MXS-619: Allow backend authentication to complete

By deferring the closing of a DCB until the protocol tells that it's in a
stable state, we avoid closing the connection mid-authentication. This
makes sure that all connections have reached a stable state before they
are closed which in turn prevents the connections from counting towards
aborted connects (or failed authentications like it did with the old fix).

include/maxscale/clock.h

@@ -30,11 +30,17 @@ int64_t mxs_clock();
 /**
  * Convert heartbeats to seconds
  */
-#define MXS_CLOCK_TO_SEC(a) ((int64_t)a / 10)
+static inline int64_t MXS_CLOCK_TO_SEC(int64_t a)
+{
+    return a / 10;
+}
 
 /**
  * Convert seconds to heartbeats
  */
-#define MXS_SEC_TO_CLOCK(a) ((int64_t)a * 10)
+static inline int64_t MXS_SEC_TO_CLOCK(int64_t a)
+{
+    return a * 10;
+}
 
 MXS_END_DECLS

include/maxscale/protocol.hh

@@ -179,6 +179,18 @@ struct MXS_PROTOCOL
      * @return A buffer containing the error message
      */
     GWBUF* (* reject)(const char* host);
+
+    /**
+     * Check if the DCB can be closed in a controlled manner
+     *
+     * The DCB will be unconditionally closed if this entry point is not implemented or a hard-coded timeout
+     * is exceeded.
+     *
+     * @param dcb DCB to check
+     *
+     * @return True if the DCB can be closed
+     */
+    bool (* can_close)(DCB*);
 };
 
 /**
@@ -186,7 +198,7 @@ struct MXS_PROTOCOL
  * the MXS_PROTOCOL structure is changed. See the rules defined in modinfo.h
  * that define how these numbers should change.
  */
-#define MXS_PROTOCOL_VERSION {2, 1, 0}
+#define MXS_PROTOCOL_VERSION {2, 2, 0}
 
 /**
  * Specifies capabilities specific for protocol.

server/core/routingworker.cc

@@ -161,6 +161,15 @@ void modules_thread_finish()
         }
     }
 }
+
+bool can_close_dcb(DCB* dcb)
+{
+    auto idle = MXS_CLOCK_TO_SEC(mxs_clock() - dcb->last_read);
+
+    return idle > 5                     // Timed out
+           || !dcb->func.can_close      // Not implemented
+           || dcb->func.can_close(dcb); // Protocol says it's OK to close
+}
 }
 
 namespace maxscale
@@ -550,6 +559,8 @@ void RoutingWorker::register_zombie(DCB* pDcb)
 
 void RoutingWorker::delete_zombies()
 {
+    Zombies not_ready;
+
     // An algorithm cannot be used, as the final closing of a DCB may cause
     // other DCBs to be registered in the zombie queue.
 
@@ -557,8 +568,18 @@ void RoutingWorker::delete_zombies()
     {
         DCB* pDcb = m_zombies.back();
         m_zombies.pop_back();
-        dcb_final_close(pDcb);
+
+        if (can_close_dcb(pDcb))
+        {
+            dcb_final_close(pDcb);
+        }
+        else
+        {
+            not_ready.push_back(pDcb);
+        }
     }
+
+    m_zombies.insert(m_zombies.end(), not_ready.begin(), not_ready.end());
 }
 
 bool RoutingWorker::pre_run()

server/modules/protocol/MySQL/mariadbbackend/mysql_backend.cc

@@ -63,6 +63,7 @@ static bool get_ip_string_and_port(struct sockaddr_storage* sa,
                                    int iplen,
                                    in_port_t* port_out);
 static bool gw_connection_established(DCB* dcb);
+static bool gw_auth_is_complete(DCB* dcb);
 json_t*     gw_json_diagnostics(DCB* dcb);
 
 extern "C"
@@ -92,6 +93,8 @@ MXS_MODULE* MXS_CREATE_MODULE()
         NULL,                               /* Connection limit reached      */
         gw_connection_established,
         gw_json_diagnostics,
+        NULL,
+        gw_auth_is_complete,
     };
 
     static MXS_MODULE info =
@@ -2018,6 +2021,24 @@ static bool gw_connection_established(DCB* dcb)
            && !proto->stored_query;
 }
 
+static bool gw_auth_is_complete(DCB* dcb)
+{
+    MySQLProtocol* proto = (MySQLProtocol*)dcb->protocol;
+
+    switch (proto->protocol_auth_state)
+    {
+    case MXS_AUTH_STATE_FAILED:
+    case MXS_AUTH_STATE_HANDSHAKE_FAILED:
+    case MXS_AUTH_STATE_COMPLETE:
+        MXS_DEBUG("(%lu) Auth is complete for DCB %lu", dcb->session->ses_id, dcb->m_uid);
+        return true;
+
+    default:
+        MXS_DEBUG("(%lu) Auth not yet complete for DCB %lu", dcb->session->ses_id, dcb->m_uid);
+        return false;
+    }
+}
+
 json_t* gw_json_diagnostics(DCB* dcb)
 {
     MySQLProtocol* proto = static_cast<MySQLProtocol*>(dcb->protocol);