api-server: an unknown logs mode leaves logs-start with no response

[DavidePrincipi]

Steps to reproduce

• Send a logs-start action over the api-server WebSocket with a mode that is neither tail nor dump, for example: {"action":"logs-start","payload":{"id":"1","mode":"foo","entity":"cluster"}}
• Alternatively, run api-server-logs logs --mode=foo

Expected behavior

The caller always gets an answer: an error message naming the unsupported mode. The CLI exits non-zero.

Actual behavior

Nothing is written back at all, and no logcli process is ever started.

logsAction.Mode is taken verbatim from the client payload. The switch at core/api-server/socket/action.go:136 handles tail and dump; any other value falls through leaving mode = "", which is appended to args as an empty argument. Neither if logsAction.Mode == "tail" nor == "dump" then matches, so no goroutine is started and no response is produced:

• Over the WebSocket, the client waits indefinitely for a logs-start event that never arrives.
• In the CLI, Logs() calls wg.Add(1) and then wg.Wait() (core/api-server/api-server-logs.go:96,122), and nothing will ever call wg.Done(), so api-server-logs --mode=foo hangs forever.

Reachable by any authenticated WebSocket client. It neither crashes nor leaks anything — the handler simply goes silent — so this is a robustness gap, not a security issue.

Suggested fix

Add a default: arm to the mode switch so the caller is always answered:

default:
	writeLogsError(s, logsAction.Id, "unknown logs mode: "+logsAction.Mode, wg)
	return

This also drops the stray empty-string argument, which would have produced a malformed logcli invocation had either branch run.

Components

ns8-core 3.21.0 (also present on main, 3.21.1-dev.1) — core/api-server, WebSocket logs-start action and the api-server-logs CLI.

See also

Pre-existing behaviour. Found while reviewing NethServer/ns8-core#1272, whose goal was to report logcli errors instead of dropping them; this is the last silent-hang path left in the handler. Deliberately kept out of that PR's scope.