Clarification regarding gmcast.listen_addr (wsrep_provider_options)

Customer claims this value for gmcast.listen_addr worked in 10.3:

gmcast.listen_addr=ssl://RH1.edw.ee:4567

I don't think a hostname could work.

In my tests on 10.4 and higher, if you use a hostname for gmcast.listen_addr, the command galera_new_cluster hangs indefinitely (unless wsrep_cluster_address is defined with only one host).

Part of this question relates to the difference between tcp and ssl. It appears that you can define in either one of these ways:

gmcast.listen_addr=tcp://192.168.8.111:4567

gmcast.listen_addr=ssl://192.168.8.111:4567

Only tcp is mentioned as a possibility in documentation. Is ssl also a supported possibility? Is ssl handled different from tcp?

IPV6 is another undocumented issue. IPV6 for gmcast.listen_addr is discussed here:
https://github.com/codership/galera/issues/534
Documentation should discuss IPV6 with an example of how to define an address.

We need to clarify what is supported and what is not. Supported configuration needs to be included in documentation. If a hostname is not possible, documentation could mention this too.