Given a RHEL machine with NetworkManager running, When running the ipv6_ip6-default_privacy' NMCI tests, Then, no failure should be seen and the test should pass successfully. Given a RHEL system with NetworkManager holding a connection with `ipv6.ip6-privacy` unset, When user activated this connection, Then NetworkManager should use the global default from NetworkManager.conf and if not set, use `/proc/sys/net/ipv6/conf/default/use_tempaddr` as default value of this interface. Given a RHEL system with NetworkManager holding a connection with `ipv6.temp-preferred-lifetime` unset, When user activated this connection, Then NetworkManager should use the global default from NetworkManager.conf and if not set, use `/proc/sys/net/ipv6/conf/default/use_tempaddr` as default value of this interface. Given a RHEL system with NetworkManager holding a connection with `ipv6.temp-valid-lifetime` unset, When user activated this connection, Then NetworkManager should use the global default from NetworkManager.conf and if not set, use `/proc/sys/net/ipv6/conf/default/use_tempaddr` as default value of this interface. Definition of Done: The implementation meets the acceptance criteria Integration tests should be added to check that the new properties work The code is part of a build attached to an errata The fix is backported into RHEL-9.4   AC and QE test alignment: This CI test: https://gitlab.freedesktop.org/NetworkManager/NetworkManager-ci/-/merge_requests/1681 has been added to ensure that the default value from /proc/sys/net/ipv6/conf/default has been applied by NetworkManager and passing.

.The value for `ipv6.ip6-privacy` no longer changes between connection activations Originally, when the global default value was not set for the `ipv6.ip6-privacy` parameter, its value reverted to the value from the `/proc/sys/net/ipv6/conf/default/use_tempaddr` file. A recent change to the NetworkManager source code caused it to incorrectly fall back to the value read from the `/proc/sys/net/ipv6/conf/IFNAME/use_tempaddr` file instead. As a consequence, IPv6 address generation changed, and the value for `ipv6.ip6-privacy` could change between connection activations. The problem has been fixed by reverting back to the original behavior. As a result, the value for `ipv6.ip6-privacy` does not change anymore between connection activations.