[metrics-bugs] #29624 [Metrics/Exit Scanner]: New version of exit list format

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#29624: New version of exit list format
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 Reporter:  irl                      |          Owner:  irl
     Type:  task                     |         Status:  needs_revision
 Priority:  Medium                   |      Milestone:
Component:  Metrics/Exit Scanner     |        Version:
 Severity:  Normal                   |     Resolution:
 Keywords:  metrics-roadmap-2019-q2  |  Actual Points:
Parent ID:  #29650                   |         Points:
 Reviewer:  irl                      |        Sponsor:
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Changes (by karsten):

 * status:  needs_review => needs_revision


Comment:

 Nice blog post! It's indeed interesting to see what fraction of IP
 addresses is only available in exit lists. If I may nitpick:
  - It's slightly confusing (to me) that the red and green line show single
 set sizes whereas the blue line shows one set minus the other one. I
 wonder if the lines would work better (for me) if they were: Found only in
 consensus, Found in consensus and exit list, and Found only in exit list.
 That way it would be possible to add up all three lines and obtain the
 total number of addresses.
  - Maybe this graph would work as a stacked area plot like
 [https://metrics.torproject.org/bandwidth-flags.html our bandwidth flags
 graph], just with three stacked areas rather than four. If you look at
 that linked bandwidth flags graph, yellow would be "Found only in
 consensus", green would be "Found in consensus and exit list" and blue
 would be "Found only in exit list". That would show pretty quickly what
 fraction someone is missing when only looking at consensuses: the blue
 part at the top.
  - If you like, I can help you with making that graph. Just give me the
 raw data, and I'll make a quick graph out of it. Also as an experience to
 learn more about the tidyverse. And for the next funding proposal, of
 course.

 Anyway, I think you wanted a review of the exit list spec! Here's what I
 found:
  - "[the identity-ed25519 line] MUST appear as the first or second element
 in the router descriptor": Why the first? In version 2 or later the first
 element is always "exit-list", so it can only be the second element. And
 why router descriptor? You mean exit list?
  - Sometimes we're using two spaces between sentences. Let's be consistent
 and either use one or two.
  - In the "location" line, should we write the AS number as AS12345 rather
 than just 12345? Technically, it's correct to just use an integer there,
 but if we think of humans reading the format, we might want to include the
 "AS" part anyway.
  - Should the "platform" line suggest a possible format for exit list
 scanner software version, Tor software version, and operating system?
 Something like "ExitScanner 55.5 using Tor 1.0.0 on Windows 10"?
  - There are at least two places where you write "[XXX: Informational:
 ...]". Can we just include those informational parts without the XXX
 stuff?
  - A bit below that you refer to the "created" timestamp, which is now
 called the "published" timestamp.
  - I wonder if the "address" part of "exit-address4" and "exit-address6"
 lines should be unique (with respect to the exit list entry, not the whole
 exit list, of course). This has implications on how somebody parsing an
 exit list entry can store and retrieve parsed addresses. Of course, if we
 think it's useful to include an address several times with different scan
 times, we'll have to say that the address is not necessarily unique. In
 any case, we should say what people can expect there, or they'll make
 assumptions.
  - The "exit-scanner-sig-ed25519" should probably specify where to expect
 the signature part. Is it going to be part of the line, separated by SP
 from the keyword? Or is it going to be an object in the next line? In the
 latter case the subsequent description would have to say "including the
 newline character after" rather than "including the first space after".

 Other than these comments, the plan to build it see if it works sounds
 reasonable to me. Thanks!

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29624#comment:18>
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