Log Message:
Update to 1.6.21

            User-Visible OpenAFS Changes

OpenAFS 1.6.21

  All platforms

    * Avoid a possible 100ms transmit delay in the RX protocol when a peer's
      receive window transitions from closed to open (12627)

    * Documentation improvements (12476 12477 12559[RT #133339])

  All server platforms

    * When bosserver is started with an unknown option, print an error message
      and exit with a non-zero value rather than failing silently (12631)

  All DB server platforms

    * Hold the DB lock while checking for an aborted write transaction (12516)

  All file server platforms

    * On demand attach fileservers, don't save or restore a client's host
      state if CPS ("Current Protection Subdomain") recalculation for it is
      in progress, to avoid fileserver thread exhaustion (12568)

    * On demand attach fileservers, avoid flooding the log with error messages,
      which could happen when the fileserver was restarted while a volume was
      offline (12569)

    * Update a volume's "Last Update" time when its content is modified by
      the salvager, to make the change visible in the output of "vos \ 
examine"
      and to backup services (12633)

  All client platforms

    * Corrected the DCentries bucket counts for very large and zero length
      files in the output of "fs getcacheparms -excessive" (12604 12605)

    * Fixed a bug that prevented users with GID 2748 and 2750 from executing
      the "fs sysname" command on clients running afsd with -rmtsys (12607)

    * Provide a new -inumcalc switch for afsd to allow enabling the alternative
      MD5 method of inode number calculation, which was previously only
      possible on Linux and through the sysctl interface (12608 12632)

  Linux clients

    * Support for mainline kernel 4.12 and distribution kernels with backports
      from it (12624 12626)

    * Re-added the improved algorithm for freeing unused vcaches to reduce
      memory consumption first introduced with the 1.6.18 release, together
      with a fix for the issue leading to its removal in 1.6.18.2 (12448..12451)

  macOS clients

    * Fixed a crash while stopping the client on macOS 10.12 "Sierra" \ 
(12602)