Tiny mDNS responder for the remarkable e-ink tablet

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README.md

rm-mdns

This repository contains a tiny multicast DNS (mDNS) responder for the remarkable 2 e-ink tablet.

Instead of using the IP address of the remarkable you can connect to remarkable.local. For example, to connect via SSH run ssh root@remarkable.local.

You can also specify a custom hostname by passing it as a argument. Note that it should end with a period to mark that fully qualified name, e.g., rm-mdns my-custom-hostname.local..

How to Build

To build a native version via nix you can run:

user@local$ git clone https://git.stha.de/stefan/rm-mdns.git
user@local$ cd rm-mdns
user@local$ nix-build -A native

To build a static binary that can run directly on the remarkable you can run:

user@local$ git clone https://git.stha.de/stefan/rm-mdns.git
user@local$ cd rm-mdns
user@local$ nix-build -A remarkable

For a non-nix build you can use meson directly.

user@local$ git clone https://git.stha.de/stefan/rm-mdns.git
user@local$ cd rm-mdns
user@local$ meson setup build
user@local$ meson compile -C build

Without nix you have to manually set up cross-compilation with the remarkable toolchain. This is not covered by this README.

How to Install

The following instruction will install the binary and the systemd unit to /root. Afterwards the systemd unit is linked to the service directory and enabled with systemd. Note that /root is on the system partition and is not encrypted only has a small amount of free space. However, the statically linked rm-mdns binary is less than 50 KiB, so it does not consume much space.

user@local$ git clone https://git.stha.de/stefan/rm-mdns.git
user@local$ cd rm-mdns
user@local$ nix-build -A remarkable2
user@local$ scp result/bin/rm-mdns root@${IP_OF_REMARKABLE}:/root/rm-mdns
user@local$ scp result/bin/rm-mdns.service root@${IP_OF_REMARKABLE}:/root/rm-mdns.service
user@local$ ssh root@${IP_OF_REMARKABLE}
root@remarkable# ln -s /root/rm-mdns.service /etc/systemd/system
root@remarkable# systemctl enable --now rm-mdns

From now on you can now connect to your remarkable tablet with by running ssh root@remarkable.local. To use a custom hostname change the ExecStart line in rm-mdns.services, e.g., ExecStart=/root/rm-mdns my-custom-hostname.local..

If you do not want to cross-compile the binary on your own, you can download prebuild binaries.

How to Uninstall

user@local ssh root@${IP_OF_REMARAKBLE}
root@remarkable# systemctl disable --now rm-mdns
root@remarkable# rm -f /etc/systemd/system/rm-mdns /root/rm-mdns /root/rm-mdns.service

Shortcomings

The mDNS responder is not fully standard compliant:

It does not check if the claimed name is already in used.
It does not handle the unicast flag in the mDNS query.
Probably other non-compliant behaviour.

Apart from this, the responder will only answer for A record requests, so it will only work with IPv4. Adding IPv6 support should be straight-forward, though.

Credits

This project uses the public domain mdns library by Mattias Jansson and contributors.