[tor-bugs] #21425 [Core Tor/Tor]: entry_list_is_constrained() should look at the guard_selection_t object

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#21425: entry_list_is_constrained() should look at the guard_selection_t object
-------------------------------------------------+-------------------------
 Reporter:  nickm                                |          Owner:  (none)
     Type:  defect                               |         Status:
                                                 |  needs_revision
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.3.3.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  guards, 031-deferred-20170425,       |  Actual Points:
  review-group-18                                |
Parent ID:  #20822                               |         Points:  .5
 Reviewer:  asn                                  |        Sponsor:
                                                 |  SponsorV-can
-------------------------------------------------+-------------------------
Changes (by asn):

 * status:  needs_review => needs_revision


Comment:

 Hello people,

 two comments on the patch so that I understand a bit better what's going
 on because it's been a while and I'm a bit confuse:

 1) What are we trying to achieve with this new
 `entry_list_is_constrained()` logic? Can someone explain to me why we
 consider the entry list constrained if it contains more than 50 guards,
 and why this logic makes sense given the way `entry_list_is_constrained()`
 is used in the rest of the code? I think this is a very important question
 and ideally we should have a clear and concise answer :)

 2) Why are we using the `capacity` field of a smartlist? We should
 (almost) never dig into the guts of smartlists. If we want to check the
 current number of sampled guards we should use `smartlist_len()`. Is that
 we are trying to do here?

 I'm marking this as `needs_revision` so that we get a good answer to (1)
 and address (2).

 Thanks for the code <3

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21425#comment:23>
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