[tor-bugs] #15463 [Tor]: Tor deals poorly with a very large number of incoming connection requests.

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#15463: Tor deals poorly with a very large number of incoming connection requests.
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     Reporter:  alberto   |      Owner:
         Type:  defect    |     Status:  new
     Priority:  critical  |  Milestone:  Tor: 0.2.7.x-final
    Component:  Tor       |    Version:  Tor: 0.2.5.11
   Resolution:            |   Keywords:  tor-hs SponsorR SponsorZ
Actual Points:            |  Parent ID:
       Points:            |
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Comment (by yawning):

 So we got profiler output and more logs and other things, and found out a
 bunch of stuff:

  * Reducing `MAX_REND_FAILURES` to `1` doesn't appear to help much if at
 all.
  * The profiler results matches dgoulet's #13739 results fairly closely,
 with `smartlist_remove` consuming more cpu, due to extra calls due to more
 `rend_service_relaunch_rendezvous`.  The largest consumer of CPU is
 Curve25519, so things like #13738 will help along with the precomputed key
 generation trickery.

 We still need mitigation (probably in the form of dropping INTRODUCE2
 cells at the HS, INTRODUCE1 cells at the IP, or both), since no matter how
 much faster we can make tor, it's easier for the adversary to increase
 malicious traffic.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/15463#comment:13>
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