do Bitcoin full node onions also relay non-bitcoin traffic?

Question

During the past week or so I am setting up a Bitcoin core full node on Raspberry Pi and making it as secure as possible. In the public mind, the onion sites and Darknet are associated with many things which are illegal. I am trying to figure out how to configure my full node to pass through only the bitcoin related traffic. Is such a configuration possible at all?

Answer 1

Bitcoin nodes cannot relay anything except Bitcoin protocol related P2P messages. You can read the packet capture logs in wireshark while using two regtest nodes with the below steps:

1. Install Wireshark: https://www.wireshark.org/download.html

2. Create two directories for regtest nodes, node1 and node2 with below bitcoin.conf:

   regtest.rpcport=18222
   rpcuser=user1
   rpcpassword=password1
   

   regtest.rpcport=18666
   rpcuser=user2
   rpcpassword=password2
   

3. Run node1 and node2 with below commands:

   bitcoind -regtest=1 -port=18333 -rpcport=18222 -datadir=/home/prayank/node1 -conf=/home/prayank/node1/bitcoin.conf -fallbackfee=0.0001
   

   bitcoind -regtest=1 -port=18777 -rpcport=18666 -datadir=/home/prayank/node2 -conf=/home/prayank/node2/bitcoin.conf -connect=127.0.0.1:18333
   

4. Both nodes are running and connected. We can create wallets in each if they don't exist already and generate some bitcoin with generatetoaddress RPC

5. Finally, we can try sending bitcoin from node1 to node2 and check p2p message in Wireshark

wtxid is highlighted in the above screenshot

You can also check this video with same steps performed: https://youtu.be/Nb32BISrdnk

In the public mind, the onion sites and Darknet are associated with many things which are illegal

Cannot change this opinion however illegal things are done using clearnet as well.

I am trying to figure out how to configure my full node to pass through only the bitcoin related traffic. Is such a configuration possible at all?

If you use Tor as proxy for outbound connections it will not use your real IP address for Bitcoin related P2P messages sent to other nodes. If you setup bitcoin core as onion service it will create an onion address for your node that other nodes can use to send Bitcoin related P2P messages.

In both cases the network used is same Tor as used by others for different things however it will be used for only Bitcoin in this context.