RFR: 8304286: java/net/SocketOption/OptionsTest.java failing after JDK-8302659

[Daniel Jeliński]

On Thu, 16 Mar 2023 19:47:13 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> I don't think so; if all interfaces are skipped, the test will fail - setting a null interface is not permitted.
>> 
>> Other multicast-related tests do similar things:
>> - `java/net/MulticastSocket/TestInterfaces.java` [skips interfaces that throw an exception](https://github.com/openjdk/jdk/blob/master/test/jdk/java/net/MulticastSocket/TestInterfaces.java#L103)
>> - `NetworkConfiguration.multicastInterfaces` [skips interfaces that don't have a network address](https://github.com/openjdk/jdk/blob/master/test/lib/jdk/test/lib/NetworkConfiguration.java#L198); we can't do that here because we're testing with a security manager and can't retrieve addresses.
>
> Could you try something like to find an interface with an IP address configured:
> 
>         boolean preferIPv4 = Boolean.getBoolean("java.net.preferIPv4Stack");
>         Class<? extends InetAddress> clazz = preferIPv4 ? Inet4Address.class : Inet6Address.class;
>         var ni = NetworkInterface.networkInterfaces()
>                 .filter(_ni -> _ni.inetAddresses().anyMatch(clazz::isInstance))
>                 .findAny()
>                 .orElse(null);

Yeah, I had something like that before. With security manager installed it will only return the loopback interface, which is not usable for multicasting on Linux.

The test is using [this SecurityManager policy](https://github.com/openjdk/jdk/blob/master/test/jdk/java/net/SocketOption/options.policy), which only allows `connect` to `localhost`, so only loopback address will be visible on NetworkInterfaces because of [this check](https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/net/NetworkInterface.java#L143)

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PR: https://git.openjdk.org/jdk/pull/13061