[jboss-jira] [JBoss JIRA] Commented: (JGRP-1207) Bind multicast send socket to specific IP when using IPv6 and NIC aliases

[Bela Ban (JIRA)]

    [ https://jira.jboss.org/browse/JGRP-1207?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12533897#action_12533897 ] 

Bela Ban commented on JGRP-1207:
--------------------------------

{Email Dennis]

The fix that works for this customer is bind()'ing the multicast socket on creation to the correct IP, instead of relying on setInterface.
Do you think that will cause issues on any other OS's?

That's easy enough on 2.4.x.  But on 2.6.x and above, I think the separate send/receive sockets would need to be restored, so receive can bind to the multicast IP and send can bind to the bind_addr.  Do you agree? 

> Bind multicast send socket to specific IP when using IPv6 and NIC aliases
> -------------------------------------------------------------------------
>
>                 Key: JGRP-1207
>                 URL: https://jira.jboss.org/browse/JGRP-1207
>             Project: JGroups
>          Issue Type: Feature Request
>    Affects Versions: 2.4.8
>            Reporter: Dennis Reed
>            Assignee: Bela Ban
>             Fix For: 2.10
>
>
> The OS-level API calls used to bind a multicast socket to a network interface are different when java.net.preferIPv4Stack is on or off.
> With preferIPv4Stack on, MulticastSocket.setInterface sets the source IP on outgoing multicast messages (IP_MULTICAST_IF ioctl option).
> With preferIPv4Stack off, it only sets the outgoing interface (a NIC index instead of an IP) (IPV6_MULTICAST_IF ioctl option).
> This becomes an issue when there are multiple aliases for the same NIC, because the OS decides which one of the IPs to set as the source.
> This doesn't break anything in JGroups, but makes it difficult for firewalls to filter the packets.

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