Crate zebra_network

Networking code for Zebra. 🦓

The Zcash network protocol is inherited from Bitcoin, which uses a stateful network protocol in which messages can arrive in any order (even before a handshake is complete!), and the same message may be a request or a response depending on context.

This crate translates the legacy Bitcoin/Zcash network protocol into a stateless, request-response oriented protocol defined by the Request and Response enums, and completely encapsulates all peer handling code behind a single tower::Service representing "the network" which load-balances outbound Requests over available peers.

Unlike the underlying legacy network protocol the provided tower::Service guarantees that each Request future will resolve to the correct Response, not a potentially random unrelated Response.

Each peer connection is a distinct task, which interprets incoming Bitcoin/Zcash messages either as Responses to pending Requests, or as an inbound Requests to an internal tower::Service representing "this node". All connection state is isolated to the peer in question, so as a side effect the design is structurally immune to the recent ping attack.

Because tower::Services provide backpressure information, we can dynamically manage the size of the connection pool according to inbound and outbound demand. The inbound service can shed load when it is not ready for requests, causing those peer connections to close, and the outbound service can connect to additional peers when it is overloaded.

Modules

constants	Definitions of constants.
types	Types used in the definition of Request and Response messages.

Structs

AddressBook	A database of peers, their advertised services, and information on when they were last seen.
Config	Configuration for networking code.
RetryErrors	A very basic retry policy that always retries failed requests.
RetryLimit	A very basic retry policy with a limited number of retry attempts.

Enums

Request	A network request, represented in internal format.
Response	A response to a network request, represented in internal format.

Functions

connect_isolated	Use the provided TCP connection to create a Zcash connection completely isolated from all other node state.
init	Initialize a peer set.

Type Definitions

BoxError

Type alias to make working with tower traits easier.