[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=12535129#action_12535129 ] 

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

IMO, IPv6 should use the IP address passed to it in MulticastSocket.setInterface() as *source* address. If it doesn't do that, then I suggest we talk to our IP gurus to see why not !
MulticastSocket.setInterface() sets the interface, but as I understand it, the kernel can pick any address on that interface.
I cannot use the MulticastSocket() constructor taking a SocketAddress and pass in the bind address, as we pass in the multicast address to prevent promiscuous traffic ! e.g. new MulticastSocket(new InetSocketAddress("224.5.6.7", 7500)); Check Util.createMulticastSocket() for details. BTW: there's a bunch of JIRAs on this.

I suggest you write a simple program which creates a MulticastSocket as described above, and calls setInterface() with an IPv6 address. Then we create a couple of aliases on the same interface as the IP address and observe that the src address is different every time.
Someone from Red Hat (preferably Neil Horman) should take a look...


> 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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