[jboss-jira] [JBoss JIRA] Commented: (JGRP-956) Binding to mcast address in UDP.java is not working on Linux with IPv6

[Richard Achmatowicz (JIRA)]

    [ https://jira.jboss.org/jira/browse/JGRP-956?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12476582#action_12476582 ] 

Richard Achmatowicz commented on JGRP-956:
------------------------------------------

May want to change the error message to:

16:35:20,231 WARN [UDP] could not bind to /ff02:0:0:0:0:1:2:3 (IPv6 address); make sure your mcast_addr is of the same type as the IP stack (IPv4 or IPv6), by checking the value of the system property java.net.preferIPv4Stack. Will ignore mcast_addr, but this may lead to cross talking (see http://www.jboss.com/wiki/Edit.jsp?page=CrossTalking for details).
Exception was: java.net.SocketException: Invalid argument


> Binding to mcast address in UDP.java is not working on Linux with IPv6
> ----------------------------------------------------------------------
>
>                 Key: JGRP-956
>                 URL: https://jira.jboss.org/jira/browse/JGRP-956
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Richard Achmatowicz
>            Assignee: Bela Ban
>            Priority: Minor
>             Fix For: 2.8
>
>
> On Linux and Solaris platforms, when setting up the main multicast receiver socket, Bela allows binding the socket to its multicast address, like this:
> InetAddress group_addr = ...
> InetAddress bind_addr = ...
> SocketAddress group_sock_addr = new InetSocketAddress(group_addr, port) ;
> MulticastSocket s = new MulticastSocket(group_sock_addr) ;    // funny
> s.joinGroup(group_addr) ;
> Binding to the multicast address on Linux and Solaris was done in order to avoid the promiscuous traffic problem. A detailed discussion on the matter can be found in the bugzilla report:https://bugzilla.redhat.com/show_bug.cgi?id=231899. 
> This works on Linux with IPv4 but is not working on Linux with IPv6 for the multicast-address ff02::1 - an error message is being generated (SocketException, invalid argument) and  the code then tries to create the same multicast address in the usual way:
> InetAddress group_addr = ...
> InetAddress bind_addr = ...
> MulticastSocket s = new MulticastSocket(port) ;
> s.setInterface(bind_addr) ;
> s.joinGroup(group_addr) ;
> This is only a problem in that it generates a confusing error message about using mixed IPv4 / IPv6 stacks, but the socket continues to work correctly as far as I can tell.
> Haven't confirmed this, but I believe the promiscuous traffic issue does not arise with IPv6 multicast sockets.

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