implement isc_nm_cancelread()

The isc_nm_cancelread() function cancels reading on a connected
socket and calls its read callback function with a 'result'
parameter of ISC_R_CANCELED.

lib/isc/include/isc/netmgr.h

@@ -195,6 +195,17 @@ isc_nm_pauseread(isc_nmsocket_t *sock);
  * Pause reading on this socket, while still remembering the callback.
  */
 
+void
+isc_nm_cancelread(isc_nmhandle_t *handle);
+/*%<
+ * Cancel reading on a connected socket. Calls the read/recv callback on
+ * active handles with a result code of ISC_R_CANCELED.
+ *
+ * Requires:
+ * \li	'sock' is a valid netmgr socket
+ * \li	...for which a read/recv callback has been defined.
+ */
+
 isc_result_t
 isc_nm_resumeread(isc_nmsocket_t *sock);
 /*%<

lib/isc/netmgr/netmgr-int.h

@@ -715,7 +715,14 @@ isc__nm_tcp_resumeread(isc_nmsocket_t *sock);
 void
 isc__nm_tcp_shutdown(isc_nmsocket_t *sock);
 /*%<
- * Called on shutdown to close and clean up a listening TCP socket.
+ * Called during the shutdown process to close and clean up connected
+ * sockets.
+ */
+
+void
+isc__nm_tcp_cancelread(isc_nmsocket_t *sock);
+/*%<
+ * Stop reading on a connected socket.
  */
 
 void

lib/isc/netmgr/netmgr.c

@@ -1346,9 +1346,24 @@ isc_nm_read(isc_nmhandle_t *handle, isc_nm_recv_cb_t cb, void *cbarg) {
 	}
 }
 
+void
+isc_nm_cancelread(isc_nmhandle_t *handle) {
+	REQUIRE(VALID_NMHANDLE(handle));
+
+	switch (handle->sock->type) {
+	case isc_nm_tcpsocket:
+		isc__nm_tcp_cancelread(handle->sock);
+		break;
+	default:
+		INSIST(0);
+		ISC_UNREACHABLE();
+	}
+}
+
 isc_result_t
 isc_nm_pauseread(isc_nmsocket_t *sock) {
 	REQUIRE(VALID_NMSOCK(sock));
+
 	switch (sock->type) {
 	case isc_nm_tcpsocket:
 		return (isc__nm_tcp_pauseread(sock));
@@ -1361,6 +1376,7 @@ isc_nm_pauseread(isc_nmsocket_t *sock) {
 isc_result_t
 isc_nm_resumeread(isc_nmsocket_t *sock) {
 	REQUIRE(VALID_NMSOCK(sock));
+
 	switch (sock->type) {
 	case isc_nm_tcpsocket:
 		return (isc__nm_tcp_resumeread(sock));
@@ -1373,6 +1389,7 @@ isc_nm_resumeread(isc_nmsocket_t *sock) {
 void
 isc_nm_stoplistening(isc_nmsocket_t *sock) {
 	REQUIRE(VALID_NMSOCK(sock));
+
 	switch (sock->type) {
 	case isc_nm_udplistener:
 		isc__nm_udp_stoplistening(sock);

lib/isc/netmgr/tcp.c

@@ -1080,3 +1080,15 @@ isc__nm_tcp_shutdown(isc_nmsocket_t *sock) {
 			       sock->rcbarg);
 	}
 }
+
+void
+isc__nm_tcp_cancelread(isc_nmsocket_t *sock) {
+	REQUIRE(VALID_NMSOCK(sock));
+
+	if (sock->type == isc_nm_tcpsocket && sock->tcphandle != NULL &&
+	    sock->rcb.recv != NULL)
+	{
+		sock->rcb.recv(sock->tcphandle, ISC_R_CANCELED, NULL,
+			       sock->rcbarg);
+	}
+}

lib/isc/win32/libisc.def.in

@@ -449,6 +449,7 @@ isc_nmhandle_peeraddr
 isc_nmhandle_ref
 isc_nmhandle_setdata
 isc_nmhandle_unref
+isc_nm_cancelread
 isc_nm_closedown
 isc_nm_destroy
 isc_nm_detach