The netd based InterfaceObserver uses two different netlink sockets for
updates on interface added / removed and link up / down events. This
means that these events are not ordered, which causes lots of
interesting issues in the ethernet service. Netd does not use
RTM_DELLINK at all, so this code has to use NetlinkMonitor to do
implement its own link tracking.
The EthernetManagerTests are currently disabled. There are still a
couple of flakes: one due to some link state issue which stops occurring
when bringing up the interface in TestNetworkService (weird -- I don't
yet know why this happens). Another due to the maybeTrackInterface
looking at the running flag (which races with the bringup code).
Test: atest EthernetManagerTest
Bug: 218785176
Bug: 234314411
Change-Id: I92b737f693402c1a8fd0a864736673de94904f2d
734f24e6d7