[tor-bugs] #20151 [Core Tor/Tor]: Fix parse_virtual_addr_network minimum network size

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#20151: Fix parse_virtual_addr_network minimum network size
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 Reporter:  teor          |          Owner:
     Type:  defect        |         Status:  new
 Priority:  Medium        |      Milestone:  Tor: 0.2.???
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:  easy intro    |  Actual Points:
Parent ID:                |         Points:  0.5
 Reviewer:                |        Sponsor:
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Comment (by eternaleye):

 I disagree with your assessment of the variable names - in particular, the
 old names refer to the minimum/maximum length of the ''network prefix'',
 which matches convention. The error message refers to a larger ''network''
 (i.e., one containing more addresses). Both of these are entirely
 sensible, IMO, even together. The former is the normal way to discuss
 allocations, while the latter is a less technical framing of the problem.

 It would likely be clearer, however, if the variable name was
 "max_prefix_bits".

 In addition, the thinko was most likely around the IPv6 guideline that
 each host should get a /64, and so the author of that code was intending
 to ensure the ability to allocate ''2^16^ /64s'' (and actually mandated
 the ability to allocate 2^24^, possibly due to "IPv6 should let people
 have more room than IPv4").

 However, the addresses allocated by VirtualAddressNetworkIPv6 are not
 actually hosts (they're services), and as a result, should have fully-
 specified addresses, not prefixes. This is, in fact, part of the reason
 IPv6 instructs that each host should get a /64.

 As a result, using /104 as the maximum prefix length seems entirely
 sensible to me.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20151#comment:2>
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