On Thu, 2019-09-26 at 13:32 +0100, Alan Bateman wrote: > On 26/09/2019 13:15, Kurt Miller wrote: > > > > : > > Hi Alan, > > > > This one I don't have any insight into. OpenBSD is like Windows > > where it does not support IPv4-mapped IPv6 address at all. There > > is no way to enable it with a knob (sysctl). Since the networking > > implementation in the JVM on the Unix side of things depends on > > this, OpenBSD can't support both IPv4 and IPv6 at the same time. > > > > Ideally the dual socket implementation on the Windows side would > > be utilized on the Unix side as well. The would allow for avoiding > > the (perhaps debatable) security issues associated IPv4-mapped > > IPv6 addresses that were raised by one of the initial pioneers of > > IPv6, Itojun (Jun-ichiro Hagino) [1]. > > > > I believe both FreeBSD and NetBSD have sysctl's to enable IPv4-mapped > > IPv6 address support, but is a system wide setting and puts an > > administrator in the position of having to enable a less secure > > setting to gain simultaneous IPv4 and IPv6 support in the JVM. > > > > Sorry I've gone off on a tangent here, but I felt it was related > > and perhaps could point out that the dual socket approach > > on the Windows side of the JVM networking implementation would > > likely be helpful for the Unix side as well. > > > Thanks anyway. As you brought up Windows, I should mention that > Microsoft added support for dual stack sockets in Windows Vista and the > JDK uses on that platform too (one only outlier is legacy > MulticastSocket where it uses the two stack implementation but that > should eventually be replaced). This allows the JDK to use IPv4-mapped > IPv6 addresses when interfacing with the operating system (not on the > wire of course). >
Ah. Good to know. As you probably guessed, my understanding of Windows networking in the JVM is pretty dated. I appreciate the clarification and update on the direction it is going in. Thanks, -Kurt
