Synopsis

The Network Block Device is a Linux-originated lightweight block access protocol that allows one to export a block device to a client.

This client is designed to run on top of FreeBSD's GEOM Gate device driver, keeping the network client in a userland daemon rather than in a kernel module.

Casper is used to sandbox the DNS lookup of the server host, and Capsicum is used to limit the capabilities of the client once connected.

Messages are logged via syslog, and to stdout and stderr when running interactively.

The client immediately daemonizes unless passed the -f flag, in which case it remains running in the foreground.

Caveats

• TLS and other extensions are not currently supported.
• Only the default (unnamed) export is used.
• Manual control (listing, naming, numbering, removal) of the device nodes is not yet provided by this tool.

Usage Example

Connect to an NBD server and print the name of the new device on stdout:

nbd-client 192.168.1.101

Connect specifying a hostname and port number:

nbd-client nbd.storage.internal-domain.net 10809

You can then use this device as a regular disk device. For example, create a ZFS pool named foo backed by the NBD storage attached to ggate0.

zpool create foo ggate0

Use the ggatec utility to list all attached GEOM Gate devices. These may not all be NBD devices:

ggatec list

Use the ggatec utility to force removal of the GEOM Gate device unit 0, which corresponds to the device named ggate0:

ggatec destroy -f -u 0

Compiling

make
make install # (optional)

Note: This project expects to be compiled with BSD make, not GNU make.

To Do

• specify named export
• list exports (work started)
• connect to multiple/all exports on a server (spawn a thread per export?)
• configuration file
• rc scripts
• option to drop to a less privileged user?

Bugs

Please report them along with steps to reproduce.

Motivation

Scaleway offers high-density dedicated servers using NBD to attach storage to each machine. FreeBSD lacks an NBD client, so Scaleway does not support FreeBSD. This project aims to implement an NBD client so that Scaleway can offer FreeBSD on their servers.

License

BSD 2-Clause License

Copyright (c) 2016, Ryan Moeller All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.