[tbb-bugs] #16747 [Tor Browser]: Tor-browser downloads favicon twice (and over different circuits)

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#16747: Tor-browser downloads favicon twice (and over different circuits)
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 Reporter:  cypherpunks      |          Owner:  tbb-team
     Type:  defect           |         Status:  needs_information
 Priority:  Medium           |      Milestone:
Component:  Tor Browser      |        Version:
 Severity:  Major            |     Resolution:
 Keywords:  tbb-linkability  |  Actual Points:
Parent ID:                   |         Points:
  Sponsor:                   |
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Comment (by cypherpunks):

 Replying to [comment:6 gk]:
 > So, there are two things here: 1) Downloading the favicon twice. I'd
 guess this is an underlying Mozilla problem:
 https://bugzilla.mozilla.org/show_bug.cgi?id=583351. 2) Downloading the
 favicon over a different circuit. I can observe 1), too, on some websites
 but it seems all those second requests go over the same circuit. Is 2)
 reproducible for you? If so, do you have an example site allowing us to
 debug the Tor Browser behavior?

 Sorry for the late reply.
 I doubt 1) is the cause here, ticket:17998#comment:2 would be my guess,
 too.

 2) It is reproducible, but:
 It happens only on the first request to the site, I could not trigger it a
 second time in the same Tor Browser session. Reloading, getting a new
 circuit in torbutton, closing/reopening tabs... nada.
 Requests to the favicon don't show up in any FF DevTool.

 Considering I don't reference the favicon in my HTML, Mozilla is doing
 some magic here. A quick search turned up complaints about it on Bugzilla
 reaching back to FF 0.10, it looks like preffing off
 browser.chrome.favicons disables this behavior and leaves correctly
 referenced favicons intact.
 So this might be a cheap and easy fix at the cost of loosing favicons on
 sites which simply dump it in their web-root directory and expect it to
 work (besides me and mozilla.org, nobody really seems to be doing this).

 I couldn't get my TB to log to a file as per your instruction in the other
 ticket, do you still want a testcase with all this info?

 Btw: opening 'Page Info' triggers resource fetches via unrelated circuits,
 too.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16747#comment:8>
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