add timeout to close path

[rlerdorf]

Apply session timeout during channel close

Problem

When a PHP script opens an SSH channel via ssh2_exec() (or similar), the
channel close path can block indefinitely. libssh2_channel_free() calls
libssh2_channel_close() internally, which waits for the remote end to send
SSH_MSG_CHANNEL_CLOSE. If the remote command hasn't finished or the
connection has been lost, this blocks forever.

The session timeout set via stream_set_timeout() is only applied around
explicit stream reads and writes but not during the close path. So even with a
timeout configured, channel cleanup during script shutdown hangs.

This also means max_execution_time / set_time_limit() won't help since
the process is blocked in a socket recv(), not consuming CPU time.

Fix

Apply the channel's timeout to the libssh2 session before calling
libssh2_channel_free(), and clear it after. This matches the existing
pattern used in the read and write stream ops. If the close blocks longer
than the configured timeout, libssh2 returns LIBSSH2_ERROR_TIMEOUT
instead of waiting forever.

Guarded by #ifdef PHP_SSH2_SESSION_TIMEOUT for compatibility with older
libssh2 versions that lack libssh2_session_set_timeout().

Reproducer

<?php
$ssh = ssh2_connect('example.com', 22);
ssh2_auth_password($ssh, 'user', 'pass');
$stream = ssh2_exec($ssh, '/usr/bin/sleep 30000');
stream_set_timeout($stream, 15);
// Without fix: script hangs for 30000 seconds during shutdown
// With fix: channel close times out after 15 seconds

[Copilot]

Pull request overview

Applies the configured PHP stream timeout to the libssh2 session during SSH channel cleanup so fclose()/shutdown won’t hang indefinitely when libssh2_channel_free() blocks waiting for SSH_MSG_CHANNEL_CLOSE.

Changes:

• Set libssh2_session_set_timeout() to the channel stream’s timeout immediately before libssh2_channel_free(), and clear it after (guarded by PHP_SSH2_SESSION_TIMEOUT).
• Add a PHPT regression test that ensures ssh2_exec() channel close returns within a bounded time when a stream timeout is set.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
ssh2_fopen_wrappers.c	Applies the stream timeout around the channel close/free path to prevent indefinite blocking.
tests/ssh2_close_timeout.phpt	Adds coverage to verify fclose() respects the configured stream timeout for long-running remote commands.

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