A0-4295: Base protocol config creation (#1711)

# Description

Config creation for the base protocol, mostly dummy values, but this is
what we want in our case. Not yet used, will have to be used in tandem
with the network building.

## Type of change

- New feature (non-breaking change which adds functionality)

# Checklist:

- I have created new documentation

Cargo.toml

@@ -52,6 +52,7 @@ aleph-bft-mock = { version = "0.14" }
 aleph-bft-rmc = { version = "0.13" }
 aleph-bft-types = { version = "0.13" }
 async-trait = { version = "0.1" }
+array-bytes = { version = "6" }
 bytes = { version = "1.6" }
 derive_more = { version = "0.99" }
 env_logger = { version = "0.10" }

finality-aleph/Cargo.toml

@@ -23,6 +23,7 @@ current-aleph-aggregator = { path = "../aggregator", package = "aggregator" }
 rate-limiter = { package = "rate-limiter", path = "../rate-limiter" }
 
 async-trait = { workspace = true }
+array-bytes = { workspace = true }
 bytes = { workspace = true }
 derive_more = { workspace = true }
 env_logger = { workspace = true }

finality-aleph/src/base_protocol/config.rs

@@ -0,0 +1,54 @@
+use std::iter;
+
+use array_bytes::bytes2hex;
+use sc_network::{
+    config::{NonDefaultSetConfig, NonReservedPeerMode, NotificationHandshake, Role, SetConfig},
+    NotificationService,
+};
+use sc_network_common::sync::message::BlockAnnouncesHandshake;
+use sp_core::H256;
+use sp_runtime::traits::{Block, Header};
+
+use crate::{BlockHash, BlockNumber};
+
+// NOTE: `set_config` will be ignored by `protocol.rs` as the base
+// protocol is still hardcoded into the peerset.
+const DUMMY_SET_CONFIG: SetConfig = SetConfig {
+    in_peers: 0,
+    out_peers: 0,
+    reserved_nodes: Vec::new(),
+    non_reserved_mode: NonReservedPeerMode::Deny,
+};
+
+/// Generate a config for the base protocol and the notification service that should be passed to its service.
+pub fn setup<B>(genesis_hash: B::Hash) -> (NonDefaultSetConfig, Box<dyn NotificationService>)
+where
+    B: Block<Hash = BlockHash>,
+    B::Header: Header<Number = BlockNumber>,
+{
+    // used for backwards compatibility with older nodes, should be safe to remove after update 14
+    let legacy_block_announces_protocol =
+        format!("/{}/block-announces/1", bytes2hex("", genesis_hash));
+    let base_protocol_name = format!("/{}/base-protocol/1", bytes2hex("", genesis_hash));
+
+    NonDefaultSetConfig::new(
+        base_protocol_name.into(),
+        iter::once(legacy_block_announces_protocol.into()).collect(),
+        // This is the maximum message size. We don't need messages at all,
+        // but we want to avoid tripping some magic value,
+        // which 0 might suddenly become, so 1.
+        1,
+        Some(NotificationHandshake::new(
+            BlockAnnouncesHandshake::<B>::build(
+                // All nodes are full nodes.
+                (&Role::Full).into(),
+                // The best block number, always send a dummy value of 0.
+                0,
+                // The best block hash, always an obviously dummy value.
+                H256([0; 32]),
+                genesis_hash,
+            ),
+        )),
+        DUMMY_SET_CONFIG,
+    )
+}

finality-aleph/src/base_protocol/mod.rs

@@ -1,8 +1,10 @@
 //TODO(A0-3750): This code should be used.
 #![allow(dead_code)]
+mod config;
 mod handler;
 mod service;
 
+pub use config::setup;
 pub use service::Service;
 
 const LOG_TARGET: &str = "aleph-base-protocol";