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diff --git a/doc/README.md b/doc/README.md index c629c2ccfa..e45460734b 100644 --- a/doc/README.md +++ b/doc/README.md @@ -76,6 +76,7 @@ The Bitcoin repo's [root README](/README.md) contains relevant information on th - [bitcoin.conf Configuration File](bitcoin-conf.md) - [Files](files.md) - [Fuzz-testing](fuzzing.md) +- [I2P Support](i2p.md) - [Reduce Memory](reduce-memory.md) - [Reduce Traffic](reduce-traffic.md) - [Tor Support](tor.md) diff --git a/doc/i2p.md b/doc/i2p.md new file mode 100644 index 0000000000..8b4607208a --- /dev/null +++ b/doc/i2p.md @@ -0,0 +1,72 @@ +# I2P support in Bitcoin Core + +It is possible to run Bitcoin Core as an +[I2P (Invisible Internet Project)](https://en.wikipedia.org/wiki/I2P) +service and connect to such services. + +This [glossary](https://geti2p.net/en/about/glossary) may be useful to get +started with I2P terminology. + +## Run Bitcoin Core with an I2P router (proxy) + +A running I2P router (proxy) with [SAM](https://geti2p.net/en/docs/api/samv3) +enabled is required (there is an [official one](https://geti2p.net) and +[a few alternatives](https://en.wikipedia.org/wiki/I2P#Routers)). Notice the IP +address and port the SAM proxy is listening to; usually, it is +`127.0.0.1:7656`. Once it is up and running with SAM enabled, use the following +Bitcoin Core options: + +``` +-i2psam=<ip:port> + I2P SAM proxy to reach I2P peers and accept I2P connections (default: + none) + +-i2pacceptincoming + If set and -i2psam is also set then incoming I2P connections are + accepted via the SAM proxy. If this is not set but -i2psam is set + then only outgoing connections will be made to the I2P network. + Ignored if -i2psam is not set. Listening for incoming I2P + connections is done through the SAM proxy, not by binding to a + local address and port (default: 1) +``` + +In a typical situation, this suffices: + +``` +bitcoind -i2psam=127.0.0.1:7656 +``` + +The first time Bitcoin Core connects to the I2P router, its I2P address (and +corresponding private key) will be automatically generated and saved in a file +named `i2p_private_key` in the Bitcoin Core data directory. + +## Additional configuration options related to I2P + +You may set the `debug=i2p` config logging option to have additional +information in the debug log about your I2P configuration and connections. Run +`bitcoin-cli help logging` for more information. + +It is possible to restrict outgoing connections in the usual way with +`onlynet=i2p`. I2P support was added to Bitcoin Core in version 22.0 (mid 2021) +and there may be fewer I2P peers than Tor or IP ones. Therefore, using +`onlynet=i2p` alone (without other `onlynet=`) may make a node more susceptible +to [Sybil attacks](https://en.bitcoin.it/wiki/Weaknesses#Sybil_attack). Use +`bitcoin-cli -addrinfo` to see the number of I2P addresses known to your node. + +## I2P related information in Bitcoin Core + +There are several ways to see your I2P address in Bitcoin Core: +- in the debug log (grep for `AddLocal`, the I2P address ends in `.b32.i2p`) +- in the output of the `getnetworkinfo` RPC in the "localaddresses" section +- in the output of `bitcoin-cli -netinfo` peer connections dashboard + +To see which I2P peers your node is connected to, use `bitcoin-cli -netinfo 4` +or the `getpeerinfo` RPC (e.g. `bitcoin-cli getpeerinfo`). + +To see which I2P addresses your node knows, use the `getnodeaddresses 0 i2p` +RPC. + +## Compatibility + +Bitcoin Core uses the [SAM v3.1](https://geti2p.net/en/docs/api/samv3) protocol +to connect to the I2P network. Any I2P router that supports it can be used. |