Pallas Network 2

A new take on the Ouroboros networking stack that prioritises P2P operation over the client / server shape used by pallas-network. The public API is split between an Interface (where IO happens) and a Behavior (the business logic), reconciled by a Manager — a layout inspired by libp2p's swarm.

Once this crate is thoroughly tested and adopted by downstream clients, network2 is intended to replace the original pallas-network.

Usage

A typical setup pairs a transport (an Interface impl, e.g. the TCP-backed TcpInterface) with a protocol (a Behavior impl, e.g. the node-to-node InitiatorBehavior) and drives both through a Manager. The Manager polls the interface for IO events, hands them to the behavior, and pushes any commands the behavior emits back at the interface — leaving you to consume the behavior's external events. The example below is illustrative (error handling and the await runtime are elided):

use pallas_network2::{
    behavior::{AnyMessage, InitiatorBehavior, InitiatorCommand, InitiatorEvent},
    interface::TcpInterface,
    Manager, PeerId,
};

let interface = TcpInterface::<AnyMessage>::new();
let behavior  = InitiatorBehavior::default();

let mut manager = Manager::new(interface, behavior);

manager.execute(InitiatorCommand::IncludePeer(
    "relays-new.cardano-mainnet.iohk.io:3001".parse::<PeerId>().unwrap(),
));

while let Some(event) = manager.poll_next().await {
    match event {
        InitiatorEvent::PeerInitialized(pid, _) => println!("up: {pid}"),
        InitiatorEvent::BlockHeaderReceived(pid, header, _) => {
            println!("hdr from {pid}: {} bytes", header.cbor.len());
        }
        _ => {}
    }
}

Overview

• Manager — drives a paired Interface + Behavior. poll_next advances IO and the behavior; execute forwards an external command to the behavior.
• Interface trait — the IO side. Receives InterfaceCommand (Connect / Send / Disconnect) and yields InterfaceEvent (Connected / Disconnected / Sent / Recv / Error / Idle).
• Behavior trait — the protocol logic. Defines its own Event, Command, PeerState, and Message, and emits BehaviorOutputs.
• Message trait — describes a mini-protocol message (channel id + payload encoding).
• OutboundQueue — convenience queue of pending BehaviorOutputs ready to be polled by the manager.
• PeerId, Channel, Payload, MAX_SEGMENT_PAYLOAD_LENGTH — the primitive vocabulary.

Modules

• bearer — low-level transport for reading and writing multiplexed segments.
• interface — Interface implementations for TCP connections.
• behavior — opinionated Behavior implementations for Cardano stacks.
• protocol — the Ouroboros mini-protocol definitions (handshake, chainsync, blockfetch, …).

Feature flags

• emulation — enables the emulation module, an in-memory test harness for exercising behaviors without real network IO.