Request for Review 6887364 [SetOutgoingIf]

[Alan Bateman]

Christopher Hegarty -Sun Microsystems Ireland wrote:
> Hi Pavel, Michael,
>
> 6887364: SetOutgoingIf.java fails if run on multihomed machine without 
> PIv6 on all interfaces [more details below]
>
> Webrev:
>   http://cr.openjdk.java.net/~chegar/6887364/webrev/
>
> I just realized why this test was failing on one of our lab machines. 
> The reason is that the test tries to join both IPv4 and IPv6 multicast 
> groups on network interfaces that are not loopback, are Up, and 
> support multicast. On our machine we have one interface that has only 
> an IPv4 address assigned to it, while another has both IPv4 and Ipv6 
> addresses.
>
> I've changed the test to only try joining the appropriate multicast 
> group if the network interface supports that IP protocol.
>
> Also, I noticed that the IPv4 mapped IPv6 address the test runs with 
> actually gets converted to a regular Inet4Address because the 
> InetAddress factory method is smarter than us! It never creates 
> Inet6Address instances that are IPv4 mapped IPv6 addresses, it just 
> creates Inet4Address. So (controversially) I manufactured an 
> Inet6Address multicast instance manually. It seems to work fine.
>
> --------------
> Details of failure and machine configuration:
> Fails with:
>   Exception in thread "main" java.net.SocketException: No such device 
> or address
>     at java.net.PlainDatagramSocketImpl.join(Native Method)
>     at 
> java.net.AbstractPlainDatagramSocketImpl.joinGroup(AbstractPlainDatagramSocketImpl.java:184) 
>
>     at java.net.MulticastSocket.joinGroup(MulticastSocket.java:382)
>     at SetOutgoingIf.main(SetOutgoingIf.java:116)
>
> Machine configuration [IP address information removed for security 
> reasons]:
>   :> ifconfig -a
> lo0: flags=2001000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 
> 8232 index 1
>     inet 127.0.0.1 netmask ff000000
> bge0: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2
>     inet XXX.XXX.XXX.160 netmask ffffff00 broadcast XXX.XXX.XXX.255
> bge3: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 5
>     inet XXX.XXX.YYY.160 netmask ffffff00 broadcast XXX.XXX.YYY.255
> bge0: flags=2000841<UP,RUNNING,MULTICAST,IPv6> mtu 1500 index 2
>     inet6 fe80::214:4fff:fe7a:b734/10
> lo0: flags=2002000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv6,VIRTUAL> mtu 
> 8252 index 1
>     inet6 ::1/128
> ---------------
>
> -Chris.
I don't know if you have a reviewer for this one yet. I went through the 
changes to the test and the overall approach seems reasonable. The one 
thing that doesn't seem right is attempting to do IPv4 multicasting when 
an interface is only plumbed with IPv6 (I'm talking about the case where 
it adds an IPv4-mapped address to the list of groups). I don't think the 
RFC dealing with migration to IPv6 covers that scenario and I'm pretty 
sure that many kernels don't support it either. I would suggest dropping 
that code so that you simple test IPv4 multicast on interfaces that have 
IPv4 address, and test IPv6 multicasting on interfaces that have IPv6 
addresses.

-Alan.