#29734: Broker should receive country stats information from Proxy and Client -------------------------------------+-------------------------------- 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 -------------------------------------+--------------------------------
Comment (by cohosh): Replying to [comment:24 dcf]: > I have just a few further changes to recommend. Updated branch: https://github.com/cohosh/snowflake/compare/geoip > > * https://github.com/cohosh/snowflake/blob/fb01c2d1c9d402cc4d96f01df2e6fb6cb37bc9a6/broker/broker.go#L221 > {{{ > strings.Split(r.RemoteAddr, ":")[0] > }}} > This will fail for IPv6 addresses. Better to use net.SplitHostPort and check the error return. The host–port splitting could also happen inside of `Metrics.UpdateCountryStats`. Ack >.< thanks. Done! > * https://github.com/cohosh/snowflake/blob/fb01c2d1c9d402cc4d96f01df2e6fb6cb37bc9a6/broker/geoip.go#L196 > {{{ > _, err = io.WriteString(hash, scanner.Text()) > }}} > A better way to do this may be to do `hashedFile := io.TeeReader(geoipFile, hash)` and then `scanner := bufio.NewScanner(hashedFile)` so that the hash is calculated as a side effect of reading the file. There's no need to handle errors when writing to a `hash.Hash` because it is documented to never error. Done > * https://github.com/cohosh/snowflake/blob/fb01c2d1c9d402cc4d96f01df2e6fb6cb37bc9a6/broker/geoip.go#L14 > {{{ > Recognized line formats for IPv4 are: > INTIPLOW,INTIPHIGH,CC > and > "INTIPLOW","INTIPHIGH","CC","CC3","COUNTRY NAME" > }}} > It looks like the code doesn't recognize the 5-element syntax, so it should be omitted here, or, if it's a common format, documented as not being supported. Documented as unsupported so we know what our line of thought was in case we want to support it later > > Okay. Let's replace the panic with a `log.Fatal` so the failure gets logged. > Done > > > * The `parseEntry` functions need error checking on `geoipStringToIP` and `net.ParseIP`, or else they will store a `nil` that will result in a panic later on. [https://github.com/cohosh/snowflake/blob/4de81ed039ce28264a98a040a0fde2237844e779/broker/geoip.go#L93 This error] will be more useful if it includes a line number. Let me suggest a different factoring of the geoip parsing code. Have `parseEntry` be a plain function, not a method on `GeoIPv4Table`, and have it return `(GeoIPEntry, error)` rather than inserting into the table itself. GeoIPLoadFile can do the entry insertion, count lines and annotate the error result from `parseEntry`. > > The difficulty in refactoring it this way is that ipv4 and ipv6 tables have differently formated entries that need to be parse differently. > > I added error checking to parseEntry and have it return `(GeoIPEntry, error)` as suggested, but leave it as a method on GeoIPv4Table and GeoIPv6Table. > > I didn't explain this well. I meant that there should be separate functions for the two formats e.g. `parseEntryIPv4` and `parseEntryIPv6`. The existing `parseEntry` methods never refer to `table`, so they don't need to be methods. But leaving them as methods is fine too. Okay, I'm going to leave them as methods to avoid having two different LoadFile functions for the different types of table. > > IMO annotating the error message with the problematic line should be done in `GeoIPLoadFile`, not in `parseEntry`. This will eliminate the duplication of the common `"Provided geoip file is incorrectly formatted"` string and ensure that all the error paths get annotated. What I mean is, in the `scanner.Scan()` loop, you can replace `return err` with `return fmt.Errorf("Provided geoip file is incorrectly formatted: %s. Line is: %+q")`. Done, is there a better way of handling the error stubs in `parseEntry` other than returning `fmt.Errorf("")`? Replying to [comment:25 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`. Okay, so I've changed the GetCountryByAddr signature to what you've suggested and then just removed the error return value from UpdateCountryStats. I've also added setting the country to `"??"` in UpdateCountryStats. -- Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29734#comment:27> Tor Bug Tracker & Wiki <https://trac.torproject.org/> The Tor Project: anonymity online
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