/** Clean up ARP table entries */
static void
free_entry(int i)
{
/* remove from SNMP ARP index tree */
snmp_delete_arpidx_tree(arp_table[i].netif, &arp_table[i].ipaddr);
#if ARP_QUEUEING
/* and empty packet queue */
if (arp_table[i].q != NULL) {
/* remove all queued packets */
LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer: freeing entry %"U16_F", packet queue %p.\n", (u16_t)i, (void *)(arp_table[i].q)));
free_etharp_q(arp_table[i].q);
arp_table[i].q = NULL;
}
#endif /* ARP_QUEUEING */
/* recycle entry for re-use */
arp_table[i].state = ETHARP_STATE_EMPTY;
#if ETHARP_SUPPORT_STATIC_ENTRIES
arp_table[i].static_entry = 0;
#endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
#ifdef LWIP_DEBUG
/* for debugging, clean out the complete entry */
arp_table[i].ctime = 0;
#if LWIP_SNMP
arp_table[i].netif = NULL;
#endif /* LWIP_SNMP */
ip_addr_set_zero(&arp_table[i].ipaddr);
arp_table[i].ethaddr = ethzero;
#endif /* LWIP_DEBUG */
}
/** Clean up ARP table entries */
static void
etharp_free_entry(int i)
{
/* remove from SNMP ARP index tree */
mib2_remove_arp_entry(arp_table[i].netif, &arp_table[i].ipaddr);
/* and empty packet queue */
if (arp_table[i].q != NULL) {
/* remove all queued packets */
LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_free_entry: freeing entry %"U16_F", packet queue %p.\n", (u16_t)i, (void *)(arp_table[i].q)));
free_etharp_q(arp_table[i].q);
arp_table[i].q = NULL;
}
/* recycle entry for re-use */
arp_table[i].state = ETHARP_STATE_EMPTY;
#ifdef LWIP_DEBUG
/* for debugging, clean out the complete entry */
arp_table[i].ctime = 0;
arp_table[i].netif = NULL;
ip4_addr_set_zero(&arp_table[i].ipaddr);
arp_table[i].ethaddr = ethzero;
#endif /* LWIP_DEBUG */
}
/**
* Clears expired entries in the ARP table.
*
* This function should be called every ETHARP_TMR_INTERVAL microseconds (5 seconds),
* in order to expire entries in the ARP table.
*/
void
etharp_tmr(void)
{
u8_t i;
LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer\n"));
/* remove expired entries from the ARP table */
for (i = 0; i < ARP_TABLE_SIZE; ++i) {
arp_table[i].ctime++;
if (((arp_table[i].state == ETHARP_STATE_STABLE) &&
(arp_table[i].ctime >= ARP_MAXAGE)) ||
((arp_table[i].state == ETHARP_STATE_PENDING) &&
(arp_table[i].ctime >= ARP_MAXPENDING))) {
/* pending or stable entry has become old! */
LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer: expired %s entry %"U16_F".\n",
arp_table[i].state == ETHARP_STATE_STABLE ? "stable" : "pending", (u16_t)i));
/* clean up entries that have just been expired */
/* remove from SNMP ARP index tree */
snmp_delete_arpidx_tree(arp_table[i].netif, &arp_table[i].ipaddr);
#if ARP_QUEUEING
/* and empty packet queue */
if (arp_table[i].q != NULL) {
/* remove all queued packets */
LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer: freeing entry %"U16_F", packet queue %p.\n", (u16_t)i, (void *)(arp_table[i].q)));
free_etharp_q(arp_table[i].q);
arp_table[i].q = NULL;
}
#endif
/* recycle entry for re-use */
arp_table[i].state = ETHARP_STATE_EMPTY;
}
#if ARP_QUEUEING
/* still pending entry? (not expired) */
if (arp_table[i].state == ETHARP_STATE_PENDING) {
/* resend an ARP query here? */
}
#endif
}
}
/**
* Search the ARP table for a matching or new entry.
*
* If an IP address is given, return a pending or stable ARP entry that matches
* the address. If no match is found, create a new entry with this address set,
* but in state ETHARP_EMPTY. The caller must check and possibly change the
* state of the returned entry.
*
* If ipaddr is NULL, return a initialized new entry in state ETHARP_EMPTY.
*
* In all cases, attempt to create new entries from an empty entry. If no
* empty entries are available and ETHARP_TRY_HARD flag is set, recycle
* old entries. Heuristic choose the least important entry for recycling.
*
* @param ipaddr IP address to find in ARP cache, or to add if not found.
* @param flags
* - ETHARP_TRY_HARD: Try hard to create a entry by allowing recycling of
* active (stable or pending) entries.
*
* @return The ARP entry index that matched or is created, ERR_MEM if no
* entry is found or could be recycled.
*/
static s8_t
#if LWIP_NETIF_HWADDRHINT
find_entry(struct ip_addr *ipaddr, u8_t flags, struct netif *netif)
#else /* LWIP_NETIF_HWADDRHINT */
find_entry(struct ip_addr *ipaddr, u8_t flags)
#endif /* LWIP_NETIF_HWADDRHINT */
{
s8_t old_pending = ARP_TABLE_SIZE, old_stable = ARP_TABLE_SIZE;
s8_t empty = ARP_TABLE_SIZE;
u8_t i = 0, age_pending = 0, age_stable = 0;
#if ARP_QUEUEING
/* oldest entry with packets on queue */
s8_t old_queue = ARP_TABLE_SIZE;
/* its age */
u8_t age_queue = 0;
#endif
/* First, test if the last call to this function asked for the
* same address. If so, we're really fast! */
if (ipaddr) {
/* ipaddr to search for was given */
#if LWIP_NETIF_HWADDRHINT
if ((netif != NULL) && (netif->addr_hint != NULL)) {
/* per-pcb cached entry was given */
u8_t per_pcb_cache = *(netif->addr_hint);
if ((per_pcb_cache < ARP_TABLE_SIZE) && arp_table[per_pcb_cache].state == ETHARP_STATE_STABLE) {
/* the per-pcb-cached entry is stable */
if (ip_addr_cmp(ipaddr, &arp_table[per_pcb_cache].ipaddr)) {
/* per-pcb cached entry was the right one! */
ETHARP_STATS_INC(etharp.cachehit);
return per_pcb_cache;
}
}
}
#else /* #if LWIP_NETIF_HWADDRHINT */
if (arp_table[etharp_cached_entry].state == ETHARP_STATE_STABLE) {
/* the cached entry is stable */
if (ip_addr_cmp(ipaddr, &arp_table[etharp_cached_entry].ipaddr)) {
/* cached entry was the right one! */
ETHARP_STATS_INC(etharp.cachehit);
return etharp_cached_entry;
}
}
#endif /* #if LWIP_NETIF_HWADDRHINT */
}
/**
* a) do a search through the cache, remember candidates
* b) select candidate entry
* c) create new entry
*/
/* a) in a single search sweep, do all of this
* 1) remember the first empty entry (if any)
* 2) remember the oldest stable entry (if any)
* 3) remember the oldest pending entry without queued packets (if any)
* 4) remember the oldest pending entry with queued packets (if any)
* 5) search for a matching IP entry, either pending or stable
* until 5 matches, or all entries are searched for.
*/
for (i = 0; i < ARP_TABLE_SIZE; ++i) {
/* no empty entry found yet and now we do find one? */
if ((empty == ARP_TABLE_SIZE) && (arp_table[i].state == ETHARP_STATE_EMPTY)) {
LWIP_DEBUGF(ETHARP_DEBUG, ("find_entry: found empty entry %"U16_F"\n", (u16_t)i));
/* remember first empty entry */
empty = i;
}
/* pending entry? */
else if (arp_table[i].state == ETHARP_STATE_PENDING) {
/* if given, does IP address match IP address in ARP entry? */
if (ipaddr && ip_addr_cmp(ipaddr, &arp_table[i].ipaddr)) {
LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("find_entry: found matching pending entry %"U16_F"\n", (u16_t)i));
/* found exact IP address match, simply bail out */
#if LWIP_NETIF_HWADDRHINT
NETIF_SET_HINT(netif, i);
#else /* #if LWIP_NETIF_HWADDRHINT */
etharp_cached_entry = i;
#endif /* #if LWIP_NETIF_HWADDRHINT */
return i;
#if ARP_QUEUEING
/* pending with queued packets? */
} else if (arp_table[i].q != NULL) {
if (arp_table[i].ctime >= age_queue) {
old_queue = i;
age_queue = arp_table[i].ctime;
}
#endif
/* pending without queued packets? */
} else {
if (arp_table[i].ctime >= age_pending) {
old_pending = i;
age_pending = arp_table[i].ctime;
}
}
}
/* stable entry? */
else if (arp_table[i].state == ETHARP_STATE_STABLE) {
/* if given, does IP address match IP address in ARP entry? */
if (ipaddr && ip_addr_cmp(ipaddr, &arp_table[i].ipaddr)) {
LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("find_entry: found matching stable entry %"U16_F"\n", (u16_t)i));
/* found exact IP address match, simply bail out */
#if LWIP_NETIF_HWADDRHINT
NETIF_SET_HINT(netif, i);
#else /* #if LWIP_NETIF_HWADDRHINT */
etharp_cached_entry = i;
#endif /* #if LWIP_NETIF_HWADDRHINT */
return i;
/* remember entry with oldest stable entry in oldest, its age in maxtime */
} else if (arp_table[i].ctime >= age_stable) {
old_stable = i;
age_stable = arp_table[i].ctime;
}
}
}
/* { we have no match } => try to create a new entry */
/* no empty entry found and not allowed to recycle? */
if (((empty == ARP_TABLE_SIZE) && ((flags & ETHARP_TRY_HARD) == 0))
/* or don't create new entry, only search? */
|| ((flags & ETHARP_FIND_ONLY) != 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_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));
}
/* 2) found recyclable stable entry? */
else 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));
#if ARP_QUEUEING
/* no queued packets should exist on stable entries */
LWIP_ASSERT("arp_table[i].q == NULL", arp_table[i].q == NULL);
#endif
/* 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));
#if ARP_QUEUEING
/* 4) found recyclable pending entry with queued packets? */
} else if (old_queue < ARP_TABLE_SIZE) {
/* recycle oldest pending */
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)));
free_etharp_q(arp_table[i].q);
arp_table[i].q = NULL;
#endif
/* no empty or recyclable entries found */
} else {
return (s8_t)ERR_MEM;
}
/* { empty or recyclable entry found } */
LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
if (arp_table[i].state != ETHARP_STATE_EMPTY)
{
snmp_delete_arpidx_tree(arp_table[i].netif, &arp_table[i].ipaddr);
}
/* recycle entry (no-op for an already empty entry) */
arp_table[i].state = ETHARP_STATE_EMPTY;
/* IP address given? */
if (ipaddr != NULL) {
/* set IP address */
ip_addr_set(&arp_table[i].ipaddr, ipaddr);
}
arp_table[i].ctime = 0;
#if LWIP_NETIF_HWADDRHINT
NETIF_SET_HINT(netif, i);
#else /* #if LWIP_NETIF_HWADDRHINT */
etharp_cached_entry = i;
#endif /* #if LWIP_NETIF_HWADDRHINT */
return (err_t)i;
}
