[tor-bugs] #25252 [Core Tor/Tor]: Rust implementation of protover code deviates from C in some cases

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#25252: Rust implementation of protover code deviates from C in some cases
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 Reporter:  nickm                   |          Owner:  nickm
     Type:  defect                  |         Status:  needs_review
 Priority:  High                    |      Milestone:  Tor: 0.3.3.x-final
Component:  Core Tor/Tor            |        Version:
 Severity:  Normal                  |     Resolution:
 Keywords:  033-must protover rust  |  Actual Points:
Parent ID:                          |         Points:
 Reviewer:                          |        Sponsor:
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Changes (by nickm):

 * status:  assigned => needs_review
 * priority:  Medium => High


Comment:

 Update: most of the issues here are solvable with a little tweaking.  I've
 made changes in torspec in  a8455f4d1a6ef7 to define the C behavior as
 "right" a little more.

 The one issue that will be trickiest to handle is that the Rust code
 stores versions in a hashset of u32, whereas the C code stores an array of
 (lo,hi) pairs.  As such, the Rust code needs to reject 1-4000000000 as a
 range, or else it will fill up RAM.  C accepts such a range everywhere
 except during voting.

 I propose that we handle that last issue separately from the others.

 The easier issues are solved in my branch `protover_rust_compat_v3`, along
 with a fix for #25250.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25252#comment:1>
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