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cg-net: reap disconnected clients with a process sentinel

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Finding 5 of the 2026-07-29 security review: nothing watched for a
connection ending, so players who left stayed on the client list
forever and the host kept trying to send to them.

cg-net--host-sentinel removes a closed connection from the list; it is
installed on every accepted connection.  This also tidies the drops
made by the Finding 4 bounds, which delete-process over-limit peers.

Seat numbers are still not reused after a departure -- deliberate, and
recorded in the sentinel docstring: a stale seat must not be inherited
by a stranger mid-game.  Named in the handback as remaining behavior.

Test cgt-net-reaps-disconnected fails against the previous code: after
the client disconnected the list still held it (= 0 1).
This commit is contained in:
Claude 2026-08-03 20:35:27 -05:00 • committed by Corwin Brust
parent 640aaca1ae
commit ade2f38ee3
2 changed files with 37 additions and 0 deletions
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26
test/card-games-tests.el
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@ -181,6 +181,32 @@ Finding 4's second bound: the client list cannot grow without limit."
(dolist (p procs) (when (process-live-p p) (delete-process p)))
(cg-net-host-stop)))))
(ert-deftest cgt-net-reaps-disconnected ()
"A client that disconnects is removed from the host's client list.
Finding 5 of the 2026-07-29 review: nothing watched for a connection
ending, so departed players stayed listed forever and the host kept
sending to them. A process sentinel now reaps them."
(condition-case _
(delete-process
(make-network-process :name "cgt-probe7" :server t :service 0
:host "127.0.0.1" :family 'ipv4))
(error (ert-skip "TCP not available")))
(cl-flet ((pump () (dotimes (_ 12) (accept-process-output nil 0.05))))
(let* ((hgame (make-instance 'cgt-net-game :env (list :counter 0)))
(srv (cg-net-host-start hgame 0))
(port (process-contact srv :service))
(cgame (make-instance 'cgt-net-game :env (list :counter 0))))
(unwind-protect
(progn
(cg-net-connect "127.0.0.1" port "Test" cgame)
(pump)
(should (= 1 (length (cg-net-host-clients cg-net--host))))
(cg-net-disconnect)
(pump)
(should (= 0 (length (cg-net-host-clients cg-net--host)))))
(cg-net-disconnect)
(cg-net-host-stop)))))
;;;; Gaps
(ert-deftest cgt-gaps-deal ()