Add TCP, TCPDNS and TLSDNS write timer

When the outgoing TCP write buffers are full because the other party is
not reading the data, the uv_write() could wait indefinitely on the
uv_loop and never calling the callback.  Add a new write timer that uses
the `tcp-idle-timeout` value to interrupt the TCP connection when we are
not able to send data for defined period of time.

lib/isc/netmgr/netmgr-int.h

@@ -954,6 +954,13 @@ struct isc_nmsocket {
 	uint64_t read_timeout;
 	uint64_t connect_timeout;
 
+	/*%
+	 * TCP write timeout timer.
+	 */
+	uv_timer_t write_timer;
+	uint64_t write_timeout;
+	int64_t writes;
+
 	/*% outer socket is for 'wrapped' sockets - e.g. tcpdns in tcp */
 	isc_nmsocket_t *outer;
 
@@ -2071,12 +2078,25 @@ isc__nm_failed_connect_cb(isc_nmsocket_t *sock, isc__nm_uvreq_t *req,
 void
 isc__nm_failed_read_cb(isc_nmsocket_t *sock, isc_result_t result, bool async);
 
-void
-isc__nmsocket_connecttimeout_cb(uv_timer_t *timer);
-
 void
 isc__nm_accept_connection_log(isc_result_t result, bool can_log_quota);
 
+/*
+ * Timeout callbacks
+ */
+void
+isc__nmsocket_connecttimeout_cb(uv_timer_t *timer);
+void
+isc__nmsocket_readtimeout_cb(uv_timer_t *timer);
+void
+isc__nmsocket_writetimeout_cb(uv_timer_t *timer);
+
+/*%<
+ *
+ * Maximum number of simultaneous handles in flight supported for a single
+ * connected TCPDNS socket. This value was chosen arbitrarily, and may be
+ * changed in the future.
+ */
 #define STREAM_CLIENTS_PER_CONN 23
 
 #define UV_RUNTIME_CHECK(func, ret)                                           \

lib/isc/netmgr/netmgr.c

@@ -2070,7 +2070,21 @@ isc__nm_accept_connection_log(isc_result_t result, bool can_log_quota) {
 		      isc_result_totext(result));
 }
 
-static void
+void
+isc__nmsocket_writetimeout_cb(uv_timer_t *timer) {
+	isc_nmsocket_t *sock = uv_handle_get_data((uv_handle_t *)timer);
+
+	int r = uv_timer_stop(&sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_stop, r);
+
+	/* The shutdown will be handled in the respective close functions */
+	r = uv_tcp_close_reset(&sock->uv_handle.tcp, NULL);
+	UV_RUNTIME_CHECK(uv_tcp_close_reset, r);
+
+	isc__nmsocket_shutdown(sock);
+}
+
+void
 isc__nmsocket_readtimeout_cb(uv_timer_t *timer) {
 	isc_nmsocket_t *sock = uv_handle_get_data((uv_handle_t *)timer);
 
@@ -2447,6 +2461,8 @@ isc_nmhandle_keepalive(isc_nmhandle_t *handle, bool value) {
 		atomic_store(&sock->keepalive, value);
 		sock->read_timeout = value ? atomic_load(&sock->mgr->keepalive)
 					   : atomic_load(&sock->mgr->idle);
+		sock->write_timeout = value ? atomic_load(&sock->mgr->keepalive)
+					    : atomic_load(&sock->mgr->idle);
 		break;
 #if HAVE_LIBNGHTTP2
 	case isc_nm_tlssocket:

lib/isc/netmgr/tcp.c

@@ -144,6 +144,10 @@ tcp_connect_direct(isc_nmsocket_t *sock, isc__nm_uvreq_t *req) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
 
+	r = uv_timer_init(&worker->loop, &sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+
 	r = uv_tcp_open(&sock->uv_handle.tcp, sock->fd);
 	if (r != 0) {
 		isc__nm_closesocket(sock->fd);
@@ -533,6 +537,10 @@ isc__nm_async_tcplisten(isc__networker_t *worker, isc__netievent_t *ev0) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
 
+	r = uv_timer_init(&worker->loop, &sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+
 	LOCK(&sock->parent->lock);
 
 	r = uv_tcp_open(&sock->uv_handle.tcp, sock->fd);
@@ -979,6 +987,10 @@ accept_connection(isc_nmsocket_t *ssock, isc_quota_t *quota) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&csock->read_timer, csock);
 
+	r = uv_timer_init(&worker->loop, &csock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&csock->write_timer, csock);
+
 	r = uv_accept(&ssock->uv_handle.stream, &csock->uv_handle.stream);
 	if (r != 0) {
 		result = isc__nm_uverr2result(r);
@@ -1072,6 +1084,13 @@ isc__nm_tcp_send(isc_nmhandle_t *handle, const isc_region_t *region,
 	uvreq->cb.send = cb;
 	uvreq->cbarg = cbarg;
 
+	if (sock->write_timeout == 0) {
+		sock->write_timeout =
+			(atomic_load(&sock->keepalive)
+				 ? atomic_load(&sock->mgr->keepalive)
+				 : atomic_load(&sock->mgr->idle));
+	}
+
 	ievent = isc__nm_get_netievent_tcpsend(sock->mgr, sock, uvreq);
 	isc__nm_maybe_enqueue_ievent(&sock->mgr->workers[sock->tid],
 				     (isc__netievent_t *)ievent);
@@ -1082,11 +1101,17 @@ isc__nm_tcp_send(isc_nmhandle_t *handle, const isc_region_t *region,
 static void
 tcp_send_cb(uv_write_t *req, int status) {
 	isc__nm_uvreq_t *uvreq = (isc__nm_uvreq_t *)req->data;
+
 	REQUIRE(VALID_UVREQ(uvreq));
 	REQUIRE(VALID_NMHANDLE(uvreq->handle));
 
 	isc_nmsocket_t *sock = uvreq->sock;
 
+	if (--sock->writes == 0) {
+		int r = uv_timer_stop(&sock->write_timer);
+		UV_RUNTIME_CHECK(uv_timer_stop, r);
+	}
+
 	if (status < 0) {
 		isc__nm_incstats(sock, STATID_SENDFAIL);
 		failed_send_cb(sock, uvreq, isc__nm_uverr2result(status));
@@ -1130,6 +1155,11 @@ tcp_send_direct(isc_nmsocket_t *sock, isc__nm_uvreq_t *req) {
 		return (ISC_R_CANCELED);
 	}
 
+	r = uv_timer_start(&sock->write_timer, isc__nmsocket_writetimeout_cb,
+			   sock->write_timeout, 0);
+	UV_RUNTIME_CHECK(uv_timer_start, r);
+	RUNTIME_CHECK(sock->writes++ >= 0);
+
 	r = uv_write(&req->uv_req.write, &sock->uv_handle.stream, &req->uvbuf,
 		     1, tcp_send_cb);
 	if (r < 0) {
@@ -1193,7 +1223,7 @@ tcp_close_cb(uv_handle_t *handle) {
 }
 
 static void
-timer_close_cb(uv_handle_t *handle) {
+read_timer_close_cb(uv_handle_t *handle) {
 	isc_nmsocket_t *sock = uv_handle_get_data(handle);
 	uv_handle_set_data(handle, NULL);
 
@@ -1206,6 +1236,17 @@ timer_close_cb(uv_handle_t *handle) {
 	}
 }
 
+static void
+write_timer_close_cb(uv_handle_t *timer) {
+	isc_nmsocket_t *sock = uv_handle_get_data(timer);
+	uv_handle_set_data(timer, NULL);
+
+	REQUIRE(VALID_NMSOCK(sock));
+
+	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
+	uv_close((uv_handle_t *)&sock->read_timer, read_timer_close_cb);
+}
+
 static void
 stop_tcp_child(isc_nmsocket_t *sock) {
 	REQUIRE(sock->type == isc_nm_tcpsocket);
@@ -1258,6 +1299,8 @@ stop_tcp_parent(isc_nmsocket_t *sock) {
 
 static void
 tcp_close_direct(isc_nmsocket_t *sock) {
+	int r;
+
 	REQUIRE(VALID_NMSOCK(sock));
 	REQUIRE(sock->tid == isc_nm_tid());
 	REQUIRE(atomic_load(&sock->closing));
@@ -1279,8 +1322,10 @@ tcp_close_direct(isc_nmsocket_t *sock) {
 	isc__nmsocket_timer_stop(sock);
 	isc__nm_stop_reading(sock);
 
-	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
-	uv_close((uv_handle_t *)&sock->read_timer, timer_close_cb);
+	r = uv_timer_stop(&sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_stop, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+	uv_close((uv_handle_t *)&sock->write_timer, write_timer_close_cb);
 }
 
 void

lib/isc/netmgr/tcpdns.c

@@ -37,13 +37,6 @@
 #include "netmgr-int.h"
 #include "uv-compat.h"
 
-/*%<
- *
- * Maximum number of simultaneous handles in flight supported for a single
- * connected TCPDNS socket. This value was chosen arbitrarily, and may be
- * changed in the future.
- */
-
 static atomic_uint_fast32_t last_tcpdnsquota_log = ATOMIC_VAR_INIT(0);
 
 static bool
@@ -109,6 +102,10 @@ tcpdns_connect_direct(isc_nmsocket_t *sock, isc__nm_uvreq_t *req) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
 
+	r = uv_timer_init(&worker->loop, &sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+
 	if (isc__nm_closing(sock)) {
 		result = ISC_R_SHUTTINGDOWN;
 		goto error;
@@ -503,6 +500,10 @@ isc__nm_async_tcpdnslisten(isc__networker_t *worker, isc__netievent_t *ev0) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
 
+	r = uv_timer_init(&worker->loop, &sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+
 	LOCK(&sock->parent->lock);
 
 	r = uv_tcp_open(&sock->uv_handle.tcp, sock->fd);
@@ -972,6 +973,10 @@ accept_connection(isc_nmsocket_t *ssock, isc_quota_t *quota) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&csock->read_timer, csock);
 
+	r = uv_timer_init(&worker->loop, &csock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&csock->write_timer, csock);
+
 	r = uv_accept(&ssock->uv_handle.stream, &csock->uv_handle.stream);
 	if (r != 0) {
 		result = isc__nm_uverr2result(r);
@@ -1088,6 +1093,13 @@ isc__nm_tcpdns_send(isc_nmhandle_t *handle, isc_region_t *region,
 	uvreq->cb.send = cb;
 	uvreq->cbarg = cbarg;
 
+	if (sock->write_timeout == 0) {
+		sock->write_timeout =
+			(atomic_load(&sock->keepalive)
+				 ? atomic_load(&sock->mgr->keepalive)
+				 : atomic_load(&sock->mgr->idle));
+	}
+
 	ievent = isc__nm_get_netievent_tcpdnssend(sock->mgr, sock, uvreq);
 	isc__nm_maybe_enqueue_ievent(&sock->mgr->workers[sock->tid],
 				     (isc__netievent_t *)ievent);
@@ -1105,6 +1117,11 @@ tcpdns_send_cb(uv_write_t *req, int status) {
 
 	sock = uvreq->sock;
 
+	if (--sock->writes == 0) {
+		int r = uv_timer_stop(&sock->write_timer);
+		UV_RUNTIME_CHECK(uv_timer_stop, r);
+	}
+
 	if (status < 0) {
 		isc__nm_incstats(sock, STATID_SENDFAIL);
 		isc__nm_failed_send_cb(sock, uvreq,
@@ -1171,6 +1188,11 @@ isc__nm_async_tcpdnssend(isc__networker_t *worker, isc__netievent_t *ev0) {
 		goto fail;
 	}
 
+	r = uv_timer_start(&sock->write_timer, isc__nmsocket_writetimeout_cb,
+			   sock->write_timeout, 0);
+	UV_RUNTIME_CHECK(uv_timer_start, r);
+	RUNTIME_CHECK(sock->writes++ >= 0);
+
 	r = uv_write(&uvreq->uv_req.write, &sock->uv_handle.stream, bufs, nbufs,
 		     tcpdns_send_cb);
 	if (r < 0) {
@@ -1240,7 +1262,7 @@ tcpdns_close_cb(uv_handle_t *handle) {
 }
 
 static void
-timer_close_cb(uv_handle_t *timer) {
+read_timer_close_cb(uv_handle_t *timer) {
 	isc_nmsocket_t *sock = uv_handle_get_data(timer);
 	uv_handle_set_data(timer, NULL);
 
@@ -1255,6 +1277,17 @@ timer_close_cb(uv_handle_t *timer) {
 	}
 }
 
+static void
+write_timer_close_cb(uv_handle_t *timer) {
+	isc_nmsocket_t *sock = uv_handle_get_data(timer);
+	uv_handle_set_data(timer, NULL);
+
+	REQUIRE(VALID_NMSOCK(sock));
+
+	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
+	uv_close((uv_handle_t *)&sock->read_timer, read_timer_close_cb);
+}
+
 static void
 stop_tcpdns_child(isc_nmsocket_t *sock) {
 	REQUIRE(sock->type == isc_nm_tcpdnssocket);
@@ -1307,6 +1340,7 @@ stop_tcpdns_parent(isc_nmsocket_t *sock) {
 
 static void
 tcpdns_close_direct(isc_nmsocket_t *sock) {
+	int r;
 	REQUIRE(VALID_NMSOCK(sock));
 	REQUIRE(sock->tid == isc_nm_tid());
 	REQUIRE(atomic_load(&sock->closing));
@@ -1322,8 +1356,10 @@ tcpdns_close_direct(isc_nmsocket_t *sock) {
 	isc__nmsocket_timer_stop(sock);
 	isc__nm_stop_reading(sock);
 
-	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
-	uv_close((uv_handle_t *)&sock->read_timer, timer_close_cb);
+	r = uv_timer_stop(&sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_stop, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+	uv_close((uv_handle_t *)&sock->write_timer, write_timer_close_cb);
 }
 
 void

lib/isc/netmgr/tlsdns.c

@@ -38,13 +38,6 @@
 #include "openssl_shim.h"
 #include "uv-compat.h"
 
-/*%<
- *
- * Maximum number of simultaneous handles in flight supported for a single
- * connected TLSDNS socket. This value was chosen arbitrarily, and may be
- * changed in the future.
- */
-
 static atomic_uint_fast32_t last_tlsdnsquota_log = ATOMIC_VAR_INIT(0);
 
 static void
@@ -125,6 +118,10 @@ tlsdns_connect_direct(isc_nmsocket_t *sock, isc__nm_uvreq_t *req) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
 
+	r = uv_timer_init(&worker->loop, &sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+
 	if (isc__nm_closing(sock)) {
 		result = ISC_R_SHUTTINGDOWN;
 		goto error;
@@ -574,6 +571,10 @@ isc__nm_async_tlsdnslisten(isc__networker_t *worker, isc__netievent_t *ev0) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
 
+	r = uv_timer_init(&worker->loop, &sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+
 	LOCK(&sock->parent->lock);
 
 	r = uv_tcp_open(&sock->uv_handle.tcp, sock->fd);
@@ -1165,6 +1166,11 @@ tls_write_cb(uv_write_t *req, int status) {
 	isc__nm_uvreq_t *uvreq = (isc__nm_uvreq_t *)req->data;
 	isc_nmsocket_t *sock = uvreq->sock;
 
+	if (--sock->writes == 0) {
+		int r = uv_timer_stop(&sock->write_timer);
+		UV_RUNTIME_CHECK(uv_timer_stop, r);
+	}
+
 	free_senddata(sock);
 
 	isc__nm_uvreq_put(&uvreq, sock);
@@ -1238,6 +1244,12 @@ tls_cycle_output(isc_nmsocket_t *sock) {
 			break;
 		}
 
+		r = uv_timer_start(&sock->write_timer,
+				   isc__nmsocket_writetimeout_cb,
+				   sock->write_timeout, 0);
+		UV_RUNTIME_CHECK(uv_timer_start, r);
+		RUNTIME_CHECK(sock->writes++ >= 0);
+
 		r = uv_write(&req->uv_req.write, &sock->uv_handle.stream,
 			     &req->uvbuf, 1, tls_write_cb);
 		if (r < 0) {
@@ -1482,6 +1494,10 @@ accept_connection(isc_nmsocket_t *ssock, isc_quota_t *quota) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&csock->read_timer, csock);
 
+	r = uv_timer_init(&worker->loop, &csock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&csock->write_timer, csock);
+
 	r = uv_accept(&ssock->uv_handle.stream, &csock->uv_handle.stream);
 	if (r != 0) {
 		result = isc__nm_uverr2result(r);
@@ -1629,6 +1645,13 @@ isc__nm_tlsdns_send(isc_nmhandle_t *handle, isc_region_t *region,
 	uvreq->cb.send = cb;
 	uvreq->cbarg = cbarg;
 
+	if (sock->write_timeout == 0) {
+		sock->write_timeout =
+			(atomic_load(&sock->keepalive)
+				 ? atomic_load(&sock->mgr->keepalive)
+				 : atomic_load(&sock->mgr->idle));
+	}
+
 	ievent = isc__nm_get_netievent_tlsdnssend(sock->mgr, sock, uvreq);
 	isc__nm_enqueue_ievent(&sock->mgr->workers[sock->tid],
 			       (isc__netievent_t *)ievent);
@@ -1806,7 +1829,7 @@ tlsdns_close_cb(uv_handle_t *handle) {
 }
 
 static void
-timer_close_cb(uv_handle_t *handle) {
+read_timer_close_cb(uv_handle_t *handle) {
 	isc_nmsocket_t *sock = uv_handle_get_data(handle);
 	uv_handle_set_data(handle, NULL);
 
@@ -1821,6 +1844,17 @@ timer_close_cb(uv_handle_t *handle) {
 	}
 }
 
+static void
+write_timer_close_cb(uv_handle_t *timer) {
+	isc_nmsocket_t *sock = uv_handle_get_data(timer);
+	uv_handle_set_data(timer, NULL);
+
+	REQUIRE(VALID_NMSOCK(sock));
+
+	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
+	uv_close((uv_handle_t *)&sock->read_timer, read_timer_close_cb);
+}
+
 static void
 stop_tlsdns_child(isc_nmsocket_t *sock) {
 	REQUIRE(sock->type == isc_nm_tlsdnssocket);
@@ -1874,6 +1908,8 @@ stop_tlsdns_parent(isc_nmsocket_t *sock) {
 
 static void
 tlsdns_close_direct(isc_nmsocket_t *sock) {
+	int r;
+
 	REQUIRE(VALID_NMSOCK(sock));
 	REQUIRE(sock->tid == isc_nm_tid());
 	REQUIRE(atomic_load(&sock->closing));
@@ -1891,8 +1927,10 @@ tlsdns_close_direct(isc_nmsocket_t *sock) {
 	isc__nmsocket_timer_stop(sock);
 	isc__nm_stop_reading(sock);
 
-	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
-	uv_close((uv_handle_t *)&sock->read_timer, timer_close_cb);
+	r = uv_timer_stop(&sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_stop, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+	uv_close((uv_handle_t *)&sock->write_timer, write_timer_close_cb);
 }
 
 void

lib/isc/netmgr/udp.c

@@ -74,7 +74,10 @@ static void
 udp_close_cb(uv_handle_t *handle);
 
 static void
-timer_close_cb(uv_handle_t *handle);
+read_timer_close_cb(uv_handle_t *handle);
+
+static void
+write_timer_close_cb(uv_handle_t *handle);
 
 static void
 udp_close_direct(isc_nmsocket_t *sock);
@@ -269,6 +272,10 @@ route_connect_direct(isc_nmsocket_t *sock) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
 
+	r = uv_timer_init(&worker->loop, &sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+
 	if (isc__nm_closing(sock)) {
 		result = ISC_R_SHUTTINGDOWN;
 		goto error;
@@ -445,6 +452,10 @@ isc__nm_async_udplisten(isc__networker_t *worker, isc__netievent_t *ev0) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
 
+	r = uv_timer_init(&worker->loop, &sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+
 	LOCK(&sock->parent->lock);
 
 	r = uv_udp_open(&sock->uv_handle.udp, sock->fd);
@@ -861,6 +872,10 @@ udp_connect_direct(isc_nmsocket_t *sock, isc__nm_uvreq_t *req) {
 	UV_RUNTIME_CHECK(uv_timer_init, r);
 	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
 
+	r = uv_timer_init(&worker->loop, &sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_init, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+
 	if (isc__nm_closing(sock)) {
 		result = ISC_R_SHUTTINGDOWN;
 		goto error;
@@ -1210,7 +1225,7 @@ udp_close_cb(uv_handle_t *handle) {
 }
 
 static void
-timer_close_cb(uv_handle_t *handle) {
+read_timer_close_cb(uv_handle_t *handle) {
 	isc_nmsocket_t *sock = uv_handle_get_data(handle);
 	uv_handle_set_data(handle, NULL);
 
@@ -1221,6 +1236,17 @@ timer_close_cb(uv_handle_t *handle) {
 	}
 }
 
+static void
+write_timer_close_cb(uv_handle_t *timer) {
+	isc_nmsocket_t *sock = uv_handle_get_data(timer);
+	uv_handle_set_data(timer, NULL);
+
+	REQUIRE(VALID_NMSOCK(sock));
+
+	uv_handle_set_data((uv_handle_t *)&sock->read_timer, sock);
+	uv_close((uv_handle_t *)&sock->read_timer, read_timer_close_cb);
+}
+
 static void
 stop_udp_child(isc_nmsocket_t *sock) {
 	REQUIRE(sock->type == isc_nm_udpsocket);
@@ -1273,10 +1299,14 @@ stop_udp_parent(isc_nmsocket_t *sock) {
 
 static void
 udp_close_direct(isc_nmsocket_t *sock) {
+	int r;
 	REQUIRE(VALID_NMSOCK(sock));
 	REQUIRE(sock->tid == isc_nm_tid());
 
-	uv_close((uv_handle_t *)&sock->read_timer, timer_close_cb);
+	r = uv_timer_stop(&sock->write_timer);
+	UV_RUNTIME_CHECK(uv_timer_stop, r);
+	uv_handle_set_data((uv_handle_t *)&sock->write_timer, sock);
+	uv_close((uv_handle_t *)&sock->write_timer, write_timer_close_cb);
 }
 
 void