Re: [tor-bugs] #25614 [Core Tor/Tor]: tor sets `TOR_PT_EXIT_ON_STDIN_CLOSE=1` only for server transports, not client transports

["Tor Bug Tracker & Wiki" <blackhole@xxxxxxxxxxxxxx>]

#25614: tor sets `TOR_PT_EXIT_ON_STDIN_CLOSE=1` only for server transports, not
client transports
--------------------------+----------------------------------
 Reporter:  dcf           |          Owner:  (none)
     Type:  defect        |         Status:  new
 Priority:  Medium        |      Milestone:  Tor: unspecified
Component:  Core Tor/Tor  |        Version:
 Severity:  Minor         |     Resolution:
 Keywords:                |  Actual Points:
Parent ID:                |         Points:
 Reviewer:                |        Sponsor:
--------------------------+----------------------------------

Comment (by dcf):

 Replying to [comment:2 arma]:
 > David, is this bug preventing specific expected behavior from client-
 side transports right now? Assuming yes, can you give us some specifics?

 No, it's not causing any problems. On non-Windows platforms, tor sends a
 SIGTERM, which the client transport plugin can catch and terminate
 cleanly. On Windows, tor has no choice but to call `TerminateProcess`,
 which doesn't give the child process a chance to terminate cleanly.
 Unclean termination isn't a problem for obfs4proxy, because it doesn't
 manage any external resources. Unclean termination ''is'' a problem for
 meek-client, because meek-client starts its own child processes that would
 be left orphaned. That's the reason for the now three-year-old
 [https://gitweb.torproject.org/pluggable-transports/meek.git/tree
 /terminateprocess-buffer/terminateprocess-buffer.go?h=0.30
 terminateprocess-buffer] hack, which interposes a process between tor and
 meek-client that absorbs `TerminateProcess` and allows meek-client to
 terminate cleanly. [[comment:21:ticket:15435|I thought]] we would be able
 to get rid of terminateprocess-buffer eventually, once tor started
 supporting `TOR_PT_EXIT_ON_STDIN_CLOSE` for clients. But it turns out that
 hasn't happened yet.

 It just seems like an oversight, as there's nothing in the spec that says
 it's only for server transports. I know I always anticipated that it would
 work for clients as well, and was surprised to learn that it wasn't the
 case.

 > (E.g. "when meek-browser closes on the client side, Tor doesn't notice
 that it's finished so it doesn't report any problems to the user")

 You have it backwards: `TOR_PT_EXIT_ON_STDIN_CLOSE` is for tor to ''tell''
 a child process to terminate, not to detect when a child process has
 decided to terminate on its own.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25614#comment:3>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online

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