[tor-bugs] #24767 [Core Tor/Tor]: All relays are constantly connecting to down relays and failing over and over

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#24767: All relays are constantly connecting to down relays and failing over and
over
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 Reporter:  arma                                 |          Owner:  dgoulet
     Type:  enhancement                          |         Status:
                                                 |  needs_revision
 Priority:  Very High                            |      Milestone:  Tor:
                                                 |  0.3.3.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-relay, tor-dos, performance,     |  Actual Points:
  review-group-32, 033-must, review-group-34,    |
  033-triage-20180320, 033-included-20180320     |
Parent ID:                                       |         Points:
 Reviewer:  asn                                  |        Sponsor:
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Comment (by dgoulet):

 Replying to [comment:31 nickm]:
 > So on the hash function: You can't use a memcpy(tor_addr_t) like that,
 because some of the bytes of the tor_addr_t can be unspecified.  I can fix
 that up.

 Oh damn because of the union, if it is a v4, we'll copy bunch of uninit
 bytes from the larger v6. I guess setting the size according to the family
 is the way to do it.

 > On unable_connect_since_ts: Do we ever clear this field (re-set it to
 zero) on success?  It seems like it just stays set forever.  If so maybe a
 better name would be something like "last_failed_connect_ts"?

 It is a timestamp, we don't need to reset it. It always being compared to
 a cutoff so even thought it is set once and never touched again, that is
 fine since it will at some point always pass the cutoff.

 >  Oh, and one more thing I noticed: It is not enough to just check
 "node_get_pref_orport(node, &node_addr_port);" -- the node may have
 multiple addresses, and "pref" just returns the one you would prefer to
 use yourself.

 Not sure it is a problem here. We use `node_get_pref_orport()` only to
 make sure the or connection we are about to note down as a failure matches
 the `node_t` we have from the identity digest. In this case, we use the
 node_t to keep the timestamp. If it doesn't match (because other port/addr
 for the identity), we note it down as a "unknown".

 This ends up to be the same result but just more precisely indexed by addr
 + port + digest always.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24767#comment:34>
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