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_IPV4 && LWIP_ARP /* don't build if not configured for use in lwipopts.h */
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 "lwip/prot/iana.h"
00056 #include "netif/ethernet.h"
00057 
00058 #include <string.h>
00059 
00060 #ifdef LWIP_HOOK_FILENAME
00061 #include LWIP_HOOK_FILENAME
00062 #endif
00063 
00064 /** Re-request a used ARP entry 1 minute before it would expire to prevent
00065  *  breaking a steadily used connection because the ARP entry timed out. */
00066 #define ARP_AGE_REREQUEST_USED_UNICAST   (ARP_MAXAGE - 30)
00067 #define ARP_AGE_REREQUEST_USED_BROADCAST (ARP_MAXAGE - 15)
00068 
00069 /** the time an ARP entry stays pending after first request,
00070  *  for ARP_TMR_INTERVAL = 1000, this is
00071  *  10 seconds.
00072  *
00073  *  @internal Keep this number at least 2, otherwise it might
00074  *  run out instantly if the timeout occurs directly after a request.
00075  */
00076 #define ARP_MAXPENDING 5
00077 
00078 /** ARP states */
00079 enum etharp_state {
00080   ETHARP_STATE_EMPTY = 0,
00081   ETHARP_STATE_PENDING,
00082   ETHARP_STATE_STABLE,
00083   ETHARP_STATE_STABLE_REREQUESTING_1,
00084   ETHARP_STATE_STABLE_REREQUESTING_2
00085 #if ETHARP_SUPPORT_STATIC_ENTRIES
00086   , ETHARP_STATE_STATIC
00087 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00088 };
00089 
00090 struct etharp_entry {
00091 #if ARP_QUEUEING
00092   /** Pointer to queue of pending outgoing packets on this ARP entry. */
00093   struct etharp_q_entry *q;
00094 #else /* ARP_QUEUEING */
00095   /** Pointer to a single pending outgoing packet on this ARP entry. */
00096   struct pbuf *q;
00097 #endif /* ARP_QUEUEING */
00098   ip4_addr_t ipaddr;
00099   struct netif *netif;
00100   struct eth_addr ethaddr;
00101   u16_t ctime;
00102   u8_t state;
00103 };
00104 
00105 static struct etharp_entry arp_table[ARP_TABLE_SIZE];
00106 
00107 #if !LWIP_NETIF_HWADDRHINT
00108 static netif_addr_idx_t etharp_cached_entry;
00109 #endif /* !LWIP_NETIF_HWADDRHINT */
00110 
00111 /** Try hard to create a new entry - we want the IP address to appear in
00112     the cache (even if this means removing an active entry or so). */
00113 #define ETHARP_FLAG_TRY_HARD     1
00114 #define ETHARP_FLAG_FIND_ONLY    2
00115 #if ETHARP_SUPPORT_STATIC_ENTRIES
00116 #define ETHARP_FLAG_STATIC_ENTRY 4
00117 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00118 
00119 #if LWIP_NETIF_HWADDRHINT
00120 #define ETHARP_SET_ADDRHINT(netif, addrhint)  do { if (((netif) != NULL) && ((netif)->hints != NULL)) { \
00121                                               (netif)->hints->addr_hint = (addrhint); }} while(0)
00122 #else /* LWIP_NETIF_HWADDRHINT */
00123 #define ETHARP_SET_ADDRHINT(netif, addrhint)  (etharp_cached_entry = (addrhint))
00124 #endif /* LWIP_NETIF_HWADDRHINT */
00125 
00126 
00127 /* Check for maximum ARP_TABLE_SIZE */
00128 #if (ARP_TABLE_SIZE > NETIF_ADDR_IDX_MAX)
00129 #error "ARP_TABLE_SIZE must fit in an s16_t, you have to reduce it in your lwipopts.h"
00130 #endif
00131 
00132 
00133 static err_t etharp_request_dst(struct netif *netif, const ip4_addr_t *ipaddr, const struct eth_addr *hw_dst_addr);
00134 static err_t etharp_raw(struct netif *netif,
00135                         const struct eth_addr *ethsrc_addr, const struct eth_addr *ethdst_addr,
00136                         const struct eth_addr *hwsrc_addr, const ip4_addr_t *ipsrc_addr,
00137                         const struct eth_addr *hwdst_addr, const ip4_addr_t *ipdst_addr,
00138                         const u16_t opcode);
00139 
00140 #if ARP_QUEUEING
00141 /**
00142  * Free a complete queue of etharp entries
00143  *
00144  * @param q a qeueue of etharp_q_entry's to free
00145  */
00146 static void
00147 free_etharp_q(struct etharp_q_entry *q)
00148 {
00149   struct etharp_q_entry *r;
00150   LWIP_ASSERT("q != NULL", q != NULL);
00151   while (q) {
00152     r = q;
00153     q = q->next;
00154     LWIP_ASSERT("r->p != NULL", (r->p != NULL));
00155     pbuf_free(r->p);
00156     memp_free(MEMP_ARP_QUEUE, r);
00157   }
00158 }
00159 #else /* ARP_QUEUEING */
00160 
00161 /** Compatibility define: free the queued pbuf */
00162 #define free_etharp_q(q) pbuf_free(q)
00163 
00164 #endif /* ARP_QUEUEING */
00165 
00166 /** Clean up ARP table entries */
00167 static void
00168 etharp_free_entry(int i)
00169 {
00170   /* remove from SNMP ARP index tree */
00171   mib2_remove_arp_entry(arp_table[i].netif, &arp_table[i].ipaddr);
00172   /* and empty packet queue */
00173   if (arp_table[i].q != NULL) {
00174     /* remove all queued packets */
00175     LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_free_entry: freeing entry %"U16_F", packet queue %p.\n", (u16_t)i, (void *)(arp_table[i].q)));
00176     free_etharp_q(arp_table[i].q);
00177     arp_table[i].q = NULL;
00178   }
00179   /* recycle entry for re-use */
00180   arp_table[i].state = ETHARP_STATE_EMPTY;
00181 #ifdef LWIP_DEBUG
00182   /* for debugging, clean out the complete entry */
00183   arp_table[i].ctime = 0;
00184   arp_table[i].netif = NULL;
00185   ip4_addr_set_zero(&arp_table[i].ipaddr);
00186   arp_table[i].ethaddr = ethzero;
00187 #endif /* LWIP_DEBUG */
00188 }
00189 
00190 /**
00191  * Clears expired entries in the ARP table.
00192  *
00193  * This function should be called every ARP_TMR_INTERVAL milliseconds (1 second),
00194  * in order to expire entries in the ARP table.
00195  */
00196 void
00197 etharp_tmr(void)
00198 {
00199   int i;
00200 
00201   LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer\n"));
00202   /* remove expired entries from the ARP table */
00203   for (i = 0; i < ARP_TABLE_SIZE; ++i) {
00204     u8_t state = arp_table[i].state;
00205     if (state != ETHARP_STATE_EMPTY
00206 #if ETHARP_SUPPORT_STATIC_ENTRIES
00207         && (state != ETHARP_STATE_STATIC)
00208 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00209        ) {
00210       arp_table[i].ctime++;
00211       if ((arp_table[i].ctime >= ARP_MAXAGE) ||
00212           ((arp_table[i].state == ETHARP_STATE_PENDING)  &&
00213            (arp_table[i].ctime >= ARP_MAXPENDING))) {
00214         /* pending or stable entry has become old! */
00215         LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer: expired %s entry %d.\n",
00216                                    arp_table[i].state >= ETHARP_STATE_STABLE ? "stable" : "pending", i));
00217         /* clean up entries that have just been expired */
00218         etharp_free_entry(i);
00219       } else if (arp_table[i].state == ETHARP_STATE_STABLE_REREQUESTING_1) {
00220         /* Don't send more than one request every 2 seconds. */
00221         arp_table[i].state = ETHARP_STATE_STABLE_REREQUESTING_2;
00222       } else if (arp_table[i].state == ETHARP_STATE_STABLE_REREQUESTING_2) {
00223         /* Reset state to stable, so that the next transmitted packet will
00224            re-send an ARP request. */
00225         arp_table[i].state = ETHARP_STATE_STABLE;
00226       } else if (arp_table[i].state == ETHARP_STATE_PENDING) {
00227         /* still pending, resend an ARP query */
00228         etharp_request(arp_table[i].netif, &arp_table[i].ipaddr);
00229       }
00230     }
00231   }
00232 }
00233 
00234 /**
00235  * Search the ARP table for a matching or new entry.
00236  *
00237  * If an IP address is given, return a pending or stable ARP entry that matches
00238  * the address. If no match is found, create a new entry with this address set,
00239  * but in state ETHARP_EMPTY. The caller must check and possibly change the
00240  * state of the returned entry.
00241  *
00242  * If ipaddr is NULL, return a initialized new entry in state ETHARP_EMPTY.
00243  *
00244  * In all cases, attempt to create new entries from an empty entry. If no
00245  * empty entries are available and ETHARP_FLAG_TRY_HARD flag is set, recycle
00246  * old entries. Heuristic choose the least important entry for recycling.
00247  *
00248  * @param ipaddr IP address to find in ARP cache, or to add if not found.
00249  * @param flags See @ref etharp_state
00250  * @param netif netif related to this address (used for NETIF_HWADDRHINT)
00251  *
00252  * @return The ARP entry index that matched or is created, ERR_MEM if no
00253  * entry is found or could be recycled.
00254  */
00255 static s16_t
00256 etharp_find_entry(const ip4_addr_t *ipaddr, u8_t flags, struct netif *netif)
00257 {
00258   s16_t old_pending = ARP_TABLE_SIZE, old_stable = ARP_TABLE_SIZE;
00259   s16_t empty = ARP_TABLE_SIZE;
00260   s16_t i = 0;
00261   /* oldest entry with packets on queue */
00262   s16_t old_queue = ARP_TABLE_SIZE;
00263   /* its age */
00264   u16_t age_queue = 0, age_pending = 0, age_stable = 0;
00265 
00266   LWIP_UNUSED_ARG(netif);
00267 
00268   /**
00269    * a) do a search through the cache, remember candidates
00270    * b) select candidate entry
00271    * c) create new entry
00272    */
00273 
00274   /* a) in a single search sweep, do all of this
00275    * 1) remember the first empty entry (if any)
00276    * 2) remember the oldest stable entry (if any)
00277    * 3) remember the oldest pending entry without queued packets (if any)
00278    * 4) remember the oldest pending entry with queued packets (if any)
00279    * 5) search for a matching IP entry, either pending or stable
00280    *    until 5 matches, or all entries are searched for.
00281    */
00282 
00283   for (i = 0; i < ARP_TABLE_SIZE; ++i) {
00284     u8_t state = arp_table[i].state;
00285     /* no empty entry found yet and now we do find one? */
00286     if ((empty == ARP_TABLE_SIZE) && (state == ETHARP_STATE_EMPTY)) {
00287       LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_find_entry: found empty entry %d\n", (int)i));
00288       /* remember first empty entry */
00289       empty = i;
00290     } else if (state != ETHARP_STATE_EMPTY) {
00291       LWIP_ASSERT("state == ETHARP_STATE_PENDING || state >= ETHARP_STATE_STABLE",
00292                   state == ETHARP_STATE_PENDING || state >= ETHARP_STATE_STABLE);
00293       /* if given, does IP address match IP address in ARP entry? */
00294       if (ipaddr && ip4_addr_cmp(ipaddr, &arp_table[i].ipaddr)
00295 #if ETHARP_TABLE_MATCH_NETIF
00296           && ((netif == NULL) || (netif == arp_table[i].netif))
00297 #endif /* ETHARP_TABLE_MATCH_NETIF */
00298          ) {
00299         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: found matching entry %d\n", (int)i));
00300         /* found exact IP address match, simply bail out */
00301         return i;
00302       }
00303       /* pending entry? */
00304       if (state == ETHARP_STATE_PENDING) {
00305         /* pending with queued packets? */
00306         if (arp_table[i].q != NULL) {
00307           if (arp_table[i].ctime >= age_queue) {
00308             old_queue = i;
00309             age_queue = arp_table[i].ctime;
00310           }
00311         } else
00312           /* pending without queued packets? */
00313         {
00314           if (arp_table[i].ctime >= age_pending) {
00315             old_pending = i;
00316             age_pending = arp_table[i].ctime;
00317           }
00318         }
00319         /* stable entry? */
00320       } else if (state >= ETHARP_STATE_STABLE) {
00321 #if ETHARP_SUPPORT_STATIC_ENTRIES
00322         /* don't record old_stable for static entries since they never expire */
00323         if (state < ETHARP_STATE_STATIC)
00324 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00325         {
00326           /* remember entry with oldest stable entry in oldest, its age in maxtime */
00327           if (arp_table[i].ctime >= age_stable) {
00328             old_stable = i;
00329             age_stable = arp_table[i].ctime;
00330           }
00331         }
00332       }
00333     }
00334   }
00335   /* { we have no match } => try to create a new entry */
00336 
00337   /* don't create new entry, only search? */
00338   if (((flags & ETHARP_FLAG_FIND_ONLY) != 0) ||
00339       /* or no empty entry found and not allowed to recycle? */
00340       ((empty == ARP_TABLE_SIZE) && ((flags & ETHARP_FLAG_TRY_HARD) == 0))) {
00341     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: no empty entry found and not allowed to recycle\n"));
00342     return (s16_t)ERR_MEM;
00343   }
00344 
00345   /* b) choose the least destructive entry to recycle:
00346    * 1) empty entry
00347    * 2) oldest stable entry
00348    * 3) oldest pending entry without queued packets
00349    * 4) oldest pending entry with queued packets
00350    *
00351    * { ETHARP_FLAG_TRY_HARD is set at this point }
00352    */
00353 
00354   /* 1) empty entry available? */
00355   if (empty < ARP_TABLE_SIZE) {
00356     i = empty;
00357     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting empty entry %d\n", (int)i));
00358   } else {
00359     /* 2) found recyclable stable entry? */
00360     if (old_stable < ARP_TABLE_SIZE) {
00361       /* recycle oldest stable*/
00362       i = old_stable;
00363       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest stable entry %d\n", (int)i));
00364       /* no queued packets should exist on stable entries */
00365       LWIP_ASSERT("arp_table[i].q == NULL", arp_table[i].q == NULL);
00366       /* 3) found recyclable pending entry without queued packets? */
00367     } else if (old_pending < ARP_TABLE_SIZE) {
00368       /* recycle oldest pending */
00369       i = old_pending;
00370       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest pending entry %d (without queue)\n", (int)i));
00371       /* 4) found recyclable pending entry with queued packets? */
00372     } else if (old_queue < ARP_TABLE_SIZE) {
00373       /* recycle oldest pending (queued packets are free in etharp_free_entry) */
00374       i = old_queue;
00375       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest pending entry %d, freeing packet queue %p\n", (int)i, (void *)(arp_table[i].q)));
00376       /* no empty or recyclable entries found */
00377     } else {
00378       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: no empty or recyclable entries found\n"));
00379       return (s16_t)ERR_MEM;
00380     }
00381 
00382     /* { empty or recyclable entry found } */
00383     LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
00384     etharp_free_entry(i);
00385   }
00386 
00387   LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
00388   LWIP_ASSERT("arp_table[i].state == ETHARP_STATE_EMPTY",
00389               arp_table[i].state == ETHARP_STATE_EMPTY);
00390 
00391   /* IP address given? */
00392   if (ipaddr != NULL) {
00393     /* set IP address */
00394     ip4_addr_copy(arp_table[i].ipaddr, *ipaddr);
00395   }
00396   arp_table[i].ctime = 0;
00397 #if ETHARP_TABLE_MATCH_NETIF
00398   arp_table[i].netif = netif;
00399 #endif /* ETHARP_TABLE_MATCH_NETIF */
00400   return (s16_t)i;
00401 }
00402 
00403 /**
00404  * Update (or insert) a IP/MAC address pair in the ARP cache.
00405  *
00406  * If a pending entry is resolved, any queued packets will be sent
00407  * at this point.
00408  *
00409  * @param netif netif related to this entry (used for NETIF_ADDRHINT)
00410  * @param ipaddr IP address of the inserted ARP entry.
00411  * @param ethaddr Ethernet address of the inserted ARP entry.
00412  * @param flags See @ref etharp_state
00413  *
00414  * @return
00415  * - ERR_OK Successfully updated ARP cache.
00416  * - ERR_MEM If we could not add a new ARP entry when ETHARP_FLAG_TRY_HARD was set.
00417  * - ERR_ARG Non-unicast address given, those will not appear in ARP cache.
00418  *
00419  * @see pbuf_free()
00420  */
00421 static err_t
00422 etharp_update_arp_entry(struct netif *netif, const ip4_addr_t *ipaddr, struct eth_addr *ethaddr, u8_t flags)
00423 {
00424   s16_t i;
00425   LWIP_ASSERT("netif->hwaddr_len == ETH_HWADDR_LEN", netif->hwaddr_len == ETH_HWADDR_LEN);
00426   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",
00427               ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr),
00428               (u16_t)ethaddr->addr[0], (u16_t)ethaddr->addr[1], (u16_t)ethaddr->addr[2],
00429               (u16_t)ethaddr->addr[3], (u16_t)ethaddr->addr[4], (u16_t)ethaddr->addr[5]));
00430   /* non-unicast address? */
00431   if (ip4_addr_isany(ipaddr) ||
00432       ip4_addr_isbroadcast(ipaddr, netif) ||
00433       ip4_addr_ismulticast(ipaddr)) {
00434     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_update_arp_entry: will not add non-unicast IP address to ARP cache\n"));
00435     return ERR_ARG;
00436   }
00437   /* find or create ARP entry */
00438   i = etharp_find_entry(ipaddr, flags, netif);
00439   /* bail out if no entry could be found */
00440   if (i < 0) {
00441     return (err_t)i;
00442   }
00443 
00444 #if ETHARP_SUPPORT_STATIC_ENTRIES
00445   if (flags & ETHARP_FLAG_STATIC_ENTRY) {
00446     /* record static type */
00447     arp_table[i].state = ETHARP_STATE_STATIC;
00448   } else if (arp_table[i].state == ETHARP_STATE_STATIC) {
00449     /* found entry is a static type, don't overwrite it */
00450     return ERR_VAL;
00451   } else
00452 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00453   {
00454     /* mark it stable */
00455     arp_table[i].state = ETHARP_STATE_STABLE;
00456   }
00457 
00458   /* record network interface */
00459   arp_table[i].netif = netif;
00460   /* insert in SNMP ARP index tree */
00461   mib2_add_arp_entry(netif, &arp_table[i].ipaddr);
00462 
00463   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_update_arp_entry: updating stable entry %"S16_F"\n", i));
00464   /* update address */
00465   SMEMCPY(&arp_table[i].ethaddr, ethaddr, ETH_HWADDR_LEN);
00466   /* reset time stamp */
00467   arp_table[i].ctime = 0;
00468   /* this is where we will send out queued packets! */
00469 #if ARP_QUEUEING
00470   while (arp_table[i].q != NULL) {
00471     struct pbuf *p;
00472     /* remember remainder of queue */
00473     struct etharp_q_entry *q = arp_table[i].q;
00474     /* pop first item off the queue */
00475     arp_table[i].q = q->next;
00476     /* get the packet pointer */
00477     p = q->p;
00478     /* now queue entry can be freed */
00479     memp_free(MEMP_ARP_QUEUE, q);
00480 #else /* ARP_QUEUEING */
00481   if (arp_table[i].q != NULL) {
00482     struct pbuf *p = arp_table[i].q;
00483     arp_table[i].q = NULL;
00484 #endif /* ARP_QUEUEING */
00485     /* send the queued IP packet */
00486     ethernet_output(netif, p, (struct eth_addr *)(netif->hwaddr), ethaddr, ETHTYPE_IP);
00487     /* free the queued IP packet */
00488     pbuf_free(p);
00489   }
00490   return ERR_OK;
00491 }
00492 
00493 #if ETHARP_SUPPORT_STATIC_ENTRIES
00494 /** Add a new static entry to the ARP table. If an entry exists for the
00495  * specified IP address, this entry is overwritten.
00496  * If packets are queued for the specified IP address, they are sent out.
00497  *
00498  * @param ipaddr IP address for the new static entry
00499  * @param ethaddr ethernet address for the new static entry
00500  * @return See return values of etharp_add_static_entry
00501  */
00502 err_t
00503 etharp_add_static_entry(const ip4_addr_t *ipaddr, struct eth_addr *ethaddr)
00504 {
00505   struct netif *netif;
00506   LWIP_ASSERT_CORE_LOCKED();
00507   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",
00508               ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr),
00509               (u16_t)ethaddr->addr[0], (u16_t)ethaddr->addr[1], (u16_t)ethaddr->addr[2],
00510               (u16_t)ethaddr->addr[3], (u16_t)ethaddr->addr[4], (u16_t)ethaddr->addr[5]));
00511 
00512   netif = ip4_route(ipaddr);
00513   if (netif == NULL) {
00514     return ERR_RTE;
00515   }
00516 
00517   return etharp_update_arp_entry(netif, ipaddr, ethaddr, ETHARP_FLAG_TRY_HARD | ETHARP_FLAG_STATIC_ENTRY);
00518 }
00519 
00520 /** Remove a static entry from the ARP table previously added with a call to
00521  * etharp_add_static_entry.
00522  *
00523  * @param ipaddr IP address of the static entry to remove
00524  * @return ERR_OK: entry removed
00525  *         ERR_MEM: entry wasn't found
00526  *         ERR_ARG: entry wasn't a static entry but a dynamic one
00527  */
00528 err_t
00529 etharp_remove_static_entry(const ip4_addr_t *ipaddr)
00530 {
00531   s16_t i;
00532   LWIP_ASSERT_CORE_LOCKED();
00533   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_remove_static_entry: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00534               ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr)));
00535 
00536   /* find or create ARP entry */
00537   i = etharp_find_entry(ipaddr, ETHARP_FLAG_FIND_ONLY, NULL);
00538   /* bail out if no entry could be found */
00539   if (i < 0) {
00540     return (err_t)i;
00541   }
00542 
00543   if (arp_table[i].state != ETHARP_STATE_STATIC) {
00544     /* entry wasn't a static entry, cannot remove it */
00545     return ERR_ARG;
00546   }
00547   /* entry found, free it */
00548   etharp_free_entry(i);
00549   return ERR_OK;
00550 }
00551 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00552 
00553 /**
00554  * Remove all ARP table entries of the specified netif.
00555  *
00556  * @param netif points to a network interface
00557  */
00558 void
00559 etharp_cleanup_netif(struct netif *netif)
00560 {
00561   int i;
00562 
00563   for (i = 0; i < ARP_TABLE_SIZE; ++i) {
00564     u8_t state = arp_table[i].state;
00565     if ((state != ETHARP_STATE_EMPTY) && (arp_table[i].netif == netif)) {
00566       etharp_free_entry(i);
00567     }
00568   }
00569 }
00570 
00571 /**
00572  * Finds (stable) ethernet/IP address pair from ARP table
00573  * using interface and IP address index.
00574  * @note the addresses in the ARP table are in network order!
00575  *
00576  * @param netif points to interface index
00577  * @param ipaddr points to the (network order) IP address index
00578  * @param eth_ret points to return pointer
00579  * @param ip_ret points to return pointer
00580  * @return table index if found, -1 otherwise
00581  */
00582 ssize_t
00583 etharp_find_addr(struct netif *netif, const ip4_addr_t *ipaddr,
00584                  struct eth_addr **eth_ret, const ip4_addr_t **ip_ret)
00585 {
00586   s16_t i;
00587 
00588   LWIP_ASSERT("eth_ret != NULL && ip_ret != NULL",
00589               eth_ret != NULL && ip_ret != NULL);
00590 
00591   LWIP_UNUSED_ARG(netif);
00592 
00593   i = etharp_find_entry(ipaddr, ETHARP_FLAG_FIND_ONLY, netif);
00594   if ((i >= 0) && (arp_table[i].state >= ETHARP_STATE_STABLE)) {
00595     *eth_ret = &arp_table[i].ethaddr;
00596     *ip_ret = &arp_table[i].ipaddr;
00597     return i;
00598   }
00599   return -1;
00600 }
00601 
00602 /**
00603  * Possibility to iterate over stable ARP table entries
00604  *
00605  * @param i entry number, 0 to ARP_TABLE_SIZE
00606  * @param ipaddr return value: IP address
00607  * @param netif return value: points to interface
00608  * @param eth_ret return value: ETH address
00609  * @return 1 on valid index, 0 otherwise
00610  */
00611 int
00612 etharp_get_entry(size_t i, ip4_addr_t **ipaddr, struct netif **netif, struct eth_addr **eth_ret)
00613 {
00614   LWIP_ASSERT("ipaddr != NULL", ipaddr != NULL);
00615   LWIP_ASSERT("netif != NULL", netif != NULL);
00616   LWIP_ASSERT("eth_ret != NULL", eth_ret != NULL);
00617 
00618   if ((i < ARP_TABLE_SIZE) && (arp_table[i].state >= ETHARP_STATE_STABLE)) {
00619     *ipaddr  = &arp_table[i].ipaddr;
00620     *netif   = arp_table[i].netif;
00621     *eth_ret = &arp_table[i].ethaddr;
00622     return 1;
00623   } else {
00624     return 0;
00625   }
00626 }
00627 
00628 /**
00629  * Responds to ARP requests to us. Upon ARP replies to us, add entry to cache
00630  * send out queued IP packets. Updates cache with snooped address pairs.
00631  *
00632  * Should be called for incoming ARP packets. The pbuf in the argument
00633  * is freed by this function.
00634  *
00635  * @param p The ARP packet that arrived on netif. Is freed by this function.
00636  * @param netif The lwIP network interface on which the ARP packet pbuf arrived.
00637  *
00638  * @see pbuf_free()
00639  */
00640 void
00641 etharp_input(struct pbuf *p, struct netif *netif)
00642 {
00643   struct etharp_hdr *hdr;
00644   /* these are aligned properly, whereas the ARP header fields might not be */
00645   ip4_addr_t sipaddr, dipaddr;
00646   u8_t for_us;
00647 
00648   LWIP_ASSERT_CORE_LOCKED();
00649 
00650   LWIP_ERROR("netif != NULL", (netif != NULL), return;);
00651 
00652   hdr = (struct etharp_hdr *)p->payload;
00653 
00654   /* RFC 826 "Packet Reception": */
00655   if ((hdr->hwtype != PP_HTONS(LWIP_IANA_HWTYPE_ETHERNET)) ||
00656       (hdr->hwlen != ETH_HWADDR_LEN) ||
00657       (hdr->protolen != sizeof(ip4_addr_t)) ||
00658       (hdr->proto != PP_HTONS(ETHTYPE_IP)))  {
00659     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING,
00660                 ("etharp_input: packet dropped, wrong hw type, hwlen, proto, protolen or ethernet type (%"U16_F"/%"U16_F"/%"U16_F"/%"U16_F")\n",
00661                  hdr->hwtype, (u16_t)hdr->hwlen, hdr->proto, (u16_t)hdr->protolen));
00662     ETHARP_STATS_INC(etharp.proterr);
00663     ETHARP_STATS_INC(etharp.drop);
00664     pbuf_free(p);
00665     return;
00666   }
00667   ETHARP_STATS_INC(etharp.recv);
00668 
00669 #if LWIP_AUTOIP
00670   /* We have to check if a host already has configured our random
00671    * created link local address and continuously check if there is
00672    * a host with this IP-address so we can detect collisions */
00673   autoip_arp_reply(netif, hdr);
00674 #endif /* LWIP_AUTOIP */
00675 
00676   /* Copy struct ip4_addr_wordaligned to aligned ip4_addr, to support compilers without
00677    * structure packing (not using structure copy which breaks strict-aliasing rules). */
00678   IPADDR_WORDALIGNED_COPY_TO_IP4_ADDR_T(&sipaddr, &hdr->sipaddr);
00679   IPADDR_WORDALIGNED_COPY_TO_IP4_ADDR_T(&dipaddr, &hdr->dipaddr);
00680 
00681   /* this interface is not configured? */
00682   if (ip4_addr_isany_val(*netif_ip4_addr(netif))) {
00683     for_us = 0;
00684   } else {
00685     /* ARP packet directed to us? */
00686     for_us = (u8_t)ip4_addr_cmp(&dipaddr, netif_ip4_addr(netif));
00687   }
00688 
00689   /* ARP message directed to us?
00690       -> add IP address in ARP cache; assume requester wants to talk to us,
00691          can result in directly sending the queued packets for this host.
00692      ARP message not directed to us?
00693       ->  update the source IP address in the cache, if present */
00694   etharp_update_arp_entry(netif, &sipaddr, &(hdr->shwaddr),
00695                           for_us ? ETHARP_FLAG_TRY_HARD : ETHARP_FLAG_FIND_ONLY);
00696 
00697   /* now act on the message itself */
00698   switch (hdr->opcode) {
00699     /* ARP request? */
00700     case PP_HTONS(ARP_REQUEST):
00701       /* ARP request. If it asked for our address, we send out a
00702        * reply. In any case, we time-stamp any existing ARP entry,
00703        * and possibly send out an IP packet that was queued on it. */
00704 
00705       LWIP_DEBUGF (ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: incoming ARP request\n"));
00706       /* ARP request for our address? */
00707       if (for_us) {
00708         /* send ARP response */
00709         etharp_raw(netif,
00710                    (struct eth_addr *)netif->hwaddr, &hdr->shwaddr,
00711                    (struct eth_addr *)netif->hwaddr, netif_ip4_addr(netif),
00712                    &hdr->shwaddr, &sipaddr,
00713                    ARP_REPLY);
00714         /* we are not configured? */
00715       } else if (ip4_addr_isany_val(*netif_ip4_addr(netif))) {
00716         /* { for_us == 0 and netif->ip_addr.addr == 0 } */
00717         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: we are unconfigured, ARP request ignored.\n"));
00718         /* request was not directed to us */
00719       } else {
00720         /* { for_us == 0 and netif->ip_addr.addr != 0 } */
00721         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: ARP request was not for us.\n"));
00722       }
00723       break;
00724     case PP_HTONS(ARP_REPLY):
00725       /* ARP reply. We already updated the ARP cache earlier. */
00726       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: incoming ARP reply\n"));
00727 #if (LWIP_DHCP && DHCP_DOES_ARP_CHECK)
00728       /* DHCP wants to know about ARP replies from any host with an
00729        * IP address also offered to us by the DHCP server. We do not
00730        * want to take a duplicate IP address on a single network.
00731        * @todo How should we handle redundant (fail-over) interfaces? */
00732       dhcp_arp_reply(netif, &sipaddr);
00733 #endif /* (LWIP_DHCP && DHCP_DOES_ARP_CHECK) */
00734       break;
00735     default:
00736       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: ARP unknown opcode type %"S16_F"\n", lwip_htons(hdr->opcode)));
00737       ETHARP_STATS_INC(etharp.err);
00738       break;
00739   }
00740   /* free ARP packet */
00741   pbuf_free(p);
00742 }
00743 
00744 /** Just a small helper function that sends a pbuf to an ethernet address
00745  * in the arp_table specified by the index 'arp_idx'.
00746  */
00747 static err_t
00748 etharp_output_to_arp_index(struct netif *netif, struct pbuf *q, netif_addr_idx_t arp_idx)
00749 {
00750   LWIP_ASSERT("arp_table[arp_idx].state >= ETHARP_STATE_STABLE",
00751               arp_table[arp_idx].state >= ETHARP_STATE_STABLE);
00752   /* if arp table entry is about to expire: re-request it,
00753      but only if its state is ETHARP_STATE_STABLE to prevent flooding the
00754      network with ARP requests if this address is used frequently. */
00755   if (arp_table[arp_idx].state == ETHARP_STATE_STABLE) {
00756     if (arp_table[arp_idx].ctime >= ARP_AGE_REREQUEST_USED_BROADCAST) {
00757       /* issue a standard request using broadcast */
00758       if (etharp_request(netif, &arp_table[arp_idx].ipaddr) == ERR_OK) {
00759         arp_table[arp_idx].state = ETHARP_STATE_STABLE_REREQUESTING_1;
00760       }
00761     } else if (arp_table[arp_idx].ctime >= ARP_AGE_REREQUEST_USED_UNICAST) {
00762       /* issue a unicast request (for 15 seconds) to prevent unnecessary broadcast */
00763       if (etharp_request_dst(netif, &arp_table[arp_idx].ipaddr, &arp_table[arp_idx].ethaddr) == ERR_OK) {
00764         arp_table[arp_idx].state = ETHARP_STATE_STABLE_REREQUESTING_1;
00765       }
00766     }
00767   }
00768 
00769   return ethernet_output(netif, q, (struct eth_addr *)(netif->hwaddr), &arp_table[arp_idx].ethaddr, ETHTYPE_IP);
00770 }
00771 
00772 /**
00773  * Resolve and fill-in Ethernet address header for outgoing IP packet.
00774  *
00775  * For IP multicast and broadcast, corresponding Ethernet addresses
00776  * are selected and the packet is transmitted on the link.
00777  *
00778  * For unicast addresses, the packet is submitted to etharp_query(). In
00779  * case the IP address is outside the local network, the IP address of
00780  * the gateway is used.
00781  *
00782  * @param netif The lwIP network interface which the IP packet will be sent on.
00783  * @param q The pbuf(s) containing the IP packet to be sent.
00784  * @param ipaddr The IP address of the packet destination.
00785  *
00786  * @return
00787  * - ERR_RTE No route to destination (no gateway to external networks),
00788  * or the return type of either etharp_query() or ethernet_output().
00789  */
00790 err_t
00791 etharp_output(struct netif *netif, struct pbuf *q, const ip4_addr_t *ipaddr)
00792 {
00793   const struct eth_addr *dest;
00794   struct eth_addr mcastaddr;
00795   const ip4_addr_t *dst_addr = ipaddr;
00796 
00797   LWIP_ASSERT_CORE_LOCKED();
00798   LWIP_ASSERT("netif != NULL", netif != NULL);
00799   LWIP_ASSERT("q != NULL", q != NULL);
00800   LWIP_ASSERT("ipaddr != NULL", ipaddr != NULL);
00801 
00802   /* Determine on destination hardware address. Broadcasts and multicasts
00803    * are special, other IP addresses are looked up in the ARP table. */
00804 
00805   /* broadcast destination IP address? */
00806   if (ip4_addr_isbroadcast(ipaddr, netif)) {
00807     /* broadcast on Ethernet also */
00808     dest = (const struct eth_addr *)&ethbroadcast;
00809     /* multicast destination IP address? */
00810   } else if (ip4_addr_ismulticast(ipaddr)) {
00811     /* Hash IP multicast address to MAC address.*/
00812     mcastaddr.addr[0] = LL_IP4_MULTICAST_ADDR_0;
00813     mcastaddr.addr[1] = LL_IP4_MULTICAST_ADDR_1;
00814     mcastaddr.addr[2] = LL_IP4_MULTICAST_ADDR_2;
00815     mcastaddr.addr[3] = ip4_addr2(ipaddr) & 0x7f;
00816     mcastaddr.addr[4] = ip4_addr3(ipaddr);
00817     mcastaddr.addr[5] = ip4_addr4(ipaddr);
00818     /* destination Ethernet address is multicast */
00819     dest = &mcastaddr;
00820     /* unicast destination IP address? */
00821   } else {
00822     netif_addr_idx_t i;
00823     /* outside local network? if so, this can neither be a global broadcast nor
00824        a subnet broadcast. */
00825     if (!ip4_addr_netcmp(ipaddr, netif_ip4_addr(netif), netif_ip4_netmask(netif)) &&
00826         !ip4_addr_islinklocal(ipaddr)) {
00827 #if LWIP_AUTOIP
00828       struct ip_hdr *iphdr = LWIP_ALIGNMENT_CAST(struct ip_hdr *, q->payload);
00829       /* According to RFC 3297, chapter 2.6.2 (Forwarding Rules), a packet with
00830          a link-local source address must always be "directly to its destination
00831          on the same physical link. The host MUST NOT send the packet to any
00832          router for forwarding". */
00833       if (!ip4_addr_islinklocal(&iphdr->src))
00834 #endif /* LWIP_AUTOIP */
00835       {
00836 #ifdef LWIP_HOOK_ETHARP_GET_GW
00837         /* For advanced routing, a single default gateway might not be enough, so get
00838            the IP address of the gateway to handle the current destination address. */
00839         dst_addr = LWIP_HOOK_ETHARP_GET_GW(netif, ipaddr);
00840         if (dst_addr == NULL)
00841 #endif /* LWIP_HOOK_ETHARP_GET_GW */
00842         {
00843           /* interface has default gateway? */
00844           if (!ip4_addr_isany_val(*netif_ip4_gw(netif))) {
00845             /* send to hardware address of default gateway IP address */
00846             dst_addr = netif_ip4_gw(netif);
00847             /* no default gateway available */
00848           } else {
00849             /* no route to destination error (default gateway missing) */
00850             return ERR_RTE;
00851           }
00852         }
00853       }
00854     }
00855 #if LWIP_NETIF_HWADDRHINT
00856     if (netif->hints != NULL) {
00857       /* per-pcb cached entry was given */
00858       netif_addr_idx_t etharp_cached_entry = netif->hints->addr_hint;
00859       if (etharp_cached_entry < ARP_TABLE_SIZE) {
00860 #endif /* LWIP_NETIF_HWADDRHINT */
00861         if ((arp_table[etharp_cached_entry].state >= ETHARP_STATE_STABLE) &&
00862 #if ETHARP_TABLE_MATCH_NETIF
00863             (arp_table[etharp_cached_entry].netif == netif) &&
00864 #endif
00865             (ip4_addr_cmp(dst_addr, &arp_table[etharp_cached_entry].ipaddr))) {
00866           /* the per-pcb-cached entry is stable and the right one! */
00867           ETHARP_STATS_INC(etharp.cachehit);
00868           return etharp_output_to_arp_index(netif, q, etharp_cached_entry);
00869         }
00870 #if LWIP_NETIF_HWADDRHINT
00871       }
00872     }
00873 #endif /* LWIP_NETIF_HWADDRHINT */
00874 
00875     /* find stable entry: do this here since this is a critical path for
00876        throughput and etharp_find_entry() is kind of slow */
00877     for (i = 0; i < ARP_TABLE_SIZE; i++) {
00878       if ((arp_table[i].state >= ETHARP_STATE_STABLE) &&
00879 #if ETHARP_TABLE_MATCH_NETIF
00880           (arp_table[i].netif == netif) &&
00881 #endif
00882           (ip4_addr_cmp(dst_addr, &arp_table[i].ipaddr))) {
00883         /* found an existing, stable entry */
00884         ETHARP_SET_ADDRHINT(netif, i);
00885         return etharp_output_to_arp_index(netif, q, i);
00886       }
00887     }
00888     /* no stable entry found, use the (slower) query function:
00889        queue on destination Ethernet address belonging to ipaddr */
00890     return etharp_query(netif, dst_addr, q);
00891   }
00892 
00893   /* continuation for multicast/broadcast destinations */
00894   /* obtain source Ethernet address of the given interface */
00895   /* send packet directly on the link */
00896   return ethernet_output(netif, q, (struct eth_addr *)(netif->hwaddr), dest, ETHTYPE_IP);
00897 }
00898 
00899 /**
00900  * Send an ARP request for the given IP address and/or queue a packet.
00901  *
00902  * If the IP address was not yet in the cache, a pending ARP cache entry
00903  * is added and an ARP request is sent for the given address. The packet
00904  * is queued on this entry.
00905  *
00906  * If the IP address was already pending in the cache, a new ARP request
00907  * is sent for the given address. The packet is queued on this entry.
00908  *
00909  * If the IP address was already stable in the cache, and a packet is
00910  * given, it is directly sent and no ARP request is sent out.
00911  *
00912  * If the IP address was already stable in the cache, and no packet is
00913  * given, an ARP request is sent out.
00914  *
00915  * @param netif The lwIP network interface on which ipaddr
00916  * must be queried for.
00917  * @param ipaddr The IP address to be resolved.
00918  * @param q If non-NULL, a pbuf that must be delivered to the IP address.
00919  * q is not freed by this function.
00920  *
00921  * @note q must only be ONE packet, not a packet queue!
00922  *
00923  * @return
00924  * - ERR_BUF Could not make room for Ethernet header.
00925  * - ERR_MEM Hardware address unknown, and no more ARP entries available
00926  *   to query for address or queue the packet.
00927  * - ERR_MEM Could not queue packet due to memory shortage.
00928  * - ERR_RTE No route to destination (no gateway to external networks).
00929  * - ERR_ARG Non-unicast address given, those will not appear in ARP cache.
00930  *
00931  */
00932 err_t
00933 etharp_query(struct netif *netif, const ip4_addr_t *ipaddr, struct pbuf *q)
00934 {
00935   struct eth_addr *srcaddr = (struct eth_addr *)netif->hwaddr;
00936   err_t result = ERR_MEM;
00937   int is_new_entry = 0;
00938   s16_t i_err;
00939   netif_addr_idx_t i;
00940 
00941   /* non-unicast address? */
00942   if (ip4_addr_isbroadcast(ipaddr, netif) ||
00943       ip4_addr_ismulticast(ipaddr) ||
00944       ip4_addr_isany(ipaddr)) {
00945     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: will not add non-unicast IP address to ARP cache\n"));
00946     return ERR_ARG;
00947   }
00948 
00949   /* find entry in ARP cache, ask to create entry if queueing packet */
00950   i_err = etharp_find_entry(ipaddr, ETHARP_FLAG_TRY_HARD, netif);
00951 
00952   /* could not find or create entry? */
00953   if (i_err < 0) {
00954     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: could not create ARP entry\n"));
00955     if (q) {
00956       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: packet dropped\n"));
00957       ETHARP_STATS_INC(etharp.memerr);
00958     }
00959     return (err_t)i_err;
00960   }
00961   LWIP_ASSERT("type overflow", (size_t)i_err < NETIF_ADDR_IDX_MAX);
00962   i = (netif_addr_idx_t)i_err;
00963 
00964   /* mark a fresh entry as pending (we just sent a request) */
00965   if (arp_table[i].state == ETHARP_STATE_EMPTY) {
00966     is_new_entry = 1;
00967     arp_table[i].state = ETHARP_STATE_PENDING;
00968     /* record network interface for re-sending arp request in etharp_tmr */
00969     arp_table[i].netif = netif;
00970   }
00971 
00972   /* { i is either a STABLE or (new or existing) PENDING entry } */
00973   LWIP_ASSERT("arp_table[i].state == PENDING or STABLE",
00974               ((arp_table[i].state == ETHARP_STATE_PENDING) ||
00975                (arp_table[i].state >= ETHARP_STATE_STABLE)));
00976 
00977   /* do we have a new entry? or an implicit query request? */
00978   if (is_new_entry || (q == NULL)) {
00979     /* try to resolve it; send out ARP request */
00980     result = etharp_request(netif, ipaddr);
00981     if (result != ERR_OK) {
00982       /* ARP request couldn't be sent */
00983       /* We don't re-send arp request in etharp_tmr, but we still queue packets,
00984          since this failure could be temporary, and the next packet calling
00985          etharp_query again could lead to sending the queued packets. */
00986     }
00987     if (q == NULL) {
00988       return result;
00989     }
00990   }
00991 
00992   /* packet given? */
00993   LWIP_ASSERT("q != NULL", q != NULL);
00994   /* stable entry? */
00995   if (arp_table[i].state >= ETHARP_STATE_STABLE) {
00996     /* we have a valid IP->Ethernet address mapping */
00997     ETHARP_SET_ADDRHINT(netif, i);
00998     /* send the packet */
00999     result = ethernet_output(netif, q, srcaddr, &(arp_table[i].ethaddr), ETHTYPE_IP);
01000     /* pending entry? (either just created or already pending */
01001   } else if (arp_table[i].state == ETHARP_STATE_PENDING) {
01002     /* entry is still pending, queue the given packet 'q' */
01003     struct pbuf *p;
01004     int copy_needed = 0;
01005     /* IF q includes a pbuf that must be copied, copy the whole chain into a
01006      * new PBUF_RAM. See the definition of PBUF_NEEDS_COPY for details. */
01007     p = q;
01008     while (p) {
01009       LWIP_ASSERT("no packet queues allowed!", (p->len != p->tot_len) || (p->next == 0));
01010       if (PBUF_NEEDS_COPY(p)) {
01011         copy_needed = 1;
01012         break;
01013       }
01014       p = p->next;
01015     }
01016     if (copy_needed) {
01017       /* copy the whole packet into new pbufs */
01018       p = pbuf_clone(PBUF_LINK, PBUF_RAM, q);
01019     } else {
01020       /* referencing the old pbuf is enough */
01021       p = q;
01022       pbuf_ref(p);
01023     }
01024     /* packet could be taken over? */
01025     if (p != NULL) {
01026       /* queue packet ... */
01027 #if ARP_QUEUEING
01028       struct etharp_q_entry *new_entry;
01029       /* allocate a new arp queue entry */
01030       new_entry = (struct etharp_q_entry *)memp_malloc(MEMP_ARP_QUEUE);
01031       if (new_entry != NULL) {
01032         unsigned int qlen = 0;
01033         new_entry->next = 0;
01034         new_entry->p = p;
01035         if (arp_table[i].q != NULL) {
01036           /* queue was already existent, append the new entry to the end */
01037           struct etharp_q_entry *r;
01038           r = arp_table[i].q;
01039           qlen++;
01040           while (r->next != NULL) {
01041             r = r->next;
01042             qlen++;
01043           }
01044           r->next = new_entry;
01045         } else {
01046           /* queue did not exist, first item in queue */
01047           arp_table[i].q = new_entry;
01048         }
01049 #if ARP_QUEUE_LEN
01050         if (qlen >= ARP_QUEUE_LEN) {
01051           struct etharp_q_entry *old;
01052           old = arp_table[i].q;
01053           arp_table[i].q = arp_table[i].q->next;
01054           pbuf_free(old->p);
01055           memp_free(MEMP_ARP_QUEUE, old);
01056         }
01057 #endif
01058         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: queued packet %p on ARP entry %"U16_F"\n", (void *)q, i));
01059         result = ERR_OK;
01060       } else {
01061         /* the pool MEMP_ARP_QUEUE is empty */
01062         pbuf_free(p);
01063         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));
01064         result = ERR_MEM;
01065       }
01066 #else /* ARP_QUEUEING */
01067       /* always queue one packet per ARP request only, freeing a previously queued packet */
01068       if (arp_table[i].q != NULL) {
01069         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: dropped previously queued packet %p for ARP entry %"U16_F"\n", (void *)q, (u16_t)i));
01070         pbuf_free(arp_table[i].q);
01071       }
01072       arp_table[i].q = p;
01073       result = ERR_OK;
01074       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: queued packet %p on ARP entry %"U16_F"\n", (void *)q, (u16_t)i));
01075 #endif /* ARP_QUEUEING */
01076     } else {
01077       ETHARP_STATS_INC(etharp.memerr);
01078       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));
01079       result = ERR_MEM;
01080     }
01081   }
01082   return result;
01083 }
01084 
01085 /**
01086  * Send a raw ARP packet (opcode and all addresses can be modified)
01087  *
01088  * @param netif the lwip network interface on which to send the ARP packet
01089  * @param ethsrc_addr the source MAC address for the ethernet header
01090  * @param ethdst_addr the destination MAC address for the ethernet header
01091  * @param hwsrc_addr the source MAC address for the ARP protocol header
01092  * @param ipsrc_addr the source IP address for the ARP protocol header
01093  * @param hwdst_addr the destination MAC address for the ARP protocol header
01094  * @param ipdst_addr the destination IP address for the ARP protocol header
01095  * @param opcode the type of the ARP packet
01096  * @return ERR_OK if the ARP packet has been sent
01097  *         ERR_MEM if the ARP packet couldn't be allocated
01098  *         any other err_t on failure
01099  */
01100 static err_t
01101 etharp_raw(struct netif *netif, const struct eth_addr *ethsrc_addr,
01102            const struct eth_addr *ethdst_addr,
01103            const struct eth_addr *hwsrc_addr, const ip4_addr_t *ipsrc_addr,
01104            const struct eth_addr *hwdst_addr, const ip4_addr_t *ipdst_addr,
01105            const u16_t opcode)
01106 {
01107   struct pbuf *p;
01108   err_t result = ERR_OK;
01109   struct etharp_hdr *hdr;
01110 
01111   LWIP_ASSERT("netif != NULL", netif != NULL);
01112 
01113   /* allocate a pbuf for the outgoing ARP request packet */
01114   p = pbuf_alloc(PBUF_LINK, SIZEOF_ETHARP_HDR, PBUF_RAM);
01115   /* could allocate a pbuf for an ARP request? */
01116   if (p == NULL) {
01117     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS,
01118                 ("etharp_raw: could not allocate pbuf for ARP request.\n"));
01119     ETHARP_STATS_INC(etharp.memerr);
01120     return ERR_MEM;
01121   }
01122   LWIP_ASSERT("check that first pbuf can hold struct etharp_hdr",
01123               (p->len >= SIZEOF_ETHARP_HDR));
01124 
01125   hdr = (struct etharp_hdr *)p->payload;
01126   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_raw: sending raw ARP packet.\n"));
01127   hdr->opcode = lwip_htons(opcode);
01128 
01129   LWIP_ASSERT("netif->hwaddr_len must be the same as ETH_HWADDR_LEN for etharp!",
01130               (netif->hwaddr_len == ETH_HWADDR_LEN));
01131 
01132   /* Write the ARP MAC-Addresses */
01133   SMEMCPY(&hdr->shwaddr, hwsrc_addr, ETH_HWADDR_LEN);
01134   SMEMCPY(&hdr->dhwaddr, hwdst_addr, ETH_HWADDR_LEN);
01135   /* Copy struct ip4_addr_wordaligned to aligned ip4_addr, to support compilers without
01136    * structure packing. */
01137   IPADDR_WORDALIGNED_COPY_FROM_IP4_ADDR_T(&hdr->sipaddr, ipsrc_addr);
01138   IPADDR_WORDALIGNED_COPY_FROM_IP4_ADDR_T(&hdr->dipaddr, ipdst_addr);
01139 
01140   hdr->hwtype = PP_HTONS(LWIP_IANA_HWTYPE_ETHERNET);
01141   hdr->proto = PP_HTONS(ETHTYPE_IP);
01142   /* set hwlen and protolen */
01143   hdr->hwlen = ETH_HWADDR_LEN;
01144   hdr->protolen = sizeof(ip4_addr_t);
01145 
01146   /* send ARP query */
01147 #if LWIP_AUTOIP
01148   /* If we are using Link-Local, all ARP packets that contain a Link-Local
01149    * 'sender IP address' MUST be sent using link-layer broadcast instead of
01150    * link-layer unicast. (See RFC3927 Section 2.5, last paragraph) */
01151   if (ip4_addr_islinklocal(ipsrc_addr)) {
01152     ethernet_output(netif, p, ethsrc_addr, &ethbroadcast, ETHTYPE_ARP);
01153   } else
01154 #endif /* LWIP_AUTOIP */
01155   {
01156     ethernet_output(netif, p, ethsrc_addr, ethdst_addr, ETHTYPE_ARP);
01157   }
01158 
01159   ETHARP_STATS_INC(etharp.xmit);
01160   /* free ARP query packet */
01161   pbuf_free(p);
01162   p = NULL;
01163   /* could not allocate pbuf for ARP request */
01164 
01165   return result;
01166 }
01167 
01168 /**
01169  * Send an ARP request packet asking for ipaddr to a specific eth address.
01170  * Used to send unicast request to refresh the ARP table just before an entry
01171  * times out
01172  *
01173  * @param netif the lwip network interface on which to send the request
01174  * @param ipaddr the IP address for which to ask
01175  * @param hw_dst_addr the ethernet address to send this packet to
01176  * @return ERR_OK if the request has been sent
01177  *         ERR_MEM if the ARP packet couldn't be allocated
01178  *         any other err_t on failure
01179  */
01180 static err_t
01181 etharp_request_dst(struct netif *netif, const ip4_addr_t *ipaddr, const struct eth_addr *hw_dst_addr)
01182 {
01183   return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, hw_dst_addr,
01184                     (struct eth_addr *)netif->hwaddr, netif_ip4_addr(netif), &ethzero,
01185                     ipaddr, ARP_REQUEST);
01186 }
01187 
01188 /**
01189  * Send an ARP request packet asking for ipaddr.
01190  *
01191  * @param netif the lwip network interface on which to send the request
01192  * @param ipaddr the IP address for which to ask
01193  * @return ERR_OK if the request has been sent
01194  *         ERR_MEM if the ARP packet couldn't be allocated
01195  *         any other err_t on failure
01196  */
01197 err_t
01198 etharp_request(struct netif *netif, const ip4_addr_t *ipaddr)
01199 {
01200   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_request: sending ARP request.\n"));
01201   return etharp_request_dst(netif, ipaddr, &ethbroadcast);
01202 }
01203 
01204 #endif /* LWIP_IPV4 && LWIP_ARP */