From 7867b8b57d60d93da3f5f15f0a049fba5fbff35a Mon Sep 17 00:00:00 2001
From: Evan Hunt <each@isc.org>
Date: Mon, 2 Nov 2020 18:33:20 -0800
Subject: [PATCH] enable keepalive when the keepalive EDNS option is seen

previously, receiving a keepalive option had no effect on how
long named would keep the connection open; there was a place to
configure the keepalive timeout but it was never used. this commit
corrects that.

this also fixes an error in isc__nm_{tcp,tls}dns_keepalive()
in which the sense of a REQUIRE test was reversed; previously this
error had not been noticed because the functions were not being
used.
---
 lib/isc/include/isc/netmgr.h | 12 ++++++++++++
 lib/isc/netmgr/netmgr.c      | 16 ++++++++++++++++
 lib/isc/netmgr/tcpdns.c      |  2 +-
 lib/isc/netmgr/tlsdns.c      |  2 +-
 lib/ns/client.c              |  1 +
 5 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/lib/isc/include/isc/netmgr.h b/lib/isc/include/isc/netmgr.h
index 2a1a2dc86c..f9433754bd 100644
--- a/lib/isc/include/isc/netmgr.h
+++ b/lib/isc/include/isc/netmgr.h
@@ -161,6 +161,18 @@ isc_nmhandle_cleartimeout(isc_nmhandle_t *handle);
  * both socket layers.
  */
 
+void
+isc_nmhandle_keepalive(isc_nmhandle_t *handle, bool value);
+/*%<
+ * Enable/disable keepalive on this connection by setting it to 'value'.
+ *
+ * When keepalive is active, we switch to using the keepalive timeout
+ * to determine when to close a connection, rather than the idle timeout.
+ *
+ * This applies only to TCP-based DNS connections (i.e., TCPDNS or
+ * TLSDNS). On other types of connection it has no effect.
+ */
+
 isc_sockaddr_t
 isc_nmhandle_peeraddr(isc_nmhandle_t *handle);
 /*%<
diff --git a/lib/isc/netmgr/netmgr.c b/lib/isc/netmgr/netmgr.c
index 975e8cc427..45b768d069 100644
--- a/lib/isc/netmgr/netmgr.c
+++ b/lib/isc/netmgr/netmgr.c
@@ -2365,6 +2365,22 @@ isc_nmhandle_settimeout(isc_nmhandle_t *handle, uint32_t timeout) {
 	}
 }
 
+void
+isc_nmhandle_keepalive(isc_nmhandle_t *handle, bool value) {
+	REQUIRE(VALID_NMHANDLE(handle));
+
+	switch (handle->sock->type) {
+	case isc_nm_tcpdnssocket:
+		isc__nm_tcpdns_keepalive(handle, value);
+		break;
+	case isc_nm_tlsdnssocket:
+		isc__nm_tlsdns_keepalive(handle, value);
+		break;
+	default:
+		return;
+	}
+}
+
 void *
 isc_nmhandle_getextra(isc_nmhandle_t *handle) {
 	REQUIRE(VALID_NMHANDLE(handle));
diff --git a/lib/isc/netmgr/tcpdns.c b/lib/isc/netmgr/tcpdns.c
index a26d0fc44b..a612bbbd31 100644
--- a/lib/isc/netmgr/tcpdns.c
+++ b/lib/isc/netmgr/tcpdns.c
@@ -1442,7 +1442,7 @@ isc__nm_tcpdns_keepalive(isc_nmhandle_t *handle, bool value) {
 
 	REQUIRE(VALID_NMHANDLE(handle));
 	REQUIRE(VALID_NMSOCK(handle->sock));
-	REQUIRE(handle->sock->type != isc_nm_tcpdnssocket);
+	REQUIRE(handle->sock->type == isc_nm_tcpdnssocket);
 
 	sock = handle->sock;
 
diff --git a/lib/isc/netmgr/tlsdns.c b/lib/isc/netmgr/tlsdns.c
index c4bba552f8..7e2f83e526 100644
--- a/lib/isc/netmgr/tlsdns.c
+++ b/lib/isc/netmgr/tlsdns.c
@@ -2012,7 +2012,7 @@ isc__nm_tlsdns_keepalive(isc_nmhandle_t *handle, bool value) {
 
 	REQUIRE(VALID_NMHANDLE(handle));
 	REQUIRE(VALID_NMSOCK(handle->sock));
-	REQUIRE(handle->sock->type != isc_nm_tlsdnssocket);
+	REQUIRE(handle->sock->type == isc_nm_tlsdnssocket);
 
 	sock = handle->sock;
 
diff --git a/lib/ns/client.c b/lib/ns/client.c
index 1a12fb9c87..34d94d15e7 100644
--- a/lib/ns/client.c
+++ b/lib/ns/client.c
@@ -1508,6 +1508,7 @@ process_opt(ns_client_t *client, dns_rdataset_t *opt) {
 				}
 				client->attributes |=
 					NS_CLIENTATTR_USEKEEPALIVE;
+				isc_nmhandle_keepalive(client->handle, true);
 				isc_buffer_forward(&optbuf, optlen);
 				break;
 			case DNS_OPT_PAD: