[tor-bugs] #24902 [Core Tor/Tor]: Denial of Service mitigation subsystem

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#24902: Denial of Service mitigation subsystem
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 Reporter:  dgoulet                              |          Owner:  dgoulet
     Type:  enhancement                          |         Status:
                                                 |  needs_review
 Priority:  Very High                            |      Milestone:  Tor:
                                                 |  0.3.3.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  ddos, tor-relay, review-group-30,    |  Actual Points:
  029-backport, 031-backport, 032-backport,      |
  review-group-31                                |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by arma):

 And thus ends my review. Looking good!

 I've been trying to figure out if I would want to set the consensus params
 with these defaults -- "if 100 concurrent conns, ones after that are
 refused" and "90 circuits, refilled 3 per second" -- and I think yes I am
 comfortable with those.

 In the future, I plan to advocate for merging dos_cc_new_create_cell() and
 dos_cc_get_defense_type() into a single function, which notes the
 existence of the new create cell and also tells us whether to apply a
 defense. And I plan to advocate for a second cc defense, which returns
 DOS_CC_DEFENSE_REFUSE_CELL simply when stats->cc_stats.circuit_bucket ==
 0, without any marking or checking of stats->concurrent_count. I think I
 will want to instrument a real relay to see how often it would trigger
 that new defense, though, and I am happy to delay my future plans so we
 can get this patch out the door.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24902#comment:46>
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