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Make max staleness of stale cache entries configurable and default to one day.

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This commit is contained in:
Dominik Derigs
2022-11-26 21:18:34 +00:00
committed by Simon Kelley
parent 022ad63f0c
commit efbf80be58
5 changed files with 39 additions and 11 deletions
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16
src/cache.c
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@@ -380,9 +380,17 @@ static int is_outdated_cname_pointer(struct crec *crecp)
static int is_expired(time_t now, struct crec *crecp)
{
/* Don't dump expired entries if we're using them, cache becomes strictly LRU in that case.
Never use expired DS or DNSKEY entries. */
if (option_bool(OPT_STALE_CACHE) && !(crecp->flags & (F_DS | F_DNSKEY)))
/* Don't dump expired entries if they are within the accepted timeout range.
The cache becomes approx. LRU. Never use expired DS or DNSKEY entries.
Possible values for daemon->cache_max_expiry:
-1 == serve cached content regardless how long ago it expired
0 == the option is disabled, expired content isn't served
<n> == serve cached content only if it expire less than <n> seconds
ago (where n is a positive integer) */
if (daemon->cache_max_expiry != 0 &&
(daemon->cache_max_expiry == -1 ||
difftime(now, crecp->ttd) < daemon->cache_max_expiry) &&
!(crecp->flags & (F_DS | F_DNSKEY)))
return 0;
if (crecp->flags & F_IMMORTAL)
@@ -1762,7 +1770,7 @@ void dump_cache(time_t now)
daemon->cachesize, daemon->metrics[METRIC_DNS_CACHE_LIVE_FREED], daemon->metrics[METRIC_DNS_CACHE_INSERTED]);
my_syslog(LOG_INFO, _("queries forwarded %u, queries answered locally %u"),
daemon->metrics[METRIC_DNS_QUERIES_FORWARDED], daemon->metrics[METRIC_DNS_LOCAL_ANSWERED]);
if (option_bool(OPT_STALE_CACHE))
if (daemon->cache_max_expiry != 0)
my_syslog(LOG_INFO, _("queries answered from stale cache %u"), daemon->metrics[METRIC_DNS_STALE_ANSWERED]);
#ifdef HAVE_AUTH
my_syslog(LOG_INFO, _("queries for authoritative zones %u"), daemon->metrics[METRIC_DNS_AUTH_ANSWERED]);

1
src/config.h
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@@ -60,6 +60,7 @@
#define LOOP_TEST_DOMAIN "test" /* domain for loop testing, "test" is reserved by RFC 2606 and won't therefore clash */
#define LOOP_TEST_TYPE T_TXT
#define DEFAULT_FAST_RETRY 1000 /* ms, default delay before fast retry */
#define STALE_CACHE_EXPIRY 86400 /* 1 day in secs, default maximum expiry time for stale cache data */
/* compile-time options: uncomment below to enable or do eg.
make COPTS=-DHAVE_BROKEN_RTC

6
src/dnsmasq.h
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@@ -280,9 +280,8 @@ struct event_desc {
#define OPT_FILTER_AAAA 68
#define OPT_STRIP_ECS 69
#define OPT_STRIP_MAC 70
#define OPT_STALE_CACHE 71
#define OPT_NORR 72
#define OPT_LAST 73
#define OPT_NORR 71
#define OPT_LAST 72
#define OPTION_BITS (sizeof(unsigned int)*8)
#define OPTION_SIZE ( (OPT_LAST/OPTION_BITS)+((OPT_LAST%OPTION_BITS)!=0) )
@@ -1201,6 +1200,7 @@ extern struct daemon {
unsigned long soa_sn, soa_refresh, soa_retry, soa_expiry;
u32 metrics[__METRIC_MAX];
int fast_retry_time, fast_retry_timeout;
int cache_max_expiry;
#ifdef HAVE_DNSSEC
struct ds_config *ds;
char *timestamp_file;

22
src/option.c
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@@ -373,7 +373,7 @@ static const struct myoption opts[] =
{ "quiet-tftp", 0, 0, LOPT_QUIET_TFTP },
{ "port-limit", 1, 0, LOPT_RANDPORT_LIM },
{ "fast-dns-retry", 2, 0, LOPT_FAST_RETRY },
{ "use-stale-cache", 0, 0 , LOPT_STALE_CACHE },
{ "use-stale-cache", 2, 0 , LOPT_STALE_CACHE },
{ NULL, 0, 0, 0 }
};
@@ -431,7 +431,7 @@ static struct {
{ 'M', ARG_DUP, "<bootp opts>", gettext_noop("Specify BOOTP options to DHCP server."), NULL },
{ 'n', OPT_NO_POLL, NULL, gettext_noop("Do NOT poll %s file, reload only on SIGHUP."), RESOLVFILE },
{ 'N', OPT_NO_NEG, NULL, gettext_noop("Do NOT cache failed search results."), NULL },
{ LOPT_STALE_CACHE, OPT_STALE_CACHE, NULL, gettext_noop("Use expired cache data for faster reply."), NULL },
{ LOPT_STALE_CACHE, ARG_ONE, "[=<max_expired>]", gettext_noop("Use expired cache data for faster reply."), NULL },
{ 'o', OPT_ORDER, NULL, gettext_noop("Use nameservers strictly in the order given in %s."), RESOLVFILE },
{ 'O', ARG_DUP, "<optspec>", gettext_noop("Specify options to be sent to DHCP clients."), NULL },
{ LOPT_FORCE, ARG_DUP, "<optspec>", gettext_noop("DHCP option sent even if the client does not request it."), NULL},
@@ -5151,6 +5151,24 @@ err:
break;
}
case LOPT_STALE_CACHE:
{
int max_expiry = STALE_CACHE_EXPIRY;
if (arg)
{
/* Don't accept negative TTLs here, they'd have the counter-intuitive
side-effect of evicting cache records before they expire */
if (!atoi_check(arg, &max_expiry) || max_expiry < 0)
ret_err(gen_err);
/* Store "serve expired forever" as -1 internally, the option isn't
active for daemon->cache_max_expiry == 0 */
if (max_expiry == 0)
max_expiry = -1;
}
daemon->cache_max_expiry = max_expiry;
break;
}
#ifdef HAVE_DNSSEC
case LOPT_DNSSEC_STAMP: /* --dnssec-timestamp */
daemon->timestamp_file = opt_string_alloc(arg);