James Tucker 5a05ac11d5 ssh/tailssh: bound session teardown so shutdown can't wedge on it ...

Bound the server shutdown wait and the output drain after a session
process exits. Descendants can keep stdio open after the session
process exits, so neither wait can depend on EOF alone. Abort the SSH
channel on drain timeout without sending EOF concurrently with an
outstanding output write.

Close all PTY master descriptors on cancellation and let the terminal
driver send SIGHUP. Duplicate the masters with CLOEXEC and O_NONBLOCK
before wrapping them with os.NewFile so the runtime poller can
interrupt pending I/O on Close. Keep the PTY child's blocking mode intact.
Use RawConn.Control for duplication and window changes to synchronize
with Close and avoid restoring blocking mode on the original master
through File.Fd.

Non-PTY sessions receive SIGHUP explicitly. Keep SIGKILL escalation
for monitor sessions and add it for directly launched sessions. Use
os.Process.Signal on the direct path to synchronize signaling with
reaping. Make the escalation delay configurable alongside the
shutdown and I/O drain timeouts.

Use a process-completion channel to stop the cancellation worker on
normal exit, and join the worker before sending exit status so any
cancellation message is written before channel teardown. Cover normal
completion and cancellation through live monitored SSH sessions.

Fixes tailscale/corp#50380
Fixes #22059
Updates #20628
Updates #21827

Signed-off-by: James Tucker <james@tailscale.com>
Change-Id: I2a66741ba156a607dc3df70a79e140f19737b7a5

2026-10-29 15:43:08 -07:00

..

tailssh

ssh/tailssh: bound session teardown so shutdown can't wedge on it

2026-10-29 15:43:08 -07:00