;;; Consfigurator -- Lisp declarative configuration management system

;;; Copyright (C) 2021  Sean Whitton <spwhitton@spwhitton.name>

;;; This file is free software; you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3, or (at your option)
;;; any later version.

;;; This file is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.

;;; You should have received a copy of the GNU General Public License
;;; along with this program.  If not, see <http://www.gnu.org/licenses/>.

(in-package :consfigurator.connection.chroot)
(named-readtables:in-readtable :consfigurator)

;; currently we only check whether we're root, but, for example, on Linux, we
;; might have a CAP_* which lets us chroot as non-root
(defun can-chroot ()
  (zerop (foreign-funcall "geteuid" :int)))

(defun can-probably-fork ()
  "Return nil if we can detect other running threads, and the Lisp
implementation is known not to support forking when there are other threads.
A return value other than nil indicates only that we couldn't detect
circumstances in which it is known that we cannot fork, not that we are sure
we can fork -- a thread might be only partly initialised at the time we check,
for example, such that we don't see it."
  (and
   #+sbcl (> 2 (length (sb-thread:list-all-threads)))))

(defmethod establish-connection ((type (eql :chroot)) remaining &key into)
  (establish-connection (if (and (lisp-connection-p)
				 (can-chroot)
				 (can-probably-fork))
			    :chroot.fork
			    :chroot.shell)
			remaining
			:into into))