Add ability to use random routing ids for outgoing

lokimq/lokimq.cpp

@@ -561,7 +561,14 @@ void LokiMQ::setup_outgoing_socket(zmq::socket_t& socket, string_view remote_pub
     }
     socket.setsockopt(ZMQ_HANDSHAKE_IVL, (int) HANDSHAKE_TIME.count());
     socket.setsockopt<int64_t>(ZMQ_MAXMSGSIZE, MAX_MSG_SIZE);
-    socket.setsockopt(ZMQ_ROUTING_ID, pubkey.data(), pubkey.size());
+    if (PUBKEY_BASED_ROUTING_ID) {
+        std::string routing_id;
+        routing_id.reserve(33);
+        routing_id += 'L'; // Prefix because routing id's starting with \0 are reserved by zmq (and our pubkey might start with \0)
+        routing_id.append(pubkey.begin(), pubkey.end());
+        socket.setsockopt(ZMQ_ROUTING_ID, routing_id.data(), routing_id.size());
+    }
+    // else let ZMQ pick a random one
 }
 
 std::pair<zmq::socket_t *, std::string>

lokimq/lokimq.h

@@ -320,6 +320,16 @@ public:
      * closing the connection.  Setting this only affects new outgoing connections. */
     std::chrono::milliseconds HANDSHAKE_TIME = 10s;
 
+    /** Whether to use a zmq routing ID based on the pubkey for new outgoing connections.  This is
+     * normally desirable as it allows the listener to recognize that the incoming connection is a
+     * reconnection from the same remote and handover routing to the new socket while closing off
+     * the (likely dead) old socket.  This, however, prevents a single LokiMQ instance from
+     * establishing multiple connections to the same listening LokiMQ, which is sometimes useful
+     * (for example when testing), and so this option can be overridden to `false` to use completely
+     * random zmq routing ids on outgoing connections (which will thus allow multiple connections).
+     */
+    bool PUBKEY_BASED_ROUTING_ID = true;
+
     /** Maximum incoming message size; if a remote tries sending a message larger than this they get
      * disconnected. -1 means no limit. */
     int64_t MAX_MSG_SIZE = 1 * 1024 * 1024;