[tor-bugs] #24797 [Core Tor/Tor]: Add an option that makes Tor use fewer connections

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#24797: Add an option that makes Tor use fewer connections
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 Reporter:  teor                                 |          Owner:  neel
     Type:  enhancement                          |         Status:
                                                 |  assigned
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  unspecified
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-relay, tor-dos,                  |  Actual Points:
  034-triage-20180328, 034-removed-20180328      |
Parent ID:                                       |         Points:  1
 Reviewer:                                       |        Sponsor:
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Comment (by teor):

 Don't change set_max_file_descriptors(), it works well, and does exactly
 what arma says: gets the most file descriptors from the system.

 Instead, look at the out of socket check code. It is enabled by
 "DisableOOSCheck 0". It uses the socket limit that
 set_max_file_descriptors() discovers from the system. But you could add a
 torrc option that allows the user to set a lower limit for the out of
 socket check. It would only work if the out of socket check was enabled.

 Then the tor process could have the maximum number of sockets available,
 but choose not to use them. (For example, during the extra client load, I
 would have set the socket limit to half the number of file descriptors, so
 that the connection closing logic ran less frequently.)

 Since I opened this ticket, we also added DoSConnectionMaxConcurrentCount.
 Maybe that makes this ticket less important?
 But it would still be good for operators who run all their tor instances
 under the same user.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24797#comment:11>
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