Move gossipsub into a separate crate (#5401)

* move gossipsub into a separate crate

* Merge branch 'unstable' of github.com:sigp/lighthouse into separate-gossipsub

* address review 2

* clippy beta

* update logging to log gossipsub logs

beacon_node/lighthouse_network/gossipsub/src/mod.rs

@@ -0,0 +1,111 @@
+//! Implementation of the [Gossipsub](https://github.com/libp2p/specs/blob/master/pubsub/gossipsub/README.md) protocol.
+//!
+//! Gossipsub is a P2P pubsub (publish/subscription) routing layer designed to extend upon
+//! floodsub and meshsub routing protocols.
+//!
+//! # Overview
+//!
+//! *Note: The gossipsub protocol specifications
+//! (<https://github.com/libp2p/specs/tree/master/pubsub/gossipsub>) provide an outline for the
+//! routing protocol. They should be consulted for further detail.*
+//!
+//! Gossipsub  is a blend of meshsub for data and randomsub for mesh metadata. It provides bounded
+//! degree and amplification factor with the meshsub construction and augments it using gossip
+//! propagation of metadata with the randomsub technique.
+//!
+//! The router maintains an overlay mesh network of peers on which to efficiently send messages and
+//! metadata.  Peers use control messages to broadcast and request known messages and
+//! subscribe/unsubscribe from topics in the mesh network.
+//!
+//! # Important Discrepancies
+//!
+//! This section outlines the current implementation's potential discrepancies from that of other
+//! implementations, due to undefined elements in the current specification.
+//!
+//! - **Topics** -  In gossipsub, topics configurable by the `hash_topics` configuration parameter.
+//! Topics are of type [`TopicHash`]. The current go implementation uses raw utf-8 strings, and this
+//! is default configuration in rust-libp2p. Topics can be hashed (SHA256 hashed then base64
+//! encoded) by setting the `hash_topics` configuration parameter to true.
+//!
+//! - **Sequence Numbers** - A message on the gossipsub network is identified by the source
+//! [`PeerId`](libp2p_identity::PeerId) and a nonce (sequence number) of the message. The sequence numbers in
+//! this implementation are sent as raw bytes across the wire. They are 64-bit big-endian unsigned
+//! integers. When messages are signed, they are monotonically increasing integers starting from a
+//! random value and wrapping around u64::MAX. When messages are unsigned, they are chosen at random.
+//! NOTE: These numbers are sequential in the current go implementation.
+//!
+//! # Peer Discovery
+//!
+//! Gossipsub does not provide peer discovery by itself. Peer discovery is the process by which
+//! peers in a p2p network exchange information about each other among other reasons to become resistant
+//! against the failure or replacement of the
+//! [boot nodes](https://docs.libp2p.io/reference/glossary/#boot-node) of the network.
+//!
+//! Peer
+//! discovery can e.g. be implemented with the help of the [Kademlia](https://github.com/libp2p/specs/blob/master/kad-dht/README.md) protocol
+//! in combination with the [Identify](https://github.com/libp2p/specs/tree/master/identify) protocol. See the
+//! Kademlia implementation documentation for more information.
+//!
+//! # Using Gossipsub
+//!
+//! ## Gossipsub Config
+//!
+//! The [`Config`] struct specifies various network performance/tuning configuration
+//! parameters. Specifically it specifies:
+//!
+//! [`Config`]: struct.Config.html
+//!
+//! This struct implements the [`Default`] trait and can be initialised via
+//! [`Config::default()`].
+//!
+//!
+//! ## Behaviour
+//!
+//! The [`Behaviour`] struct implements the [`libp2p_swarm::NetworkBehaviour`] trait allowing it to
+//! act as the routing behaviour in a [`libp2p_swarm::Swarm`]. This struct requires an instance of
+//! [`PeerId`](libp2p_identity::PeerId) and [`Config`].
+//!
+//! [`Behaviour`]: struct.Behaviour.html
+
+//! ## Example
+//!
+//! For an example on how to use gossipsub, see the [chat-example](https://github.com/libp2p/rust-libp2p/tree/master/examples/chat).
+
+#![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
+
+mod backoff;
+mod behaviour;
+mod config;
+mod error;
+mod gossip_promises;
+mod handler;
+mod mcache;
+mod metrics;
+mod peer_score;
+mod protocol;
+mod rpc_proto;
+mod subscription_filter;
+mod time_cache;
+mod topic;
+mod transform;
+mod types;
+
+pub use self::behaviour::{Behaviour, Event, MessageAuthenticity};
+pub use self::config::{Config, ConfigBuilder, ValidationMode, Version};
+pub use self::error::{ConfigBuilderError, PublishError, SubscriptionError, ValidationError};
+pub use self::metrics::Config as MetricsConfig;
+pub use self::peer_score::{
+    score_parameter_decay, score_parameter_decay_with_base, PeerScoreParams, PeerScoreThresholds,
+    TopicScoreParams,
+};
+pub use self::subscription_filter::{
+    AllowAllSubscriptionFilter, CallbackSubscriptionFilter, CombinedSubscriptionFilters,
+    MaxCountSubscriptionFilter, RegexSubscriptionFilter, TopicSubscriptionFilter,
+    WhitelistSubscriptionFilter,
+};
+pub use self::topic::{Hasher, Topic, TopicHash};
+pub use self::transform::{DataTransform, IdentityTransform};
+pub use self::types::{Message, MessageAcceptance, MessageId, RawMessage};
+pub type IdentTopic = Topic<self::topic::IdentityHash>;
+pub type Sha256Topic = Topic<self::topic::Sha256Hash>;
+pub use self::types::FailedMessages;