Re: how do I disable IPv6?

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Tue, 27 Feb 2018 19:28:15 +0100
    From:        Martin Husemann <martin%duskware.de@localhost>
    Message-ID:  <20180227182814.GA9310%mail.duskware.de@localhost>

  | Right -  but on wifi interfaces it usually doesn't work.

Huh?   I'm using a wifi interface, and DAD happens, and "works"
(at least it fails to discover any duplicates, which should be correct
as there should be none, but until it does find a legitimate one, I
cannot really be sure it is working).

Why would a wifi interface be different from any other for this?

  | The "can not bind to addresses in duplicated state" is a new thing in -8
  | (and current), which is why the config always used to work.

While that change can cause some other issues, and sometimes be
a nuisance (and while I also don't agree with it) I fail to see how it
can possibly cause a duplicate address to be detected, which is
the error reported here.

  | I do this on my notebook as well, and still am typing this mail over
  | an IPv6 connection.

That's expected - duplicate addresses are rare, and not checking for
something that most likely does not exist is rarely going to cause any
problems.   Until it does.

I agree with Joerg, telling people to turn off DAD, especially when what
they asked was to disable IPv6, is very poor advice.

We don't really have a "disable IPv6" (or IPv4) mechanism right now
I don't think - years ago, I mentioned a project I had some students
implement to add exactly that functionality - the result gets moderately
complex, but in its simplest form can be trivial.  If there is still interest
in that, I could ressurect it (for just the simplest form, there is no need,
I remember that part, and could reimplement in minutes, most of which
would be recalling the magic to create the sysctl variables to control it).
But that ought to be discussed on tech-net@ not here.

kre