[tbb-bugs] #16028 [Tor Browser]: Many users seem to be failing incremental updates to 4.5.1

[Tor Bug Tracker & Wiki]

#16028: Many users seem to be failing incremental updates to 4.5.1
-----------------------------+-------------------------
     Reporter:  mikeperry    |      Owner:  tbb-team
         Type:  defect       |     Status:  new
     Priority:  major        |  Milestone:
    Component:  Tor Browser  |    Version:
   Resolution:               |   Keywords:  tbb-updater
Actual Points:               |  Parent ID:
       Points:               |
-----------------------------+-------------------------

Comment (by mcs):

 Kathy and I have come up with a few scenarios that may be causing the TB
 updater to fallback to a full MAR:
 1. The user makes changes to torrc-defaults (the 4.0.8 -> 4.5.1
 incremental MAR tries to patch that file).  There are a bunch of files
 that the incremental MAR tries to patch, any of which would cause this
 same problem; torrc-defaults just seems more likely to be modified by
 users than the others.
 2. A network failure of the wrong kind occurs during download of the
 incremental MAR.  In our testing on Windows, New Identity triggered a
 complete MAR download.
 3. The user exits the browser (or a crash occurs) during the download.
 When this happens, the update service is supposed to resume the
 incremental MAR download when the browser is restarted, but we have seen
 it treat this as a network error in some cases.

 We should be able to distinguish 1. above from 2. and 3. because if a
 failure occurs while trying to apply the incremental MAR it should have
 been completely downloaded (and only partially downloaded in the other two
 situations).  So maybe check the size field within the Apache logs if we
 have that info.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16028#comment:5>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online