P2P

A Library for writing Peer-to-Peer applications.

Many peer-to-peer libraries go to great lengths to provide a reliable stream abstraction over as many different transports as possible. That makes them unsuitable for modeling protocols over lossy mediums (UDP, IP, ethernet). This library takes a message oriented approach instead of a stream oriented approach.

Unreliable, fire-and-forget communication is provided using Tell and Receive methods. Reliable request-response communication is provided using Ask and ServeAsk methods.

The core abstraction is the Swarm. Which represents a group of nodes which can send messages to one another.

type Swarm[A Addr] interface {
    Tell(ctx context.Context, dst A, data []byte) error
    Receive(ctx context.Context, fn func(Message[A])) error

    ParseAddr(data []byte) (A, error)
    LocalAddrs() []A
    MTU(A) int
    Close() error
}

Addr is an interface type.

Overlay networks are a common pattern in p2p systems. Swarms have methods for introspection such as LocalAddrs and MTU. Addrs also have a canonical serialization provided by MarshalText and ParseAddr These two features make Swarms the building blocks for higher order swarms, which can be overlay networks. The underlying swarm is often referred to as the transport throughout these packages.

The power of the Swarm abstraction is exemplified by the fact we merely call some Swarms "transports" in certain contexts rather than having a separate Transport type, as other libraries do.

Swarms provide a Tell method, which makes a best effort to send the message payload to the destination. It will error if the message cannot be set in flight, but does not guarantee the transmision of the message if the error is nil.

Directory Organization

F is for Formats

Formats are just protocols that send/write once and receive/read many times.

• x509 Deals with the formats in the x509 public key infrastructure.

S is for Swarm

• In-Memory Swarm A swarm which transfers data to other swarms in memory. Useful for testing.

• Multi Swarm Creates a multiplexed addressed space using names given to each subswarm. Applications can use this to "future-proof" their transport layer.

• P2PKE Swarm A Secure Swarm which can secure any underlying Swarm.

• QUIC Swarm A secure swarm supporting Asks built on the QUIC protocol. It can wrap any other p2p.Swarm, and provide a p2p.SecureAskSwarm

• SSH Swarm A secure swarm supporting Asks built on the SSH protocol (TCP based).

• UDP Swarm An insecure swarm, included mainly as a building block.

• Fragmenting Swarm A higher order swarm which increases the MTU of an underlying swarm by breaking apart messages, and assembling them on the other side.

• Virtual Swarm A swarm which can be used to mock swarms of any comparable address type, and any public key type.

The swarmutil package contains utilities for writing Swarms. The swarmtest package contains a test suite which checks that a given Swarm implementation exhibits all the behaviors expected.

P is for Protocols

• Chord A package for the Chord DHT algorithm.

• Kademlia A package for the Kademlia DHT algorithm.

• Multiplexing Multiplexing creates multiple logical swarms on top of a single swarm. The p2pmux package provides string and integer multiplexers.

• P2PKE P2PKE is an authenticated key exchange suitable for securing p2p.Swarms. Provides a session state machine, and a long-lived secure channel, which is used by s/p2pkeswarm

Test Utilities

The p2ptest packages contains utilities for testing, such as generating adjacency matricies for networks of various connectivities.