[tor-bugs] #29734 [Obfuscation/Snowflake]: Broker should receive country stats information from Proxy and Client

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#29734: Broker should receive country stats information from Proxy and Client
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 Reporter:  cohosh                   |          Owner:  cohosh
     Type:  enhancement              |         Status:  needs_revision
 Priority:  Medium                   |      Milestone:
Component:  Obfuscation/Snowflake    |        Version:
 Severity:  Normal                   |     Resolution:
 Keywords:  snowflake, geoip, stats  |  Actual Points:  2
Parent ID:  #29207                   |         Points:  1
 Reviewer:  ahf                      |        Sponsor:  Sponsor19
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Comment (by dcf):

 Oh and it looks like country stats don't get incremented whenever
 `GetCountryByAddr` doesn't find a match. I'm afraid this will make
 analysis difficult if a large fraction of proxies aren't covered by the
 geoip database, or the database is improperly installed, or something.
 Could we count them with a country code of `"??"` or something?

 https://github.com/cohosh/snowflake/blob/fb01c2d1c9d402cc4d96f01df2e6fb6cb37bc9a6/broker/geoip.go#L213
 `GetCountryByAddr` returns `(string, error)`, but failure to find an entry
 in a database is not really an "error". It makes it seem like there are
 three return stats possible (found, not found, error) when really there
 are only two (found, not found). How about changing the signature to
 {{{
 func GetCountryByAddr(table GeoIPTable, ip net.IP) (string, bool)
 }}}
 where the second return value is an `ok` flag, like when indexing a map or
 reading from a channel. The caller can then do the `"??"` substitution
 whenever `!ok`.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29734#comment:25>
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