[tor-bugs] #20895 [Core Tor/Tor]: Split node_supports_ed25519_link_authentication into two or three separate functions

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#20895: Split node_supports_ed25519_link_authentication into two or three separate
functions
--------------------------+------------------------------------
 Reporter:  nickm         |          Owner:  nickm
     Type:  task          |         Status:  needs_revision
 Priority:  Low           |      Milestone:  Tor: 0.3.2.x-final
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:  refactor      |  Actual Points:
Parent ID:  #15054        |         Points:  2
 Reviewer:  dgoulet       |        Sponsor:
--------------------------+------------------------------------
Changes (by dgoulet):

 * status:  needs_review => needs_revision
 * reviewer:   => dgoulet


Comment:

 I'm not sure I fully understand here the use of
 `protocol_list_supports_protocol_or_later()` which goes like this:

 {{{
 +      if (range->high >= version) {
 +        contains = 1;
 +        goto found;
 }}}

 So let's say I have a relay with `LinkAuth 2,4` which deliberately not
 list "3", this "or later" function will return true for `return
 protocol_list_supports_protocol_or_later(protos, PRT_LINKAUTH, 3);` but it
 should really not actually say that it supports LinkAuth 3

 Can we really imply that if a relay supports 4 then it has to support 3 ?
 What if we disabled it or made it obsolete or consensus put if off?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20895#comment:12>
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