[tor-bugs] #15545 [Pluggable transport]: Document TOR_PT_EXIT_ON_STDIN_CLOSE in the pt-spec.

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#15545: Document TOR_PT_EXIT_ON_STDIN_CLOSE in the pt-spec.
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     Reporter:  yawning              |      Owner:  yawning
         Type:  task                 |     Status:  needs_revision
     Priority:  normal               |  Milestone:  Tor: 0.2.7.x-final
    Component:  Pluggable transport  |    Version:
   Resolution:                       |   Keywords:  pt-spec pt-wants
Actual Points:                       |  Parent ID:
       Points:                       |
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Changes (by yawning):

 * status:  new => needs_revision


Comment:

 Interesting, the current revision of pt-spec.txt doesn't mention the
 SIGINT behavior at all.  I guess this is ok, since it's not actually
 implemented in the tor side code, and I don't really see a good case for
 keeping it.

 Anyway, this documents the PT termination behavior, including the shutdown
 on close stuff:
 https://github.com/Yawning/torspec/compare/bug15545

 My plans going forward to bring some sanity to the PT shutdown process,
 now that `TOR_PT_EXIT_ON_STDIN_CLOSE` exists is to change the tor side PT
 teardown code to:

  1. Close stdin (and on U*IX, send a `SIGTERM`, PT behavior here is
 equivalent).
  2. Wait for a grace period (~1 sec?)
  3. If the child still is not dead, send a `SIGKILL`/`TerminateProcess()`.

 I think that behavior reflects what's in the spec, is far more
 portable/sane than what currently exists, and will fix #9330 since PTs
 that have their own children will have ample time to clean up.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/15545#comment:1>
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