clean up outerhandle when a tcpdns socket is disconnected

this prevents a crash when some non-netmgr thread, such as a
recursive lookup, times out after the TCP socket is already
disconnected.

lib/isc/netmgr/netmgr-int.h

@@ -98,14 +98,6 @@ struct isc_nmhandle {
 	isc_nmsocket_t *sock;
 	size_t ah_pos; /* Position in the socket's 'active handles' array */
 
-	/*
-	 * The handle is 'inflight' if netmgr is not currently processing
-	 * it in any way - it might mean that e.g. a recursive resolution
-	 * is happening. For an inflight handle we must wait for the
-	 * calling code to finish before we can free it.
-	 */
-	atomic_bool inflight;
-
 	isc_sockaddr_t peer;
 	isc_sockaddr_t local;
 	isc_nm_opaquecb_t doreset; /* reset extra callback, external */
@@ -650,6 +642,12 @@ isc__nmsocket_active(isc_nmsocket_t *sock);
  * or, for child sockets, 'sock->parent->active'.
  */
 
+void
+isc__nmsocket_clearcb(isc_nmsocket_t *sock);
+/*%<
+ * Clear the recv and accept callbacks in 'sock'.
+ */
+
 void
 isc__nm_async_closecb(isc__networker_t *worker, isc__netievent_t *ev0);
 /*%<

lib/isc/netmgr/netmgr.c

@@ -987,6 +987,16 @@ isc__nmsocket_init(isc_nmsocket_t *sock, isc_nm_t *mgr, isc_nmsocket_type type,
 	sock->magic = NMSOCK_MAGIC;
 }
 
+void
+isc__nmsocket_clearcb(isc_nmsocket_t *sock) {
+	REQUIRE(VALID_NMSOCK(sock));
+
+	sock->rcb.recv = NULL;
+	sock->rcbarg = NULL;
+	sock->accept_cb.accept = NULL;
+	sock->accept_cbarg = NULL;
+}
+
 void
 isc__nm_alloc_cb(uv_handle_t *handle, size_t size, uv_buf_t *buf) {
 	isc_nmsocket_t *sock = uv_handle_get_data(handle);

lib/isc/netmgr/tcp.c

@@ -584,6 +584,7 @@ readtimeout_cb(uv_timer_t *handle) {
 	if (sock->rcb.recv != NULL) {
 		sock->rcb.recv(sock->tcphandle, ISC_R_TIMEDOUT, NULL,
 			       sock->rcbarg);
+		isc__nmsocket_clearcb(sock);
 	}
 }
 
@@ -682,7 +683,9 @@ isc__nm_tcp_resumeread(isc_nmsocket_t *sock) {
 	isc__netievent_startread_t *ievent = NULL;
 
 	REQUIRE(VALID_NMSOCK(sock));
-	REQUIRE(sock->rcb.recv != NULL);
+	if (sock->rcb.recv == NULL) {
+		return (ISC_R_CANCELED);
+	}
 
 	if (!atomic_load(&sock->readpaused)) {
 		return (ISC_R_SUCCESS);
@@ -744,6 +747,7 @@ read_cb(uv_stream_t *stream, ssize_t nread, const uv_buf_t *buf) {
 	if (sock->rcb.recv != NULL) {
 		isc__nm_incstats(sock->mgr, sock->statsindex[STATID_RECVFAIL]);
 		sock->rcb.recv(sock->tcphandle, ISC_R_EOF, NULL, sock->rcbarg);
+		isc__nmsocket_clearcb(sock);
 	}
 
 	/*
@@ -1080,6 +1084,7 @@ isc__nm_tcp_shutdown(isc_nmsocket_t *sock) {
 	{
 		sock->rcb.recv(sock->tcphandle, ISC_R_CANCELED, NULL,
 			       sock->rcbarg);
+		isc__nmsocket_clearcb(sock);
 	}
 }
 
@@ -1092,5 +1097,6 @@ isc__nm_tcp_cancelread(isc_nmsocket_t *sock) {
 	{
 		sock->rcb.recv(sock->tcphandle, ISC_R_CANCELED, NULL,
 			       sock->rcbarg);
+		isc__nmsocket_clearcb(sock);
 	}
 }

lib/isc/netmgr/tcpdns.c

@@ -231,6 +231,11 @@ dnslisten_readcb(isc_nmhandle_t *handle, isc_result_t eresult,
 		if (dnssock->self != NULL) {
 			isc__nmsocket_detach(&dnssock->self);
 		}
+		isc__nmsocket_clearcb(dnssock);
+		if (dnssock->outerhandle != NULL) {
+			isc_nmhandle_unref(dnssock->outerhandle);
+			dnssock->outerhandle = NULL;
+		}
 		return;
 	}
 
@@ -340,8 +345,7 @@ isc__nm_tcpdns_stoplistening(isc_nmsocket_t *sock) {
 
 	atomic_store(&sock->listening, false);
 	atomic_store(&sock->closed, true);
-	sock->rcb.recv = NULL;
+	isc__nmsocket_clearcb(sock);
-	sock->rcbarg = NULL;
 
 	if (sock->outer != NULL) {
 		isc__nm_tcp_stoplistening(sock->outer);
@@ -431,7 +435,11 @@ resume_processing(void *arg) {
 			}
 			isc_nmhandle_unref(handle);
 		} else if (sock->outerhandle != NULL) {
-			isc_nm_resumeread(sock->outerhandle->sock);
+			result = isc_nm_resumeread(sock->outerhandle->sock);
+			if (result != ISC_R_SUCCESS) {
+				isc_nmhandle_unref(sock->outerhandle);
+				sock->outerhandle = NULL;
+			}
 		}
 
 		return;
@@ -524,7 +532,9 @@ tcpdns_close_direct(isc_nmsocket_t *sock) {
 	REQUIRE(sock->tid == isc_nm_tid());
 
 	/* We don't need atomics here, it's all in single network thread */
-	if (sock->timer_initialized) {
+	if (sock->self != NULL) {
+		isc__nmsocket_detach(&sock->self);
+	} else if (sock->timer_initialized) {
 		/*
 		 * We need to fire the timer callback to clean it up,
 		 * it will then call us again (via detach) so that we
@@ -533,15 +543,13 @@ tcpdns_close_direct(isc_nmsocket_t *sock) {
 		sock->timer_initialized = false;
 		uv_timer_stop(&sock->timer);
 		uv_close((uv_handle_t *)&sock->timer, timer_close_cb);
-	} else if (sock->self != NULL) {
-		isc__nmsocket_detach(&sock->self);
 	} else {
 		/*
 		 * At this point we're certain that there are no external
 		 * references, we can close everything.
 		 */
 		if (sock->outerhandle != NULL) {
-			sock->outerhandle->sock->rcb.recv = NULL;
+			isc__nmsocket_clearcb(sock->outerhandle->sock);
 			isc_nmhandle_unref(sock->outerhandle);
 			sock->outerhandle = NULL;
 		}