The device must not directly add addresses or routes. Instead, it must track the addresses/routes it wants to add in the NMIP6Config.
Otherwise, during reapply, the information is lost and the next sync will remove them.
78ed0a4a2 device: add IPv6 link local address via merge-and-apply
src/devices/nm-device.c | 126 ++++++++++++++++++++++++++++++++++--------------
1 file changed, 90 insertions(+), 36 deletions(-)