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Only start stale refresh window when resuming

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If we did not attempt a fetch due to fetch-limits, we should not start
the stale-refresh-time window.

Introduce a new flag DNS_DBFIND_STALESTART to differentiate between
a resolver failure and unexpected error. If we are resuming, this
indicates a resolver failure, then start the stale-refresh-time window,
otherwise don't start the stale-refresh-time window, but still fall
back to using stale data.

(This commit also wraps some docstrings to 80 characters width)
This commit is contained in:
Matthijs Mekking 2021-01-27 16:59:27 +01:00
parent c6fd02aed5
commit aabdedeae3
3 changed files with 33 additions and 21 deletions
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37
lib/dns/include/dns/db.h
View File

@ -241,33 +241,36 @@ struct dns_dbonupdatelistener {
#define DNS_DBFIND_NOZONECUT 0x0200
/*
* DNS_DBFIND_STALEOK: This flag is set when BIND fails to refresh a
* RRset due to timeout (resolver-query-timeout), its intent is to
* try to look for stale data in cache as a fallback, but only if
* stale answers are enabled in configuration.
*
* This flag is also used to activate stale-refresh-time window, since it
* is the only way the database knows that a resolution has failed.
* DNS_DBFIND_STALEOK: This flag is set when BIND fails to refresh a RRset due
* to timeout (resolver-query-timeout). Its intent is to try to look for stale
* data in cache as a fallback, but only if stale answers are enabled in
* configuration.
*/
#define DNS_DBFIND_STALEOK 0x0400
/*
* DNS_DBFIND_STALEENABLED: This flag is used as a hint to the database
* that it may use stale data. It is always set during query lookup if
* stale answers are enabled, but only effectively used during
* stale-refresh-time window. Also during this window, the resolver will
* not try to resolve the query, in other words no attempt to refresh the
* data in cache is made when the stale-refresh-time window is active.
* DNS_DBFIND_STALEENABLED: This flag is used as a hint to the database that
* it may use stale data. It is always set during query lookup if stale
* answers are enabled, but only effectively used during stale-refresh-time
* window. Also during this window, the resolver will not try to resolve the
* query, in other words no attempt to refresh the data in cache is made when
* the stale-refresh-time window is active.
*/
#define DNS_DBFIND_STALEENABLED 0x0800
/*
* DNS_DBFIND_STALEONLY: This new introduced flag is used when we want
* stale data from the database, but not due to a failure in resolution,
* it also doesn't require stale-refresh-time window timer to be active.
* As long as there is a stale RRset available, it should be returned.
* DNS_DBFIND_STALEONLY: This flag is used when we want stale data from the
* database, but not due to a failure in resolution, it also doesn't require
* stale-refresh-time window timer to be active. As long as there is a stale
* RRset available, it should be returned.
*/
#define DNS_DBFIND_STALEONLY 0x1000
/*
* DNS_DBFIND_STALESTART: This flag is used to activate stale-refresh-time
* window.
*/
#define DNS_DBFIND_STALESTART 0x2000
/*@}*/
/*@{*/

9
lib/dns/rbtdb.c
View File

@ -4565,11 +4565,12 @@ check_stale_header(dns_rbtnode_t *node, rdatasetheader_t *header,
mark_header_stale(search->rbtdb, header);
*header_prev = header;
/*
* If DNS_DBFIND_STALEOK is set then it means we failed
* to resolve the name during recursion, in this case we
* mark the time in which the refresh failed.
* If DNS_DBFIND_STALESTART is set then it means we
* failed to resolve the name during recursion, in
* this case we mark the time in which the refresh
* failed.
*/
if ((search->options & DNS_DBFIND_STALEOK) != 0) {
if ((search->options & DNS_DBFIND_STALESTART) != 0) {
header->last_refresh_fail_ts = search->now;
} else if ((search->options &
DNS_DBFIND_STALEENABLED) != 0 &&

8
lib/ns/query.c
View File

@ -7560,7 +7560,15 @@ query_gotanswer(query_ctx_t *qctx, isc_result_t res) {
/*
* If serve-stale is enabled, query_usestale() already
* set up 'qctx' for looking up a stale response.
*
* We only need to check if the query timed out or
* something else has gone wrong. If the query timed
* out, we will start the stale-refresh-time window.
*/
if (qctx->resuming && result == ISC_R_TIMEDOUT) {
qctx->client->query.dboptions |=
DNS_DBFIND_STALESTART;
}
return (query_lookup(qctx));
}