[jboss-jira] [JBoss JIRA] (WFLY-4685) Do not transform IPv4 multicast address to IPv6 anycast address on dual stack machines

[Miroslav Novak (JIRA)]

    [ https://issues.jboss.org/browse/WFLY-4685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13071521#comment-13071521 ] 

Miroslav Novak commented on WFLY-4685:
--------------------------------------

It's possible to start server with -Djava.net.preferIPv4Stack set to true to avoid IPv4 multicast ->IPv6 anycast conversion. Question is what should happen if java.net.preferIPv4Stack is false?

It allows to bind server to IPv4 or IPv6 address per need. At this moment it respects whether IPv4 or IPv6 address is specified. Setting 192.168.40.1 as bind address (with -Djava.net.preferIPv4Stack=false) does not bind server to IPv4-mapped IPv6 address ::192.168.40.1. From user point of view it's not intuitive IPv4 multicast ->IPv6 anycast conversion if IPv4 multicast was set.

I've added Richard as he knows a lot about IPv6.

It's not possible to clone jira to another project. I had to clone it first and then move to Wildfly. JBEAP-189 was temp product before moving it here, to WFLY-4685. 

> Do not transform IPv4 multicast address to IPv6 anycast address on dual stack machines
> --------------------------------------------------------------------------------------
>
>                 Key: WFLY-4685
>                 URL: https://issues.jboss.org/browse/WFLY-4685
>             Project: WildFly
>          Issue Type: Bug
>          Components: Clustering
>    Affects Versions: 10.0.0.Alpha1
>            Reporter: Miroslav Novak
>            Assignee: Bela Ban
>
> If EAP 7.0.0.DR2 is started with -Djava.net.preferIPv4Stack=false (and java.net.preferIPv6Addresses=false) then JGroups convert IPv4 multicast address (jboss.default.multicast.address=230.0.0.4) to IPv6 anycast address on dualstack machines.
> This is done in class org.jgroups.conf.PropertyConverters (line 291-295):
> {code}
> ...
>                 if(retval instanceof Inet4Address && retval.isMulticastAddress() && Util.getIpStackType() == StackType.IPv6) {
>                     String tmp=prefix + propertyValue;
>                     retval=InetAddress.getByName(tmp);
>                     return retval;
>                 }
> ...
> {code}
> This behaviour is overriding user preference to use IPv4 multicast instead of IPv6 anycast. Can this conversion be removed? 



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