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Re: [tor-bugs] #28780 [Core Tor/Tor]: circpadding: Add machine flag for not closing circuit if machine is active
#28780: circpadding: Add machine flag for not closing circuit if machine is active
-------------------------------------------------+-------------------------
Reporter: asn | Owner: (none)
Type: defect | Status:
| needs_review
Priority: Very High | Milestone: Tor:
| 0.4.1.x-final
Component: Core Tor/Tor | Version:
Severity: Normal | Resolution:
Keywords: wtf-pad, tor-relay, tor-cell, | Actual Points: 6
padding, 041-proposed, network-team- |
roadmap-2019-Q1Q2 |
Parent ID: #28634 | Points: 5
Reviewer: asn | Sponsor:
| Sponsor2
-------------------------------------------------+-------------------------
Changes (by mikeperry):
* status: needs_revision => needs_review
Comment:
Freshly squashed nicely organized PR that addresses previous comments:
https://github.com/torproject/tor/pull/1015
Summary of branch:
* Still hooks circuit_mark_for_close(), but the
circpad_is_using_circuit_for_padding() function name and mechanism are
much clearer.
* Only one return branch in the circpad_is_using_circuit_for_padding()
function keeps the circuit open. All others result in relinquishing
ownership to
circuit_mark_for_close()/circuit_expire_old_circuits_clientside().
* It is easy to see that this one branch cannot hold the circuit open for
more than CIRCPAD_DELAY_MAX_SECS (1.25hr) of inactivity on a circuit, even
if it is deadlocked. This is also verified in the unit tests, by testing
circuit_expire_old_circuits_clientside() directly.
* If padding machines deadlock by ping-ponging (sending padding back and
forth forever), then they will hit their machine-specific padding overhead
limits, and cease padding. At which point, network activity on the circuit
will cease, and circpad_is_using_circuit_for_padding() will return 0 and
allow circuit_expire_old_circuits_clientside() to close the circuit
(machine-specific padding limits are tested in a previously existing
test).
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28780#comment:39>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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