Simple definition
SSH ControlMaster allows multiple SSH sessions to reuse one authenticated network connection.
Purpose and use
ControlMaster reuses an OpenSSH connection for multiple sessions, potentially reducing connection setup overhead.
How does it work?
Clients contact a master connection through a control socket; ControlPersist can manage how long it remains available.
Example and verification
Inspect the socket and master connection when a new session appears to reuse an existing context.
Points to watch
Reuse does not imply fresh authentication for every session. Protect the socket and control the persistence period.
In short
Multiplexing shares a connection rather than creating a new identity or trust level.