RFR : 8182672: Java 8u121 on Linux intermittently returns null for MAC address

[Langer, Christoph]

Hi Sean,

I played with it a bit more and now really understand Vyoms observation. So, what he sees is not the original concurrency issue but he encounters a SocketException on some interface, where this is supposed to occur upon calling getHardwareAddress().

So, to enable the testcase to run robustly on any platform, any hardware and any network configuration, I suggest to modify the test like this:

1. In main, enumerate all interfaces once
2. Iterate over all interfaces, exlude loopback and see if a single call to getHardwareAddress() won't yield null or an Exception.
3. For each interface where a valid mac address could be obtained once, start the executor threads to stress getHardwareAddress() in parallel, e.g. like 5 threads doing it 100 times in parallel. I would also suggest to use per thread counters instead of one global 'count' as we have right now.

Furthermore, the test output could be improved a bit, e.g. when it comes to an exception, the thread name could be mentioned, too.

Best regards
Christoph

> -----Original Message-----
> From: net-dev [mailto:net-dev-bounces at openjdk.java.net] On Behalf Of
> Seán Coffey
> Sent: Donnerstag, 22. Juni 2017 20:17
> To: Vyom Tewari <vyom.tewari at oracle.com>; net-dev <net-
> dev at openjdk.java.net>
> Subject: Re: RFR : 8182672: Java 8u121 on Linux intermittently returns null for
> MAC address
> 
> Hi Vyom,
> 
> thanks for testing. Null is a valid value for some interfaces. I've
> excluded the loopback interface from being testing. Perhaps there's
> other issues at play here.  We know that getHardwareAddress() can throw
> SocketException if I/O fails. For this particular scenario we're not
> interested in that and perhaps that can be ignored.
> 
> I'll take another look.
> 
> regards,
> Sean.
> 
> On 22/06/2017 18:50, Vyom Tewari wrote:
> > Hi Sean,
> >
> > with your patch as well your test case is failing on my
> > laptop(Ubuntu16.04), when i tried to run  on jdk8 i am getting below
> > error.
> >
> > java.net.SocketException: No such device (ioctl(SIOCGIFHWADDR) failed)
> >     at java.net.NetworkInterface.getMacAddr0(Native Method)
> >     at
> >
> java.net.NetworkInterface.getHardwareAddress(NetworkInterface.java:457
> )
> >     at com.java.test.GetMacAddress.run(GetMacAddress.java:66)
> >     at
> >
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.jav
> a:1142)
> >     at
> >
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.ja
> va:617)
> >     at java.lang.Thread.run(Thread.java:745)
> > java.net.SocketException: No such device (ioctl(SIOCGIFHWADDR) failed)
> >     at java.net.NetworkInterface.getMacAddr0(Native Method)
> >     at
> >
> java.net.NetworkInterface.getHardwareAddress(NetworkInterface.java:457
> )
> >     at com.java.test.GetMacAddress.run(GetMacAddress.java:66)
> >     at
> >
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.jav
> a:1142)
> >     at
> >
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.ja
> va:617)
> >     at java.lang.Thread.run(Thread.java:745)
> > Exception in thread "main" java.lang.RuntimeException: Failed
> >     at com.java.test.GetMacAddress.main(GetMacAddress.java:96)
> > mac id is null for interface cscotun0- Thread0
> > Testing: cscotun0
> > mac id is null for interface cscotun0- Thread3
> > Testing: cscotun0
> >
> > Thanks,
> >
> > Vyom
> >
> >
> > On Thursday 22 June 2017 09:59 PM, Seán Coffey wrote:
> >> JDK 10 fix required to correct a race issue in NetworkInterface. I
> >> don't believe the ifreq struct needs to be static in any case. New
> >> auto unit testcase also. I propose to skip this fix for JDK 9 and fix
> >> in an update release for that family. I also plan to port this to
> >> jdk8u-dev.
> >>
> >> https://bugs.openjdk.java.net/browse/JDK-8182672
> >> webrev :
> >> http://cr.openjdk.java.net/~coffeys/webrev.8182672.jdk10/webrev/
> >>
> >> regards,
> >> Sean.
> >