Module devp2p 

Ethereum devp2p node: RLPx over TCP, the base protocol, and eth/68 / eth/69.

NetGet owns the transport and the encoding — the ECIES handshake, frame encryption and MACs, Snappy, RLP, Hello, Ping/Pong — and computes every block hash. The model owns policy and content: which peers to admit and with what Status (eth_status), what to answer when a peer asks for headers, bodies or pooled transactions, and what to ask the peer for.

A session runs: RLPx handshake and Hello (Rust, session::establish) → the peer’s Status → eth_status to the model → this node’s Status or a Disconnect → requests both ways until one side disconnects. The reader task answers the peer’s Pings itself, so a slow model never makes go-ethereum’s 30-second read deadline fire.

Failing closed

Disconnect is the only refusal devp2p has, and it is what every failure here sends:

• eth_status with no usable answer (backend down, nothing, a refused Status) → Disconnect subprotocol_error, decision=fail_closed_* / model_silent. An answer without eth_send_status is a refusal: Disconnect useless_peer, decision=model_reject.
• A peer request (headers, bodies, pooled transactions) still unanswered after the model’s turn → Disconnect subprotocol_error. NetGet never invents an answer: a header the model did not write is never sent, and an empty answer is only ever the model’s own.
• A frame that fails its MAC, a message past the bounds, a malformed message → Disconnect breach_of_protocol, decision=protocol_error / fail_closed_message_too_large, before any model call.

Every outcome writes one decision= line.

Modules

actions

What the model decides on a devp2p node: whether to admit a peer and with what Status, how to answer its eth requests, and what to ask it for.

crypto

The cryptography devp2p is built from: secp256k1 node keys, ECDH, recoverable signatures, keccak-256, and the ECIES variant the RLPx handshake encrypts with.

eth

The messages: the devp2p base protocol (Hello, Disconnect, Ping, Pong) and the eth subprotocol at versions 68 and 69, plus the pieces they are made of — block headers as structured JSON and their hashes, fork identifiers (EIP-2124), enode URLs, transactions.

rlp

Recursive Length Prefix (RLP), Ethereum’s serialisation, with the bounds a peer cannot move.

rlpx

RLPx: the encrypted, authenticated transport every devp2p connection runs on.

session

One devp2p session after the TCP connection, shared by the server and the client.

Structs

Devp2pServer

Constants

MAX_FOLLOWUP_DEPTH

How many model turns may follow from one another (a request whose answer prompts a request).

STATUS_TIMEOUT

How long after Hello the peer has to send its Status.

Functions

event_type_for

The event type the model hears for a session event.