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.

diff --git a/lib/isc/netmgr/netmgr-int.h b/lib/isc/netmgr/netmgr-int.h
index 4c84047e23cee59feb83ea1da5c0cada1a0be3ba..188d90340e20c850320cfb5d8e7fd932262a0911 100644 (file)
--- a/lib/isc/netmgr/netmgr-int.h
+++ b/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;
 
@@ -2072,11 +2079,24 @@ 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);
+isc__nm_accept_connection_log(isc_result_t result, bool can_log_quota);
 
+/*
+ * Timeout callbacks
+ */
 void
-isc__nm_accept_connection_log(isc_result_t result, bool can_log_quota);
+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)                                           \

diff --git a/lib/isc/netmgr/netmgr.c b/lib/isc/netmgr/netmgr.c
index 1574ad2a31fb783e872bd04842ee30ccecf55b7b..b63f990163f13a7d6068800e7083ea5631d9a359 100644 (file)
--- a/lib/isc/netmgr/netmgr.c
+++ b/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:

diff --git a/lib/isc/netmgr/tcp.c b/lib/isc/netmgr/tcp.c
index aef698a79d1ebd5cbafb6a121e7180e1faf6e727..e179bc05b0c1f444c6a874bcd6c5b667bc9c81c5 100644 (file)
--- a/lib/isc/netmgr/tcp.c
+++ b/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

diff --git a/lib/isc/netmgr/tcpdns.c b/lib/isc/netmgr/tcpdns.c
index ac8fbca33cc4f0cff4b7d60ed21bbdd8c2b120c8..9244320ec0fc1204dcbc0335ec7c387931d0e9f4 100644 (file)
--- a/lib/isc/netmgr/tcpdns.c
+++ b/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

diff --git a/lib/isc/netmgr/tlsdns.c b/lib/isc/netmgr/tlsdns.c
index fc61e918aa0d8cb9355a39e37d92c6ce93447a70..d91e04489df68c21ac73f455bca70249f37104c7 100644 (file)
--- a/lib/isc/netmgr/tlsdns.c
+++ b/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

diff --git a/lib/isc/netmgr/udp.c b/lib/isc/netmgr/udp.c
index 7d8c5f4b9af9eb0b514b68ad181ec78f67f35d4b..e8ef4100f1c0cdac42c369c816d8f85c4b0f92ab 100644 (file)
--- a/lib/isc/netmgr/udp.c
+++ b/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