[tor-reports] Andrea's June 2013 status report
andrea at torproject.org
Tue Jul 2 00:44:51 UTC 2013
In June 2013:
* Investigated non-blocking socket behavior on OpenBSD for #9017
* Added instrumentation and did testing for #7912
* Implemented cell queue length fix, then rolled it back because the
protocol is stupid in a way that meant it enable a different attack
* Reviewed #8822
* Had a first look at refactoring cmux code to pick among all writeable
channels rather than just one at a time; did profiling tests on existing
Nearly all calls into channel_flush_from_first_active_circuit() in
the current code flow from the read-driven end through
append_cell_to_circuit_queue() or the write-driven end through
channel_flush_some_cells(). The proportion depends on where the rate-
limiting point is (outgoing bandwidth or throttling).
- Proposed strategy for cmux refactor:
- Keep track, per channel, of whether the channel wants to
write (update in append_cell_to_circuit_queue()) and whether it
can write (update in the write-driven pathway instead of
- Changes to these bits trigger running the scheduling algorithm,
but at most once per event loop.
- Scheduler calls enhanced cmux mechanism to use a pluggable scheduling
policy to choose circuits in preference order *among all available
channels* rather than one at a time.
<andrea at torproject.org>
PGP fingerprint: 3611 95A4 0740 ED1B 7EA5 DF7E 4191 13D9 D0CF BDA5
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