RFR: 8280113: (dc) DatagramSocket.receive does not always throw when the channel is closed [v2]

[Daniel Fuchs]

On Tue, 21 Feb 2023 08:06:59 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> This is an issue with the async close of a DatagramChannel when a thread is blocked in its adaptor's receive method and the underlying socket is non-blocking.  The async close causes poll to wakeup and the underlying receive to return 0 so it can't be distinguished from a receive of a zero-length datagram. The channel state needs to be checked to distinguish the two cases so that AsynchronousCloseException can be thrown if the channel has been closed. The bug goes back to JDK 14 when caching of sockaddr structured was introduced.
>> 
>> The test case creates the conditions to exercise the case for both the timed and untimed receive. The bug report is the timed case, which receives two datagrams before attempting a timed receive. The harder case to test is the untimed case so the test uses a virtual thread to force the underlying socket to be non-blocking.
>
> Alan Bateman has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update test to eliminate potential ffor setSoTimeout throwing

LGTM. Though we can't rule that this test will fail intermittently if it receives stray datagrams sent by other tests / processes. I wonder if the lambda passed to assertThrows should be modified to return to receive if it receives a datagram whose socket address is not null and not that of `dc`.

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PR: https://git.openjdk.org/jdk/pull/12674