Revert "BUG/MEDIUM: cli: fix master CLI connection slot leak on client disconnect"

This reverts commit 64383e655b23e1240dd0043a18ca020994c60022.

As reported by Alexander Stephan in issue #3351, it causes problems.
First, as seen in the issue, the "reload" operation, handled by an applet
local to the master process, is being interrupted by the timeout so that
the client never gets the result (though the timeout is applied). A fix
for this was found (ignore client-fin/server-fin on applets, as they make
no sense there), but it only hides a deeper problem. Indeed, issuing
"@1 debug dev delay 2000" still stops at 1s with an error, indicating
that commands are systematically being sent with a shutdown, and thus
that the server-fin always applies. This is a problem because it means
that any long command will now be interrupted after one second.

All of this needs to be put back into perspective before progressing
further on this issue, and the reason for sending the shutdown should
be reconsidered in the context of the current version, as it looks
like this was once necessary but no longer is.

In addition, the issue encountered by Alexander, of a frozen worker,
was essentially reported once in many years, so it's totally acceptable
to leave older versions unfixed and figure what's the best solution for
modern versions only.

Let's just revert to the pre-fix situation so as to avoid causing
breakage everywhere. This revert should be backported to all versions
(2.4 included).

reg-tests/mcli/mcli_master_socket_leak.vtc

@@ -1,66 +0,0 @@
-varnishtest "Bug fix: master CLI connection slots freed on client disconnect"
-
-# Regression test for a master CLI socket connection leak in master-worker mode.
-#
-# mworker_proxy has a fixed maxconn of 10.  When clients connect to the master
-# socket, send a command that is forwarded to a busy worker, and then close
-# the connection due to a client-side receive timeout, haproxy must free each
-# slot as the client disconnects.
-#
-# Without the fix: slots remain occupied after the client disconnects, so the
-# master CLI becomes unreachable once all 10 slots are filled.
-# With the fix: slots are freed on client disconnect and the master CLI keeps
-# accepting new connections.
-#
-# The worker is made unresponsive using "debug dev delay" (expert-mode) with
-# nbthread 1 so a single delay blocks the entire worker CLI.  This avoids
-# using SIGSTOP/SIGCONT which can be unreliable in CI environments.
-
-#REGTEST_TYPE=bug
-
-feature cmd "command -v socat"
-feature cmd "command -v timeout"
-feature ignore_unknown_macro
-
-server s1 {
-} -start
-
-haproxy h1 -W -S -conf {
-    global
-        nbthread 1
-
-    defaults
-        mode http
-        timeout connect "${HAPROXY_TEST_TIMEOUT-5s}"
-        timeout client  "${HAPROXY_TEST_TIMEOUT-5s}"
-        timeout server  "${HAPROXY_TEST_TIMEOUT-5s}"
-
-    frontend fe
-        bind "fd@${fe}"
-        default_backend be
-
-    backend be
-        server s1 ${s1_addr}:${s1_port}
-} -start
-
-# Fill all 10 master CLI slots (mworker_proxy->maxconn is hardcoded to 10).
-# Each socat sends "expert-mode on" followed by "@1 debug dev delay 10000"
-# which blocks the single worker thread for 10 s.  After 2 s the timeout(1)
-# wrapper kills socat, simulating a client-side receive timeout.  "wait"
-# ensures all background processes have exited before proceeding.
-shell {
-    for i in $(seq 1 10); do
-        (printf "expert-mode on\n@1 debug dev delay 10000\n" \
-         | timeout 2 socat TCP:${h1_mcli_addr}:${h1_mcli_port} - 2>/dev/null) &
-    done
-    wait
-}
-
-# This is the key assertion: after all 10 clients have disconnected, a new
-# connection to the master CLI must succeed.  With the bug all 10 slots are
-# still marked occupied and this connect is refused or times out.
-haproxy h1 -mcli {
-    send "show version"
-    expect ~ "3."
-}
-

src/cli.c

@@ -3907,9 +3907,8 @@ int mworker_cli_create_master_proxy(char **errmsg)
 	mworker_proxy->mode = PR_MODE_CLI;
 	/* default to 10 concurrent connections */
 	mworker_proxy->maxconn = 10;
-	mworker_proxy->timeout.client = 0; /* no timeout */
-	mworker_proxy->timeout.serverfin = MS_TO_TICKS(1000); /* 1s timeout in case worker is not responding on shutdown */
-
+	/* no timeout */
+	mworker_proxy->timeout.client = 0;
 	mworker_proxy->conf.file = strdup("MASTER");
 	mworker_proxy->conf.line = 0;
 	mworker_proxy->accept = frontend_accept;