See issue. This is a baby step towards passing through deltas
end-to-end from node to control back to node and down to the various
engine subsystems, not computing diffs from two full netmaps at
various levels. This will then let us support larger netmaps without
burning CPU.
But this change itself changes no behavior. It just changes a func
type to an interface with one method. That paves the way for future
changes to then add new NetmapUpdater methods that do more
fine-grained work than updating the whole world.
Updates #1909
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Brad FitzpatrickandBrad Fitzpatrick
2398993804