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129 lines
4.1 KiB
129 lines
4.1 KiB
From 20424b3bfe8d3fae92c11a30e79aeffd26dc2891 Mon Sep 17 00:00:00 2001
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From: Aram Sargsyan <aram@isc.org>
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Date: Mon, 14 Nov 2022 12:18:06 +0000
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Subject: [PATCH] Cancel all fetch events in dns_resolver_cancelfetch()
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Although 'dns_fetch_t' fetch can have two associated events, one for
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each of 'DNS_EVENT_FETCHDONE' and 'DNS_EVENT_TRYSTALE' types, the
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dns_resolver_cancelfetch() function is designed in a way that it
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expects only one existing event, which it must cancel, and when it
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happens so that 'stale-answer-client-timeout' is enabled and there
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are two events, only one of them is canceled, and it results in an
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assertion in dns_resolver_destroyfetch(), when it finds a dangling
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event.
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Change the logic of dns_resolver_cancelfetch() function so that it
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cancels both the events (if they exist), and in the right order.
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(cherry picked from commit ec2098ca35039e4f81fd0aa7c525eb960b8f47bf)
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---
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lib/dns/resolver.c | 53 +++++++++++++++++++++++++++++++++++-----------
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lib/ns/query.c | 4 +++-
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2 files changed, 44 insertions(+), 13 deletions(-)
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diff --git a/lib/dns/resolver.c b/lib/dns/resolver.c
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index 18585b5..7cbfbb2 100644
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--- a/lib/dns/resolver.c
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+++ b/lib/dns/resolver.c
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@@ -11254,8 +11254,9 @@ void
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dns_resolver_cancelfetch(dns_fetch_t *fetch) {
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fetchctx_t *fctx;
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dns_resolver_t *res;
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- dns_fetchevent_t *event, *next_event;
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- isc_task_t *etask;
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+ dns_fetchevent_t *event = NULL;
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+ dns_fetchevent_t *event_trystale = NULL;
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+ dns_fetchevent_t *event_fetchdone = NULL;
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REQUIRE(DNS_FETCH_VALID(fetch));
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fctx = fetch->private;
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@@ -11267,32 +11268,60 @@ dns_resolver_cancelfetch(dns_fetch_t *fetch) {
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LOCK(&res->buckets[fctx->bucketnum].lock);
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/*
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- * Find the completion event for this fetch (as opposed
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+ * Find the events for this fetch (as opposed
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* to those for other fetches that have joined the same
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- * fctx) and send it with result = ISC_R_CANCELED.
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+ * fctx) and send them with result = ISC_R_CANCELED.
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*/
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- event = NULL;
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if (fctx->state != fetchstate_done) {
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+ dns_fetchevent_t *next_event = NULL;
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for (event = ISC_LIST_HEAD(fctx->events); event != NULL;
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event = next_event) {
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next_event = ISC_LIST_NEXT(event, ev_link);
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if (event->fetch == fetch) {
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ISC_LIST_UNLINK(fctx->events, event, ev_link);
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- break;
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+ switch (event->ev_type) {
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+ case DNS_EVENT_TRYSTALE:
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+ INSIST(event_trystale == NULL);
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+ event_trystale = event;
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+ break;
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+ case DNS_EVENT_FETCHDONE:
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+ INSIST(event_fetchdone == NULL);
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+ event_fetchdone = event;
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+ break;
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+ default:
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+ ISC_UNREACHABLE();
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+ }
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+ if (event_trystale != NULL &&
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+ event_fetchdone != NULL)
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+ {
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+ break;
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+ }
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}
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}
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}
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- if (event != NULL) {
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- etask = event->ev_sender;
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- event->ev_sender = fctx;
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- event->result = ISC_R_CANCELED;
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- isc_task_sendanddetach(&etask, ISC_EVENT_PTR(&event));
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+
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+ /*
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+ * The "trystale" event must be sent before the "fetchdone" event,
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+ * because the latter clears the "recursing" query attribute, which is
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+ * required by both events (handled by the same callback function).
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+ */
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+ if (event_trystale != NULL) {
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+ isc_task_t *etask = event_trystale->ev_sender;
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+ event_trystale->ev_sender = fctx;
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+ event_trystale->result = ISC_R_CANCELED;
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+ isc_task_sendanddetach(&etask, ISC_EVENT_PTR(&event_trystale));
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}
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+ if (event_fetchdone != NULL) {
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+ isc_task_t *etask = event_fetchdone->ev_sender;
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+ event_fetchdone->ev_sender = fctx;
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+ event_fetchdone->result = ISC_R_CANCELED;
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+ isc_task_sendanddetach(&etask, ISC_EVENT_PTR(&event_fetchdone));
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+ }
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+
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/*
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* The fctx continues running even if no fetches remain;
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* the answer is still cached.
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*/
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-
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UNLOCK(&res->buckets[fctx->bucketnum].lock);
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}
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diff --git a/lib/ns/query.c b/lib/ns/query.c
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index f66bab4..4f61374 100644
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--- a/lib/ns/query.c
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+++ b/lib/ns/query.c
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@@ -6021,7 +6021,9 @@ fetch_callback(isc_task_t *task, isc_event_t *event) {
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CTRACE(ISC_LOG_DEBUG(3), "fetch_callback");
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if (event->ev_type == DNS_EVENT_TRYSTALE) {
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- query_lookup_stale(client);
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+ if (devent->result != ISC_R_CANCELED) {
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+ query_lookup_stale(client);
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+ }
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isc_event_free(ISC_EVENT_PTR(&event));
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return;
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}
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--
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2.39.1
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