diff --git a/substrate/core/network/src/protocol/consensus_gossip.rs b/substrate/core/network/src/protocol/consensus_gossip.rs index 328fe197ea54055ed0a3cde9c70437dae4128b19..d916e9aace7044cd1a048b641ba91cd0696ef120 100644 --- a/substrate/core/network/src/protocol/consensus_gossip.rs +++ b/substrate/core/network/src/protocol/consensus_gossip.rs @@ -14,8 +14,34 @@ // You should have received a copy of the GNU General Public License // along with Substrate. If not, see <http://www.gnu.org/licenses/>. -//! Utility for gossip of network messages between authorities. +//! Utility for gossip of network messages between nodes. //! Handles chain-specific and standard BFT messages. +//! +//! Gossip messages are separated by two categories: "topics" and consensus engine ID. +//! The consensus engine ID is sent over the wire with the message, while the topic is not, +//! with the expectation that the topic can be derived implicitly from the content of the +//! message, assuming it is valid. +//! +//! Topics are a single 32-byte tag associated with a message, used to group those messages +//! in an opaque way. Consensus code can invoke `broadcast_topic` to attempt to send all messages +//! under a single topic to all peers who don't have them yet, and `send_topic` to +//! send all messages under a single topic to a specific peer. +//! +//! Each consensus engine ID must have an associated, +//! registered `Validator` for all gossip messages. The primary role of this `Validator` is +//! to process incoming messages from peers, and decide whether to discard them or process +//! them. It also decides whether to re-broadcast the message. +//! +//! The secondary role of the `Validator` is to check if a message is allowed to be sent to a given +//! peer. All messages, before being sent, will be checked against this filter. +//! This enables the validator to use information it's aware of about connected peers to decide +//! whether to send messages to them at any given moment in time - In particular, to wait until +//! peers can accept and process the message before sending it. +//! +//! Lastly, the fact that gossip validators can decide not to rebroadcast messages +//! opens the door for neighbor status packets to be baked into the gossip protocol. +//! These status packets will typically contain light pieces of information +//! used to inform peers of a current view of protocol state. use std::collections::{HashMap, HashSet, hash_map::Entry}; use std::sync::Arc;