4212324: Packets sent to broadcast address not received on servers bound to specific addr

[Alan Bateman]

Damjan Jovanovic wrote:
> Hi
>
> Is this the right place to discuss/post patches for Java 1.7? If not,
> what is? Sun's websites are so confusing...
>   
Yes, this is right place.

> Has there been any work on the bug I referred to in the subject? If
> not, read on.
>   
Michael McMahon is probably the best person to reply to you on this. 
Last year he had a proposal and implementation that updated 
DatagramPacket with methods to obtain the datagram destination address 
and the network interface that it was received on. I believe he parked 
it temporarily to work on some higher priority tasks with a view to 
coming back to it later. [ Michael - can you give an updated status on 
this? ]


> :
>
> Also java.nio.channels.DatagramChannel seems very limited compared to
> java.net.DatagramSocket, is it worth patching?
>   
DatagramChannel is more suited to applications where the socket is 
connected or where non-blocking is required. Aside a DHCP server, I 
haven't come across many applications needing access to the ancillary 
data. If required then it would be possible to have DatagramChannel 
define a new receive method that returns this information but it may not 
be worth it.

> >From what I've observed in Java 1.6 on Linux,
> java.net.NetworkInterface.getNetworkInterfaces() doesn't list
> interfaces without an IP address, even if they are up. The
> documentation says it will list all interfaces, so is this a bug?
>   
The specification should probably be clarified here as that assertion 
may be too strong or ambiguous. On Linux, the interfaces are enumerated 
using the SIOCGIFCONF ioctl which, if I recall, is tied to the socket 
protocol and so only returns address with IPv4 addresses (to check this 
I would suggest stepping through in the debugger to see the names and 
index of the interfaces that are returned). When this was implemented 
back in 1.4 I recall the equivalent ioctl to get interfaces with IPv6 
addresses wasn't implemented on Linux so we had to pull this from /proc.

-Alan.