MXS-1459: Assign binlog checksum value at startup

Binlog checksum default value is wrong if a slave connects with
checksum = NONE before master registration or master is not accessible
at startup

server/modules/routing/binlogrouter/blr.c

@@ -124,6 +124,8 @@ static void stats_func(void *);
 static bool rses_begin_locked_router_action(ROUTER_SLAVE *);
 static void rses_end_locked_router_action(ROUTER_SLAVE *);
 GWBUF *blr_cache_read_response(ROUTER_INSTANCE *router, char *response);
+/* Set checksum value in router instance from a master reply or saved buffer */
+extern void blr_set_checksum(ROUTER_INSTANCE *instance, GWBUF *buf);
 
 static SPINLOCK instlock;
 static ROUTER_INSTANCE *instances;
@@ -828,6 +830,18 @@ createInstance(SERVICE *service, char **options)
         /* Read any cached response messages */
         blr_cache_read_master_data(inst);
 
+        /**
+         * The value of master checksum is known only at registration time, so
+         * as soon as replication succeds the value is updated.
+         * Set now the binlog checksum from the saved value.
+         * This is very useful in case of possible failure in the
+         * registration phase for any reason: master is down, wrong password etc.
+         * In this case a connecting slave will get the checksum value
+         * from previous registration instead of default one (CRC32)
+         * which can be wrong if slave has binlog_checksum = NONE.
+         */
+        blr_set_checksum(inst, inst->saved_master.chksum2);
+
         /* Find latest binlog file or create a new one (000001) */
         if (blr_file_init(inst) == 0)
         {

server/modules/routing/binlogrouter/blr_master.c

@@ -513,16 +513,9 @@ blr_master_response(ROUTER_INSTANCE *router, GWBUF *buf)
         break;
     case BLRM_CHKSUM2:
         {
-            char *val = blr_extract_column(buf, 1);
+            // Set checksum from master reply
+            blr_set_checksum(router, buf);
 
-            if (val && strncasecmp(val, "NONE", 4) == 0)
-            {
-                router->master_chksum = false;
-            }
-            if (val)
-            {
-                MXS_FREE(val);
-            }
             // Response to the master_binlog_checksum, should be stored
             if (router->saved_master.chksum2)
             {
@@ -2619,3 +2612,25 @@ void blr_notify_all_slaves(ROUTER_INSTANCE *router)
         MXS_DEBUG("Notified %d slaves about new data.", notified);
     }
 }
+
+/**
+ * Set checksum value in router instance
+ *
+ * @param inst    The router instance
+ * @param buf     The buffer with checksum value
+ */
+void blr_set_checksum(ROUTER_INSTANCE *inst, GWBUF *buf)
+{
+    if (buf)
+    {
+        char *val = blr_extract_column(buf, 1);
+        if (val && strncasecmp(val, "NONE", 4) == 0)
+        {
+            inst->master_chksum = false;
+        }
+        if (val)
+        {
+            MXS_FREE(val);
+        }
+    }
+}