From: Michał Kępień <michal@isc.org>
Date: Mon, 27 Apr 2020 05:46:01 +0000 (+0200)
Subject: Make dnstap work reliably with netmgr
X-Git-Tag: v9.16.3~14^2~2
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=299954d006ae6d2a2e8fd78d86faab1c00e6fb32;p=thirdparty%2Fbind9.git

Make dnstap work reliably with netmgr

The introduction of netmgr doubled the number of threads from which
dnstap data may be logged: previously, it could only happen from within
taskmgr worker threads; with netmgr, it can happen both from taskmgr
worker threads and from network threads.  Since the argument passed to
fstrm_iothr_options_set_num_input_queues() was not updated to reflect
this change, some calls to fstrm_iothr_get_input_queue() can now return
NULL, effectively preventing some dnstap data from being logged.
Whether this bug is triggered or not depends on thread scheduling order
and packet distribution between network threads, but will almost
certainly be triggered on any recursive resolver sooner or later.  Fix
by requesting the correct number of dnstap input queues to be allocated.

(cherry picked from commit 77dc091855fa106ecb3197618f40561c09b9976c)
---

diff --git a/bin/named/server.c b/bin/named/server.c
index d9f5d291299..119dde556d7 100644
--- a/bin/named/server.c
+++ b/bin/named/server.c
@@ -3672,7 +3672,11 @@ configure_dnstap(const cfg_obj_t **maps, dns_view_t *view) {
 		}
 
 		fopt = fstrm_iothr_options_init();
-		fstrm_iothr_options_set_num_input_queues(fopt, named_g_cpus);
+		/*
+		 * Both network threads and worker threads may log dnstap data.
+		 */
+		fstrm_iothr_options_set_num_input_queues(fopt,
+							 2 * named_g_cpus);
 		fstrm_iothr_options_set_queue_model(
 			fopt, FSTRM_IOTHR_QUEUE_MODEL_MPSC);
 
diff --git a/bin/tests/system/dnstap/ns3/named.args b/bin/tests/system/dnstap/ns3/named.args
new file mode 100644
index 00000000000..b746de58fe2
--- /dev/null
+++ b/bin/tests/system/dnstap/ns3/named.args
@@ -0,0 +1,2 @@
+# Using "-n 1" allows GL #1795 to be reliably reproduced
+-D dnstap-ns3 -X named.lock -m record,size,mctx -c named.conf -d 99 -g -U 4 -n 1
diff --git a/util/copyrights b/util/copyrights
index c064f64874e..faa6e89fddd 100644
--- a/util/copyrights
+++ b/util/copyrights
@@ -546,6 +546,7 @@
 ./bin/tests/system/dnstap/README		TXT.BRIEF	2019,2020
 ./bin/tests/system/dnstap/clean.sh		SH	2015,2016,2017,2018,2019,2020
 ./bin/tests/system/dnstap/large-answer.fstrm	X	2019,2020
+./bin/tests/system/dnstap/ns3/named.args	X	2020
 ./bin/tests/system/dnstap/setup.sh		SH	2018,2019,2020
 ./bin/tests/system/dnstap/tests.sh		SH	2015,2016,2017,2018,2019,2020
 ./bin/tests/system/dnstap/ydump.py		PYTHON	2016,2017,2018,2019,2020