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 #ifdef LWIP_HOOK_FILENAME
00060 #include LWIP_HOOK_FILENAME
00061 #endif
00062 
00063 #if LWIP_IPV4 && LWIP_ARP /* don't build if not configured for use in lwipopts.h */
00064 
00065 /** Re-request a used ARP entry 1 minute before it would expire to prevent
00066  *  breaking a steadily used connection because the ARP entry timed out. */
00067 #define ARP_AGE_REREQUEST_USED_UNICAST   (ARP_MAXAGE - 30)
00068 #define ARP_AGE_REREQUEST_USED_BROADCAST (ARP_MAXAGE - 15)
00069 
00070 /** the time an ARP entry stays pending after first request,
00071  *  for ARP_TMR_INTERVAL = 1000, this is
00072  *  10 seconds.
00073  *
00074  *  @internal Keep this number at least 2, otherwise it might
00075  *  run out instantly if the timeout occurs directly after a request.
00076  */
00077 #define ARP_MAXPENDING 5
00078 
00079 /** ARP states */
00080 enum etharp_state {
00081   ETHARP_STATE_EMPTY = 0,
00082   ETHARP_STATE_PENDING,
00083   ETHARP_STATE_STABLE,
00084   ETHARP_STATE_STABLE_REREQUESTING_1,
00085   ETHARP_STATE_STABLE_REREQUESTING_2
00086 #if ETHARP_SUPPORT_STATIC_ENTRIES
00087   ,ETHARP_STATE_STATIC
00088 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00089 };
00090 
00091 struct etharp_entry {
00092 #if ARP_QUEUEING
00093   /** Pointer to queue of pending outgoing packets on this ARP entry. */
00094   struct etharp_q_entry *q;
00095 #else /* ARP_QUEUEING */
00096   /** Pointer to a single pending outgoing packet on this ARP entry. */
00097   struct pbuf *q;
00098 #endif /* ARP_QUEUEING */
00099   ip4_addr_t ipaddr;
00100   struct netif *netif;
00101   struct eth_addr ethaddr;
00102   u16_t ctime;
00103   u8_t state;
00104 };
00105 
00106 static struct etharp_entry arp_table[ARP_TABLE_SIZE];
00107 
00108 #if !LWIP_NETIF_HWADDRHINT
00109 static u8_t etharp_cached_entry;
00110 #endif /* !LWIP_NETIF_HWADDRHINT */
00111 
00112 /** Try hard to create a new entry - we want the IP address to appear in
00113     the cache (even if this means removing an active entry or so). */
00114 #define ETHARP_FLAG_TRY_HARD     1
00115 #define ETHARP_FLAG_FIND_ONLY    2
00116 #if ETHARP_SUPPORT_STATIC_ENTRIES
00117 #define ETHARP_FLAG_STATIC_ENTRY 4
00118 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00119 
00120 #if LWIP_NETIF_HWADDRHINT
00121 #define ETHARP_SET_HINT(netif, hint)  if (((netif) != NULL) && ((netif)->addr_hint != NULL))  \
00122                                       *((netif)->addr_hint) = (hint);
00123 #else /* LWIP_NETIF_HWADDRHINT */
00124 #define ETHARP_SET_HINT(netif, hint)  (etharp_cached_entry = (hint))
00125 #endif /* LWIP_NETIF_HWADDRHINT */
00126 
00127 
00128 /* Some checks, instead of etharp_init(): */
00129 #if (LWIP_ARP && (ARP_TABLE_SIZE > 0x7f))
00130   #error "ARP_TABLE_SIZE must fit in an s8_t, you have to reduce it in your lwipopts.h"
00131 #endif
00132 
00133 
00134 static err_t etharp_request_dst(struct netif *netif, const ip4_addr_t *ipaddr, const struct eth_addr* hw_dst_addr);
00135 static err_t etharp_raw(struct netif *netif,
00136                         const struct eth_addr *ethsrc_addr, const struct eth_addr *ethdst_addr,
00137                         const struct eth_addr *hwsrc_addr, const ip4_addr_t *ipsrc_addr,
00138                         const struct eth_addr *hwdst_addr, const ip4_addr_t *ipdst_addr,
00139                         const u16_t opcode);
00140 
00141 #if ARP_QUEUEING
00142 /**
00143  * Free a complete queue of etharp entries
00144  *
00145  * @param q a qeueue of etharp_q_entry's to free
00146  */
00147 static void
00148 free_etharp_q(struct etharp_q_entry *q)
00149 {
00150   struct etharp_q_entry *r;
00151   LWIP_ASSERT("q != NULL", q != NULL);
00152   LWIP_ASSERT("q->p != NULL", q->p != NULL);
00153   while (q) {
00154     r = q;
00155     q = q->next;
00156     LWIP_ASSERT("r->p != NULL", (r->p != NULL));
00157     pbuf_free(r->p);
00158     memp_free(MEMP_ARP_QUEUE, r);
00159   }
00160 }
00161 #else /* ARP_QUEUEING */
00162 
00163 /** Compatibility define: free the queued pbuf */
00164 #define free_etharp_q(q) pbuf_free(q)
00165 
00166 #endif /* ARP_QUEUEING */
00167 
00168 /** Clean up ARP table entries */
00169 static void
00170 etharp_free_entry(int i)
00171 {
00172   /* remove from SNMP ARP index tree */
00173   mib2_remove_arp_entry(arp_table[i].netif, &arp_table[i].ipaddr);
00174   /* and empty packet queue */
00175   if (arp_table[i].q != NULL) {
00176     /* remove all queued packets */
00177     LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_free_entry: freeing entry %"U16_F", packet queue %p.\n", (u16_t)i, (void *)(arp_table[i].q)));
00178     free_etharp_q(arp_table[i].q);
00179     arp_table[i].q = NULL;
00180   }
00181   /* recycle entry for re-use */
00182   arp_table[i].state = ETHARP_STATE_EMPTY;
00183 #ifdef LWIP_DEBUG
00184   /* for debugging, clean out the complete entry */
00185   arp_table[i].ctime = 0;
00186   arp_table[i].netif = NULL;
00187   ip4_addr_set_zero(&arp_table[i].ipaddr);
00188   arp_table[i].ethaddr = ethzero;
00189 #endif /* LWIP_DEBUG */
00190 }
00191 
00192 /**
00193  * Clears expired entries in the ARP table.
00194  *
00195  * This function should be called every ARP_TMR_INTERVAL milliseconds (1 second),
00196  * in order to expire entries in the ARP table.
00197  */
00198 void
00199 etharp_tmr(void)
00200 {
00201   u8_t i;
00202 
00203   LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer\n"));
00204   /* remove expired entries from the ARP table */
00205   for (i = 0; i < ARP_TABLE_SIZE; ++i) {
00206     u8_t state = arp_table[i].state;
00207     if (state != ETHARP_STATE_EMPTY
00208 #if ETHARP_SUPPORT_STATIC_ENTRIES
00209       && (state != ETHARP_STATE_STATIC)
00210 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00211       ) {
00212       arp_table[i].ctime++;
00213       if ((arp_table[i].ctime >= ARP_MAXAGE) ||
00214           ((arp_table[i].state == ETHARP_STATE_PENDING)  &&
00215            (arp_table[i].ctime >= ARP_MAXPENDING))) {
00216         /* pending or stable entry has become old! */
00217         LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer: expired %s entry %"U16_F".\n",
00218              arp_table[i].state >= ETHARP_STATE_STABLE ? "stable" : "pending", (u16_t)i));
00219         /* clean up entries that have just been expired */
00220         etharp_free_entry(i);
00221       } else if (arp_table[i].state == ETHARP_STATE_STABLE_REREQUESTING_1) {
00222         /* Don't send more than one request every 2 seconds. */
00223         arp_table[i].state = ETHARP_STATE_STABLE_REREQUESTING_2;
00224       } else if (arp_table[i].state == ETHARP_STATE_STABLE_REREQUESTING_2) {
00225         /* Reset state to stable, so that the next transmitted packet will
00226            re-send an ARP request. */
00227         arp_table[i].state = ETHARP_STATE_STABLE;
00228       } else if (arp_table[i].state == ETHARP_STATE_PENDING) {
00229         /* still pending, resend an ARP query */
00230         etharp_request(arp_table[i].netif, &arp_table[i].ipaddr);
00231       }
00232     }
00233   }
00234 }
00235 
00236 /**
00237  * Search the ARP table for a matching or new entry.
00238  *
00239  * If an IP address is given, return a pending or stable ARP entry that matches
00240  * the address. If no match is found, create a new entry with this address set,
00241  * but in state ETHARP_EMPTY. The caller must check and possibly change the
00242  * state of the returned entry.
00243  *
00244  * If ipaddr is NULL, return a initialized new entry in state ETHARP_EMPTY.
00245  *
00246  * In all cases, attempt to create new entries from an empty entry. If no
00247  * empty entries are available and ETHARP_FLAG_TRY_HARD flag is set, recycle
00248  * old entries. Heuristic choose the least important entry for recycling.
00249  *
00250  * @param ipaddr IP address to find in ARP cache, or to add if not found.
00251  * @param flags See @ref etharp_state
00252  * @param netif netif related to this address (used for NETIF_HWADDRHINT)
00253  *
00254  * @return The ARP entry index that matched or is created, ERR_MEM if no
00255  * entry is found or could be recycled.
00256  */
00257 static s8_t
00258 etharp_find_entry(const ip4_addr_t *ipaddr, u8_t flags, struct netif* netif)
00259 {
00260   s8_t old_pending = ARP_TABLE_SIZE, old_stable = ARP_TABLE_SIZE;
00261   s8_t empty = ARP_TABLE_SIZE;
00262   u8_t i = 0;
00263   /* oldest entry with packets on queue */
00264   s8_t old_queue = ARP_TABLE_SIZE;
00265   /* its age */
00266   u16_t age_queue = 0, age_pending = 0, age_stable = 0;
00267 
00268   LWIP_UNUSED_ARG(netif);
00269 
00270   /**
00271    * a) do a search through the cache, remember candidates
00272    * b) select candidate entry
00273    * c) create new entry
00274    */
00275 
00276   /* a) in a single search sweep, do all of this
00277    * 1) remember the first empty entry (if any)
00278    * 2) remember the oldest stable entry (if any)
00279    * 3) remember the oldest pending entry without queued packets (if any)
00280    * 4) remember the oldest pending entry with queued packets (if any)
00281    * 5) search for a matching IP entry, either pending or stable
00282    *    until 5 matches, or all entries are searched for.
00283    */
00284 
00285   for (i = 0; i < ARP_TABLE_SIZE; ++i) {
00286     u8_t state = arp_table[i].state;
00287     /* no empty entry found yet and now we do find one? */
00288     if ((empty == ARP_TABLE_SIZE) && (state == ETHARP_STATE_EMPTY)) {
00289       LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_find_entry: found empty entry %"U16_F"\n", (u16_t)i));
00290       /* remember first empty entry */
00291       empty = i;
00292     } else if (state != ETHARP_STATE_EMPTY) {
00293       LWIP_ASSERT("state == ETHARP_STATE_PENDING || state >= ETHARP_STATE_STABLE",
00294         state == ETHARP_STATE_PENDING || state >= ETHARP_STATE_STABLE);
00295       /* if given, does IP address match IP address in ARP entry? */
00296       if (ipaddr && ip4_addr_cmp(ipaddr, &arp_table[i].ipaddr)
00297 #if ETHARP_TABLE_MATCH_NETIF
00298           && ((netif == NULL) || (netif == arp_table[i].netif))
00299 #endif /* ETHARP_TABLE_MATCH_NETIF */
00300         ) {
00301         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: found matching entry %"U16_F"\n", (u16_t)i));
00302         /* found exact IP address match, simply bail out */
00303         return i;
00304       }
00305       /* pending entry? */
00306       if (state == ETHARP_STATE_PENDING) {
00307         /* pending with queued packets? */
00308         if (arp_table[i].q != NULL) {
00309           if (arp_table[i].ctime >= age_queue) {
00310             old_queue = i;
00311             age_queue = arp_table[i].ctime;
00312           }
00313         } else
00314         /* pending without queued packets? */
00315         {
00316           if (arp_table[i].ctime >= age_pending) {
00317             old_pending = i;
00318             age_pending = arp_table[i].ctime;
00319           }
00320         }
00321       /* stable entry? */
00322       } else if (state >= ETHARP_STATE_STABLE) {
00323 #if ETHARP_SUPPORT_STATIC_ENTRIES
00324         /* don't record old_stable for static entries since they never expire */
00325         if (state < ETHARP_STATE_STATIC)
00326 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00327         {
00328           /* remember entry with oldest stable entry in oldest, its age in maxtime */
00329           if (arp_table[i].ctime >= age_stable) {
00330             old_stable = i;
00331             age_stable = arp_table[i].ctime;
00332           }
00333         }
00334       }
00335     }
00336   }
00337   /* { we have no match } => try to create a new entry */
00338 
00339   /* don't create new entry, only search? */
00340   if (((flags & ETHARP_FLAG_FIND_ONLY) != 0) ||
00341       /* or no empty entry found and not allowed to recycle? */
00342       ((empty == ARP_TABLE_SIZE) && ((flags & ETHARP_FLAG_TRY_HARD) == 0))) {
00343     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: no empty entry found and not allowed to recycle\n"));
00344     return (s8_t)ERR_MEM;
00345   }
00346 
00347   /* b) choose the least destructive entry to recycle:
00348    * 1) empty entry
00349    * 2) oldest stable entry
00350    * 3) oldest pending entry without queued packets
00351    * 4) oldest pending entry with queued packets
00352    *
00353    * { ETHARP_FLAG_TRY_HARD is set at this point }
00354    */
00355 
00356   /* 1) empty entry available? */
00357   if (empty < ARP_TABLE_SIZE) {
00358     i = empty;
00359     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting empty entry %"U16_F"\n", (u16_t)i));
00360   } else {
00361     /* 2) found recyclable stable entry? */
00362     if (old_stable < ARP_TABLE_SIZE) {
00363       /* recycle oldest stable*/
00364       i = old_stable;
00365       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest stable entry %"U16_F"\n", (u16_t)i));
00366       /* no queued packets should exist on stable entries */
00367       LWIP_ASSERT("arp_table[i].q == NULL", arp_table[i].q == NULL);
00368     /* 3) found recyclable pending entry without queued packets? */
00369     } else if (old_pending < ARP_TABLE_SIZE) {
00370       /* recycle oldest pending */
00371       i = old_pending;
00372       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest pending entry %"U16_F" (without queue)\n", (u16_t)i));
00373     /* 4) found recyclable pending entry with queued packets? */
00374     } else if (old_queue < ARP_TABLE_SIZE) {
00375       /* recycle oldest pending (queued packets are free in etharp_free_entry) */
00376       i = old_queue;
00377       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)));
00378       /* no empty or recyclable entries found */
00379     } else {
00380       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: no empty or recyclable entries found\n"));
00381       return (s8_t)ERR_MEM;
00382     }
00383 
00384     /* { empty or recyclable entry found } */
00385     LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
00386     etharp_free_entry(i);
00387   }
00388 
00389   LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
00390   LWIP_ASSERT("arp_table[i].state == ETHARP_STATE_EMPTY",
00391     arp_table[i].state == ETHARP_STATE_EMPTY);
00392 
00393   /* IP address given? */
00394   if (ipaddr != NULL) {
00395     /* set IP address */
00396     ip4_addr_copy(arp_table[i].ipaddr, *ipaddr);
00397   }
00398   arp_table[i].ctime = 0;
00399 #if ETHARP_TABLE_MATCH_NETIF
00400   arp_table[i].netif = netif;
00401 #endif /* ETHARP_TABLE_MATCH_NETIF*/
00402   return (err_t)i;
00403 }
00404 
00405 /**
00406  * Update (or insert) a IP/MAC address pair in the ARP cache.
00407  *
00408  * If a pending entry is resolved, any queued packets will be sent
00409  * at this point.
00410  *
00411  * @param netif netif related to this entry (used for NETIF_ADDRHINT)
00412  * @param ipaddr IP address of the inserted ARP entry.
00413  * @param ethaddr Ethernet address of the inserted ARP entry.
00414  * @param flags See @ref etharp_state
00415  *
00416  * @return
00417  * - ERR_OK Successfully updated ARP cache.
00418  * - ERR_MEM If we could not add a new ARP entry when ETHARP_FLAG_TRY_HARD was set.
00419  * - ERR_ARG Non-unicast address given, those will not appear in ARP cache.
00420  *
00421  * @see pbuf_free()
00422  */
00423 static err_t
00424 etharp_update_arp_entry(struct netif *netif, const ip4_addr_t *ipaddr, struct eth_addr *ethaddr, u8_t flags)
00425 {
00426   s8_t i;
00427   LWIP_ASSERT("netif->hwaddr_len == ETH_HWADDR_LEN", netif->hwaddr_len == ETH_HWADDR_LEN);
00428   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",
00429     ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr),
00430     (u16_t)ethaddr->addr[0], (u16_t)ethaddr->addr[1], (u16_t)ethaddr->addr[2],
00431     (u16_t)ethaddr->addr[3], (u16_t)ethaddr->addr[4], (u16_t)ethaddr->addr[5]));
00432   /* non-unicast address? */
00433   if (ip4_addr_isany(ipaddr) ||
00434       ip4_addr_isbroadcast(ipaddr, netif) ||
00435       ip4_addr_ismulticast(ipaddr)) {
00436     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_update_arp_entry: will not add non-unicast IP address to ARP cache\n"));
00437     return ERR_ARG;
00438   }
00439   /* find or create ARP entry */
00440   i = etharp_find_entry(ipaddr, flags, netif);
00441   /* bail out if no entry could be found */
00442   if (i < 0) {
00443     return (err_t)i;
00444   }
00445 
00446 #if ETHARP_SUPPORT_STATIC_ENTRIES
00447   if (flags & ETHARP_FLAG_STATIC_ENTRY) {
00448     /* record static type */
00449     arp_table[i].state = ETHARP_STATE_STATIC;
00450   } else if (arp_table[i].state == ETHARP_STATE_STATIC) {
00451     /* found entry is a static type, don't overwrite it */
00452     return ERR_VAL;
00453   } else
00454 #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
00455   {
00456     /* mark it stable */
00457     arp_table[i].state = ETHARP_STATE_STABLE;
00458   }
00459 
00460   /* record network interface */
00461   arp_table[i].netif = netif;
00462   /* insert in SNMP ARP index tree */
00463   mib2_add_arp_entry(netif, &arp_table[i].ipaddr);
00464 
00465   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_update_arp_entry: updating stable entry %"S16_F"\n", (s16_t)i));
00466   /* update address */
00467   ETHADDR32_COPY(&arp_table[i].ethaddr, ethaddr);
00468   /* reset time stamp */
00469   arp_table[i].ctime = 0;
00470   /* this is where we will send out queued packets! */
00471 #if ARP_QUEUEING
00472   while (arp_table[i].q != NULL) {
00473     struct pbuf *p;
00474     /* remember remainder of queue */
00475     struct etharp_q_entry *q = arp_table[i].q;
00476     /* pop first item off the queue */
00477     arp_table[i].q = q->next;
00478     /* get the packet pointer */
00479     p = q->p;
00480     /* now queue entry can be freed */
00481     memp_free(MEMP_ARP_QUEUE, q);
00482 #else /* ARP_QUEUEING */
00483   if (arp_table[i].q != NULL) {
00484     struct pbuf *p = arp_table[i].q;
00485     arp_table[i].q = NULL;
00486 #endif /* ARP_QUEUEING */
00487     /* send the queued IP packet */
00488     ethernet_output(netif, p, (struct eth_addr*)(netif->hwaddr), ethaddr, ETHTYPE_IP);
00489     /* free the queued IP packet */
00490     pbuf_free(p);
00491   }
00492   return ERR_OK;
00493 }
00494 
00495 #if ETHARP_SUPPORT_STATIC_ENTRIES
00496 /** Add a new static entry to the ARP table. If an entry exists for the
00497  * specified IP address, this entry is overwritten.
00498  * If packets are queued for the specified IP address, they are sent out.
00499  *
00500  * @param ipaddr IP address for the new static entry
00501  * @param ethaddr ethernet address for the new static entry
00502  * @return See return values of etharp_add_static_entry
00503  */
00504 err_t
00505 etharp_add_static_entry(const ip4_addr_t *ipaddr, struct eth_addr *ethaddr)
00506 {
00507   struct netif *netif;
00508   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",
00509     ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr),
00510     (u16_t)ethaddr->addr[0], (u16_t)ethaddr->addr[1], (u16_t)ethaddr->addr[2],
00511     (u16_t)ethaddr->addr[3], (u16_t)ethaddr->addr[4], (u16_t)ethaddr->addr[5]));
00512 
00513   netif = ip4_route(ipaddr);
00514   if (netif == NULL) {
00515     return ERR_RTE;
00516   }
00517 
00518   return etharp_update_arp_entry(netif, ipaddr, ethaddr, ETHARP_FLAG_TRY_HARD | ETHARP_FLAG_STATIC_ENTRY);
00519 }
00520 
00521 /** Remove a static entry from the ARP table previously added with a call to
00522  * etharp_add_static_entry.
00523  *
00524  * @param ipaddr IP address of the static entry to remove
00525  * @return ERR_OK: entry removed
00526  *         ERR_MEM: entry wasn't found
00527  *         ERR_ARG: entry wasn't a static entry but a dynamic one
00528  */
00529 err_t
00530 etharp_remove_static_entry(const ip4_addr_t *ipaddr)
00531 {
00532   s8_t i;
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   u8_t 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 s8_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   s8_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 u8_t
00612 etharp_get_entry(u8_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_ERROR("netif != NULL", (netif != NULL), return;);
00649 
00650   hdr = (struct etharp_hdr *)p->payload;
00651 
00652   /* RFC 826 "Packet Reception": */
00653   if ((hdr->hwtype != PP_HTONS(HWTYPE_ETHERNET)) ||
00654       (hdr->hwlen != ETH_HWADDR_LEN) ||
00655       (hdr->protolen != sizeof(ip4_addr_t)) ||
00656       (hdr->proto != PP_HTONS(ETHTYPE_IP)))  {
00657     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING,
00658       ("etharp_input: packet dropped, wrong hw type, hwlen, proto, protolen or ethernet type (%"U16_F"/%"U16_F"/%"U16_F"/%"U16_F")\n",
00659       hdr->hwtype, (u16_t)hdr->hwlen, hdr->proto, (u16_t)hdr->protolen));
00660     ETHARP_STATS_INC(etharp.proterr);
00661     ETHARP_STATS_INC(etharp.drop);
00662     pbuf_free(p);
00663     return;
00664   }
00665   ETHARP_STATS_INC(etharp.recv);
00666 
00667 #if LWIP_AUTOIP
00668   /* We have to check if a host already has configured our random
00669    * created link local address and continuously check if there is
00670    * a host with this IP-address so we can detect collisions */
00671   autoip_arp_reply(netif, hdr);
00672 #endif /* LWIP_AUTOIP */
00673 
00674   /* Copy struct ip4_addr2 to aligned ip4_addr, to support compilers without
00675    * structure packing (not using structure copy which breaks strict-aliasing rules). */
00676   IPADDR2_COPY(&sipaddr, &hdr->sipaddr);
00677   IPADDR2_COPY(&dipaddr, &hdr->dipaddr);
00678 
00679   /* this interface is not configured? */
00680   if (ip4_addr_isany_val(*netif_ip4_addr(netif))) {
00681     for_us = 0;
00682   } else {
00683     /* ARP packet directed to us? */
00684     for_us = (u8_t)ip4_addr_cmp(&dipaddr, netif_ip4_addr(netif));
00685   }
00686 
00687   /* ARP message directed to us?
00688       -> add IP address in ARP cache; assume requester wants to talk to us,
00689          can result in directly sending the queued packets for this host.
00690      ARP message not directed to us?
00691       ->  update the source IP address in the cache, if present */
00692   etharp_update_arp_entry(netif, &sipaddr, &(hdr->shwaddr),
00693                    for_us ? ETHARP_FLAG_TRY_HARD : ETHARP_FLAG_FIND_ONLY);
00694 
00695   /* now act on the message itself */
00696   switch (hdr->opcode) {
00697   /* ARP request? */
00698   case PP_HTONS(ARP_REQUEST):
00699     /* ARP request. If it asked for our address, we send out a
00700      * reply. In any case, we time-stamp any existing ARP entry,
00701      * and possibly send out an IP packet that was queued on it. */
00702 
00703     LWIP_DEBUGF (ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: incoming ARP request\n"));
00704     /* ARP request for our address? */
00705     if (for_us) {
00706       /* send ARP response */
00707       etharp_raw(netif,
00708                  (struct eth_addr *)netif->hwaddr, &hdr->shwaddr,
00709                  (struct eth_addr *)netif->hwaddr, netif_ip4_addr(netif),
00710                  &hdr->shwaddr, &sipaddr,
00711                  ARP_REPLY);
00712     /* we are not configured? */
00713     } else if (ip4_addr_isany_val(*netif_ip4_addr(netif))) {
00714       /* { for_us == 0 and netif->ip_addr.addr == 0 } */
00715       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: we are unconfigured, ARP request ignored.\n"));
00716     /* request was not directed to us */
00717     } else {
00718       /* { for_us == 0 and netif->ip_addr.addr != 0 } */
00719       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: ARP request was not for us.\n"));
00720     }
00721     break;
00722   case PP_HTONS(ARP_REPLY):
00723     /* ARP reply. We already updated the ARP cache earlier. */
00724     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: incoming ARP reply\n"));
00725 #if (LWIP_DHCP && DHCP_DOES_ARP_CHECK)
00726     /* DHCP wants to know about ARP replies from any host with an
00727      * IP address also offered to us by the DHCP server. We do not
00728      * want to take a duplicate IP address on a single network.
00729      * @todo How should we handle redundant (fail-over) interfaces? */
00730     dhcp_arp_reply(netif, &sipaddr);
00731 #endif /* (LWIP_DHCP && DHCP_DOES_ARP_CHECK) */
00732     break;
00733   default:
00734     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_input: ARP unknown opcode type %"S16_F"\n", lwip_htons(hdr->opcode)));
00735     ETHARP_STATS_INC(etharp.err);
00736     break;
00737   }
00738   /* free ARP packet */
00739   pbuf_free(p);
00740 }
00741 
00742 /** Just a small helper function that sends a pbuf to an ethernet address
00743  * in the arp_table specified by the index 'arp_idx'.
00744  */
00745 static err_t
00746 etharp_output_to_arp_index(struct netif *netif, struct pbuf *q, u8_t arp_idx)
00747 {
00748   LWIP_ASSERT("arp_table[arp_idx].state >= ETHARP_STATE_STABLE",
00749               arp_table[arp_idx].state >= ETHARP_STATE_STABLE);
00750   /* if arp table entry is about to expire: re-request it,
00751      but only if its state is ETHARP_STATE_STABLE to prevent flooding the
00752      network with ARP requests if this address is used frequently. */
00753   if (arp_table[arp_idx].state == ETHARP_STATE_STABLE) {
00754     if (arp_table[arp_idx].ctime >= ARP_AGE_REREQUEST_USED_BROADCAST) {
00755       /* issue a standard request using broadcast */
00756       if (etharp_request(netif, &arp_table[arp_idx].ipaddr) == ERR_OK) {
00757         arp_table[arp_idx].state = ETHARP_STATE_STABLE_REREQUESTING_1;
00758       }
00759     } else if (arp_table[arp_idx].ctime >= ARP_AGE_REREQUEST_USED_UNICAST) {
00760       /* issue a unicast request (for 15 seconds) to prevent unnecessary broadcast */
00761       if (etharp_request_dst(netif, &arp_table[arp_idx].ipaddr, &arp_table[arp_idx].ethaddr) == ERR_OK) {
00762         arp_table[arp_idx].state = ETHARP_STATE_STABLE_REREQUESTING_1;
00763       }
00764     }
00765   }
00766 
00767   return ethernet_output(netif, q, (struct eth_addr*)(netif->hwaddr), &arp_table[arp_idx].ethaddr, ETHTYPE_IP);
00768 }
00769 
00770 /**
00771  * Resolve and fill-in Ethernet address header for outgoing IP packet.
00772  *
00773  * For IP multicast and broadcast, corresponding Ethernet addresses
00774  * are selected and the packet is transmitted on the link.
00775  *
00776  * For unicast addresses, the packet is submitted to etharp_query(). In
00777  * case the IP address is outside the local network, the IP address of
00778  * the gateway is used.
00779  *
00780  * @param netif The lwIP network interface which the IP packet will be sent on.
00781  * @param q The pbuf(s) containing the IP packet to be sent.
00782  * @param ipaddr The IP address of the packet destination.
00783  *
00784  * @return
00785  * - ERR_RTE No route to destination (no gateway to external networks),
00786  * or the return type of either etharp_query() or ethernet_output().
00787  */
00788 err_t
00789 etharp_output(struct netif *netif, struct pbuf *q, const ip4_addr_t *ipaddr)
00790 {
00791   const struct eth_addr *dest;
00792   struct eth_addr mcastaddr;
00793   const ip4_addr_t *dst_addr = ipaddr;
00794 
00795   LWIP_ASSERT("netif != NULL", netif != NULL);
00796   LWIP_ASSERT("q != NULL", q != NULL);
00797   LWIP_ASSERT("ipaddr != NULL", ipaddr != NULL);
00798 
00799   /* Determine on destination hardware address. Broadcasts and multicasts
00800    * are special, other IP addresses are looked up in the ARP table. */
00801 
00802   /* broadcast destination IP address? */
00803   if (ip4_addr_isbroadcast(ipaddr, netif)) {
00804     /* broadcast on Ethernet also */
00805     dest = (const struct eth_addr *)&ethbroadcast;
00806   /* multicast destination IP address? */
00807   } else if (ip4_addr_ismulticast(ipaddr)) {
00808     /* Hash IP multicast address to MAC address.*/
00809     mcastaddr.addr[0] = LL_IP4_MULTICAST_ADDR_0;
00810     mcastaddr.addr[1] = LL_IP4_MULTICAST_ADDR_1;
00811     mcastaddr.addr[2] = LL_IP4_MULTICAST_ADDR_2;
00812     mcastaddr.addr[3] = ip4_addr2(ipaddr) & 0x7f;
00813     mcastaddr.addr[4] = ip4_addr3(ipaddr);
00814     mcastaddr.addr[5] = ip4_addr4(ipaddr);
00815     /* destination Ethernet address is multicast */
00816     dest = &mcastaddr;
00817   /* unicast destination IP address? */
00818   } else {
00819     s8_t i;
00820     /* outside local network? if so, this can neither be a global broadcast nor
00821        a subnet broadcast. */
00822     if (!ip4_addr_netcmp(ipaddr, netif_ip4_addr(netif), netif_ip4_netmask(netif)) &&
00823         !ip4_addr_islinklocal(ipaddr)) {
00824 #if LWIP_AUTOIP
00825       struct ip_hdr *iphdr = LWIP_ALIGNMENT_CAST(struct ip_hdr*, q->payload);
00826       /* According to RFC 3297, chapter 2.6.2 (Forwarding Rules), a packet with
00827          a link-local source address must always be "directly to its destination
00828          on the same physical link. The host MUST NOT send the packet to any
00829          router for forwarding". */
00830       if (!ip4_addr_islinklocal(&iphdr->src))
00831 #endif /* LWIP_AUTOIP */
00832       {
00833 #ifdef LWIP_HOOK_ETHARP_GET_GW
00834         /* For advanced routing, a single default gateway might not be enough, so get
00835            the IP address of the gateway to handle the current destination address. */
00836         dst_addr = LWIP_HOOK_ETHARP_GET_GW(netif, ipaddr);
00837         if (dst_addr == NULL)
00838 #endif /* LWIP_HOOK_ETHARP_GET_GW */
00839         {
00840           /* interface has default gateway? */
00841           if (!ip4_addr_isany_val(*netif_ip4_gw(netif))) {
00842             /* send to hardware address of default gateway IP address */
00843             dst_addr = netif_ip4_gw(netif);
00844           /* no default gateway available */
00845           } else {
00846             /* no route to destination error (default gateway missing) */
00847             return ERR_RTE;
00848           }
00849         }
00850       }
00851     }
00852 #if LWIP_NETIF_HWADDRHINT
00853     if (netif->addr_hint != NULL) {
00854       /* per-pcb cached entry was given */
00855       u8_t etharp_cached_entry = *(netif->addr_hint);
00856       if (etharp_cached_entry < ARP_TABLE_SIZE) {
00857 #endif /* LWIP_NETIF_HWADDRHINT */
00858         if ((arp_table[etharp_cached_entry].state >= ETHARP_STATE_STABLE) &&
00859 #if ETHARP_TABLE_MATCH_NETIF
00860             (arp_table[etharp_cached_entry].netif == netif) &&
00861 #endif
00862             (ip4_addr_cmp(dst_addr, &arp_table[etharp_cached_entry].ipaddr))) {
00863           /* the per-pcb-cached entry is stable and the right one! */
00864           ETHARP_STATS_INC(etharp.cachehit);
00865           return etharp_output_to_arp_index(netif, q, etharp_cached_entry);
00866         }
00867 #if LWIP_NETIF_HWADDRHINT
00868       }
00869     }
00870 #endif /* LWIP_NETIF_HWADDRHINT */
00871 
00872     /* find stable entry: do this here since this is a critical path for
00873        throughput and etharp_find_entry() is kind of slow */
00874     for (i = 0; i < ARP_TABLE_SIZE; i++) {
00875       if ((arp_table[i].state >= ETHARP_STATE_STABLE) &&
00876 #if ETHARP_TABLE_MATCH_NETIF
00877           (arp_table[i].netif == netif) &&
00878 #endif
00879           (ip4_addr_cmp(dst_addr, &arp_table[i].ipaddr))) {
00880         /* found an existing, stable entry */
00881         ETHARP_SET_HINT(netif, i);
00882         return etharp_output_to_arp_index(netif, q, i);
00883       }
00884     }
00885     /* no stable entry found, use the (slower) query function:
00886        queue on destination Ethernet address belonging to ipaddr */
00887     return etharp_query(netif, dst_addr, q);
00888   }
00889 
00890   /* continuation for multicast/broadcast destinations */
00891   /* obtain source Ethernet address of the given interface */
00892   /* send packet directly on the link */
00893   return ethernet_output(netif, q, (struct eth_addr*)(netif->hwaddr), dest, ETHTYPE_IP);
00894 }
00895 
00896 /**
00897  * Send an ARP request for the given IP address and/or queue a packet.
00898  *
00899  * If the IP address was not yet in the cache, a pending ARP cache entry
00900  * is added and an ARP request is sent for the given address. The packet
00901  * is queued on this entry.
00902  *
00903  * If the IP address was already pending in the cache, a new ARP request
00904  * is sent for the given address. The packet is queued on this entry.
00905  *
00906  * If the IP address was already stable in the cache, and a packet is
00907  * given, it is directly sent and no ARP request is sent out.
00908  *
00909  * If the IP address was already stable in the cache, and no packet is
00910  * given, an ARP request is sent out.
00911  *
00912  * @param netif The lwIP network interface on which ipaddr
00913  * must be queried for.
00914  * @param ipaddr The IP address to be resolved.
00915  * @param q If non-NULL, a pbuf that must be delivered to the IP address.
00916  * q is not freed by this function.
00917  *
00918  * @note q must only be ONE packet, not a packet queue!
00919  *
00920  * @return
00921  * - ERR_BUF Could not make room for Ethernet header.
00922  * - ERR_MEM Hardware address unknown, and no more ARP entries available
00923  *   to query for address or queue the packet.
00924  * - ERR_MEM Could not queue packet due to memory shortage.
00925  * - ERR_RTE No route to destination (no gateway to external networks).
00926  * - ERR_ARG Non-unicast address given, those will not appear in ARP cache.
00927  *
00928  */
00929 err_t
00930 etharp_query(struct netif *netif, const ip4_addr_t *ipaddr, struct pbuf *q)
00931 {
00932   struct eth_addr * srcaddr = (struct eth_addr *)netif->hwaddr;
00933   err_t result = ERR_MEM;
00934   int is_new_entry = 0;
00935   s8_t i; /* ARP entry index */
00936 
00937   /* non-unicast address? */
00938   if (ip4_addr_isbroadcast(ipaddr, netif) ||
00939       ip4_addr_ismulticast(ipaddr) ||
00940       ip4_addr_isany(ipaddr)) {
00941     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: will not add non-unicast IP address to ARP cache\n"));
00942     return ERR_ARG;
00943   }
00944 
00945   /* find entry in ARP cache, ask to create entry if queueing packet */
00946   i = etharp_find_entry(ipaddr, ETHARP_FLAG_TRY_HARD, netif);
00947 
00948   /* could not find or create entry? */
00949   if (i < 0) {
00950     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: could not create ARP entry\n"));
00951     if (q) {
00952       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: packet dropped\n"));
00953       ETHARP_STATS_INC(etharp.memerr);
00954     }
00955     return (err_t)i;
00956   }
00957 
00958   /* mark a fresh entry as pending (we just sent a request) */
00959   if (arp_table[i].state == ETHARP_STATE_EMPTY) {
00960     is_new_entry = 1;
00961     arp_table[i].state = ETHARP_STATE_PENDING;
00962     /* record network interface for re-sending arp request in etharp_tmr */
00963     arp_table[i].netif = netif;
00964   }
00965 
00966   /* { i is either a STABLE or (new or existing) PENDING entry } */
00967   LWIP_ASSERT("arp_table[i].state == PENDING or STABLE",
00968   ((arp_table[i].state == ETHARP_STATE_PENDING) ||
00969    (arp_table[i].state >= ETHARP_STATE_STABLE)));
00970 
00971   /* do we have a new entry? or an implicit query request? */
00972   if (is_new_entry || (q == NULL)) {
00973     /* try to resolve it; send out ARP request */
00974     result = etharp_request(netif, ipaddr);
00975     if (result != ERR_OK) {
00976       /* ARP request couldn't be sent */
00977       /* We don't re-send arp request in etharp_tmr, but we still queue packets,
00978          since this failure could be temporary, and the next packet calling
00979          etharp_query again could lead to sending the queued packets. */
00980     }
00981     if (q == NULL) {
00982       return result;
00983     }
00984   }
00985 
00986   /* packet given? */
00987   LWIP_ASSERT("q != NULL", q != NULL);
00988   /* stable entry? */
00989   if (arp_table[i].state >= ETHARP_STATE_STABLE) {
00990     /* we have a valid IP->Ethernet address mapping */
00991     ETHARP_SET_HINT(netif, i);
00992     /* send the packet */
00993     result = ethernet_output(netif, q, srcaddr, &(arp_table[i].ethaddr), ETHTYPE_IP);
00994   /* pending entry? (either just created or already pending */
00995   } else if (arp_table[i].state == ETHARP_STATE_PENDING) {
00996     /* entry is still pending, queue the given packet 'q' */
00997     struct pbuf *p;
00998     int copy_needed = 0;
00999     /* IF q includes a PBUF_REF, PBUF_POOL or PBUF_RAM, we have no choice but
01000      * to copy the whole queue into a new PBUF_RAM (see bug #11400)
01001      * PBUF_ROMs can be left as they are, since ROM must not get changed. */
01002     p = q;
01003     while (p) {
01004       LWIP_ASSERT("no packet queues allowed!", (p->len != p->tot_len) || (p->next == 0));
01005       if (p->type != PBUF_ROM) {
01006         copy_needed = 1;
01007         break;
01008       }
01009       p = p->next;
01010     }
01011     if (copy_needed) {
01012       /* copy the whole packet into new pbufs */
01013       p = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM);
01014       if (p != NULL) {
01015         if (pbuf_copy(p, q) != ERR_OK) {
01016           pbuf_free(p);
01017           p = NULL;
01018         }
01019       }
01020     } else {
01021       /* referencing the old pbuf is enough */
01022       p = q;
01023       pbuf_ref(p);
01024     }
01025     /* packet could be taken over? */
01026     if (p != NULL) {
01027       /* queue packet ... */
01028 #if ARP_QUEUEING
01029       struct etharp_q_entry *new_entry;
01030       /* allocate a new arp queue entry */
01031       new_entry = (struct etharp_q_entry *)memp_malloc(MEMP_ARP_QUEUE);
01032       if (new_entry != NULL) {
01033         unsigned int qlen = 0;
01034         new_entry->next = 0;
01035         new_entry->p = p;
01036         if (arp_table[i].q != NULL) {
01037           /* queue was already existent, append the new entry to the end */
01038           struct etharp_q_entry *r;
01039           r = arp_table[i].q;
01040           qlen++;
01041           while (r->next != NULL) {
01042             r = r->next;
01043             qlen++;
01044           }
01045           r->next = new_entry;
01046         } else {
01047           /* queue did not exist, first item in queue */
01048           arp_table[i].q = new_entry;
01049         }
01050 #if ARP_QUEUE_LEN
01051         if (qlen >= ARP_QUEUE_LEN) {
01052           struct etharp_q_entry *old;
01053           old = arp_table[i].q;
01054           arp_table[i].q = arp_table[i].q->next;
01055           pbuf_free(old->p);
01056           memp_free(MEMP_ARP_QUEUE, old);
01057         }
01058 #endif
01059         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: queued packet %p on ARP entry %"S16_F"\n", (void *)q, (s16_t)i));
01060         result = ERR_OK;
01061       } else {
01062         /* the pool MEMP_ARP_QUEUE is empty */
01063         pbuf_free(p);
01064         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));
01065         result = ERR_MEM;
01066       }
01067 #else /* ARP_QUEUEING */
01068       /* always queue one packet per ARP request only, freeing a previously queued packet */
01069       if (arp_table[i].q != NULL) {
01070         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));
01071         pbuf_free(arp_table[i].q);
01072       }
01073       arp_table[i].q = p;
01074       result = ERR_OK;
01075       LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: queued packet %p on ARP entry %"S16_F"\n", (void *)q, (s16_t)i));
01076 #endif /* ARP_QUEUEING */
01077     } else {
01078       ETHARP_STATS_INC(etharp.memerr);
01079       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));
01080       result = ERR_MEM;
01081     }
01082   }
01083   return result;
01084 }
01085 
01086 /**
01087  * Send a raw ARP packet (opcode and all addresses can be modified)
01088  *
01089  * @param netif the lwip network interface on which to send the ARP packet
01090  * @param ethsrc_addr the source MAC address for the ethernet header
01091  * @param ethdst_addr the destination MAC address for the ethernet header
01092  * @param hwsrc_addr the source MAC address for the ARP protocol header
01093  * @param ipsrc_addr the source IP address for the ARP protocol header
01094  * @param hwdst_addr the destination MAC address for the ARP protocol header
01095  * @param ipdst_addr the destination IP address for the ARP protocol header
01096  * @param opcode the type of the ARP packet
01097  * @return ERR_OK if the ARP packet has been sent
01098  *         ERR_MEM if the ARP packet couldn't be allocated
01099  *         any other err_t on failure
01100  */
01101 static err_t
01102 etharp_raw(struct netif *netif, const struct eth_addr *ethsrc_addr,
01103            const struct eth_addr *ethdst_addr,
01104            const struct eth_addr *hwsrc_addr, const ip4_addr_t *ipsrc_addr,
01105            const struct eth_addr *hwdst_addr, const ip4_addr_t *ipdst_addr,
01106            const u16_t opcode)
01107 {
01108   struct pbuf *p;
01109   err_t result = ERR_OK;
01110   struct etharp_hdr *hdr;
01111 
01112   LWIP_ASSERT("netif != NULL", netif != NULL);
01113 
01114   /* allocate a pbuf for the outgoing ARP request packet */
01115   p = pbuf_alloc(PBUF_LINK, SIZEOF_ETHARP_HDR, PBUF_RAM);
01116   /* could allocate a pbuf for an ARP request? */
01117   if (p == NULL) {
01118     LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS,
01119       ("etharp_raw: could not allocate pbuf for ARP request.\n"));
01120     ETHARP_STATS_INC(etharp.memerr);
01121     return ERR_MEM;
01122   }
01123   LWIP_ASSERT("check that first pbuf can hold struct etharp_hdr",
01124               (p->len >= SIZEOF_ETHARP_HDR));
01125 
01126   hdr = (struct etharp_hdr *)p->payload;
01127   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_raw: sending raw ARP packet.\n"));
01128   hdr->opcode = lwip_htons(opcode);
01129 
01130   LWIP_ASSERT("netif->hwaddr_len must be the same as ETH_HWADDR_LEN for etharp!",
01131               (netif->hwaddr_len == ETH_HWADDR_LEN));
01132 
01133   /* Write the ARP MAC-Addresses */
01134   ETHADDR16_COPY(&hdr->shwaddr, hwsrc_addr);
01135   ETHADDR16_COPY(&hdr->dhwaddr, hwdst_addr);
01136   /* Copy struct ip4_addr2 to aligned ip4_addr, to support compilers without
01137    * structure packing. */
01138   IPADDR2_COPY(&hdr->sipaddr, ipsrc_addr);
01139   IPADDR2_COPY(&hdr->dipaddr, ipdst_addr);
01140 
01141   hdr->hwtype = PP_HTONS(HWTYPE_ETHERNET);
01142   hdr->proto = PP_HTONS(ETHTYPE_IP);
01143   /* set hwlen and protolen */
01144   hdr->hwlen = ETH_HWADDR_LEN;
01145   hdr->protolen = sizeof(ip4_addr_t);
01146 
01147   /* send ARP query */
01148 #if LWIP_AUTOIP
01149   /* If we are using Link-Local, all ARP packets that contain a Link-Local
01150    * 'sender IP address' MUST be sent using link-layer broadcast instead of
01151    * link-layer unicast. (See RFC3927 Section 2.5, last paragraph) */
01152   if(ip4_addr_islinklocal(ipsrc_addr)) {
01153     ethernet_output(netif, p, ethsrc_addr, &ethbroadcast, ETHTYPE_ARP);
01154   } else
01155 #endif /* LWIP_AUTOIP */
01156   {
01157     ethernet_output(netif, p, ethsrc_addr, ethdst_addr, ETHTYPE_ARP);
01158   }
01159 
01160   ETHARP_STATS_INC(etharp.xmit);
01161   /* free ARP query packet */
01162   pbuf_free(p);
01163   p = NULL;
01164   /* could not allocate pbuf for ARP request */
01165 
01166   return result;
01167 }
01168 
01169 /**
01170  * Send an ARP request packet asking for ipaddr to a specific eth address.
01171  * Used to send unicast request to refresh the ARP table just before an entry
01172  * times out
01173  *
01174  * @param netif the lwip network interface on which to send the request
01175  * @param ipaddr the IP address for which to ask
01176  * @param hw_dst_addr the ethernet address to send this packet to
01177  * @return ERR_OK if the request has been sent
01178  *         ERR_MEM if the ARP packet couldn't be allocated
01179  *         any other err_t on failure
01180  */
01181 static err_t
01182 etharp_request_dst(struct netif *netif, const ip4_addr_t *ipaddr, const struct eth_addr* hw_dst_addr)
01183 {
01184   return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, hw_dst_addr,
01185                     (struct eth_addr *)netif->hwaddr, netif_ip4_addr(netif), &ethzero,
01186                     ipaddr, ARP_REQUEST);
01187 }
01188 
01189 /**
01190  * Send an ARP request packet asking for ipaddr.
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  * @return ERR_OK if the request has been sent
01195  *         ERR_MEM if the ARP packet couldn't be allocated
01196  *         any other err_t on failure
01197  */
01198 err_t
01199 etharp_request(struct netif *netif, const ip4_addr_t *ipaddr)
01200 {
01201   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_request: sending ARP request.\n"));
01202   return etharp_request_dst(netif, ipaddr, &ethbroadcast);
01203 }
01204 #endif /* LWIP_IPV4 && LWIP_ARP */
01205 
01206 #endif /* LWIP_ARP || LWIP_ETHERNET */