Heads up: Rawhide NetworkManager and RFC7217

[Lubomir Rintel]

Hi,

starting with NetworkManager-1.2.0-0.3.20151112gitec4d653.fc24 the IPv6
connections will default to using the RFC7217 "stable privacy"
addressing mode for new connections.

This feature is intended to improve privacy of the IPv6 users by using
a different host part in each network while maintaining the address
stability (the address will remain the same when the user reconnects to
the same network). It also improves addressing robustness by dealing
with duplicate address failures.

For most users this change won't affect anything user-visible.

However, this can potentially cause problems in setups which rely on
the IPv6 addresses to be derived from the interface MAC address. If you
suspect this is the case please read on.

The change in defaults does not affect existing configurations -- if
you have your IPv6 connections already configured their addresses will
_not_ change.

There's also a way to revert to the old behavior. The address
generation mode is controlled with "ipv6.addr-gen-mode" property.

To use the older mechanism, set the property as follows:

  # nmcli c modify <con> ipv6.addr-gen-mode eui64

To switch it to the RFC7217 mode do:

  # nmcli c modify <con> ipv6.addr-gen-mode stable-privacy

If you're creating the ifcfg files by hand, the equivalent key is
ADDR_GEN_MODE. If it's missing, the eui64 mode is assumed.

Please see nm-settings-ifcfg-rh(5) manual for details.

If anything breaks, we'd like to hear! Feel free to follow up on this
or file a bug report.

♥,
Lubo