Client ACL configuration

`client_acls[].source`

Type: device ID or any
Required: Yes
Default: None
Validation: Existing device ID or the reserved value any; cannot equal target.
Secret classification: No; access-policy metadata.
Side effects: Selects which enrolled clients may initiate the flow.
Minimal example: laptop

`client_acls[].target`

Type: device ID
Required: Yes
Default: None
Validation: Must name an existing device and differ from source.
Secret classification: No.
Side effects: Selects the enrolled destination address.
Minimal example: server

`client_acls[].protocol`

Type: enum
Required: Yes
Default: None
Validation: Exactly tcp or udp.
Secret classification: No.
Side effects: Adds a protocol-specific nftables accept rule.
Minimal example: tcp

`client_acls[].port`

Type: uint16
Required: Yes
Default: None
Validation: Numeric port 1–65535; the complete ACL tuple must be unique.
Secret classification: No.
Side effects: Limits the exception to one destination port.
Minimal example: 22

client_acls:
  - source: laptop
    target: server
    protocol: tcp
    port: 22

An ACL is directional. Connection tracking admits replies, but it does not let server initiate an unrelated connection back to laptop. The target service still needs authentication and its own host security.

Next: Isolation model.