[Bug 412413] Re: zsync 32bit cannot download DVD

[Steve Langasek]

I've prepared a fix for this issue in zsync and uploaded it to the
unapproved queue.  Subscribing motu-sru for approval.  debdiff is
attached.

** Also affects: zsync (Ubuntu Karmic)
   Importance: Undecided
       Status: New

** Also affects: zsync (Ubuntu Lucid)
   Importance: Undecided
       Status: Confirmed

** Changed in: zsync (Ubuntu Karmic)
       Status: New => In Progress

** Changed in: zsync (Ubuntu Karmic)
   Importance: Undecided => High

** Changed in: zsync (Ubuntu Karmic)
     Assignee: (unassigned) => Steve Langasek (vorlon)

** Changed in: zsync (Ubuntu Lucid)
     Assignee: (unassigned) => Steve Langasek (vorlon)

** Changed in: zsync (Ubuntu Lucid)
       Status: Confirmed => In Progress

** Changed in: zsync (Ubuntu Lucid)
   Importance: Undecided => High

** Attachment added: "zsync-412413.diff"
   http://launchpadlibrarian.net/35148650/zsync-412413.diff

** Description changed:

  Binary package hint: zsync
  
  Ubuntu 9.04 i386, zsync 0.5
  
  zsync cannot download DVD image of Ubuntu (karmic-dvd-i386.iso). DVD
  image has size 4355870720 but zsync downloads only 2147483647 bytes.
  Problem could be related to 32-bit Ubuntu I run, DVD size is greater
  than 2^31. I think rsync doesn't have similar limitation, I can download
  the same DVD image with rsync at 32-bit Linux.
  
  To test it, try command like this one:
  # zsync http://cdimage.ubuntu.com/dvd/current/karmic-dvd-i386.iso.zsync
  
  In the case that zsync has this limit by design, it should warn the user
  that it cannot download such huge file and give up. Better way is to fix
  zsync to don't have such limit...
+ 
+ SRU JUSTIFICATION: zsync on i386 is currently broken on i386 for all
+ files over 2GB.  The larger the file, the more important it is that we
+ have reliable and robust methods for optimizing download times, and we
+ have common files now over 2GB in size - DVD images.
+ 
+ REGRESSION POTENTIAL: we could break zsync support for files less than
+ 2GB in size on i386 (worth the risk), or we could break zsync support on
+ amd64 (very unlikely).
+ 
+ TEST CASE:
+ - run zsync on i386 against http://cdimage.ubuntu.com/dvd/current/karmic-dvd-i386.iso.zsync
+ - observe that everything about this is broken, including the download time, the reported file size, and (eventually) the downloaded image, which will be truncated at 2GB.
+ - upgrade to zsync from -proposed
+ - run zsync again against the same partially-downloaded image, and observe that everything looks sane
+ - verify that the md5sum is correct at the end of the download by comparing with http://cdimage.ubuntu.com/dvd/current/MD5SUMS

** Description changed:

-- 
zsync 32bit cannot download DVD
https://bugs.launchpad.net/bugs/412413
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