前阵子为PXC集群配置IPv6支持，遇见奇怪的问题，就是SST同步时总是报错，为此在官网论坛提交了问题，未得到答案，最后偶然得到了答案，详见官方论坛：
https://forums.percona.com/t/sst-cant-support-ipv6/26140
结论如下。
Finally, I found the solution is turn off pxc_encrypt_cluster_traffic, then it works well.
And this is my major part of conf file:
[mysqld]
wsrep_cluster_address=gcomm://[fd15:4ba5:5a2b:1008:f814:e50e:acbd:11]:4567,[fd15:4ba5:5a2b:1008:f814:e50e:acbd:12]:4567
wsrep_node_address=[fd15:4ba5:5a2b:1008:f814:e50e:acbd:11]:4567
wsrep_node_incoming_address=[fd15:4ba5:5a2b:1008:f814:e50e:acbd:11]:3306
wsrep_sst_receive_address=[fd15:4ba5:5a2b:1008:f814:e50e:acbd:11]:4444
wsrep_cluster_name=pxc-cluster
pxc_strict_mode=ENFORCING
wsrep_sst_method=xtrabackup-v2
pxc_encrypt_cluster_traffic=OFF
wsrep_provider_options="gmcast.listen_addr=tcp://[fd15:4ba5:5a2b:1008:f814:e50e:acbd:11]:4567;ist.recv_addr=tcp://[fd15:4ba5:5a2b:1008:f814:e50e:acbd:11]:4568"
So the most important things are these two:
1. Set every port of IPv6 like above
2. Set pxc_encrypt_cluster_traffic=OFF
