Redis two redis cluster are merged unexpectedlly

Hi: i faced a problem about cluster as described following. redis-version: 3.2.12 && 4.0.14. 1. first，i have a cluster A ,it consists of p1、p2 、p3、p4、p5、p6，p4 replicate p1 ,p5 replicate p2，p6 replicate p3. 2. after some time，p1、p5、p6 fails，these fail nodes are not deleted from Cluster A；in addition，we join p7 、p8、p9 nodes to cluster A，p7 replicate p4 ，p8 replicate p2，p9 replicate p3. 3. from p2、p3、p4 cluster nodes view， p1、p5、p6 state/flag was fail；from p7、p8、p9 cluster nodes view，p1、p5、p6 state/flag was handshake. 4. now we need to create a new cluster B,cluster B select p1、p5、p6 （ nodes.conf 、dump.rdb etc about cluster A were deleted） and p10 、p11、p12 consist cluster B.
5. Unfortunately，we find cluster A and Cluster B are merged。

i read the source code，i think in clusterProcessGossipSection (https://github.com/antirez/redis/blob/23a85ba191ed4d42cc88b76972dc3cb409e765dc/src/cluster.c#L1472)， when by nodename find node ==NULL, server try to handshake with node should consider node flag, if node flag/state is fail ,we don't start to handshake。

thanks for reply！

Comment From: liuzhen

It is believed to be a breach of promise by the redis cluster spec which claims that:

 trust the nodes introduced by already trusted nodes

does not merge clusters.

Turn out newly joined node would unconditionally bring "imposters" in.