These are the release notes for nbdkit stable release 1.18. This describes the major changes since 1.16.
nbdkit 1.18.0 was released on 27th February 2020.
Security
There were no security issues found. All past security issues and information about how to report new
ones can be found in nbdkit-security(1).
Plugins
New nbdkit-eval-plugin(1) lets you write a plugin entirely on a single command line. It is similar to
nbdkit-sh-plugin(3).
nbdkit-ext2-plugin is deprecated and will be removed in the next release after this one (nbdkit 1.20).
As a replacement use nbdkit-ext2-filter(1) like this:
nbdkit --filter=ext2 file fs.img ext2file=/disks/disk.raw
nbdkit-python-plugin(3) now offers a version 2 API which avoids copying the data buffer, improving
performance. The original protocol (now retrospectively called version 1) is still supported for
backwards compatibility. The version 1 protocol was also enhanced to support the buffer protocol for the
pread method, and memoryview for pwrite, improving performance by reducing copies (Nir Soffer).
The Python plugin now prints readable stack traces when an exception is thrown (Nir Soffer).
New methods implemented in the Python plugin: cache, can_cache, can_zero, can_fast_zero, can_multi_conn,
can_fua.
In nbdkit-curl-plugin(1), new options "cainfo" and "capath" (Wiktor Gołgowski).
nbdkit-split-plugin(1) now supports extents (Eric Blake).
In nbdkit-vddk-plugin(1), "file=" is now a magic config key, meaning it can be omitted in most
circumstances (Eric Blake).
The VDDK plugin now no longer needs $LD_LIBRARY_PATH to be set. The correct library load path is
automatically inferred from the "libdir" parameter (Eric Blake).
Verbose messages about calls to VDDK functions Read and Write can now be suppressed by setting
-Dvddk.datapath=0.
Filters
New nbdkit-ext2-filter(1), which replaces the deprecated nbdkit-ext2-plugin. This filter allows you to
read and write files inside ext2, ext3 or ext4 filesystems. The new filter has the same features as the
plugin, and one enhancement: optionally the name of the file to serve can be picked from the client-
supplied exportname. The old plugin will be removed in nbdkit 1.20 (Eric Blake).
New nbdkit-extentlist-filter(1) lets you specify a static list of extents from a file which can be placed
on top of plugins which don't export extent information.
New nbdkit-ip-filter(1) lets you allow and deny incoming connections by client IP address, similar to TCP
wrappers or a firewall.
New nbdkit-nofilter-filter(1) is a null filter, used for testing.
The stats filter now collects time elapsed per operation, per operation and total rates, and adds stats
for the flush method. The output is shown in human sizes making it easier to understand. (Nir Soffer).
Server
New --swap option which allows nbdkit to be safely used to serve swap space to the same machine.
Debug flags (-D) can now be applied to the server core (using -Dnbdkit.*). Underscores in debug flags
can now be replaced by dots, allowing a kind of namespacing. Debug flags which are not consumed now no
longer give an error, so you can use them without needing to detect if the plugin supports them. New
server debug flags -Dnbdkit.backend.controlpath=0 and -Dnbdkit.backend.datapath=0 were added to
suppress some very verbose messages when verbose mode is enabled.
API
There is a new ".get_ready" method which is called after ".config_complete" and before the server forks
or changes directory. It is the last chance to do any global preparation that is needed to serve
connections. Plugins have previously done this work in ".config_complete", but by splitting this into a
new method it makes the API clearer. (Note that existing plugins may continue to use ".config_complete"
for this work if they prefer.)
There is a new ".preconnect" method available which is called just after the client makes a connection
but before any NBD negotiation or TLS authentication is done. It can be used for early whitelisting or
rate limiting of connections, and in particular is used by the new nbdkit-ip-filter(1).
Bugfixes
In nbdkit-curl-plugin(1), "CURLINFO_CONTENT_LENGTH_DOWNLOAD_T" is used (if available) so that file sizes
up to 63 bits should now work on all platforms (Pino Toscano and Adrian Ambrożewicz).
nbdkit is now compatible with OCaml 4.10.
nbdkit-memory-plugin(1) now supports "size=0" (Eric Blake).
Documentation
Plugins which were actually added in nbdkit 1.0.0 are now documented as such properly.
Improved methods for probing plugins and filters are documented in nbdkit-probing(1).
Tests
Old plugins from nbdkit 1.0, 1.2, 1.8 and 1.12 are now bundled with the nbdkit sources and tested to try
to ensure that they do not accidentally regress. Note these are included as binary blobs. See
tests/old-plugins/README for more information about this, including how to delete these tests.
Various tests, especially ones which rely on timeouts, have been made more stable so they should not fail
on slow or overloaded machines.
Many tests now use libnbd and nbdsh (instead of libguestfs and guestfish) as the test client. This
should improve the performance of the tests for most people.
The --vsock option (added in nbdkit 1.16) can now be tested if the host is running Linux ≥ 5.6 (Stefano
Garzarella).
Build
You can use "./configure --disable-nbd-plugin" to completely disable the NBD plugin.
The automake feature "subdir-objects" is no longer used, which may improve compatibility on platforms
with ancient and buggy automake (RHEL 7 being one such platform).
Internals
The explicit connection parameter passed around many functions in the server is now fetched from thread-
local storage.
The server no longer calls the finalize method if prepare fails. Also failing to reopen the plugin from
nbdkit-retry-filter(1) no longer hangs (Eric Blake).
"git.orderfile" was enhanced to make patches easier to read (Eric Blake).
Internal calls to methods like get_size, can_write will now no longer produce debug messages if the data
is simply being returned from the internal cache (but calls into the plugin are still logged).
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