Hacking on I2PD

This document contains notes compiled from hacking on i2pd

prerequisites

This guide assumes:

  • a decent understanding of c++
  • basic understanding of how i2p works at i2np level and up

general structure

Notes on multithreading

  • every compontent runs in its own thread

  • each component (usually) has a public function GetService() which can be used to obtain the boost::asio::io_service that it uses.

  • when talking between components/threads, always use GetService().post() and be mindfull of stack allocated memory.

NetDb

NetDb.h

The i2p::data::netdb is a i2p::data::NetDb instance processes and dispatches inbound i2np messages passed in from transports.

global singleton at i2p::data::netdb as of 2.10.1

NetDbRequests.h

For Pending RouterInfo/LeaseSet lookup and store requests

ClientContext

ClientContext.h

i2p::client::ClientContext spawns all destinations used by the i2p router including the shared local destination.

global singleton at i2p::client::context as of 2.10.1

Daemon

File: Daemon.cpp

i2p::util::Daemon_Singleton_Private subclasses implement the daemon start-up and tear-down, creates Http Webui and i2p control server.

Destinations

Destination.h

each destination runs in its own thread

i2p::client::LeaseSetDestination

Base for i2p::client::ClientDestination

i2p::client::ClientDestination

Destination capable of creating (tcp/i2p) streams and datagram sessions.

Streaming.h

i2p::stream::StreamingDestination

Does not implement any destination related members, the name is a bit misleading.

Owns a i2p::client::ClientDestination and runs in the destination thread.

Anyone creating or using streams outside of the destination thread MUST be aware of the consequences of multithreaded c++ :^)

If you use streaming please consider running all code within the destination thread using ClientDestination::GetService().post()

Garlic.h

Provides Inter-Destination routing primatives.

i2p::garlic::GarlicDestination

sublcass of i2p::client::LeaseSetDestination for sending messages down shared routing paths.

i2p::garlic::GarlicRoutingSession

a point to point conversation between us and 1 other destination.

i2p::garlic::GarlicRoutingPath

A routing path currently used by a routing session. specifies which outbound tunnel to use and which remote lease set to use for OBEP to IBGW inter tunnel communication.

members:

  • outboundTunnel (OBEP)
  • remoteLease (IBGW)
  • rtt (round trip time)
  • updatedTime (last time this path's IBGW/OBEP was updated)
  • numTimesUsesd (number of times this path was used)

Transports

each transport runs in its own thread

Transports.h

i2p::transport::Transports contains NTCP and SSU transport instances