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diff --git a/doc/cjdns.md b/doc/cjdns.md new file mode 100644 index 0000000000..b69564729f --- /dev/null +++ b/doc/cjdns.md @@ -0,0 +1,116 @@ +# CJDNS support in Bitcoin Core + +It is possible to run Bitcoin Core over CJDNS, an encrypted IPv6 network that +uses public-key cryptography for address allocation and a distributed hash table +for routing. + +## What is CJDNS? + +CJDNS is like a distributed, shared VPN with multiple entry points where every +participant can reach any other participant. All participants use addresses from +the `fc00::/8` network (reserved IPv6 range). Installation and configuration is +done outside of Bitcoin Core, similarly to a VPN (either in the host/OS or on +the network router). See https://github.com/cjdelisle/cjdns#readme and +https://github.com/hyperboria/docs#hyperboriadocs for more information. + +Compared to IPv4/IPv6, CJDNS provides end-to-end encryption and protects nodes +from traffic analysis and filtering. + +Used with Tor and I2P, CJDNS is a complementary option that can enhance network +redundancy and robustness for both the Bitcoin network and individual nodes. + +Each network has different characteristics. For instance, Tor is widely used but +somewhat centralized. I2P connections have a source address and I2P is slow. +CJDNS is fast but does not hide the sender and the recipient from intermediate +routers. + +## Installing CJDNS and finding a peer to connect to the network + +To install and set up CJDNS, follow the instructions at +https://github.com/cjdelisle/cjdns#how-to-install-cjdns. + +You need to initiate an outbound connection to a peer on the CJDNS network +before it will work with your Bitcoin Core node. This is described in steps +["2. Find a friend"](https://github.com/cjdelisle/cjdns#2-find-a-friend) and +["3. Connect your node to your friend's +node"](https://github.com/cjdelisle/cjdns#3-connect-your-node-to-your-friends-node) +in the CJDNS documentation. + +One quick way to accomplish these two steps is to query for available public +peers on [Hyperboria](https://github.com/hyperboria) by running the following: + +``` +git clone https://github.com/hyperboria/peers hyperboria-peers +cd hyperboria-peers +./testAvailable.py +``` + +For each peer, the `./testAvailable.py` script prints the filename of the peer's +credentials followed by the ping result. + +Choose one or several peers, copy their credentials from their respective files, +paste them into the relevant IPv4 or IPv6 "connectTo" JSON object in the +`cjdroute.conf` file you created in step ["1. Generate a new configuration +file"](https://github.com/cjdelisle/cjdns#1-generate-a-new-configuration-file), +and save the file. + +## Launching CJDNS + +Typically, CJDNS might be launched from its directory with +`sudo ./cjdroute < cjdroute.conf` and it sheds permissions after setting up the +[TUN](https://en.wikipedia.org/wiki/TUN/TAP) interface. You may also [launch it as an +unprivileged user](https://github.com/cjdelisle/cjdns/blob/master/doc/non-root-user.md) +with some additional setup. + +The network connection can be checked by running `./tools/peerStats` from the +CJDNS directory. + +## Run Bitcoin Core with CJDNS + +Once you are connected to the CJDNS network, the following Bitcoin Core +configuration option makes CJDNS peers automatically reachable: + +``` +-cjdnsreachable +``` + +When enabled, this option tells Bitcoin Core that it is running in an +environment where a connection to an `fc00::/8` address will be to the CJDNS +network instead of to an [RFC4193](https://datatracker.ietf.org/doc/html/rfc4193) +IPv6 local network. This helps Bitcoin Core perform better address management: + - Your node can consider incoming `fc00::/8` connections to be from the CJDNS + network rather than from an IPv6 private one. + - If one of your node's local addresses is `fc00::/8`, then it can choose to + gossip that address to peers. + +## Additional configuration options related to CJDNS + +``` +-onlynet=cjdns +``` + +Make automatic outbound connections only to CJDNS addresses. Inbound and manual +connections are not affected by this option. It can be specified multiple times +to allow multiple networks, e.g. onlynet=cjdns, onlynet=i2p, onlynet=onion. + +CJDNS support was added to Bitcoin Core in version 23.0 and there may be fewer +CJDNS peers than Tor or IP ones. You can use `bitcoin-cli -addrinfo` to see the +number of CJDNS addresses known to your node. + +In general, a node can be run with both an onion service and CJDNS (or any/all +of IPv4/IPv6/onion/I2P/CJDNS), which can provide a potential fallback if one of +the networks has issues. There are a number of ways to configure this; see +[doc/tor.md](https://github.com/bitcoin/bitcoin/blob/master/doc/tor.md) for +details. + +## CJDNS-related information in Bitcoin Core + +There are several ways to see your CJDNS address in Bitcoin Core: +- in the "Local addresses" output of CLI `-netinfo` +- in the "localaddresses" output of RPC `getnetworkinfo` + +To see which CJDNS peers your node is connected to, use `bitcoin-cli -netinfo 4` +or the `getpeerinfo` RPC (i.e. `bitcoin-cli getpeerinfo`). + +To see which CJDNS addresses your node knows, use the `getnodeaddresses 0 cjdns` +RPC. |