Monitor teardown SIGHUPed and SIGKILLed every remembered child group
when the transport closed. sshd signals nothing at a non-PTY session
end; background jobs with redirected stdio survive and reparent to
init. Clients rely on that: VS Code Remote-SSH starts its remote
server as a plain background job in the session's group and expects
it to outlive connection drops, and tailscale upgrades run as
non-PTY execs whose work should survive a daemon restart.
Use an explicit graceful monitor close to preserve session jobs on
ordinary disconnect and daemon shutdown. Close PTY masters normally,
letting the terminal driver signal the foreground group, but do not
signal non-PTY jobs. Remove Linux Pdeathsig from session children;
forwarding children retain it and always die with the connection.
Commit duration and recording-failure termination to the monitor
before publishing cancellation or writing the termination message.
The monitor owns per-session HUP-to-KILL escalation even after the
leader exits or the connection closes. Revocation arms connection-wide
cleanup. Pin every termination target's leader until after SIGKILL,
including during teardown, so group signaling cannot hit reused PIDs.
Select teardown targets explicitly and leave graceful survivors alone.
Unexpected RPC loss fails closed. If a termination mandate cannot be
delivered, close the RPC rather than subsequently requesting graceful
teardown; this may also kill sibling jobs on a broken channel. Keep
both the escalation and monitor shutdown waits bounded.
Add coverage for default-HUP graceful survivors, actual duration and
recording-failure termination followed by immediate disconnect, sibling
survival, HUP-exiting leaders with immune group members, broken RPCs,
and leader pinning through teardown's SIGKILL pass.
Fixes#22076
Signed-off-by: James Tucker <james@tailscale.com>
Change-Id: I70b4ef40035330dd542d256ba79d889a12426a74
Move lazy monitor startup, credentials, and cleanup into connmonitor.go and rename the connection state and accessors. The monitor owns session processes as well as forwarding children. Move the session exit registry alongside session monitor handling and keep the Plan 9 stub in a matching file.
Update callers, tests, and diagnostic prefixes without changing monitor lifecycle behavior.
Updates tailscale/corp#50380
Change-Id: I760fa009176491da426639615907d129b68026fc
Signed-off-by: James Tucker <james@tailscale.com>
James Tucker