RFR [11] 8200304: TwoStacksPlainDatagramSocketImpl and socket cleaner

[Alan Bateman]

On 28/03/2018 10:08, Chris Hegarty wrote:
> 8195059 [1] updated the socket implementation to use a cleaner,
> rather than the previous finalizer implementation. Unfortunately the
> TwoStacksPlainDatagramSocketImpl on Windows, that uses two
> native file descriptors, may close one or other when binding, or it
> may in fact close both sockets and create two completely new
> ones. This is problematic since the cleaner has been registered
> with the native file descriptors of the original `fd` and `fd1` when
> the impl was created. As such, the cleaner may interfere with
> other resources that happen to re-use the native file descriptor.
>
> This area of code is ultimately destined for replacement with the
> dual stack implementation, but unfortunately we’re not quite at
> that point yet, so I would like to resolve this issue with a small
> localised fix that checks the file descriptors before and after the
> actual bind call, unregistering and re-registering the cleaner as
> necessary.
>
> http://cr.openjdk.java.net/~chegar/8200304/00/
>
It's great that this issue has been tracked down.

bind0 can try an exception so shouldn't there be a try-finally around 
this? Also would it be saner to unregister before bind0 and register 
afresh after it is called so that there is no point where a closed 
socket is registered with the cleaner?

-Alan