mDNS Tunneller

⚠️ Warning: you can do serious damage to the network(s) you are running this in. Use this only as a last resort measure, when you have absolutely exhausted all other options. Try avahi-reflector and mdns-repeater first.

What does it do

It creates a 1:1 pipe tunnel over simple HTTP and passes all the mDNS requests and responses back and forth through it, effectively merging two multicast DNS domains. You can connect more than one client to the server (but should you?) - making one big multicast DNS domain. See how dangerous it is?!

Features

• Automatic reconnection upon connection loss
• Basic firewall for DNS queries - only packets containing info about services from the whitelist will travel through the tunnel
• Built in multicast storm prevention - won't relay packets that already been relayed

But why?..

There are certain services that operate over mDNS and refuse to work altogether without it, but mDNS stands for "Multicast DNS" (duh) and multicast communication inherently has many limitations. If you just need to re-transmit multicast packets from one network to another - avahi in reflector mode would fit your bill 100%, but if you need something more complex like multicasts through Wireguard in a separate heavily-firewalled VLAN over IP-over-Fiber-Channel over IP-over-Avian-Carriers - it's much easier to just establish a tunnel specifically for mDNS.

By using mDNS Tunneller you can expose your private details to somewhere where they were not intended to be. mDNS in a typical home includes A LOT of information about what devices are online (who's home) and what are they doing. mDNS Tunneller has rudimentary built-in firewall that is supposed to mitigate some risks, but as of now it's very basic and does not offer sufficient personal data protection (no, seriously).

Configuration files

Default configuration values are stored in config/default.yml, however it's not advised to edit this file directly as this will mark your git tree with uncommitted changes. Instead, create a local.yml file in config directory and set any values you want to override there.

Configuration with Environmental Variables

You can use environmental variables to override every configuration parameter from config/default.yml. Check out file custom-environment-variables.yml for the list of all names of environmental variables.

To specify arrays, provide them in yaml format:

SENDERS_BLACKLIST='[192.168.1.69, 192.168.10.11]'

Installation

mDNS Tunneller requires Node.js 10+ and npm to be installed.

Both client and server will need to pull this repo and install all the dependencies:

git clone https://github.com/toxuin/mdns-tunneller
npm install
npm run build
npm run start:prod

Or, you can use Docker:

docker run -v your_config_file.yml:/app/config/local.yml -p 42069:42069 toxuin/mdns-tunneller

Then, on the server adjust the interface to be listening for HTTP connections from clients at in config/local.yml (by default it listens on all interfaces, 0.0.0.0):

interface: 192.168.1.69

Optionally, uncomment and adjust the list of names of interfaces where mDNS packets should be injected (by default, will listen and broadcast on all interfaces):

mdnsInterfaces:
  - en0

Start the server with

npm run start

On the client you have to set where to connect to (otherwise it will start as another server - and that would be dumb) in config/local.yml:

remote: 192.168.1.69

Start the client with

npm run start

Upgrading

Just do a git pull on the directory you've cloned this project into.

Make sure you have client and server using same version - otherwise you'll see an endless stream of parsing errors, you then may inject garbage into your network, may quit your job and become a travelling mime. Don't do that.

mDNS Tunneller is beta quality software - please don't use for any critical systems (unless in the events of a zombie apocalypse - then all bets are off, of course).

Because it is beta quality software - there are no guarantees that API/configuration structure will remain compatible across versions (it probably won't), so read the changelogs before updating.