etharp.c

lwip-1.4.0

  /* { we have no match } => try to create a new entry */
   
  /* don't create new entry, only search? */
  if (((flags & ETHARP_FLAG_FIND_ONLY) != 0) ||
      /* or no empty entry found and not allowed to recycle? */
      ((empty == ARP_TABLE_SIZE) && ((flags & ETHARP_FLAG_TRY_HARD) == 0))) {
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("find_entry: no empty entry found and not allowed to recycle\n"));
    return (s8_t)ERR_MEM;
  }
  
  /* b) choose the least destructive entry to recycle:
   * 1) empty entry
   * 2) oldest stable entry
   * 3) oldest pending entry without queued packets
   * 4) oldest pending entry with queued packets
   * 
   * { ETHARP_FLAG_TRY_HARD is set at this point }
   */ 

  /* 1) empty entry available? */
  if (empty < ARP_TABLE_SIZE) {
    i = empty;
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("find_entry: selecting empty entry %"U16_F"\n", (u16_t)i));
  } else {
    /* 2) found recyclable stable entry? */
    if (old_stable < ARP_TABLE_SIZE) {
      /* recycle oldest stable*/
      i = old_stable;
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("find_entry: selecting oldest stable entry %"U16_F"\n", (u16_t)i));
      /* no queued packets should exist on stable entries */
      LWIP_ASSERT("arp_table[i].q == NULL", arp_table[i].q == NULL);
    /* 3) found recyclable pending entry without queued packets? */
    } else if (old_pending < ARP_TABLE_SIZE) {
      /* recycle oldest pending */
      i = old_pending;
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("find_entry: selecting oldest pending entry %"U16_F" (without queue)\n", (u16_t)i));
    /* 4) found recyclable pending entry with queued packets? */
    } else if (old_queue < ARP_TABLE_SIZE) {
      /* recycle oldest pending (queued packets are free in free_entry) */
      i = old_queue;
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("find_entry: selecting oldest pending entry %"U16_F", freeing packet queue %p\n", (u16_t)i, (void *)(arp_table[i].q)));
      /* no empty or recyclable entries found */
    } else {
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("find_entry: no empty or recyclable entries found\n"));
      return (s8_t)ERR_MEM;
    }

    /* { empty or recyclable entry found } */
    LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
    free_entry(i);
  }

  LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
  LWIP_ASSERT("arp_table[i].state == ETHARP_STATE_EMPTY",
    arp_table[i].state == ETHARP_STATE_EMPTY);

  /* IP address given? */
  if (ipaddr != NULL) {
    /* set IP address */
    ip_addr_copy(arp_table[i].ipaddr, *ipaddr);
  }
  arp_table[i].ctime = 0;
#if ETHARP_SUPPORT_STATIC_ENTRIES
  arp_table[i].static_entry = 0;
#endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
  return (err_t)i;
}

/**
 * Send an IP packet on the network using netif->linkoutput
 * The ethernet header is filled in before sending.
 *
 * @params netif the lwIP network interface on which to send the packet
 * @params p the packet to send, p->payload pointing to the (uninitialized) ethernet header
 * @params src the source MAC address to be copied into the ethernet header
 * @params dst the destination MAC address to be copied into the ethernet header
 * @return ERR_OK if the packet was sent, any other err_t on failure
 */
static err_t
etharp_send_ip(struct netif *netif, struct pbuf *p, struct eth_addr *src, struct eth_addr *dst)
{
  struct eth_hdr *ethhdr = (struct eth_hdr *)p->payload;

  LWIP_ASSERT("netif->hwaddr_len must be the same as ETHARP_HWADDR_LEN for etharp!",
              (netif->hwaddr_len == ETHARP_HWADDR_LEN));
  ETHADDR32_COPY(&ethhdr->dest, dst);
  ETHADDR16_COPY(&ethhdr->src, src);
  ethhdr->type = PP_HTONS(ETHTYPE_IP);
  LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_send_ip: sending packet %p\n", (void *)p));
  /* send the packet */
  return netif->linkoutput(netif, p);
}

/**
 * Update (or insert) a IP/MAC address pair in the ARP cache.
 *
 * If a pending entry is resolved, any queued packets will be sent
 * at this point.
 * 
 * @param netif netif related to this entry (used for NETIF_ADDRHINT)
 * @param ipaddr IP address of the inserted ARP entry.
 * @param ethaddr Ethernet address of the inserted ARP entry.
 * @param flags @see definition of ETHARP_FLAG_*
 *
 * @return
 * - ERR_OK Succesfully updated ARP cache.
 * - ERR_MEM If we could not add a new ARP entry when ETHARP_FLAG_TRY_HARD was set.
 * - ERR_ARG Non-unicast address given, those will not appear in ARP cache.
 *
 * @see pbuf_free()
 */
static err_t
update_arp_entry(struct netif *netif, ip_addr_t *ipaddr, struct eth_addr *ethaddr, u8_t flags)
{
  s8_t i;
  LWIP_ASSERT("netif->hwaddr_len == ETHARP_HWADDR_LEN", netif->hwaddr_len == ETHARP_HWADDR_LEN);
  LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("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",
    ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr),
    ethaddr->addr[0], ethaddr->addr[1], ethaddr->addr[2],
    ethaddr->addr[3], ethaddr->addr[4], ethaddr->addr[5]));
  /* non-unicast address? */
  if (ip_addr_isany(ipaddr) ||
      ip_addr_isbroadcast(ipaddr, netif) ||
      ip_addr_ismulticast(ipaddr)) {
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("update_arp_entry: will not add non-unicast IP address to ARP cache\n"));
    return ERR_ARG;
  }
  /* find or create ARP entry */
  i = find_entry(ipaddr, flags);
  /* bail out if no entry could be found */
  if (i < 0) {
    return (err_t)i;
  }

#if ETHARP_SUPPORT_STATIC_ENTRIES
  if (flags & ETHARP_FLAG_STATIC_ENTRY) {
    /* record static type */
    arp_table[i].static_entry = 1;
  }
#endif /* ETHARP_SUPPORT_STATIC_ENTRIES */

  /* mark it stable */
  arp_table[i].state = ETHARP_STATE_STABLE;

#if LWIP_SNMP
  /* record network interface */
  arp_table[i].netif = netif;
#endif /* LWIP_SNMP */
  /* insert in SNMP ARP index tree */
  snmp_insert_arpidx_tree(netif, &arp_table[i].ipaddr);

  LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("update_arp_entry: updating stable entry %"S16_F"\n", (s16_t)i));
  /* update address */
  ETHADDR32_COPY(&arp_table[i].ethaddr, ethaddr);
  /* reset time stamp */
  arp_table[i].ctime = 0;
  /* this is where we will send out queued packets! */
#if ARP_QUEUEING
  while (arp_table[i].q != NULL) {
    struct pbuf *p;
    /* remember remainder of queue */
    struct etharp_q_entry *q = arp_table[i].q;
    /* pop first item off the queue */
    arp_table[i].q = q->next;
    /* get the packet pointer */
    p = q->p;
    /* now queue entry can be freed */
    memp_free(MEMP_ARP_QUEUE, q);
#else /* ARP_QUEUEING */
  if (arp_table[i].q != NULL) {
    struct pbuf *p = arp_table[i].q;
    arp_table[i].q = NULL;
#endif /* ARP_QUEUEING */
    /* send the queued IP packet */
    etharp_send_ip(netif, p, (struct eth_addr*)(netif->hwaddr), ethaddr);
    /* free the queued IP packet */
    pbuf_free(p);
  }
  return ERR_OK;
}

#if ETHARP_SUPPORT_STATIC_ENTRIES
/** Add a new static entry to the ARP table. If an entry exists for the
 * specified IP address, this entry is overwritten.
 * If packets are queued for the specified IP address, they are sent out.
 *
 * @param ipaddr IP address for the new static entry
 * @param ethaddr ethernet address for the new static entry
 * @return @see return values of etharp_add_static_entry
 */
err_t
etharp_add_static_entry(ip_addr_t *ipaddr, struct eth_addr *ethaddr)
{
  struct netif *netif;
  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",
    ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr),
    ethaddr->addr[0], ethaddr->addr[1], ethaddr->addr[2],
    ethaddr->addr[3], ethaddr->addr[4], ethaddr->addr[5]));

  netif = ip_route(ipaddr);
  if (netif == NULL) {
    return ERR_RTE;
  }

  return update_arp_entry(netif, ipaddr, ethaddr, ETHARP_FLAG_TRY_HARD | ETHARP_FLAG_STATIC_ENTRY);
}

/** Remove a static entry from the ARP table previously added with a call to
 * etharp_add_static_entry.
 *
 * @param ipaddr IP address of the static entry to remove
 * @return ERR_OK: entry removed
 *         ERR_MEM: entry wasn't found
 *         ERR_ARG: entry wasn't a static entry but a dynamic one
 */
err_t
etharp_remove_static_entry(ip_addr_t *ipaddr)
{
  s8_t i;
  LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_remove_static_entry: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
    ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr)));

  /* find or create ARP entry */
  i = find_entry(ipaddr, ETHARP_FLAG_FIND_ONLY);
  /* bail out if no entry could be found */
  if (i < 0) {
    return (err_t)i;
  }

  if ((arp_table[i].state != ETHARP_STATE_STABLE) ||
    (arp_table[i].static_entry == 0)) {
    /* entry wasn't a static entry, cannot remove it */
    return ERR_ARG;
  }
  /* entry found, free it */
  free_entry(i);
  return ERR_OK;
}
#endif /* ETHARP_SUPPORT_STATIC_ENTRIES */

/**
 * Finds (stable) ethernet/IP address pair from ARP table
 * using interface and IP address index.
 * @note the addresses in the ARP table are in network order!
 *
 * @param netif points to interface index
 * @param ipaddr points to the (network order) IP address index
 * @param eth_ret points to return pointer
 * @param ip_ret points to return pointer
 * @return table index if found, -1 otherwise
 */
s8_t
etharp_find_addr(struct netif *netif, ip_addr_t *ipaddr,
         struct eth_addr **eth_ret, ip_addr_t **ip_ret)
{
  s8_t i;

  LWIP_ASSERT("eth_ret != NULL && ip_ret != NULL",
    eth_ret != NULL && ip_ret != NULL);

  LWIP_UNUSED_ARG(netif);

  i = find_entry(ipaddr, ETHARP_FLAG_FIND_ONLY);
  if((i >= 0) && arp_table[i].state == ETHARP_STATE_STABLE) {
      *eth_ret = &arp_table[i].ethaddr;
      *ip_ret = &arp_table[i].ipaddr;
      return i;
  }
  return -1;
}

#if ETHARP_TRUST_IP_MAC
/**
 * Updates the ARP table using the given IP packet.
 *
 * Uses the incoming IP packet's source address to update the
 * ARP cache for the local network. The function does not alter
 * or free the packet. This function must be called before the
 * packet p is passed to the IP layer.
 *
 * @param netif The lwIP network interface on which the IP packet pbuf arrived.
 * @param p The IP packet that arrived on netif.
 *
 * @return NULL
 *
 * @see pbuf_free()
 */
static void
etharp_ip_input(struct netif *netif, struct pbuf *p)
{
  struct eth_hdr *ethhdr;
  struct ip_hdr *iphdr;
  ip_addr_t iphdr_src;
  LWIP_ERROR("netif != NULL", (netif != NULL), return;);

  /* Only insert an entry if the source IP address of the
     incoming IP packet comes from a host on the local network. */
  ethhdr = (struct eth_hdr *)p->payload;
  iphdr = (struct ip_hdr *)((u8_t*)ethhdr + SIZEOF_ETH_HDR);
#if ETHARP_SUPPORT_VLAN
  if (ethhdr->type == PP_HTONS(ETHTYPE_VLAN)) {
    iphdr = (struct ip_hdr *)((u8_t*)ethhdr + SIZEOF_ETH_HDR + SIZEOF_VLAN_HDR);
  }
#endif /* ETHARP_SUPPORT_VLAN */

  ip_addr_copy(iphdr_src, iphdr->src);

  /* source is not on the local network? */
  if (!ip_addr_netcmp(&iphdr_src, &(netif->ip_addr), &(netif->netmask))) {
    /* do nothing */
    return;
  }

  LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_ip_input: updating ETHARP table.\n"));
  /* update the source IP address in the cache, if present */
  /* @todo We could use ETHARP_FLAG_TRY_HARD if we think we are going to talk
   * back soon (for example, if the destination IP address is ours. */
  update_arp_entry(netif, &iphdr_src, &(ethhdr->src), ETHARP_FLAG_FIND_ONLY);
}
#endif /* ETHARP_TRUST_IP_MAC */

/**
 * Responds to ARP requests to us. Upon ARP replies to us, add entry to cache  
 * send out queued IP packets. Updates cache with snooped address pairs.
 *
 * Should be called for incoming ARP packets. The pbuf in the argument
 * is freed by this function.
 *
 * @param netif The lwIP network interface on which the ARP packet pbuf arrived.
 * @param ethaddr Ethernet address of netif.