[tor-project] Core Tor Team work for sponsor 4 in April

[isabela]

Core Tor Team April 2017 Report:

We finished the remaining tasks related to the implemention of Proposal
140 [1], "Provide diffs between consensuses".
	
  * #21646 - Prop140/compression: Refactor "directory request" code [2]
  * #21647 - Prop140: directory caches cache multiple past diffs or
consensuses [3]
    * #21869 - Labeled storage backend for consensus docs and diffs [4]
  * #21648 - Prop140: Caches generate diffs as appropriate [5]
    * #22096 - Increase MALLOC_MP_LIM in sandbox.c [6]



We continue to work on Proposal 278 [7], "Directory Compression Scheme
Negotiation", finishing the following tasks:

  * #21664 - Prop278: Make the current 'torgzip' module a submodule of a
new 'compression' module [8]
  * #21662 - Prop278: Add support for LZMA2 and/or Zstandard [9]
  * #22066 - Add memory measurement code in LZMA and Zstandard
compression backends [10]
  * #21665 - Prop278: Establish an upper-bound for LZMA2 memory usage [11]
  * #22051 - Use streaming compression API in the non-streaming
compression API [12]
  * #21663 - Prop278: Refactor the torgzip module to support additional
compression schemes [13]
  * #22065 - Prop278: Parse the Accept-Encoding header and pass it to
"get" handlers [14]
  * #21667 - Prop278: Handle new headers in directory.c [15]
  * #22085 - Refactor and simplify compression tests [16]



We also hosted a follow-up meeting with Metrics Team regarding the
impact of these efforts on the their work. Notes from this meeting can
be found at: https://pad.riseup.net/p/chikeuBN1OUh

[1]
https://gitweb.torproject.org/torspec.git/tree/proposals/140-consensus-diffs.txt
[2] https://trac.torproject.org/projects/tor/ticket/21646
[3] https://trac.torproject.org/projects/tor/ticket/21647
[4] https://trac.torproject.org/projects/tor/ticket/21869
[5] https://trac.torproject.org/projects/tor/ticket/21648
[6] https://trac.torproject.org/projects/tor/ticket/22096
[7]
https://gitweb.torproject.org/torspec.git/tree/proposals/278-directory-compression-scheme-negotiation.txt
[8] https://trac.torproject.org/projects/tor/ticket/21664
[9] https://trac.torproject.org/projects/tor/ticket/21662
[10] https://trac.torproject.org/projects/tor/ticket/22066
[11] https://trac.torproject.org/projects/tor/ticket/21665
[12] https://trac.torproject.org/projects/tor/ticket/22051
[13] https://trac.torproject.org/projects/tor/ticket/21663
[14] https://trac.torproject.org/projects/tor/ticket/22065
[15] https://trac.torproject.org/projects/tor/ticket/21667
[16] https://trac.torproject.org/projects/tor/ticket/22085