Question re session hijacking in dual stack environments w/MacOS

Mark Andrews marka at
Fri Oct 2 08:16:54 UTC 2015

In message <132752.1443772000 at>, Valdis.Kletnieks at
> On Fri, 02 Oct 2015 00:46:47 -0500, Doug McIntyre said:
> > I suspect this is OSX implementing IPv6 Privacy Extensions. Where OSX
> > generates a new random IPv6 address, applies it to the interface, and then
> > drops the old IPv6 addresses as they stale out. Sessions in use or not.
> Isn't the OS supposed to wait for the last user of the old address to close
> their socket before dropping it?

Bowser talks to server with temp address 1.  Sockets close.  New
temp address generated.  User click submit.  New temp address used.

It is stupid web site design to assume that addresses will be stable
even within a session.

> > sudo sysctl -w net.inet6.ip6.use_tempaddr=0
> >
> > sudo sh -c 'echo net.inet6.ip6.use_tempaddr=0 >> /etc/sysctl.conf'
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at

More information about the NANOG mailing list