lwip_etharp.c

00001 /**
00002  * @file
00003  * Address Resolution Protocol module for IP over Ethernet
00004  *
00005  * Functionally, ARP is divided into two parts. The first maps an IP address
00006  * to a physical address when sending a packet, and the second part answers
00007  * requests from other machines for our physical address.
00008  *
00009  * This implementation complies with RFC 826 (Ethernet ARP). It supports
00010  * Gratuitious ARP from RFC3220 (IP Mobility Support for IPv4) section 4.6
00011  * if an interface calls etharp_gratuitous(our_netif) upon address change.
00012  */
00013 
00014 /*
00015  * Copyright (c) 2001-2003 Swedish Institute of Computer Science.
00016  * Copyright (c) 2003-2004 Leon Woestenberg <leon.woestenberg@axon.tv>
00017  * Copyright (c) 2003-2004 Axon Digital Design B.V., The Netherlands.
00018  * All rights reserved.
00019  *
00020  * Redistribution and use in source and binary forms, with or without modification,
00021  * are permitted provided that the following conditions are met:
00022  *
00023  * 1. Redistributions of source code must retain the above copyright notice,
00024  *    this list of conditions and the following disclaimer.
00025  * 2. Redistributions in binary form must reproduce the above copyright notice,
00026  *    this list of conditions and the following disclaimer in the documentation
00027  *    and/or other materials provided with the distribution.
00028  * 3. The name of the author may not be used to endorse or promote products
00029  *    derived from this software without specific prior written permission.
00030  *
00031  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
00032  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
00033  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
00034  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00035  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
00036  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00037  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
00038  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
00039  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
00040  * OF SUCH DAMAGE.
00041  *
00042  * This file is part of the lwIP TCP/IP stack.
00043  *
00044  */
00045 
00046 #include "lwip/opt.h"
00047 
00048 #if LWIP_ARP || LWIP_ETHERNET
00049 
00050 #include "lwip/etharp.h"
00051 #include "lwip/stats.h"
00052 #include "lwip/snmp.h"
00053 #include "lwip/dhcp.h"
00054 #include "lwip/autoip.h"
00055 #include "netif/lwip_ethernet.h"
00056 
00057 #include <string.h>
00058 
00059 #if LWIP_IPV4 && LWIP_ARP /* don't build if not configured for use in lwipopts.h */
00060 
00061 /** Re-request a used ARP entry 1 minute before it would expire to prevent
00062  *  breaking a steadily used connection because the ARP entry timed out. */
00063 #define ARP_AGE_REREQUEST_USED_UNICAST   (ARP_MAXAGE - 30)
00064 #define ARP_AGE_REREQUEST_USED_BROADCAST (ARP_MAXAGE - 15)
00065 
00066 /** the time an ARP entry stays pending after first request,
00067  *  for ARP_TMR_INTERVAL = 1000, this is
00068  *  10 seconds.
00069  *
00070  *  @internal Keep this number at least 2, otherwise it might
00071  *  run out instantly if the timeout occurs directly after a request.
00072  */
00073 #define ARP_MAXPENDING 5
00074 
00075 /** ARP states */
00076 enum etharp_state {
00077   ETHARP_STATE_EMPTY = 0,
00078   ETHARP_STATE_PENDING,
00079   ETHARP_STATE_STABLE,
00080   ETHARP_STATE_STABLE_REREQUESTING_1,
00081   ETHARP_STATE_STABLE_REREQUESTING_2
00082 #if ETHARP_SUPPORT_STATIC_ENTRIES
00083   ,ETHARP_STATE_STATIC
00084 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00085 };
00086 
00087 struct etharp_entry {
00088 #if ARP_QUEUEING
00089   /** Pointer to queue of pending outgoing packets on this ARP entry. */
00090   struct etharp_q_entry *q;
00091 #else /* ARP_QUEUEING */
00092   /** Pointer to a single pending outgoing packet on this ARP entry. */
00093   struct pbuf *q;
00094 #endif /* ARP_QUEUEING */
00095   ip4_addr_t ipaddr;
00096   struct netif *netif;
00097   struct eth_addr ethaddr;
00098   u16_t ctime;
00099   u8_t state;
00100 };
00101 
00102 static struct etharp_entry arp_table[ARP_TABLE_SIZE];
00103 
00104 #if !LWIP_NETIF_HWADDRHINT
00105 static u8_t etharp_cached_entry;
00106 #endif /* !LWIP_NETIF_HWADDRHINT */
00107 
00108 /** Try hard to create a new entry - we want the IP address to appear in
00109     the cache (even if this means removing an active entry or so). */
00110 #define ETHARP_FLAG_TRY_HARD     1
00111 #define ETHARP_FLAG_FIND_ONLY    2
00112 #if ETHARP_SUPPORT_STATIC_ENTRIES
00113 #define ETHARP_FLAG_STATIC_ENTRY 4
00114 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00115 
00116 #if LWIP_NETIF_HWADDRHINT
00117 #define ETHARP_SET_HINT(netif, hint)  if (((netif) != NULL) && ((netif)->addr_hint != NULL))  \
00118                                       *((netif)->addr_hint) = (hint);
00119 #else /* LWIP_NETIF_HWADDRHINT */
00120 #define ETHARP_SET_HINT(netif, hint)  (etharp_cached_entry = (hint))
00121 #endif /* LWIP_NETIF_HWADDRHINT */
00122 
00123 
00124 /* Some checks, instead of etharp_init(): */
00125 #if (LWIP_ARP && (ARP_TABLE_SIZE > 0x7f))
00126   #error "ARP_TABLE_SIZE must fit in an s8_t, you have to reduce it in your lwipopts.h"
00127 #endif
00128 
00129 
00130 static err_t etharp_request_dst(struct netif *netif, const ip4_addr_t *ipaddr, const struct eth_addr* hw_dst_addr);
00131 
00132 
00133 #if ARP_QUEUEING
00134 /**
00135  * Free a complete queue of etharp entries
00136  *
00137  * @param q a qeueue of etharp_q_entry's to free
00138  */
00139 static void
00140 free_etharp_q(struct etharp_q_entry *q)
00141 {
00142   struct etharp_q_entry *r;
00143   LWIP_ASSERT("q != NULL", q != NULL);
00144   LWIP_ASSERT("q->p != NULL", q->p != NULL);
00145   while (q) {
00146     r = q;
00147     q = q->next;
00148     LWIP_ASSERT("r->p != NULL", (r->p != NULL));
00149     pbuf_free(r->p);
00150     memp_free(MEMP_ARP_QUEUE, r);
00151   }
00152 }
00153 #else /* ARP_QUEUEING */
00154 
00155 /** Compatibility define: free the queued pbuf */
00156 #define free_etharp_q(q) pbuf_free(q)
00157 
00158 #endif /* ARP_QUEUEING */
00159 
00160 /** Clean up ARP table entries */
00161 static void
00162 etharp_free_entry(int i)
00163 {
00164   /* remove from SNMP ARP index tree */
00165   mib2_remove_arp_entry(arp_table[i].netif, &arp_table[i].ipaddr);
00166   /* and empty packet queue */
00167   if (arp_table[i].q != NULL) {
00168     /* remove all queued packets */
00169     LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_free_entry: freeing entry %"U16_F", packet queue %p.\n", (u16_t)i, (void *)(arp_table[i].q)));
00170     free_etharp_q(arp_table[i].q);
00171     arp_table[i].q = NULL;
00172   }
00173   /* recycle entry for re-use */
00174   arp_table[i].state = ETHARP_STATE_EMPTY;
00175 #ifdef LWIP_DEBUG
00176   /* for debugging, clean out the complete entry */
00177   arp_table[i].ctime = 0;
00178   arp_table[i].netif = NULL;
00179   ip4_addr_set_zero(&arp_table[i].ipaddr);
00180   arp_table[i].ethaddr = ethzero;
00181 #endif /* LWIP_DEBUG */
00182 }
00183 
00184 /**
00185  * Clears expired entries in the ARP table.
00186  *
00187  * This function should be called every ARP_TMR_INTERVAL milliseconds (1 second),
00188  * in order to expire entries in the ARP table.
00189  */
00190 void
00191 etharp_tmr(void)
00192 {
00193   u8_t i;
00194 
00195   LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer\n"));
00196   /* remove expired entries from the ARP table */
00197   for (i = 0; i < ARP_TABLE_SIZE; ++i) {
00198     u8_t state = arp_table[i].state;
00199     if (state != ETHARP_STATE_EMPTY
00200 #if ETHARP_SUPPORT_STATIC_ENTRIES
00201       && (state != ETHARP_STATE_STATIC)
00202 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00203       ) {
00204       arp_table[i].ctime++;
00205       if ((arp_table[i].ctime >= ARP_MAXAGE) ||
00206           ((arp_table[i].state == ETHARP_STATE_PENDING)  &&
00207            (arp_table[i].ctime >= ARP_MAXPENDING))) {
00208         /* pending or stable entry has become old! */
00209         LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer: expired %s entry %"U16_F".\n",
00210              arp_table[i].state >= ETHARP_STATE_STABLE ? "stable" : "pending", (u16_t)i));
00211         /* clean up entries that have just been expired */
00212         etharp_free_entry(i);
00213       } else if (arp_table[i].state == ETHARP_STATE_STABLE_REREQUESTING_1) {
00214         /* Don't send more than one request every 2 seconds. */
00215         arp_table[i].state = ETHARP_STATE_STABLE_REREQUESTING_2;
00216       } else if (arp_table[i].state == ETHARP_STATE_STABLE_REREQUESTING_2) {
00217         /* Reset state to stable, so that the next transmitted packet will
00218            re-send an ARP request. */
00219         arp_table[i].state = ETHARP_STATE_STABLE;
00220       } else if (arp_table[i].state == ETHARP_STATE_PENDING) {
00221         /* still pending, resend an ARP query */
00222         etharp_request(arp_table[i].netif, &arp_table[i].ipaddr);
00223       }
00224     }
00225   }
00226 }
00227 
00228 /**
00229  * Search the ARP table for a matching or new entry.
00230  *
00231  * If an IP address is given, return a pending or stable ARP entry that matches
00232  * the address. If no match is found, create a new entry with this address set,
00233  * but in state ETHARP_EMPTY. The caller must check and possibly change the
00234  * state of the returned entry.
00235  *
00236  * If ipaddr is NULL, return a initialized new entry in state ETHARP_EMPTY.
00237  *
00238  * In all cases, attempt to create new entries from an empty entry. If no
00239  * empty entries are available and ETHARP_FLAG_TRY_HARD flag is set, recycle
00240  * old entries. Heuristic choose the least important entry for recycling.
00241  *
00242  * @param ipaddr IP address to find in ARP cache, or to add if not found.
00243  * @param flags See @ref etharp_state
00244  * @param netif netif related to this address (used for NETIF_HWADDRHINT)
00245  *
00246  * @return The ARP entry index that matched or is created, ERR_MEM if no
00247  * entry is found or could be recycled.
00248  */
00249 static s8_t
00250 etharp_find_entry(const ip4_addr_t *ipaddr, u8_t flags, struct netif* netif)
00251 {
00252   s8_t old_pending = ARP_TABLE_SIZE, old_stable = ARP_TABLE_SIZE;
00253   s8_t empty = ARP_TABLE_SIZE;
00254   u8_t i = 0;
00255   /* oldest entry with packets on queue */
00256   s8_t old_queue = ARP_TABLE_SIZE;
00257   /* its age */
00258   u16_t age_queue = 0, age_pending = 0, age_stable = 0;
00259 
00260   LWIP_UNUSED_ARG(netif);
00261 
00262   /**
00263    * a) do a search through the cache, remember candidates
00264    * b) select candidate entry
00265    * c) create new entry
00266    */
00267 
00268   /* a) in a single search sweep, do all of this
00269    * 1) remember the first empty entry (if any)
00270    * 2) remember the oldest stable entry (if any)
00271    * 3) remember the oldest pending entry without queued packets (if any)
00272    * 4) remember the oldest pending entry with queued packets (if any)
00273    * 5) search for a matching IP entry, either pending or stable
00274    *    until 5 matches, or all entries are searched for.
00275    */
00276 
00277   for (i = 0; i < ARP_TABLE_SIZE; ++i) {
00278     u8_t state = arp_table[i].state;
00279     /* no empty entry found yet and now we do find one? */
00280     if ((empty == ARP_TABLE_SIZE) && (state == ETHARP_STATE_EMPTY)) {
00281       LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_find_entry: found empty entry %"U16_F"\n", (u16_t)i));
00282       /* remember first empty entry */
00283       empty = i;
00284     } else if (state != ETHARP_STATE_EMPTY) {
00285       LWIP_ASSERT("state == ETHARP_STATE_PENDING || state >= ETHARP_STATE_STABLE",
00286         state == ETHARP_STATE_PENDING || state >= ETHARP_STATE_STABLE);
00287       /* if given, does IP address match IP address in ARP entry? */
00288       if (ipaddr && ip4_addr_cmp(ipaddr, &arp_table[i].ipaddr)
00289 #if ETHARP_TABLE_MATCH_NETIF
00290           && ((netif == NULL) || (netif == arp_table[i].netif))
00291 #endif /* ETHARP_TABLE_MATCH_NETIF */
00292         ) {
00293         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: found matching entry %"U16_F"\n", (u16_t)i));
00294         /* found exact IP address match, simply bail out */
00295         return i;
00296       }
00297       /* pending entry? */
00298       if (state == ETHARP_STATE_PENDING) {
00299         /* pending with queued packets? */
00300         if (arp_table[i].q != NULL) {
00301           if (arp_table[i].ctime >= age_queue) {
00302             old_queue = i;
00303             age_queue = arp_table[i].ctime;
00304           }
00305         } else
00306         /* pending without queued packets? */
00307         {
00308           if (arp_table[i].ctime >= age_pending) {
00309             old_pending = i;
00310             age_pending = arp_table[i].ctime;
00311           }
00312         }
00313       /* stable entry? */
00314       } else if (state >= ETHARP_STATE_STABLE) {
00315 #if ETHARP_SUPPORT_STATIC_ENTRIES
00316         /* don't record old_stable for static entries since they never expire */
00317         if (state < ETHARP_STATE_STATIC)
00318 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00319         {
00320           /* remember entry with oldest stable entry in oldest, its age in maxtime */
00321           if (arp_table[i].ctime >= age_stable) {
00322             old_stable = i;
00323             age_stable = arp_table[i].ctime;
00324           }
00325         }
00326       }
00327     }
00328   }
00329   /* { we have no match } => try to create a new entry */
00330 
00331   /* don't create new entry, only search? */
00332   if (((flags & ETHARP_FLAG_FIND_ONLY) != 0) ||
00333       /* or no empty entry found and not allowed to recycle? */
00334       ((empty == ARP_TABLE_SIZE) && ((flags & ETHARP_FLAG_TRY_HARD) == 0))) {
00335     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: no empty entry found and not allowed to recycle\n"));
00336     return (s8_t)ERR_MEM;
00337   }
00338 
00339   /* b) choose the least destructive entry to recycle:
00340    * 1) empty entry
00341    * 2) oldest stable entry
00342    * 3) oldest pending entry without queued packets
00343    * 4) oldest pending entry with queued packets
00344    *
00345    * { ETHARP_FLAG_TRY_HARD is set at this point }
00346    */
00347 
00348   /* 1) empty entry available? */
00349   if (empty < ARP_TABLE_SIZE) {
00350     i = empty;
00351     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting empty entry %"U16_F"\n", (u16_t)i));
00352   } else {
00353     /* 2) found recyclable stable entry? */
00354     if (old_stable < ARP_TABLE_SIZE) {
00355       /* recycle oldest stable*/
00356       i = old_stable;
00357       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest stable entry %"U16_F"\n", (u16_t)i));
00358       /* no queued packets should exist on stable entries */
00359       LWIP_ASSERT("arp_table[i].q == NULL", arp_table[i].q == NULL);
00360     /* 3) found recyclable pending entry without queued packets? */
00361     } else if (old_pending < ARP_TABLE_SIZE) {
00362       /* recycle oldest pending */
00363       i = old_pending;
00364       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest pending entry %"U16_F" (without queue)\n", (u16_t)i));
00365     /* 4) found recyclable pending entry with queued packets? */
00366     } else if (old_queue < ARP_TABLE_SIZE) {
00367       /* recycle oldest pending (queued packets are free in etharp_free_entry) */
00368       i = old_queue;
00369       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest pending entry %"U16_F", freeing packet queue %p\n", (u16_t)i, (void *)(arp_table[i].q)));
00370       /* no empty or recyclable entries found */
00371     } else {
00372       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: no empty or recyclable entries found\n"));
00373       return (s8_t)ERR_MEM;
00374     }
00375 
00376     /* { empty or recyclable entry found } */
00377     LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
00378     etharp_free_entry(i);
00379   }
00380 
00381   LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
00382   LWIP_ASSERT("arp_table[i].state == ETHARP_STATE_EMPTY",
00383     arp_table[i].state == ETHARP_STATE_EMPTY);
00384 
00385   /* IP address given? */
00386   if (ipaddr != NULL) {
00387     /* set IP address */
00388     ip4_addr_copy(arp_table[i].ipaddr, *ipaddr);
00389   }
00390   arp_table[i].ctime = 0;
00391 #if ETHARP_TABLE_MATCH_NETIF
00392   arp_table[i].netif = netif;
00393 #endif /* ETHARP_TABLE_MATCH_NETIF*/
00394   return (err_t)i;
00395 }
00396 
00397 /**
00398  * Update (or insert) a IP/MAC address pair in the ARP cache.
00399  *
00400  * If a pending entry is resolved, any queued packets will be sent
00401  * at this point.
00402  *
00403  * @param netif netif related to this entry (used for NETIF_ADDRHINT)
00404  * @param ipaddr IP address of the inserted ARP entry.
00405  * @param ethaddr Ethernet address of the inserted ARP entry.
00406  * @param flags See @ref etharp_state
00407  *
00408  * @return
00409  * - ERR_OK Successfully updated ARP cache.
00410  * - ERR_MEM If we could not add a new ARP entry when ETHARP_FLAG_TRY_HARD was set.
00411  * - ERR_ARG Non-unicast address given, those will not appear in ARP cache.
00412  *
00413  * @see pbuf_free()
00414  */
00415 static err_t
00416 etharp_update_arp_entry(struct netif *netif, const ip4_addr_t *ipaddr, struct eth_addr *ethaddr, u8_t flags)
00417 {
00418   s8_t i;
00419   LWIP_ASSERT("netif->hwaddr_len == ETH_HWADDR_LEN", netif->hwaddr_len == ETH_HWADDR_LEN);
00420   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_update_arp_entry: %"U16_F".%"U16_F".%"U16_F".%"U16_F" - %02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F"\n",
00421     ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr),
00422     (u16_t)ethaddr->addr[0], (u16_t)ethaddr->addr[1], (u16_t)ethaddr->addr[2],
00423     (u16_t)ethaddr->addr[3], (u16_t)ethaddr->addr[4], (u16_t)ethaddr->addr[5]));
00424   /* non-unicast address? */
00425   if (ip4_addr_isany(ipaddr) ||
00426       ip4_addr_isbroadcast(ipaddr, netif) ||
00427       ip4_addr_ismulticast(ipaddr)) {
00428     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_update_arp_entry: will not add non-unicast IP address to ARP cache\n"));
00429     return ERR_ARG;
00430   }
00431   /* find or create ARP entry */
00432   i = etharp_find_entry(ipaddr, flags, netif);
00433   /* bail out if no entry could be found */
00434   if (i < 0) {
00435     return (err_t)i;
00436   }
00437 
00438 #if ETHARP_SUPPORT_STATIC_ENTRIES
00439   if (flags & ETHARP_FLAG_STATIC_ENTRY) {
00440     /* record static type */
00441     arp_table[i].state = ETHARP_STATE_STATIC;
00442   } else if (arp_table[i].state == ETHARP_STATE_STATIC) {
00443     /* found entry is a static type, don't overwrite it */
00444     return ERR_VAL;
00445   } else
00446 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00447   {
00448     /* mark it stable */
00449     arp_table[i].state = ETHARP_STATE_STABLE;
00450   }
00451 
00452   /* record network interface */
00453   arp_table[i].netif = netif;
00454   /* insert in SNMP ARP index tree */
00455   mib2_add_arp_entry(netif, &arp_table[i].ipaddr);
00456 
00457   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_update_arp_entry: updating stable entry %"S16_F"\n", (s16_t)i));
00458   /* update address */
00459   ETHADDR32_COPY(&arp_table[i].ethaddr, ethaddr);
00460   /* reset time stamp */
00461   arp_table[i].ctime = 0;
00462   /* this is where we will send out queued packets! */
00463 #if ARP_QUEUEING
00464   while (arp_table[i].q != NULL) {
00465     struct pbuf *p;
00466     /* remember remainder of queue */
00467     struct etharp_q_entry *q = arp_table[i].q;
00468     /* pop first item off the queue */
00469     arp_table[i].q = q->next;
00470     /* get the packet pointer */
00471     p = q->p;
00472     /* now queue entry can be freed */
00473     memp_free(MEMP_ARP_QUEUE, q);
00474 #else /* ARP_QUEUEING */
00475   if (arp_table[i].q != NULL) {
00476     struct pbuf *p = arp_table[i].q;
00477     arp_table[i].q = NULL;
00478 #endif /* ARP_QUEUEING */
00479     /* send the queued IP packet */
00480     ethernet_output(netif, p, (struct eth_addr*)(netif->hwaddr), ethaddr, ETHTYPE_IP);
00481     /* free the queued IP packet */
00482     pbuf_free(p);
00483   }
00484   return ERR_OK;
00485 }
00486 
00487 #if ETHARP_SUPPORT_STATIC_ENTRIES
00488 /** Add a new static entry to the ARP table. If an entry exists for the
00489  * specified IP address, this entry is overwritten.
00490  * If packets are queued for the specified IP address, they are sent out.
00491  *
00492  * @param ipaddr IP address for the new static entry
00493  * @param ethaddr ethernet address for the new static entry
00494  * @return See return values of etharp_add_static_entry
00495  */
00496 err_t
00497 etharp_add_static_entry(const ip4_addr_t *ipaddr, struct eth_addr *ethaddr)
00498 {
00499   struct netif *netif;
00500   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_add_static_entry: %"U16_F".%"U16_F".%"U16_F".%"U16_F" - %02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F"\n",
00501     ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr),
00502     (u16_t)ethaddr->addr[0], (u16_t)ethaddr->addr[1], (u16_t)ethaddr->addr[2],
00503     (u16_t)ethaddr->addr[3], (u16_t)ethaddr->addr[4], (u16_t)ethaddr->addr[5]));
00504 
00505   netif = ip4_route(ipaddr);
00506   if (netif == NULL) {
00507     return ERR_RTE;
00508   }
00509 
00510   return etharp_update_arp_entry(netif, ipaddr, ethaddr, ETHARP_FLAG_TRY_HARD | ETHARP_FLAG_STATIC_ENTRY);
00511 }
00512 
00513 /** Remove a static entry from the ARP table previously added with a call to
00514  * etharp_add_static_entry.
00515  *
00516  * @param ipaddr IP address of the static entry to remove
00517  * @return ERR_OK: entry removed
00518  *         ERR_MEM: entry wasn't found
00519  *         ERR_ARG: entry wasn't a static entry but a dynamic one
00520  */
00521 err_t
00522 etharp_remove_static_entry(const ip4_addr_t *ipaddr)
00523 {
00524   s8_t i;
00525   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_remove_static_entry: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00526     ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr)));
00527 
00528   /* find or create ARP entry */
00529   i = etharp_find_entry(ipaddr, ETHARP_FLAG_FIND_ONLY, NULL);
00530   /* bail out if no entry could be found */
00531   if (i < 0) {
00532     return (err_t)i;
00533   }
00534 
00535   if (arp_table[i].state != ETHARP_STATE_STATIC) {
00536     /* entry wasn't a static entry, cannot remove it */
00537     return ERR_ARG;
00538   }
00539   /* entry found, free it */
00540   etharp_free_entry(i);
00541   return ERR_OK;
00542 }
00543 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00544 
00545 /**
00546  * Remove all ARP table entries of the specified netif.
00547  *
00548  * @param netif points to a network interface
00549  */
00550 void
00551 etharp_cleanup_netif(struct netif *netif)
00552 {
00553   u8_t i;
00554 
00555   for (i = 0; i < ARP_TABLE_SIZE; ++i) {
00556     u8_t state = arp_table[i].state;
00557     if ((state != ETHARP_STATE_EMPTY) && (arp_table[i].netif == netif)) {
00558       etharp_free_entry(i);
00559     }
00560   }
00561 }
00562 
00563 /**
00564  * Finds (stable) ethernet/IP address pair from ARP table
00565  * using interface and IP address index.
00566  * @note the addresses in the ARP table are in network order!
00567  *
00568  * @param netif points to interface index
00569  * @param ipaddr points to the (network order) IP address index
00570  * @param eth_ret points to return pointer
00571  * @param ip_ret points to return pointer
00572  * @return table index if found, -1 otherwise
00573  */
00574 s8_t
00575 etharp_find_addr(struct netif *netif, const ip4_addr_t *ipaddr,
00576          struct eth_addr **eth_ret, const ip4_addr_t **ip_ret)
00577 {
00578   s8_t i;
00579 
00580   LWIP_ASSERT("eth_ret != NULL && ip_ret != NULL",
00581     eth_ret != NULL && ip_ret != NULL);
00582 
00583   LWIP_UNUSED_ARG(netif);
00584 
00585   i = etharp_find_entry(ipaddr, ETHARP_FLAG_FIND_ONLY, netif);
00586   if ((i >= 0) && (arp_table[i].state >= ETHARP_STATE_STABLE)) {
00587       *eth_ret = &arp_table[i].ethaddr;
00588       *ip_ret = &arp_table[i].ipaddr;
00589       return i;
00590   }
00591   return -1;
00592 }
00593 
00594 /**
00595  * Possibility to iterate over stable ARP table entries
00596  *
00597  * @param i entry number, 0 to ARP_TABLE_SIZE
00598  * @param ipaddr return value: IP address
00599  * @param netif return value: points to interface
00600  * @param eth_ret return value: ETH address
00601  * @return 1 on valid index, 0 otherwise
00602  */
00603 u8_t
00604 etharp_get_entry(u8_t i, ip4_addr_t **ipaddr, struct netif **netif, struct eth_addr **eth_ret)
00605 {
00606   LWIP_ASSERT("ipaddr != NULL", ipaddr != NULL);
00607   LWIP_ASSERT("netif != NULL", netif != NULL);
00608   LWIP_ASSERT("eth_ret != NULL", eth_ret != NULL);
00609 
00610   if((i < ARP_TABLE_SIZE) && (arp_table[i].state >= ETHARP_STATE_STABLE)) {
00611     *ipaddr  = &arp_table[i].ipaddr;
00612     *netif   = arp_table[i].netif;
00613     *eth_ret = &arp_table[i].ethaddr;
00614     return 1;
00615   } else {
00616     return 0;
00617   }
00618 }
00619 
00620 /**
00621  * Responds to ARP requests to us. Upon ARP replies to us, add entry to cache
00622  * send out queued IP packets. Updates cache with snooped address pairs.
00623  *
00624  * Should be called for incoming ARP packets. The pbuf in the argument
00625  * is freed by this function.
00626  *
00627  * @param p The ARP packet that arrived on netif. Is freed by this function.
00628  * @param netif The lwIP network interface on which the ARP packet pbuf arrived.
00629  *
00630  * @see pbuf_free()
00631  */
00632 void
00633 etharp_input(struct pbuf *p, struct netif *netif)
00634 {
00635   struct etharp_hdr *hdr;
00636   /* these are aligned properly, whereas the ARP header fields might not be */
00637   ip4_addr_t sipaddr, dipaddr;
00638   u8_t for_us;
00639 
00640   LWIP_ERROR("netif != NULL", (netif != NULL), return;);
00641 
00642   hdr = (struct etharp_hdr *)p->payload;
00643 
00644   /* RFC 826 "Packet Reception": */
00645   if ((hdr->hwtype != PP_HTONS(HWTYPE_ETHERNET)) ||
00646       (hdr->hwlen != ETH_HWADDR_LEN) ||
00647       (hdr->protolen != sizeof(ip4_addr_t)) ||
00648       (hdr->proto != PP_HTONS(ETHTYPE_IP)))  {
00649     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING,
00650       ("etharp_input: packet dropped, wrong hw type, hwlen, proto, protolen or ethernet type (%"U16_F"/%"U16_F"/%"U16_F"/%"U16_F")\n",
00651       hdr->hwtype, (u16_t)hdr->hwlen, hdr->proto, (u16_t)hdr->protolen));
00652     ETHARP_STATS_INC(etharp.proterr);
00653     ETHARP_STATS_INC(etharp.drop);
00654     pbuf_free(p);
00655     return;
00656   }
00657   ETHARP_STATS_INC(etharp.recv);
00658 
00659 #if LWIP_AUTOIP
00660   /* We have to check if a host already has configured our random
00661    * created link local address and continuously check if there is
00662    * a host with this IP-address so we can detect collisions */
00663   autoip_arp_reply(netif, hdr);
00664 #endif /* LWIP_AUTOIP */
00665 
00666   /* Copy struct ip4_addr2 to aligned ip4_addr, to support compilers without
00667    * structure packing (not using structure copy which breaks strict-aliasing rules). */
00668   IPADDR2_COPY(&sipaddr, &hdr->sipaddr);
00669   IPADDR2_COPY(&dipaddr, &hdr->dipaddr);
00670 
00671   /* this interface is not configured? */
00672   if (ip4_addr_isany_val(*netif_ip4_addr(netif))) {
00673     for_us = 0;
00674   } else {
00675     /* ARP packet directed to us? */
00676     for_us = (u8_t)ip4_addr_cmp(&dipaddr, netif_ip4_addr(netif));
00677   }
00678 
00679   /* ARP message directed to us?
00680       -> add IP address in ARP cache; assume requester wants to talk to us,
00681          can result in directly sending the queued packets for this host.
00682      ARP message not directed to us?
00683       ->  update the source IP address in the cache, if present */
00684   etharp_update_arp_entry(netif, &sipaddr, &(hdr->shwaddr),
00685                    for_us ? ETHARP_FLAG_TRY_HARD : ETHARP_FLAG_FIND_ONLY);
00686 
00687   /* now act on the message itself */
00688   switch (hdr->opcode) {
00689   /* ARP request? */
00690   case PP_HTONS(ARP_REQUEST):
00691     /* ARP request. If it asked for our address, we send out a
00692      * reply. In any case, we time-stamp any existing ARP entry,
00693      * and possibly send out an IP packet that was queued on it. */
00694 
00695     LWIP_DEBUGF (ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: incoming ARP request\n"));
00696     /* ARP request for our address? */
00697     if (for_us) {
00698 
00699       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: replying to ARP request for our IP address\n"));
00700       /* Re-use pbuf to send ARP reply.
00701          Since we are re-using an existing pbuf, we can't call etharp_raw since
00702          that would allocate a new pbuf. */
00703       hdr->opcode = lwip_htons(ARP_REPLY);
00704 
00705       IPADDR2_COPY(&hdr->dipaddr, &hdr->sipaddr);
00706       IPADDR2_COPY(&hdr->sipaddr, netif_ip4_addr(netif));
00707 
00708       LWIP_ASSERT("netif->hwaddr_len must be the same as ETH_HWADDR_LEN for etharp!",
00709                   (netif->hwaddr_len == ETH_HWADDR_LEN));
00710 
00711       /* hwtype, hwaddr_len, proto, protolen and the type in the ethernet header
00712          are already correct, we tested that before */
00713 
00714       ETHADDR16_COPY(&hdr->dhwaddr, &hdr->shwaddr);
00715       ETHADDR16_COPY(&hdr->shwaddr, netif->hwaddr);
00716 
00717       /* return ARP reply */
00718 #if LWIP_AUTOIP
00719       /* If we are using Link-Local, all ARP packets that contain a Link-Local
00720        * 'sender IP address' MUST be sent using link-layer broadcast instead of
00721        * link-layer unicast. (See RFC3927 Section 2.5, last paragraph) */
00722       if (ip4_addr_islinklocal(netif_ip4_addr(netif))) {
00723         ethernet_output(netif, p, &hdr->shwaddr, &ethbroadcast, ETHTYPE_ARP);
00724       } else
00725 #endif /* LWIP_AUTOIP */
00726       {
00727         ethernet_output(netif, p, &hdr->shwaddr, &hdr->dhwaddr, ETHTYPE_ARP);
00728       }
00729 
00730     /* we are not configured? */
00731     } else if (ip4_addr_isany_val(*netif_ip4_addr(netif))) {
00732       /* { for_us == 0 and netif->ip_addr.addr == 0 } */
00733       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: we are unconfigured, ARP request ignored.\n"));
00734     /* request was not directed to us */
00735     } else {
00736       /* { for_us == 0 and netif->ip_addr.addr != 0 } */
00737       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: ARP request was not for us.\n"));
00738     }
00739     break;
00740   case PP_HTONS(ARP_REPLY):
00741     /* ARP reply. We already updated the ARP cache earlier. */
00742     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: incoming ARP reply\n"));
00743 #if (LWIP_DHCP && DHCP_DOES_ARP_CHECK)
00744     /* DHCP wants to know about ARP replies from any host with an
00745      * IP address also offered to us by the DHCP server. We do not
00746      * want to take a duplicate IP address on a single network.
00747      * @todo How should we handle redundant (fail-over) interfaces? */
00748     dhcp_arp_reply(netif, &sipaddr);
00749 #endif /* (LWIP_DHCP && DHCP_DOES_ARP_CHECK) */
00750     break;
00751   default:
00752     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: ARP unknown opcode type %"S16_F"\n", lwip_htons(hdr->opcode)));
00753     ETHARP_STATS_INC(etharp.err);
00754     break;
00755   }
00756   /* free ARP packet */
00757   pbuf_free(p);
00758 }
00759 
00760 /** Just a small helper function that sends a pbuf to an ethernet address
00761  * in the arp_table specified by the index 'arp_idx'.
00762  */
00763 static err_t
00764 etharp_output_to_arp_index(struct netif *netif, struct pbuf *q, u8_t arp_idx)
00765 {
00766   LWIP_ASSERT("arp_table[arp_idx].state >= ETHARP_STATE_STABLE",
00767               arp_table[arp_idx].state >= ETHARP_STATE_STABLE);
00768   /* if arp table entry is about to expire: re-request it,
00769      but only if its state is ETHARP_STATE_STABLE to prevent flooding the
00770      network with ARP requests if this address is used frequently. */
00771   if (arp_table[arp_idx].state == ETHARP_STATE_STABLE) {
00772     if (arp_table[arp_idx].ctime >= ARP_AGE_REREQUEST_USED_BROADCAST) {
00773       /* issue a standard request using broadcast */
00774       if (etharp_request(netif, &arp_table[arp_idx].ipaddr) == ERR_OK) {
00775         arp_table[arp_idx].state = ETHARP_STATE_STABLE_REREQUESTING_1;
00776       }
00777     } else if (arp_table[arp_idx].ctime >= ARP_AGE_REREQUEST_USED_UNICAST) {
00778       /* issue a unicast request (for 15 seconds) to prevent unnecessary broadcast */
00779       if (etharp_request_dst(netif, &arp_table[arp_idx].ipaddr, &arp_table[arp_idx].ethaddr) == ERR_OK) {
00780         arp_table[arp_idx].state = ETHARP_STATE_STABLE_REREQUESTING_1;
00781       }
00782     }
00783   }
00784 
00785   return ethernet_output(netif, q, (struct eth_addr*)(netif->hwaddr), &arp_table[arp_idx].ethaddr, ETHTYPE_IP);
00786 }
00787 
00788 /**
00789  * Resolve and fill-in Ethernet address header for outgoing IP packet.
00790  *
00791  * For IP multicast and broadcast, corresponding Ethernet addresses
00792  * are selected and the packet is transmitted on the link.
00793  *
00794  * For unicast addresses, the packet is submitted to etharp_query(). In
00795  * case the IP address is outside the local network, the IP address of
00796  * the gateway is used.
00797  *
00798  * @param netif The lwIP network interface which the IP packet will be sent on.
00799  * @param q The pbuf(s) containing the IP packet to be sent.
00800  * @param ipaddr The IP address of the packet destination.
00801  *
00802  * @return
00803  * - ERR_RTE No route to destination (no gateway to external networks),
00804  * or the return type of either etharp_query() or ethernet_output().
00805  */
00806 err_t
00807 etharp_output(struct netif *netif, struct pbuf *q, const ip4_addr_t *ipaddr)
00808 {
00809   const struct eth_addr *dest;
00810   struct eth_addr mcastaddr;
00811   const ip4_addr_t *dst_addr = ipaddr;
00812 
00813   LWIP_ASSERT("netif != NULL", netif != NULL);
00814   LWIP_ASSERT("q != NULL", q != NULL);
00815   LWIP_ASSERT("ipaddr != NULL", ipaddr != NULL);
00816 
00817   /* Determine on destination hardware address. Broadcasts and multicasts
00818    * are special, other IP addresses are looked up in the ARP table. */
00819 
00820   /* broadcast destination IP address? */
00821   if (ip4_addr_isbroadcast(ipaddr, netif)) {
00822     /* broadcast on Ethernet also */
00823     dest = (const struct eth_addr *)&ethbroadcast;
00824   /* multicast destination IP address? */
00825   } else if (ip4_addr_ismulticast(ipaddr)) {
00826     /* Hash IP multicast address to MAC address.*/
00827     mcastaddr.addr[0] = LL_IP4_MULTICAST_ADDR_0;
00828     mcastaddr.addr[1] = LL_IP4_MULTICAST_ADDR_1;
00829     mcastaddr.addr[2] = LL_IP4_MULTICAST_ADDR_2;
00830     mcastaddr.addr[3] = ip4_addr2(ipaddr) & 0x7f;
00831     mcastaddr.addr[4] = ip4_addr3(ipaddr);
00832     mcastaddr.addr[5] = ip4_addr4(ipaddr);
00833     /* destination Ethernet address is multicast */
00834     dest = &mcastaddr;
00835   /* unicast destination IP address? */
00836   } else {
00837     s8_t i;
00838     /* outside local network? if so, this can neither be a global broadcast nor
00839        a subnet broadcast. */
00840     if (!ip4_addr_netcmp(ipaddr, netif_ip4_addr(netif), netif_ip4_netmask(netif)) &&
00841         !ip4_addr_islinklocal(ipaddr)) {
00842 #if LWIP_AUTOIP
00843       struct ip_hdr *iphdr = LWIP_ALIGNMENT_CAST(struct ip_hdr*, q->payload);
00844       /* According to RFC 3297, chapter 2.6.2 (Forwarding Rules), a packet with
00845          a link-local source address must always be "directly to its destination
00846          on the same physical link. The host MUST NOT send the packet to any
00847          router for forwarding". */
00848       if (!ip4_addr_islinklocal(&iphdr->src))
00849 #endif /* LWIP_AUTOIP */
00850       {
00851 #ifdef LWIP_HOOK_ETHARP_GET_GW
00852         /* For advanced routing, a single default gateway might not be enough, so get
00853            the IP address of the gateway to handle the current destination address. */
00854         dst_addr = LWIP_HOOK_ETHARP_GET_GW(netif, ipaddr);
00855         if (dst_addr == NULL)
00856 #endif /* LWIP_HOOK_ETHARP_GET_GW */
00857         {
00858           /* interface has default gateway? */
00859           if (!ip4_addr_isany_val(*netif_ip4_gw(netif))) {
00860             /* send to hardware address of default gateway IP address */
00861             dst_addr = netif_ip4_gw(netif);
00862           /* no default gateway available */
00863           } else {
00864             /* no route to destination error (default gateway missing) */
00865             return ERR_RTE;
00866           }
00867         }
00868       }
00869     }
00870 #if LWIP_NETIF_HWADDRHINT
00871     if (netif->addr_hint != NULL) {
00872       /* per-pcb cached entry was given */
00873       u8_t etharp_cached_entry = *(netif->addr_hint);
00874       if (etharp_cached_entry < ARP_TABLE_SIZE) {
00875 #endif /* LWIP_NETIF_HWADDRHINT */
00876         if ((arp_table[etharp_cached_entry].state >= ETHARP_STATE_STABLE) &&
00877 #if ETHARP_TABLE_MATCH_NETIF
00878             (arp_table[etharp_cached_entry].netif == netif) &&
00879 #endif
00880             (ip4_addr_cmp(dst_addr, &arp_table[etharp_cached_entry].ipaddr))) {
00881           /* the per-pcb-cached entry is stable and the right one! */
00882           ETHARP_STATS_INC(etharp.cachehit);
00883           return etharp_output_to_arp_index(netif, q, etharp_cached_entry);
00884         }
00885 #if LWIP_NETIF_HWADDRHINT
00886       }
00887     }
00888 #endif /* LWIP_NETIF_HWADDRHINT */
00889 
00890     /* find stable entry: do this here since this is a critical path for
00891        throughput and etharp_find_entry() is kind of slow */
00892     for (i = 0; i < ARP_TABLE_SIZE; i++) {
00893       if ((arp_table[i].state >= ETHARP_STATE_STABLE) &&
00894 #if ETHARP_TABLE_MATCH_NETIF
00895           (arp_table[i].netif == netif) &&
00896 #endif
00897           (ip4_addr_cmp(dst_addr, &arp_table[i].ipaddr))) {
00898         /* found an existing, stable entry */
00899         ETHARP_SET_HINT(netif, i);
00900         return etharp_output_to_arp_index(netif, q, i);
00901       }
00902     }
00903     /* no stable entry found, use the (slower) query function:
00904        queue on destination Ethernet address belonging to ipaddr */
00905     return etharp_query(netif, dst_addr, q);
00906   }
00907 
00908   /* continuation for multicast/broadcast destinations */
00909   /* obtain source Ethernet address of the given interface */
00910   /* send packet directly on the link */
00911   return ethernet_output(netif, q, (struct eth_addr*)(netif->hwaddr), dest, ETHTYPE_IP);
00912 }
00913 
00914 /**
00915  * Send an ARP request for the given IP address and/or queue a packet.
00916  *
00917  * If the IP address was not yet in the cache, a pending ARP cache entry
00918  * is added and an ARP request is sent for the given address. The packet
00919  * is queued on this entry.
00920  *
00921  * If the IP address was already pending in the cache, a new ARP request
00922  * is sent for the given address. The packet is queued on this entry.
00923  *
00924  * If the IP address was already stable in the cache, and a packet is
00925  * given, it is directly sent and no ARP request is sent out.
00926  *
00927  * If the IP address was already stable in the cache, and no packet is
00928  * given, an ARP request is sent out.
00929  *
00930  * @param netif The lwIP network interface on which ipaddr
00931  * must be queried for.
00932  * @param ipaddr The IP address to be resolved.
00933  * @param q If non-NULL, a pbuf that must be delivered to the IP address.
00934  * q is not freed by this function.
00935  *
00936  * @note q must only be ONE packet, not a packet queue!
00937  *
00938  * @return
00939  * - ERR_BUF Could not make room for Ethernet header.
00940  * - ERR_MEM Hardware address unknown, and no more ARP entries available
00941  *   to query for address or queue the packet.
00942  * - ERR_MEM Could not queue packet due to memory shortage.
00943  * - ERR_RTE No route to destination (no gateway to external networks).
00944  * - ERR_ARG Non-unicast address given, those will not appear in ARP cache.
00945  *
00946  */
00947 err_t
00948 etharp_query(struct netif *netif, const ip4_addr_t *ipaddr, struct pbuf *q)
00949 {
00950   struct eth_addr * srcaddr = (struct eth_addr *)netif->hwaddr;
00951   err_t result = ERR_MEM;
00952   int is_new_entry = 0;
00953   s8_t i; /* ARP entry index */
00954 
00955   /* non-unicast address? */
00956   if (ip4_addr_isbroadcast(ipaddr, netif) ||
00957       ip4_addr_ismulticast(ipaddr) ||
00958       ip4_addr_isany(ipaddr)) {
00959     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: will not add non-unicast IP address to ARP cache\n"));
00960     return ERR_ARG;
00961   }
00962 
00963   /* find entry in ARP cache, ask to create entry if queueing packet */
00964   i = etharp_find_entry(ipaddr, ETHARP_FLAG_TRY_HARD, netif);
00965 
00966   /* could not find or create entry? */
00967   if (i < 0) {
00968     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: could not create ARP entry\n"));
00969     if (q) {
00970       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: packet dropped\n"));
00971       ETHARP_STATS_INC(etharp.memerr);
00972     }
00973     return (err_t)i;
00974   }
00975 
00976   /* mark a fresh entry as pending (we just sent a request) */
00977   if (arp_table[i].state == ETHARP_STATE_EMPTY) {
00978     is_new_entry = 1;
00979     arp_table[i].state = ETHARP_STATE_PENDING;
00980     /* record network interface for re-sending arp request in etharp_tmr */
00981     arp_table[i].netif = netif;
00982   }
00983 
00984   /* { i is either a STABLE or (new or existing) PENDING entry } */
00985   LWIP_ASSERT("arp_table[i].state == PENDING or STABLE",
00986   ((arp_table[i].state == ETHARP_STATE_PENDING) ||
00987    (arp_table[i].state >= ETHARP_STATE_STABLE)));
00988 
00989   /* do we have a new entry? or an implicit query request? */
00990   if (is_new_entry || (q == NULL)) {
00991     /* try to resolve it; send out ARP request */
00992     result = etharp_request(netif, ipaddr);
00993     if (result != ERR_OK) {
00994       /* ARP request couldn't be sent */
00995       /* We don't re-send arp request in etharp_tmr, but we still queue packets,
00996          since this failure could be temporary, and the next packet calling
00997          etharp_query again could lead to sending the queued packets. */
00998     }
00999     if (q == NULL) {
01000       return result;
01001     }
01002   }
01003 
01004   /* packet given? */
01005   LWIP_ASSERT("q != NULL", q != NULL);
01006   /* stable entry? */
01007   if (arp_table[i].state >= ETHARP_STATE_STABLE) {
01008     /* we have a valid IP->Ethernet address mapping */
01009     ETHARP_SET_HINT(netif, i);
01010     /* send the packet */
01011     result = ethernet_output(netif, q, srcaddr, &(arp_table[i].ethaddr), ETHTYPE_IP);
01012   /* pending entry? (either just created or already pending */
01013   } else if (arp_table[i].state == ETHARP_STATE_PENDING) {
01014     /* entry is still pending, queue the given packet 'q' */
01015     struct pbuf *p;
01016     int copy_needed = 0;
01017     /* IF q includes a PBUF_REF, PBUF_POOL or PBUF_RAM, we have no choice but
01018      * to copy the whole queue into a new PBUF_RAM (see bug #11400)
01019      * PBUF_ROMs can be left as they are, since ROM must not get changed. */
01020     p = q;
01021     while (p) {
01022       LWIP_ASSERT("no packet queues allowed!", (p->len != p->tot_len) || (p->next == 0));
01023       if (p->type != PBUF_ROM) {
01024         copy_needed = 1;
01025         break;
01026       }
01027       p = p->next;
01028     }
01029     if (copy_needed) {
01030       /* copy the whole packet into new pbufs */
01031       p = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM);
01032       if (p != NULL) {
01033         if (pbuf_copy(p, q) != ERR_OK) {
01034           pbuf_free(p);
01035           p = NULL;
01036         }
01037       }
01038     } else {
01039       /* referencing the old pbuf is enough */
01040       p = q;
01041       pbuf_ref(p);
01042     }
01043     /* packet could be taken over? */
01044     if (p != NULL) {
01045       /* queue packet ... */
01046 #if ARP_QUEUEING
01047       struct etharp_q_entry *new_entry;
01048       /* allocate a new arp queue entry */
01049       new_entry = (struct etharp_q_entry *)memp_malloc(MEMP_ARP_QUEUE);
01050       if (new_entry != NULL) {
01051         unsigned int qlen = 0;
01052         new_entry->next = 0;
01053         new_entry->p = p;
01054         if (arp_table[i].q != NULL) {
01055           /* queue was already existent, append the new entry to the end */
01056           struct etharp_q_entry *r;
01057           r = arp_table[i].q;
01058           qlen++;
01059           while (r->next != NULL) {
01060             r = r->next;
01061             qlen++;
01062           }
01063           r->next = new_entry;
01064         } else {
01065           /* queue did not exist, first item in queue */
01066           arp_table[i].q = new_entry;
01067         }
01068 #if ARP_QUEUE_LEN
01069         if (qlen >= ARP_QUEUE_LEN) {
01070           struct etharp_q_entry *old;
01071           old = arp_table[i].q;
01072           arp_table[i].q = arp_table[i].q->next;
01073           pbuf_free(old->p);
01074           memp_free(MEMP_ARP_QUEUE, old);
01075         }
01076 #endif
01077         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: queued packet %p on ARP entry %"S16_F"\n", (void *)q, (s16_t)i));
01078         result = ERR_OK;
01079       } else {
01080         /* the pool MEMP_ARP_QUEUE is empty */
01081         pbuf_free(p);
01082         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: could not queue a copy of PBUF_REF packet %p (out of memory)\n", (void *)q));
01083         result = ERR_MEM;
01084       }
01085 #else /* ARP_QUEUEING */
01086       /* always queue one packet per ARP request only, freeing a previously queued packet */
01087       if (arp_table[i].q != NULL) {
01088         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: dropped previously queued packet %p for ARP entry %"S16_F"\n", (void *)q, (s16_t)i));
01089         pbuf_free(arp_table[i].q);
01090       }
01091       arp_table[i].q = p;
01092       result = ERR_OK;
01093       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: queued packet %p on ARP entry %"S16_F"\n", (void *)q, (s16_t)i));
01094 #endif /* ARP_QUEUEING */
01095     } else {
01096       ETHARP_STATS_INC(etharp.memerr);
01097       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: could not queue a copy of PBUF_REF packet %p (out of memory)\n", (void *)q));
01098       result = ERR_MEM;
01099     }
01100   }
01101   return result;
01102 }
01103 
01104 /**
01105  * Send a raw ARP packet (opcode and all addresses can be modified)
01106  *
01107  * @param netif the lwip network interface on which to send the ARP packet
01108  * @param ethsrc_addr the source MAC address for the ethernet header
01109  * @param ethdst_addr the destination MAC address for the ethernet header
01110  * @param hwsrc_addr the source MAC address for the ARP protocol header
01111  * @param ipsrc_addr the source IP address for the ARP protocol header
01112  * @param hwdst_addr the destination MAC address for the ARP protocol header
01113  * @param ipdst_addr the destination IP address for the ARP protocol header
01114  * @param opcode the type of the ARP packet
01115  * @return ERR_OK if the ARP packet has been sent
01116  *         ERR_MEM if the ARP packet couldn't be allocated
01117  *         any other err_t on failure
01118  */
01119 static err_t
01120 etharp_raw(struct netif *netif, const struct eth_addr *ethsrc_addr,
01121            const struct eth_addr *ethdst_addr,
01122            const struct eth_addr *hwsrc_addr, const ip4_addr_t *ipsrc_addr,
01123            const struct eth_addr *hwdst_addr, const ip4_addr_t *ipdst_addr,
01124            const u16_t opcode)
01125 {
01126   struct pbuf *p;
01127   err_t result = ERR_OK;
01128   struct etharp_hdr *hdr;
01129 
01130   LWIP_ASSERT("netif != NULL", netif != NULL);
01131 
01132   /* allocate a pbuf for the outgoing ARP request packet */
01133   p = pbuf_alloc(PBUF_LINK, SIZEOF_ETHARP_HDR, PBUF_RAM);
01134   /* could allocate a pbuf for an ARP request? */
01135   if (p == NULL) {
01136     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS,
01137       ("etharp_raw: could not allocate pbuf for ARP request.\n"));
01138     ETHARP_STATS_INC(etharp.memerr);
01139     return ERR_MEM;
01140   }
01141   LWIP_ASSERT("check that first pbuf can hold struct etharp_hdr",
01142               (p->len >= SIZEOF_ETHARP_HDR));
01143 
01144   hdr = (struct etharp_hdr *)p->payload;
01145   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_raw: sending raw ARP packet.\n"));
01146   hdr->opcode = lwip_htons(opcode);
01147 
01148   LWIP_ASSERT("netif->hwaddr_len must be the same as ETH_HWADDR_LEN for etharp!",
01149               (netif->hwaddr_len == ETH_HWADDR_LEN));
01150 
01151   /* Write the ARP MAC-Addresses */
01152   ETHADDR16_COPY(&hdr->shwaddr, hwsrc_addr);
01153   ETHADDR16_COPY(&hdr->dhwaddr, hwdst_addr);
01154   /* Copy struct ip4_addr2 to aligned ip4_addr, to support compilers without
01155    * structure packing. */
01156   IPADDR2_COPY(&hdr->sipaddr, ipsrc_addr);
01157   IPADDR2_COPY(&hdr->dipaddr, ipdst_addr);
01158 
01159   hdr->hwtype = PP_HTONS(HWTYPE_ETHERNET);
01160   hdr->proto = PP_HTONS(ETHTYPE_IP);
01161   /* set hwlen and protolen */
01162   hdr->hwlen = ETH_HWADDR_LEN;
01163   hdr->protolen = sizeof(ip4_addr_t);
01164 
01165   /* send ARP query */
01166 #if LWIP_AUTOIP
01167   /* If we are using Link-Local, all ARP packets that contain a Link-Local
01168    * 'sender IP address' MUST be sent using link-layer broadcast instead of
01169    * link-layer unicast. (See RFC3927 Section 2.5, last paragraph) */
01170   if(ip4_addr_islinklocal(ipsrc_addr)) {
01171     ethernet_output(netif, p, ethsrc_addr, &ethbroadcast, ETHTYPE_ARP);
01172   } else
01173 #endif /* LWIP_AUTOIP */
01174   {
01175     ethernet_output(netif, p, ethsrc_addr, ethdst_addr, ETHTYPE_ARP);
01176   }
01177 
01178   ETHARP_STATS_INC(etharp.xmit);
01179   /* free ARP query packet */
01180   pbuf_free(p);
01181   p = NULL;
01182   /* could not allocate pbuf for ARP request */
01183 
01184   return result;
01185 }
01186 
01187 /**
01188  * Send an ARP request packet asking for ipaddr to a specific eth address.
01189  * Used to send unicast request to refresh the ARP table just before an entry
01190  * times out
01191  *
01192  * @param netif the lwip network interface on which to send the request
01193  * @param ipaddr the IP address for which to ask
01194  * @param hw_dst_addr the ethernet address to send this packet to
01195  * @return ERR_OK if the request has been sent
01196  *         ERR_MEM if the ARP packet couldn't be allocated
01197  *         any other err_t on failure
01198  */
01199 static err_t
01200 etharp_request_dst(struct netif *netif, const ip4_addr_t *ipaddr, const struct eth_addr* hw_dst_addr)
01201 {
01202   return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, hw_dst_addr,
01203                     (struct eth_addr *)netif->hwaddr, netif_ip4_addr(netif), &ethzero,
01204                     ipaddr, ARP_REQUEST);
01205 }
01206 
01207 /**
01208  * Send an ARP request packet asking for ipaddr.
01209  *
01210  * @param netif the lwip network interface on which to send the request
01211  * @param ipaddr the IP address for which to ask
01212  * @return ERR_OK if the request has been sent
01213  *         ERR_MEM if the ARP packet couldn't be allocated
01214  *         any other err_t on failure
01215  */
01216 err_t
01217 etharp_request(struct netif *netif, const ip4_addr_t *ipaddr)
01218 {
01219   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_request: sending ARP request.\n"));
01220   return etharp_request_dst(netif, ipaddr, &ethbroadcast);
01221 }
01222 #endif /* LWIP_IPV4 && LWIP_ARP */
01223 
01224 #endif /* LWIP_ARP || LWIP_ETHERNET */