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)