From 0c0dc08d3ef26b7411cfe089e8144454831e8af5 Mon Sep 17 00:00:00 2001
From: Evan Hunt <each@isc.org>
Date: Thu, 1 Sep 2022 16:05:04 -0700
Subject: [PATCH] add an update quota
limit the number of simultaneous DNS UPDATE events that can be
processed by adding a quota for update and update forwarding.
this quota currently, arbitrarily, defaults to 100.
also add a statistics counter to record when the update quota
has been exceeded.
(cherry picked from commit 7c47254a140c3e9cf383cda73c7b6a55c4782826)
---
bin/named/bind9.xsl | 4 +++-
bin/named/bind9.xsl.h | 6 +++++-
bin/named/statschannel.c | 5 +++--
doc/arm/reference.rst | 5 +++++
lib/ns/include/ns/server.h | 1 +
lib/ns/include/ns/stats.h | 4 +++-
lib/ns/server.c | 2 ++
lib/ns/update.c | 38 +++++++++++++++++++++++++++++++++++++-
8 files changed, 59 insertions(+), 6 deletions(-)
diff --git a/bin/named/bind9.xsl b/bin/named/bind9.xsl
index 5078115..194625b 100644
--- a/bin/named/bind9.xsl
+++ b/bin/named/bind9.xsl
@@ -12,7 +12,9 @@
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns="http://www.w3.org/1999/xhtml" version="1.0">
<xsl:output method="html" indent="yes" version="4.0"/>
- <xsl:template match="statistics[@version="3.11"]">
+ <!-- the version number **below** must match version in bin/named/statschannel.c -->
+ <!-- don't forget to update "/xml/v<STATS_XML_VERSION_MAJOR>" in the HTTP endpoints listed below -->
+ <xsl:template match="statistics[@version="3.11.1"]">
<html>
<head>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
diff --git a/bin/named/bind9.xsl.h b/bin/named/bind9.xsl.h
index e30f7f5..b182742 100644
--- a/bin/named/bind9.xsl.h
+++ b/bin/named/bind9.xsl.h
@@ -20,7 +20,11 @@ static char xslmsg[] =
"<xsl:stylesheet xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\" "
"xmlns=\"http://www.w3.org/1999/xhtml\" version=\"1.0\">\n"
" <xsl:output method=\"html\" indent=\"yes\" version=\"4.0\"/>\n"
- " <xsl:template match=\"statistics[@version="3.11"]\">\n"
+ " <!-- the version number **below** must match version in "
+ "bin/named/statschannel.c -->\n"
+ " <!-- don't forget to update \"/xml/v<STATS_XML_VERSION_MAJOR>\" in "
+ "the HTTP endpoints listed below -->\n"
+ " <xsl:template match=\"statistics[@version="3.11.1"]\">\n"
" <html>\n"
" <head>\n"
" <script type=\"text/javascript\" "
diff --git a/bin/named/statschannel.c b/bin/named/statschannel.c
index 832ce93..7361ead 100644
--- a/bin/named/statschannel.c
+++ b/bin/named/statschannel.c
@@ -335,6 +335,7 @@ init_desc(void) {
SET_NSSTATDESC(reclimitdropped,
"queries dropped due to recursive client limit",
"RecLimitDropped");
+ SET_NSSTATDESC(updatequota, "Update quota exceeded", "UpdateQuota");
INSIST(i == ns_statscounter_max);
@@ -2007,7 +2008,7 @@ generatexml(named_server_t *server, uint32_t flags, int *buflen,
"href=\"/bind9.xsl\""));
TRY0(xmlTextWriterStartElement(writer, ISC_XMLCHAR "statistics"));
TRY0(xmlTextWriterWriteAttribute(writer, ISC_XMLCHAR "version",
- ISC_XMLCHAR "3.11"));
+ ISC_XMLCHAR "3.11.1"));
/* Set common fields for statistics dump */
dumparg.type = isc_statsformat_xml;
@@ -2876,7 +2877,7 @@ generatejson(named_server_t *server, size_t *msglen, const char **msg,
/*
* These statistics are included no matter which URL we use.
*/
- obj = json_object_new_string("1.5");
+ obj = json_object_new_string("1.5.1");
CHECKMEM(obj);
json_object_object_add(bindstats, "json-stats-version", obj);
diff --git a/doc/arm/reference.rst b/doc/arm/reference.rst
index 2d05aec..25c20d7 100644
--- a/doc/arm/reference.rst
+++ b/doc/arm/reference.rst
@@ -6705,6 +6705,11 @@ Name Server Statistics Counters
``UpdateBadPrereq``
This indicates the number of dynamic updates rejected due to a prerequisite failure.
+``UpdateQuota``
+ This indicates the number of times a dynamic update or update
+ forwarding request was rejected because the number of pending
+ requests exceeded the update quota.
+
``RateDropped``
This indicates the number of responses dropped due to rate limits.
diff --git a/lib/ns/include/ns/server.h b/lib/ns/include/ns/server.h
index 6a1f345..0abb579 100644
--- a/lib/ns/include/ns/server.h
+++ b/lib/ns/include/ns/server.h
@@ -84,6 +84,7 @@ struct ns_server {
isc_quota_t recursionquota;
isc_quota_t tcpquota;
isc_quota_t xfroutquota;
+ isc_quota_t updquota;
/*% Test options and other configurables */
uint32_t options;
diff --git a/lib/ns/include/ns/stats.h b/lib/ns/include/ns/stats.h
index 3c08799..95b15d0 100644
--- a/lib/ns/include/ns/stats.h
+++ b/lib/ns/include/ns/stats.h
@@ -106,7 +106,9 @@ enum {
ns_statscounter_reclimitdropped = 66,
- ns_statscounter_max = 67,
+ ns_statscounter_updatequota = 67,
+
+ ns_statscounter_max = 68,
};
void
diff --git a/lib/ns/server.c b/lib/ns/server.c
index a970a28..540bc2e 100644
--- a/lib/ns/server.c
+++ b/lib/ns/server.c
@@ -52,6 +52,7 @@ ns_server_create(isc_mem_t *mctx, ns_matchview_t matchingview,
isc_quota_init(&sctx->xfroutquota, 10);
isc_quota_init(&sctx->tcpquota, 10);
isc_quota_init(&sctx->recursionquota, 100);
+ isc_quota_init(&sctx->updquota, 100);
CHECKFATAL(dns_tkeyctx_create(mctx, &sctx->tkeyctx));
@@ -131,6 +132,7 @@ ns_server_detach(ns_server_t **sctxp) {
isc_mem_put(sctx->mctx, altsecret, sizeof(*altsecret));
}
+ isc_quota_destroy(&sctx->updquota);
isc_quota_destroy(&sctx->recursionquota);
isc_quota_destroy(&sctx->tcpquota);
isc_quota_destroy(&sctx->xfroutquota);
diff --git a/lib/ns/update.c b/lib/ns/update.c
index 546b70a..9a8c309 100644
--- a/lib/ns/update.c
+++ b/lib/ns/update.c
@@ -1544,6 +1544,19 @@ send_update_event(ns_client_t *client, dns_zone_t *zone) {
update_event_t *event = NULL;
isc_task_t *zonetask = NULL;
+ result = isc_quota_attach(&client->manager->sctx->updquota,
+ &(isc_quota_t *){ NULL });
+ if (result != ISC_R_SUCCESS) {
+ update_log(client, zone, LOGLEVEL_PROTOCOL,
+ "update failed: too many DNS UPDATEs queued (%s)",
+ isc_result_totext(result));
+ ns_stats_increment(client->manager->sctx->nsstats,
+ ns_statscounter_updatequota);
+ ns_client_drop(client, result);
+ isc_nmhandle_detach(&client->reqhandle);
+ return (DNS_R_DROP);
+ }
+
event = (update_event_t *)isc_event_allocate(
client->mctx, client, DNS_EVENT_UPDATE, update_action, NULL,
sizeof(*event));
@@ -1676,12 +1689,19 @@ failure:
dns_zone_gettype(zone) == dns_zone_mirror);
inc_stats(client, zone, ns_statscounter_updaterej);
}
+
/*
* We failed without having sent an update event to the zone.
* We are still in the client task context, so we can
* simply give an error response without switching tasks.
*/
- respond(client, result);
+ if (result == DNS_R_DROP) {
+ ns_client_drop(client, result);
+ isc_nmhandle_detach(&client->reqhandle);
+ } else {
+ respond(client, result);
+ }
+
if (zone != NULL) {
dns_zone_detach(&zone);
}
@@ -3489,6 +3509,7 @@ updatedone_action(isc_task_t *task, isc_event_t *event) {
respond(client, uev->result);
+ isc_quota_detach(&(isc_quota_t *){ &client->manager->sctx->updquota });
isc_event_free(&event);
isc_nmhandle_detach(&client->updatehandle);
}
@@ -3505,6 +3526,8 @@ forward_fail(isc_task_t *task, isc_event_t *event) {
INSIST(client->nupdates > 0);
client->nupdates--;
respond(client, DNS_R_SERVFAIL);
+
+ isc_quota_detach(&(isc_quota_t *){ &client->manager->sctx->updquota });
isc_event_free(&event);
isc_nmhandle_detach(&client->updatehandle);
}
@@ -3542,6 +3565,8 @@ forward_done(isc_task_t *task, isc_event_t *event) {
client->nupdates--;
ns_client_sendraw(client, uev->answer);
dns_message_detach(&uev->answer);
+
+ isc_quota_detach(&(isc_quota_t *){ &client->manager->sctx->updquota });
isc_event_free(&event);
isc_nmhandle_detach(&client->updatehandle);
}
@@ -3576,6 +3601,17 @@ send_forward_event(ns_client_t *client, dns_zone_t *zone) {
update_event_t *event = NULL;
isc_task_t *zonetask = NULL;
+ result = isc_quota_attach(&client->manager->sctx->updquota,
+ &(isc_quota_t *){ NULL });
+ if (result != ISC_R_SUCCESS) {
+ update_log(client, zone, LOGLEVEL_PROTOCOL,
+ "update failed: too many DNS UPDATEs queued (%s)",
+ isc_result_totext(result));
+ ns_stats_increment(client->manager->sctx->nsstats,
+ ns_statscounter_updatequota);
+ return (DNS_R_DROP);
+ }
+
event = (update_event_t *)isc_event_allocate(
client->mctx, client, DNS_EVENT_UPDATE, forward_action, NULL,
sizeof(*event));
--
2.39.1