[tor-bugs] #19910 [Applications/Tor Browser]: Rip out optimistic data socks handshake variant (#3875)

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#19910: Rip out optimistic data socks handshake variant (#3875)
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 Reporter:  cypherpunks               |          Owner:  tbb-team
     Type:  defect                    |         Status:  new
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:                            |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
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Comment (by arthuredelstein):

 Replying to [comment:13 arma]:

 > I think it would be worth exploring whether we can do the same behavior
 in a smarter way from the browser though -- the feature essentially
 removes a round-trip across the Tor network from page loads.

 Instead of implementing a patch in the browser, I wonder if we could patch
 the tor proxy instead with roughly the same speedup.

   1. The SOCKS client opens a TCP connection to the tor proxy
   2. The SOCKS client sends a SOCKS CONNECT command
   3. The proxy immediately returns a spoofed SOCKS CONNECTED notification
 to the SOCKS client, and the proxy also sends a BEGIN cell to the Exit.
   4. The SOCKS client sends some data to the OP (the GET request, for
 example).
   5. The OP sends a DATA cell to the Exit

 This arrangement doesn't require any modification to the browser's SOCKS
 implementation, but it means we don't wait for the Exit to respond with
 CONNECTED before asking the SOCKS client to send its first data. Basically
 we put the "optimism" in the proxy instead of the browser. That's nice
 because then (1) we will get a speedup to all ordinary SOCKS clients and
 (2) we're patching code controlled by Tor Project.

 Provided the round trip between the SOCKS client and proxy is very small
 compared to the round-trip through the Tor network, the performance should
 presumably be about the same as the existing patch in Tor Browser.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19910#comment:15>
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