RFR[8239355]: '(dc) Initial value of SO_SNDBUF should allow sending large datagrams (macOS)'

[Patrick Concannon]

Regarding the test to check that large datagrams are sent and received 
correctly across a network:  I've created a new issue for it and 
included the link below.

https://bugs.openjdk.java.net/browse/JDK-8240901

Kind regards,

Patrick

On 11/03/2020 16:54, Patrick Concannon wrote:
> Hi,
>
> I've included those additional changes, and they can be found in the 
> new webrev below.
>
> http://cr.openjdk.java.net/~pconcannon/8239355/webrevs/webrev.03/
>
>
> Kind regards,
>
> Patrick
>
> On 11/03/2020 12:27, Daniel Fuchs wrote:
>> Hi Alan,
>>
>> On 11/03/2020 12:08, Alan Bateman wrote:
>>>> Do we really? I am not sure we do.
>>>> We just want to verify that we don't get the "packet too large"
>>>> exception caused by the SO_SNDBUF buffer being too small.
>>> It would be great if we had a test to send large datagrams on the 
>>> network as that is the only way to properly test that they can be 
>>> re-assembled and received. I don't mind if it's a separate test, I 
>>> agree it can be tricky on systems that have unusual configurations. 
>>> I'm just pointing out that testing that the send doesn't fail and 
>>> that the datagram can be received through the loopback may not be 
>>> enough here.
>> Our test doesn't even try to receive the datagram. It just sends it.
>> We can write a new test that does the full roundtrip if you think
>> it's worthwile.
>>
>>>> Yes and no - and the test is there to verify that it doesn't have any
>>>> unexpected side effects (we know it shouldn't).
>>> My preference would be to drop these so the test only runs twice. 
>>> The reason is that the effect of setting 
>>> java.net.preferIPv6Addresses is not widely known and it will confuse 
>>> anyone that needs to maintain this test in the future.
>>
>> OK - then we can remove the preferIPv6Addresses property and replace:
>>
>>  114         populateDataProvider(testcases, datagramChannel, 
>> MAX_PAYLOAD,
>>  117                 null);
>>
>> with
>>
>>       if (hasIPv4())
>>           populateDataProvider(testcases, datagramChannel, IPV4_SNDBUF,
>>                      StandardProtocolFamily.INET);
>>       if (hasIPv6() && !preferIPv4Stack())
>>           populateDataProvider(testcases, datagramChannel, IPV6_SNDBUF,
>>                      StandardProtocolFamily.INET6);
>>
>>
>> to verify that the channel opened with the no-arg DatagramChannel.open()
>> can be used to send both IPv4 and IPv6 datagrams.
>>
>> cheers,
>>
>> -- daniel