Add ZMQ_ROUTER_NOTIFY draft socket option (#3213)

* Add ZMQ_ROUTER_NOTIFY draft socket option

Makefile.am

@@ -888,7 +888,8 @@ test_apps += tests/test_poller \
 	tests/test_radio_dish \
 	tests/test_scatter_gather \
 	tests/test_dgram \
-	tests/test_app_meta
+	tests/test_app_meta \
+	tests/test_router_notify
 
 tests_test_poller_SOURCES = tests/test_poller.cpp
 tests_test_poller_LDADD = src/libzmq.la ${UNITY_LIBS}
@@ -918,6 +919,10 @@ tests_test_dgram_LDADD = src/libzmq.la
 tests_test_app_meta_SOURCES = tests/test_app_meta.cpp
 tests_test_app_meta_LDADD = src/libzmq.la ${UNITY_LIBS}
 tests_test_app_meta_CPPFLAGS = ${UNITY_CPPFLAGS}
+
+tests_test_router_notify_SOURCES = tests/test_router_notify.cpp
+tests_test_router_notify_LDADD = src/libzmq.la ${UNITY_LIBS}
+tests_test_router_notify_CPPFLAGS = ${UNITY_CPPFLAGS}
 endif
 
 if ENABLE_STATIC

doc/zmq_getsockopt.txt

@@ -904,6 +904,23 @@ Option value unit:: 0, 1
 Default value:: 1
 Applicable socket types:: ZMQ_RADIO, when using UDP multicast transport
 
+
+ZMQ_ROUTER_NOTIFY: Retrieve router socket notification settings
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Retrieve the current notification settings of a router socket. The returned
+value is a bitmask composed of ZMQ_NOTIFY_CONNECT and ZMQ_NOTIFY_DISCONNECT
+flags, meaning connect and disconnect notifications are enabled, respectively.
+A value of '0' means the notifications are off.
+
+NOTE: in DRAFT state, not yet available in stable releases.
+
+[horizontal]
+Option value type:: int
+Option value unit:: 0, ZMQ_NOTIFY_CONNECT, ZMQ_NOTIFY_DISCONNECT, ZMQ_NOTIFY_CONNECT|ZMQ_NOTIFY_DISCONNECT
+Default value:: 0
+Applicable socket types:: ZMQ_ROUTER
+
+
 RETURN VALUE
 ------------
 The _zmq_getsockopt()_ function shall return zero if successful. Otherwise it

doc/zmq_setsockopt.txt

@@ -1289,6 +1289,24 @@ Option value unit:: 0, 1
 Default value:: 1
 Applicable socket types:: ZMQ_RADIO, when using UDP multicast transport
 
+
+ZMQ_ROUTER_NOTIFY: Send connect and disconnect notifications
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Enable connect and disconnect notifications on a ROUTER socket.
+When enabled, the socket delivers a zero-length message (with routing-id
+as first frame) when a peer connects or disconnects. It's possible
+to notify both events for a peer by OR-ing the flag values. This option
+only applies to stream oriented (tcp, ipc) transports.
+
+NOTE: in DRAFT state, not yet available in stable releases.
+
+[horizontal]
+Option value type:: int
+Option value unit:: 0, ZMQ_NOTIFY_CONNECT, ZMQ_NOTIFY_DISCONNECT, ZMQ_NOTIFY_CONNECT|ZMQ_NOTIFY_DISCONNECT
+Default value:: 0
+Applicable socket types:: ZMQ_ROUTER
+
+
 RETURN VALUE
 ------------
 The _zmq_setsockopt()_ function shall return zero if successful. Otherwise it

include/zmq.h

@@ -618,6 +618,8 @@ ZMQ_EXPORT void zmq_threadclose (void *thread_);
 #define ZMQ_LOOPBACK_FASTPATH 94
 #define ZMQ_METADATA 95
 #define ZMQ_MULTICAST_LOOP 96
+#define ZMQ_ROUTER_NOTIFY 97
+
 
 /*  DRAFT 0MQ socket events and monitoring                                    */
 /*  Unspecified system errors during handshake. Event value is an errno.      */
@@ -678,6 +680,10 @@ ZMQ_EXPORT const char *zmq_msg_group (zmq_msg_t *msg);
 #define ZMQ_MSG_PROPERTY_USER_ID "User-Id"
 #define ZMQ_MSG_PROPERTY_PEER_ADDRESS "Peer-Address"
 
+/*  Router notify options                                                     */
+#define ZMQ_NOTIFY_CONNECT 1
+#define ZMQ_NOTIFY_DISCONNECT 2
+
 /******************************************************************************/
 /*  Poller polling on sockets,fd and thread-safe sockets                      */
 /******************************************************************************/

src/options.cpp

@@ -243,7 +243,8 @@ zmq::options_t::options_t () :
     zap_enforce_domain (false),
     loopback_fastpath (false),
     multicast_loop (true),
-    zero_copy (true)
+    zero_copy (true),
+    router_notify (0)
 {
     memset (curve_public_key, 0, CURVE_KEYSIZE);
     memset (curve_secret_key, 0, CURVE_KEYSIZE);
@@ -1149,6 +1150,16 @@ int zmq::options_t::getsockopt (int option_,
             }
             break;
 
+#ifdef ZMQ_BUILD_DRAFT_API
+        case ZMQ_ROUTER_NOTIFY:
+            if (is_int) {
+                *value = router_notify;
+                return 0;
+            }
+            break;
+#endif
+
+
         default:
 #if defined(ZMQ_ACT_MILITANT)
             malformed = false;

src/options.hpp

@@ -261,6 +261,9 @@ struct options_t
     // Use zero copy strategy for storing message content when decoding.
     bool zero_copy;
 
+    // Router socket ZMQ_NOTIFY_CONNECT/ZMQ_NOTIFY_DISCONNECT notifications
+    int router_notify;
+
     // Application metadata
     std::map<std::string, std::string> app_metadata;
 };

src/router.cpp

@@ -139,6 +139,16 @@ int zmq::router_t::xsetsockopt (int option_,
             }
             break;
 
+#ifdef ZMQ_BUILD_DRAFT_API
+        case ZMQ_ROUTER_NOTIFY:
+            if (is_int && value >= 0
+                && value <= (ZMQ_NOTIFY_CONNECT | ZMQ_NOTIFY_DISCONNECT)) {
+                options.router_notify = value;
+                return 0;
+            }
+            break;
+#endif
+
         default:
             return routing_socket_base_t::xsetsockopt (option_, optval_,
                                                        optvallen_);

src/session_base.cpp

@@ -217,6 +217,12 @@ void zmq::session_base_t::flush ()
         _pipe->flush ();
 }
 
+void zmq::session_base_t::rollback ()
+{
+    if (_pipe)
+        _pipe->rollback ();
+}
+
 void zmq::session_base_t::clean_pipes ()
 {
     zmq_assert (_pipe != NULL);

src/session_base.hpp

@@ -60,6 +60,7 @@ class session_base_t : public own_t, public io_object_t, public i_pipe_events
     //  Following functions are the interface exposed towards the engine.
     virtual void reset ();
     void flush ();
+    void rollback ();
     void engine_error (zmq::stream_engine_t::error_reason_t reason_);
 
     //  i_pipe_events interface implementation.

src/stream_engine.cpp

@@ -897,6 +897,8 @@ void zmq::stream_engine_t::mechanism_ready ()
         _has_heartbeat_timer = true;
     }
 
+    bool flush_session = false;
+
     if (_options.recv_routing_id) {
         msg_t routing_id;
         _mechanism->peer_routing_id (&routing_id);
@@ -908,9 +910,26 @@ void zmq::stream_engine_t::mechanism_ready ()
             return;
         }
         errno_assert (rc == 0);
-        _session->flush ();
+        flush_session = true;
+    }
+
+    if (_options.router_notify & ZMQ_NOTIFY_CONNECT) {
+        msg_t connect_notification;
+        connect_notification.init ();
+        const int rc = _session->push_msg (&connect_notification);
+        if (rc == -1 && errno == EAGAIN) {
+            // If the write is failing at this stage with
+            // an EAGAIN the pipe must be being shut down,
+            // so we can just bail out of the notification.
+            return;
+        }
+        errno_assert (rc == 0);
+        flush_session = true;
     }
 
+    if (flush_session)
+        _session->flush ();
+
     _next_msg = &stream_engine_t::pull_and_encode;
     _process_msg = &stream_engine_t::write_credential;
 
@@ -1038,6 +1057,18 @@ void zmq::stream_engine_t::error (error_reason_t reason_)
         terminator.close ();
     }
     zmq_assert (_session);
+
+    if ((_options.router_notify & ZMQ_NOTIFY_DISCONNECT) && !_handshaking) {
+        // For router sockets with disconnect notification, rollback
+        // any incomplete message in the pipe, and push the disconnect
+        // notification message.
+        _session->rollback ();
+
+        msg_t disconnect_notification;
+        disconnect_notification.init ();
+        _session->push_msg (&disconnect_notification);
+    }
+
 #ifdef ZMQ_BUILD_DRAFT_API
     // protocol errors have been signaled already at the point where they occurred
     if (reason_ != protocol_error

src/zmq_draft.h

@@ -55,6 +55,7 @@ unsigned long zmq_stopwatch_intermediate (void *watch_);
 #define ZMQ_LOOPBACK_FASTPATH 94
 #define ZMQ_METADATA 95
 #define ZMQ_MULTICAST_LOOP 96
+#define ZMQ_ROUTER_NOTIFY 97
 
 /*  DRAFT 0MQ socket events and monitoring                                    */
 /*  Unspecified system errors during handshake. Event value is an errno.      */
@@ -115,6 +116,10 @@ const char *zmq_msg_group (zmq_msg_t *msg_);
 #define ZMQ_MSG_PROPERTY_USER_ID "User-Id"
 #define ZMQ_MSG_PROPERTY_PEER_ADDRESS "Peer-Address"
 
+/*  Router notify options                                                     */
+#define ZMQ_NOTIFY_CONNECT 1
+#define ZMQ_NOTIFY_DISCONNECT 2
+
 /******************************************************************************/
 /*  Poller polling on sockets,fd and thread-safe sockets                      */
 /******************************************************************************/

tests/CMakeLists.txt

@@ -136,6 +136,7 @@ IF (ENABLE_DRAFTS)
         test_scatter_gather
         test_dgram
         test_app_meta
+        test_router_notify
     )
 ENDIF (ENABLE_DRAFTS)