lwNBD(3) – A Lightweight NBD server library

SYNOPSIS

#include <lwnbd.h>
#include <lwnbd-server.h>
#include <lwnbd-plugin.h>

✨ DESCRIPTION

Official repository : https://github.com/bignaux/lwNBD
BSD-style socket API: lwIP 2.0.0 and Linux supported.

Targeting first the use on Playstation 2 IOP, a 37.5 MHz MIPS processor and 2 MB of RAM, lwNBD is designed to run on bare metal or OS embedded system. With modulararity and portability in mind, it is developed according to several code standards, including :

no dynamically allocate memory
static-linking
written in C99 (using -std=c99 compile-time flag), use standard library usage
thread-safe synchronous NBD protocol implementation
optional and experimental query support

The lwNBD API is broken down into 3:

an API to manage server and content to be embbed in apps. The idea is to be able to manage servers as xinetd would.
a server API to create protocol and transport plugins. Currently, only support NBD protocol, but could extend to Zmodem, AoE … You then benefit from the mechanisms put in place for NBD such as content and management plugins.
a plugin API to create content plugins. The plugin API has been entirely rewritten to be closer to the nbdkit-plugin one in order to benefit from the experience of their software architecture, and to facilitate the porting of code from one or the other library. An obstacle to this convergence is that nbdkit does not support the use of multiple plugins in a single instance.

There are 2 targets supported :

GNU/Linux that use file plugin to serve a list of files as command line parameters. For the time being, the main purpose of the support is to facilitate development. It uses libuv as event loop, and can serve multiple client.
Playstation 2 IOP via an IRX module for Open-PS2-Loader. It can export hdd drive (atad plugin), MemoryCard (mcman plugin), rom0 and IOP ram (memory plugin). Read more about this on my Playstation 2 port notes.

HISTORY

On Playstation 2, there is no standardized central partition table like GPT for hard disk partitioning, nor is there a standard file system but PFS and HDLoader. In fact, there are few tools capable of handling hard disks, especially under Linux, and the servers developed in the past to handle these disks via the network did not use a standard protocol, which required each software wishing to handle the disks to include a specific client part, which were broken when the toolchain was updated. The same goes for the memory cards and other block devices on this console, which is why I decided to implement NBD on this target first.

STATUS

Although this server is not yet complete in respect of the minimal requirements defined by the NBD protocol, it is nevertheless usable with certain clients. In a RERO spirit i publish this “AS-IS”.

Known supported clients :

nbdcopy (provided by libnbd)
nbdfuse (provided by libnbd), works on windows with WSL2.
nbd-client
Ceph for Windows (wnbd-client.exe)

🪶 AUTHOR

Bignaux Ronan <ronan at aimao.org>

LICENSE

BSD