Place checks in callback routines because DCB will not always contain a reference to a router session, and the associated data will be invalid in this case.

server/core/dcb.c

@@ -2574,11 +2574,6 @@ dcb_call_callback(DCB *dcb, DCB_REASON reason)
 {
 DCB_CALLBACK	*cb, *nextcb;
 
-    if (NULL == dcb->session->router_session)
-    {
-        dcb_close(dcb);
-        return;
-    }
 	spinlock_acquire(&dcb->cb_lock);
 	cb = dcb->callbacks;
 	while (cb)

server/modules/routing/binlog/blr_slave.c

@@ -38,6 +38,7 @@
  * 19/03/2015	Massimiliano Pinto	Addition of basic MariaDB 10 compatibility support
  * 07/05/2015   Massimiliano Pinto	Added MariaDB 10 Compatibility
  * 11/05/2015   Massimiliano Pinto	Only MariaDB 10 Slaves can register to binlog router with a MariaDB 10 Master
+ * 25/09/2015   Martin Brampton         Block callback processing when no router session in the DCB
  *
  * @endverbatim
  */
@@ -1606,6 +1607,15 @@ blr_slave_callback(DCB *dcb, DCB_REASON reason, void *data)
 ROUTER_SLAVE		*slave = (ROUTER_SLAVE *)data;
 ROUTER_INSTANCE		*router = slave->router;
 
+    if (NULL == dcb->session->router_session)
+    {
+        /*
+         * The following processing will fail if there is no router session,
+         * because the "data" parameter will not contain meaningful data,
+         * so we have no choice but to stop here.
+         */
+        return;
+    }
 	if (reason == DCB_REASON_DRAINED)
 	{
 		if (slave->state == BLRS_DUMPING)

server/modules/routing/readconnroute.c

@@ -69,6 +69,7 @@
  * 27/06/2014	Mark Riddoch		Addition of server weighting
  * 11/06/2015   Martin Brampton         Remove decrement n_current (moved to dcb.c)
  * 09/09/2015   Martin Brampton         Modify error handler
+ * 25/09/2015   Martin Brampton         Block callback processing when no router session in the DCB
  *
  * @endverbatim
  */
@@ -1010,6 +1011,14 @@ static int handle_state_switch(DCB* dcb,DCB_REASON reason, void * routersession)
     SERVICE* service = session->service;
     ROUTER* router = (ROUTER *)service->router;
 
+    if (NULL == dcb->session->router_session  && DCB_REASON_ERROR != reason)
+    {
+        /* 
+         * We cannot handle a DCB that does not have a router session,
+         * except in the case where error processing is invoked.
+         */
+        return;
+    }
     switch(reason)
     {
 	case DCB_REASON_CLOSE:

server/modules/routing/readwritesplit/readwritesplit.c

@@ -71,6 +71,7 @@ extern __thread log_info_t tls_log_info;
  * 17/07/2014	Massimiliano Pinto	Server connection counter is updated in closeSession
  * 
  * 09/09/2015   Martin Brampton         Modify error handler
+ * 25/09/2015   Martin Brampton         Block callback processing when no router session in the DCB
  *
  * @endverbatim
  */
@@ -5308,6 +5309,15 @@ static int router_handle_state_switch(
         int                rc = 1;
         SERVER*            srv;
         CHK_DCB(dcb);
+    if (NULL == dcb->session->router_session)
+    {
+        /*
+         * The following processing will fail if there is no router session,
+         * because the "data" parameter will not contain meaningful data,
+         * so we have no choice but to stop here.
+         */
+        return;
+    }
         bref = (backend_ref_t *)data;
         CHK_BACKEND_REF(bref);
        

server/modules/routing/schemarouter/schemarouter.c

@@ -59,6 +59,7 @@ extern __thread log_info_t tls_log_info;
  *  Date	Who                             Description
  *  01/12/2014	Vilho Raatikka/Markus Mäkelä	Initial implementation
  *  09/09/2015  Martin Brampton         Modify error handler
+ *  25/09/2015  Martin Brampton         Block callback processing when no router session in the DCB
  *
  * @endverbatim
  */
@@ -4404,6 +4405,15 @@ router_handle_state_switch(
     SERVER* srv;
     
     CHK_DCB(dcb);
+    if (NULL == dcb->session->router_session)
+    {
+        /*
+         * The following processing will fail if there is no router session,
+         * because the "data" parameter will not contain meaningful data,
+         * so we have no choice but to stop here.
+         */
+        return;
+    }
     bref = (backend_ref_t *) data;
     CHK_BACKEND_REF(bref);