Overlay is the only driver which makes use of the EventNotify facility,
yet all other driver implementations are forced to provide a stub
implementation. Move the EventNotify and DecodeTableEntry methods into a
new optional TableWatcher interface and remove the stubs from all the
other drivers.

Signed-off-by: Cory Snider <[email protected]>

The macAddr and ipmac types are generally useful within libnetwork. Move
them to a dedicated package and overhaul the API to be more like that of
the net/netip package.

Update the overlay driver to utilize these types, adapting to the new
API.

Signed-off-by: Cory Snider <[email protected]>

Windows and Linux overlay driver instances are interoperable, working
from the same NetworkDB table for peer discovery. As both drivers
produce and consume serialized data through the table, they both need to
have a shared understanding of the shape and semantics of that data.
The Windows overlay driver contains a duplicate copy of the protobuf
definitions used for marshaling and unmarshaling the NetworkDB peer
entries for dubious reasons. It gives us the flexibility to have the
definitions diverge, which is only really useful for shooting ourselves
in the foot.

Make daemon/libnetwork/drivers/overlay the source of truth for the peer
record definitions and the name of the NetworkDB table for distributing
peer records.

Signed-off-by: Cory Snider <[email protected]>

The eventually-consistent nature of NetworkDB means we cannot depend on
events being received in the same order that they were sent. Nor can we
depend on receiving events for all intermediate states. It is possible
for a series of entry UPDATEs, or a DELETE followed by a CREATE with the
same key, to get coalesced into a single UPDATE event on the receiving
node. Watchers of NetworkDB tables therefore need to be prepared to
gracefully handle arbitrary UPDATEs of a key, including those where the
new value may have nothing in common with the previous value.

The overlay driver naively handled events for overlay_peer_table
assuming that an endpoint leave followed by a rejoin of the same
endpoint would always be expressed as a DELETE event followed by a
CREATE. It would handle a coalesced UPDATE as a CREATE, inserting a new
entry into peerDB without removing the old one. This would
have various side effects, such as having the "transient state" of
multiple entries in peerDB with the same peer IP never settle.

Update driverapi to pass both the previous and new value of a table
entry into the driver. Modify the overlay driver to handle an UPDATE by
removing the previous peer entry from peerDB then adding the new one.
Modify the Windows overlay driver to match.

Signed-off-by: Cory Snider <[email protected]>

The eventually-consistent nature of NetworkDB means we cannot depend on
events being received in the same order that they were sent. Nor can we
depend on receiving events for all intermediate states. It is possible
for a series of entry UPDATEs, or a DELETE followed by a CREATE with the
same key, to get coalesced into a single UPDATE event on the receiving
node. Watchers of NetworkDB tables therefore need to be prepared to
gracefully handle arbitrary UPDATEs of a key, including those where the
new value may have nothing in common with the previous value.

The libnetwork controller naively handled events for endpoint_table
assuming that an endpoint leave followed by a rejoin of the same
endpoint would always be expressed as a DELETE event followed by a
CREATE. It would handle a coalesced UPDATE as a CREATE, adding a new
service binding without removing the old one. This would
have various side effects, such as having the "transient state" of
having multiple conflicting service bindings where more than one
endpoint is assigned an IP address never settling.

Modify the libnetwork controller to handle an UPDATE by removing the
previous service binding then adding the new one.

Signed-off-by: Cory Snider <[email protected]>