Support the ⚡️-Network, serve cfilters using bitcoin core now!

Why? Compact block filters, or "cfilters" for short, support new neutrino-style bitcoin light clients and are considered a huge improvement compared to traditional SPV light clients, especially from a privacy perspective. Further, these filters power many lightning mobile wallets, which are mostly served by a single btcd full-node operated by the wallet vendor, since close to nobody is serving these filters as of now. Far from ideal. This project aims to change this by making it easy to serve cfilters using bitcoin core and convince some more folks to spin up a new node and serve cfilters publicly and reverse Luke Dashjr's concerns to the contrary.

What? It is already possible to serve cfilters with bitcoin core, running this branch by Jim Posen. I am running it since a bit longer than a month without any issues. While you can compile the branch yourself and run bitcoin core natively, this project focuses on doing so with docker, which turns out to be pretty simple and additionally keeps your system clean from bitcoin core's build dependencies.

Requirements:

• docker --version 18.06.0+
• 500 GB free disk space, better more

Option a: Use pre-built images

• download above docker-compose.yml file, e.g. with

curl https://raw.githubusercontent.com/kilrau/bitcoind-cfilters/master/docker-compose.yml -o ~/docker-compose.yml

• in this file, adjust the directory to a path where you have enough free disk space and want bitcoin core to store blocks, e.g. from /media/HDD/bitcoind -> ~/.bitcoin
• adjust PID & GID to the docker user's (id -u <dockeruser> && id -g <dockeruser>)
• docker-compose up -d
• once it's synced, add your node to the list.

Option b: Don't trust, build yourself

• download above Dockerfile or just clone the repo with git clone https://github.com/kilrau/bitcoind-cfilters
• check the Dockerfile and see for yourself that it is indeed building https://github.com/jimpo/bitcoin/tree/bip157-net
• docker build . -t bitcoind && docker tag bitcoind:latest bitcoind:cfilters (the build takes a moment)
• in docker-compose.yml remove the line image: kilrau/bitcoind:cfilters and uncomment the next line to use your local image and adjust PID & GID to the docker user's (id -u <dockeruser> && id -g <dockeruser>)
• docker-compose up -d
• once it's synced, add your node to the list.

Tips 'n Tricks:

• you can run bitcoin-cli commands, e.g. bitcoin-cli getblockchaininfo using docker exec -it bitcoind_mainnet_1 bitcoin-cli getblockchaininfo to e.g. check on the sync progress
• known issue: when you need to restart an in-sync node on this branch, you'll have to temporarily remove the -peercfilters option, wait until the sync is done and then add it back
• to serve cfilters on bitcoin testnet, simply uncomment the lines in the docker-compose file

TODO:

• basic docker setup
• add tor
• monitor progress of PR 18876, change images to bitcoin core master once everything is in
• add dns seed entries to btcd/neutrino serving lists above, open to ideas how else cfilter nodes could be served upfront without requiring neutrino.addpeer