipaddr)) ||
515           (ip_addr_cmp(&dipaddr, &netif->autoip->llipaddr) &&
516            !eth_addr_cmp(&netifaddr, &hdr->shwaddr))) {
517         LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | LWIP_DBG_LEVEL_WARNING,
518           ("autoip_arp_reply(): Probe Conflict detected\n"));
519         autoip_restart(netif);
520       }
521     } else {
522      /* RFC 3927 Section 2.5:
523       * in any state we have a conflict if
524       * ip.src == llipaddr && hw.src != own hwaddr
525       */
526       if (ip_addr_cmp(&sipaddr, &netif->autoip->llipaddr) &&
527           !eth_addr_cmp(&netifaddr, &hdr->shwaddr)) {
528         LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | LWIP_DBG_LEVEL_WARNING,
529           ("autoip_arp_reply(): Conflicting ARP-Packet detected\n"));
530         autoip_handle_arp_conflict(netif);
531       }
532     }
533   }
534 }
535 
536 #endif /* LWIP_AUTOIP */
537