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etharp.c: re-arranged code in find_entry(), supposedly making it more readable for all cases.

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likewise 2004-11-29 11:01:20 +00:00
parent 62a37a4876
commit b429918b32
1 changed files with 29 additions and 32 deletions
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61
src/netif/etharp.c
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@ -178,7 +178,7 @@ etharp_tmr(void)
}
/**
* Search the ARP table for a specific entry.
* 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,
@ -193,23 +193,23 @@ etharp_tmr(void)
*
* @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.
* - 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 find_entry(struct ip_addr *ipaddr, u8_t flags)
{
s8_t old_pending, old_stable, empty, i;
u8_t age_pending, age_stable;
s8_t old_pending = ARP_TABLE_SIZE, old_stable = ARP_TABLE_SIZE, empty = ARP_TABLE_SIZE, i;
u8_t 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
old_pending = old_stable = empty = ARP_TABLE_SIZE;
age_pending = age_stable = 0;
/**
* a) do a search through the cache, remember candidates
* b) select candidate entry
@ -237,7 +237,7 @@ static s8_t find_entry(struct ip_addr *ipaddr, u8_t flags)
/* 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 | DBG_TRACE, ("find_entry: found matching pending entry %d\n", i));
/* found match, simply bail out */
/* found exact IP address match, simply bail out */
return i;
#if ARP_QUEUEING
/* pending with queued packets? */
@ -260,7 +260,7 @@ static s8_t find_entry(struct ip_addr *ipaddr, u8_t flags)
/* 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 | DBG_TRACE, ("find_entry: found matching stable entry %d\n", i));
/* found match, simply bail out */
/* found exact IP address match, simply bail out */
return i;
/* remember entry with oldest stable entry in oldest, its age in maxtime */
} else if (arp_table[i].ctime >= age_stable) {
@ -269,12 +269,21 @@ static s8_t find_entry(struct ip_addr *ipaddr, u8_t flags)
}
}
}
/* { we have no match } => try to create a new entry */
/* no empty entry found and not allowed to recycle? */
if ((i == ARP_TABLE_SIZE) && ((flags & ETHARP_TRY_HARD) == 0))
{
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 without queued packets
*
* { ETHARP_TRY_HARD is set at this point }
*/
/* 1) empty entry available? */
@ -305,38 +314,26 @@ static s8_t find_entry(struct ip_addr *ipaddr, u8_t flags)
/* no empty or recyclable entries found */
#endif
} else {
return ERR_MEM;
return (s8_t)ERR_MEM;
}
/* { empty or recyclable entry found } */
LWIP_ASSERT("i >= 0", i >= 0);
LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
/* allowed to recycle a entry? */
if (flags & ETHARP_TRY_HARD) {
/* recycle (no-op for an already empty entry) */
arp_table[i].state = ETHARP_STATE_EMPTY;
/* 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);
}
/* empty entry found or created? */
if (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;
arp_table[i].ctime = 0;
#if ARP_QUEUEING
/* remove any queued packets */
if (arp_table[i].p != NULL) pbuf_free(arp_table[i].p);
arp_table[i].p = NULL;
/* remove any queued packets */
if (arp_table[i].p != NULL) pbuf_free(arp_table[i].p);
arp_table[i].p = NULL;
#endif
/* no entry available */
} else {
/* return failure */
i = (s8_t)ERR_MEM;
}
return (err_t)i;
}