Add new clientmetric counters for establishing contact with peers while using
cached network map data. To do this, instrument the magicsock.Conn with a bit
to indicate whether its peer data came from a cached netmap. If so, there are
two conditions we will count as establishing connectivity to a peer:
- Receipt of a CallMeMaybe from a peer via disco.
- Establishing a valid endpoint address for a peer.
In vmtest, add Env.ClientMetrics to scrape metrics from the specified node.
Use this to check that counters were updated in caching tests.
Updates https://github.com/tailscale/projects/issues/13
Updates #12639
Change-Id: Ie8cf3244ac8af4f5bcfe4d0d944078da2ba08990
Signed-off-by: M. J. Fromberger <fromberger@tailscale.com>
9f48567bf1