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- If a client renews before 'dhcp-cache-threshold' percent of its lease

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has elapsed (default 25%), the server will reuse the allocated lease
  (provide a lease within the currently allocated lease-time) rather
  than extend or renew the lease.  This absolves the server of needing
  to perform an fsync() operation on the lease database before reply,
  which improves performance. [ISC-Bugs #22228]
This commit is contained in:
Tomek Mrugalski
2011-05-12 13:26:55 +00:00
parent c616de4f1e
commit 929a236497
5 changed files with 116 additions and 25 deletions
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61
server/dhcp.c
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@@ -1502,6 +1502,10 @@ void ack_lease (packet, lease, offer, when, msg, ms_nulltp, hp)
struct in_addr from;
TIME remaining_time;
struct iaddr cip;
#if defined(DELAYED_ACK)
isc_boolean_t enqueue = ISC_TRUE;
#endif
int use_old_lease = 0;
unsigned i, j;
int s1;
@@ -2445,6 +2449,48 @@ void ack_lease (packet, lease, offer, when, msg, ms_nulltp, hp)
packet -> raw -> chaddr,
sizeof packet -> raw -> chaddr); /* XXX */
} else {
int commit = (!offer || (offer == DHCPACK));
int thresh = DEFAULT_CACHE_THRESHOLD;
/*
* Check if the lease was issued recently, if so replay the
* current lease and do not require a database sync event.
* Recently is defined as being issued less than a given
* percentage of the lease previously. The percentage can be
* chosen either from a default value or via configuration.
*
*/
if ((oc = lookup_option(&server_universe, state->options,
SV_CACHE_THRESHOLD)) &&
evaluate_option_cache(&d1, packet, lt, NULL,
packet->options, state->options,
&lt->scope, oc, MDL)) {
if (d1.len == 1 &&
(d1.data[0] >= 0) && (d1.data[0] < 100))
thresh = d1.data[0];
data_string_forget(&d1, MDL);
}
if ((thresh > 0) && (offer == DHCPACK) &&
(lease->binding_state == FTS_ACTIVE)) {
int limit;
int prev_lease = lease->ends - lease->starts;
/* it is better to avoid division by 0 */
if (prev_lease <= (INT_MAX / thresh))
limit = prev_lease * thresh / 100;
else
limit = prev_lease / 100 * thresh;
if ((lt->starts - lease->starts) <= limit) {
lt->starts = lease->starts;
state->offered_expiry = lt->ends = lease->ends;
commit = 0;
use_old_lease = 1;
}
}
#if !defined(DELAYED_ACK)
/* Install the new information on 'lt' onto the lease at
* 'lease'. If this is a DHCPOFFER, it is a 'soft' promise,
@@ -2454,9 +2500,19 @@ void ack_lease (packet, lease, offer, when, msg, ms_nulltp, hp)
* the same lease to another client later, and that would be
* a conflict.
*/
if (!supersede_lease(lease, lt, !offer || (offer == DHCPACK),
if (!use_old_lease && !supersede_lease(lease, lt, commit,
offer == DHCPACK, offer == DHCPACK)) {
#else /* defined(DELAYED_ACK) */
/*
* If there already isn't a need for a lease commit, and we
* can just answer right away, set a flag to indicate this.
*/
if (commit && !(lease->flags & STATIC_LEASE) &&
(!offer || (offer == DHCPACK)))
enqueue = ISC_TRUE;
else
enqueue = ISC_FALSE;
/* Install the new information on 'lt' onto the lease at
* 'lease'.  We will not 'commit' this information to disk
* yet (fsync()), we will 'propogate' the information if
@@ -2865,8 +2921,7 @@ void ack_lease (packet, lease, offer, when, msg, ms_nulltp, hp)
} else {
lease->cltt = cur_time;
#if defined(DELAYED_ACK)
if (!(lease->flags & STATIC_LEASE) &&
(!offer || (offer == DHCPACK)))
if (enqueue)
delayed_ack_enqueue(lease);
else
#endif