Comment 13 for bug 647212

Also, the fix has been released in quantal:

Changes:
 apt-cacher-ng (0.7.7-1ubuntu1) quantal; urgency=low
 .
   * Merge from Debian. Remaining changes:
     - debian/apt-cacher-ng.logrotate:
       Comment out the "su" lines as this requires logrotate 3.8.1 which isn't
       in Ubuntu yet.
     - drop conflict on logrotate < 3.8.1
 .
 apt-cacher-ng (0.7.7-1) experimental; urgency=low
 .
   * New upstream releasee
     + pass-through mode for allowed hosts (LP: #647212)
     + possible fixes of file descriptor objects expiration (closes: #677983)