MXS-2196: Preload DCB entry points in Listener

By loading the entry points required by a DCB when the Listener is
created, the extra cost of finding the module is removed. It also
simplifies DCB creation by removing the possibility of all failures to
load modules at DCB creation time.

include/maxscale/listener.hh

@@ -124,6 +124,16 @@ public:
      */
     const char* protocol() const;
 
+    /**
+     * The protocol module entry points
+     */
+    const MXS_PROTOCOL& protocol_func() const;
+
+    /**
+     * The authenticator module entry points
+     */
+    const MXS_AUTHENTICATOR& auth_func() const;
+
     /**
      * The authenticator instance
      */
@@ -180,6 +190,8 @@ private:
     struct users*     m_users;          /**< The user data for this listener */
     SERVICE*          m_service;        /**< The service which used by this listener */
     std::atomic<bool> m_active;         /**< True if the port has not been deleted */
+    MXS_PROTOCOL      m_proto_func;     /**< Preloaded protocol functions */
+    MXS_AUTHENTICATOR m_auth_func;      /**< Preloaded authenticator functions */
 
     /**
      * Creates a new listener that points to a service

server/core/dcb.cc

@@ -2390,11 +2390,8 @@ int dcb_connect_SSL(DCB* dcb)
 DCB* dcb_accept(DCB* dcb)
 {
     DCB* client_dcb = NULL;
-    MXS_PROTOCOL* protocol_funcs = &dcb->func;
     int c_sock;
-    int sendbuf;
     struct sockaddr_storage client_conn;
-    socklen_t optlen = sizeof(sendbuf);
 
     if ((c_sock = dcb_accept_one_connection(dcb, (struct sockaddr*)&client_conn)) >= 0)
     {
@@ -2402,7 +2399,7 @@ DCB* dcb_accept(DCB* dcb)
 
         configure_network_socket(c_sock, client_conn.ss_family);
 
-        client_dcb = dcb_alloc(DCB_ROLE_CLIENT_HANDLER, dcb->listener, dcb->service);
+        client_dcb = dcb_alloc(DCB_ROLE_CLIENT_HANDLER, dcb->listener, dcb->listener->service());
 
         if (client_dcb == NULL)
         {
@@ -2411,10 +2408,7 @@ DCB* dcb_accept(DCB* dcb)
         }
         else
         {
-            const char* authenticator_name = "NullAuthDeny";
+            client_dcb->service = dcb->listener->service();
-            MXS_AUTHENTICATOR* authfuncs;
-
-            client_dcb->service = dcb->session->service;
             client_dcb->session = session_set_dummy(client_dcb);
             client_dcb->fd = c_sock;
 
@@ -2452,27 +2446,8 @@ DCB* dcb_accept(DCB* dcb)
                 }
             }
 
-            memcpy(&client_dcb->func, protocol_funcs, sizeof(MXS_PROTOCOL));
+            client_dcb->func = dcb->listener->protocol_func();
-            if (*dcb->listener->authenticator())
+            client_dcb->authfunc = dcb->listener->auth_func();
-            {
-                authenticator_name = dcb->listener->authenticator();
-            }
-            else if (client_dcb->func.auth_default != NULL)
-            {
-                authenticator_name = client_dcb->func.auth_default();
-            }
-            if ((authfuncs = (MXS_AUTHENTICATOR*)load_module(authenticator_name,
-                                                             MODULE_AUTHENTICATOR)) == NULL)
-            {
-                if ((authfuncs = (MXS_AUTHENTICATOR*)load_module("NullAuthDeny",
-                                                                 MODULE_AUTHENTICATOR)) == NULL)
-                {
-                    MXS_ERROR("Failed to load authenticator module '%s'", authenticator_name);
-                    dcb_close(client_dcb);
-                    return NULL;
-                }
-            }
-            memcpy(&(client_dcb->authfunc), authfuncs, sizeof(MXS_AUTHENTICATOR));
 
             /** Allocate DCB specific authentication data */
             if (client_dcb->authfunc.create

server/core/listener.cc

@@ -57,6 +57,8 @@ Listener::Listener(SERVICE* service, const std::string& name, const std::string&
     , m_listener(nullptr)
     , m_users(nullptr)
     , m_service(service)
+    , m_proto_func(*(MXS_PROTOCOL*)load_module(protocol.c_str(), MODULE_PROTOCOL))
+    , m_auth_func(*(MXS_AUTHENTICATOR*)load_module(authenticator.c_str(), MODULE_AUTHENTICATOR))
 {
 }
 
@@ -103,11 +105,19 @@ SListener Listener::create(SERVICE* service,
         return nullptr;
     }
 
+    // Add protocol and authenticator capabilities from the listener
+    const MXS_MODULE* proto_mod = get_module(protocol.c_str(), MODULE_PROTOCOL);
+    const MXS_MODULE* auth_mod = get_module(auth, MODULE_AUTHENTICATOR);
+    mxb_assert(proto_mod && auth_mod);
+
     SListener listener(new(std::nothrow) Listener(service, name, address, port, protocol, auth,
                                                   auth_options, auth_instance, ssl));
 
     if (listener)
     {
+        // Note: This isn't good: we modify the service from a listener and the service itself should do this.
+        service->capabilities |= proto_mod->module_capabilities | auth_mod->module_capabilities;
+
         std::lock_guard<std::mutex> guard(listener_lock);
         all_listeners.push_back(listener);
     }
@@ -593,9 +603,9 @@ json_t* Listener::to_json() const
     json_object_set_new(attr, CN_STATE, json_string(state()));
     json_object_set_new(attr, CN_PARAMETERS, param);
 
-    if (m_listener->authfunc.diagnostic_json)
+    if (m_auth_func.diagnostic_json)
     {
-        json_t* diag = m_listener->authfunc.diagnostic_json(this);
+        json_t* diag = m_auth_func.diagnostic_json(this);
 
         if (diag)
         {
@@ -641,6 +651,16 @@ const char* Listener::protocol() const
     return m_protocol.c_str();
 }
 
+const MXS_PROTOCOL& Listener::protocol_func() const
+{
+    return m_proto_func;
+}
+
+const MXS_AUTHENTICATOR& Listener::auth_func() const
+{
+    return m_auth_func;
+}
+
 void* Listener::auth_instance() const
 {
     return m_auth_instance;
@@ -719,39 +739,8 @@ bool Listener::listen()
         return false;
     }
 
-    MXS_PROTOCOL* funcs = (MXS_PROTOCOL*)load_module(protocol(), MODULE_PROTOCOL);
+    m_listener->func = m_proto_func;
-
+    m_listener->authfunc = m_auth_func;
-    if (!funcs)
-    {
-        MXS_ERROR("Unable to load protocol module %s. Listener for service %s not started.",
-                  protocol(), m_service->name);
-        return false;
-    }
-
-    memcpy(&(m_listener->func), funcs, sizeof(MXS_PROTOCOL));
-
-    if (m_authenticator.empty())
-    {
-        m_authenticator = m_listener->func.auth_default();
-    }
-
-    MXS_AUTHENTICATOR* authfuncs = (MXS_AUTHENTICATOR*)load_module(authenticator(), MODULE_AUTHENTICATOR);
-
-    if (!authfuncs)
-    {
-        MXS_ERROR("Failed to load authenticator module '%s' for listener '%s'", authenticator(), name());
-        return false;
-    }
-
-    // Add protocol and authenticator capabilities from the listener
-    const MXS_MODULE* proto_mod = get_module(protocol(), MODULE_PROTOCOL);
-    const MXS_MODULE* auth_mod = get_module(authenticator(), MODULE_AUTHENTICATOR);
-    mxb_assert(proto_mod && auth_mod);
-
-    // Note: This isn't good: we modify the service from a listener and the service itself should do this.
-    m_service->capabilities |= proto_mod->module_capabilities | auth_mod->module_capabilities;
-
-    memcpy(&m_listener->authfunc, authfuncs, sizeof(MXS_AUTHENTICATOR));
 
     /**
      * Normally, we'd allocate the DCB specific authentication data. As the