cuprated: Blockchain Manager (#274)

* add cuprated skeleton

* fmt and add deny exception

* add main chain batch handler

* add blockchain init

* very rough block manager

* misc changes

* move more config values

* add new tables & types

* add function to fully add an alt block

* resolve current todo!s

* add new requests

* WIP: starting re-orgs

* add last service request

* commit Cargo.lock

* add test

* more docs + cleanup + alt blocks request

* clippy + fmt

* document types

* move tx_fee to helper

* more doc updates

* fmt

* fix imports

* remove config files

* fix merge errors

* fix generated coins

* handle more p2p requests + alt blocks

* clean up handler code

* add function for incoming blocks

* add docs to handler functions

* broadcast new blocks + add commands

* add fluffy block handler

* fix new block handling

* small cleanup

* increase outbound peer count

* fix merge

* clean up the blockchain manger

* add more docs + cleanup imports

* fix typo

* fix doc

* remove unrelated changes

* improve interface globals

* manger -> manager

* enums instead of bools

* move chain service to separate file

* more review fixes

* add link to issue

* fix syncer + update comment

* fmt

Cargo.lock

@@ -1906,6 +1906,16 @@ dependencies = [
  "tokio",
 ]
 
+[[package]]
+name = "nu-ansi-term"
+version = "0.46.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77a8165726e8236064dbb45459242600304b42a5ea24ee2948e18e023bf7ba84"
+dependencies = [
+ "overload",
+ "winapi",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"
@@ -1943,6 +1953,12 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "04744f49eae99ab78e0d5c0b603ab218f515ea8cfe5a456d7629ad883a3b6e7d"
 
+[[package]]
+name = "overload"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b15813163c1d831bf4a13c3610c05c0d03b39feb07f7e09fa234dac9b15aaf39"
+
 [[package]]
 name = "page_size"
 version = "0.6.0"
@@ -2564,6 +2580,15 @@ dependencies = [
  "keccak",
 ]
 
+[[package]]
+name = "sharded-slab"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f40ca3c46823713e0d4209592e8d6e826aa57e928f09752619fc696c499637f6"
+dependencies = [
+ "lazy_static",
+]
+
 [[package]]
 name = "shlex"
 version = "1.3.0"
@@ -2960,6 +2985,18 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c06d3da6113f116aaee68e4d601191614c9053067f9ab7f6edbcb161237daa54"
 dependencies = [
  "once_cell",
+ "valuable",
+]
+
+[[package]]
+name = "tracing-log"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee855f1f400bd0e5c02d150ae5de3840039a3f54b025156404e34c23c03f47c3"
+dependencies = [
+ "log",
+ "once_cell",
+ "tracing-core",
 ]
 
 [[package]]
@@ -2968,7 +3005,12 @@ version = "0.3.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ad0f048c97dbd9faa9b7df56362b8ebcaa52adb06b498c050d2f4e32f90a7a8b"
 dependencies = [
+ "nu-ansi-term",
+ "sharded-slab",
+ "smallvec",
+ "thread_local",
  "tracing-core",
+ "tracing-log",
 ]
 
 [[package]]
@@ -3051,6 +3093,12 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "valuable"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "830b7e5d4d90034032940e4ace0d9a9a057e7a45cd94e6c007832e39edb82f6d"
+
 [[package]]
 name = "version_check"
 version = "0.9.5"

binaries/cuprated/Cargo.toml

@@ -23,7 +23,7 @@ cuprate-p2p-core         = { path = "../../p2p/p2p-core" }
 cuprate-dandelion-tower  = { path = "../../p2p/dandelion-tower" }
 cuprate-async-buffer     = { path = "../../p2p/async-buffer" }
 cuprate-address-book     = { path = "../../p2p/address-book" }
-cuprate-blockchain       = { path = "../../storage/blockchain" }
+cuprate-blockchain       = { path = "../../storage/blockchain", features = ["service"] }
 cuprate-database-service = { path = "../../storage/service" }
 cuprate-txpool           = { path = "../../storage/txpool" }
 cuprate-database         = { path = "../../storage/database" }
@@ -70,8 +70,14 @@ tokio-util            = { workspace = true }
 tokio-stream          = { workspace = true }
 tokio                 = { workspace = true }
 tower                 = { workspace = true }
-tracing-subscriber    = { workspace = true }
+tracing-subscriber    = { workspace = true, features = ["std", "fmt", "default"] }
 tracing               = { workspace = true }
 
 [lints]
 workspace = true
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"

binaries/cuprated/src/blockchain.rs

@@ -1,6 +1,101 @@
 //! Blockchain
 //!
-//! Will contain the chain manager and syncer.
+//! Contains the blockchain manager, syncer and an interface to mutate the blockchain.
+use std::sync::Arc;
 
+use futures::FutureExt;
+use tokio::sync::{mpsc, Notify};
+use tower::{BoxError, Service, ServiceExt};
+
+use cuprate_blockchain::service::{BlockchainReadHandle, BlockchainWriteHandle};
+use cuprate_consensus::{generate_genesis_block, BlockChainContextService, ContextConfig};
+use cuprate_cryptonight::cryptonight_hash_v0;
+use cuprate_p2p::{block_downloader::BlockDownloaderConfig, NetworkInterface};
+use cuprate_p2p_core::{ClearNet, Network};
+use cuprate_types::{
+    blockchain::{BlockchainReadRequest, BlockchainWriteRequest},
+    VerifiedBlockInformation,
+};
+
+use crate::constants::PANIC_CRITICAL_SERVICE_ERROR;
+
+mod chain_service;
+pub mod interface;
 mod manager;
 mod syncer;
+mod types;
+
+use types::{
+    ConcreteBlockVerifierService, ConcreteTxVerifierService, ConsensusBlockchainReadHandle,
+};
+
+/// Checks if the genesis block is in the blockchain and adds it if not.
+pub async fn check_add_genesis(
+    blockchain_read_handle: &mut BlockchainReadHandle,
+    blockchain_write_handle: &mut BlockchainWriteHandle,
+    network: Network,
+) {
+    // Try to get the chain height, will fail if the genesis block is not in the DB.
+    if blockchain_read_handle
+        .ready()
+        .await
+        .expect(PANIC_CRITICAL_SERVICE_ERROR)
+        .call(BlockchainReadRequest::ChainHeight)
+        .await
+        .is_ok()
+    {
+        return;
+    }
+
+    let genesis = generate_genesis_block(network);
+
+    assert_eq!(genesis.miner_transaction.prefix().outputs.len(), 1);
+    assert!(genesis.transactions.is_empty());
+
+    blockchain_write_handle
+        .ready()
+        .await
+        .expect(PANIC_CRITICAL_SERVICE_ERROR)
+        .call(BlockchainWriteRequest::WriteBlock(
+            VerifiedBlockInformation {
+                block_blob: genesis.serialize(),
+                txs: vec![],
+                block_hash: genesis.hash(),
+                pow_hash: cryptonight_hash_v0(&genesis.serialize_pow_hash()),
+                height: 0,
+                generated_coins: genesis.miner_transaction.prefix().outputs[0]
+                    .amount
+                    .unwrap(),
+                weight: genesis.miner_transaction.weight(),
+                long_term_weight: genesis.miner_transaction.weight(),
+                cumulative_difficulty: 1,
+                block: genesis,
+            },
+        ))
+        .await
+        .expect(PANIC_CRITICAL_SERVICE_ERROR);
+}
+
+/// Initializes the consensus services.
+pub async fn init_consensus(
+    blockchain_read_handle: BlockchainReadHandle,
+    context_config: ContextConfig,
+) -> Result<
+    (
+        ConcreteBlockVerifierService,
+        ConcreteTxVerifierService,
+        BlockChainContextService,
+    ),
+    BoxError,
+> {
+    let read_handle = ConsensusBlockchainReadHandle::new(blockchain_read_handle, BoxError::from);
+
+    let ctx_service =
+        cuprate_consensus::initialize_blockchain_context(context_config, read_handle.clone())
+            .await?;
+
+    let (block_verifier_svc, tx_verifier_svc) =
+        cuprate_consensus::initialize_verifier(read_handle, ctx_service.clone());
+
+    Ok((block_verifier_svc, tx_verifier_svc, ctx_service))
+}

binaries/cuprated/src/blockchain/chain_service.rs

@@ -0,0 +1,72 @@
+use std::task::{Context, Poll};
+
+use futures::{future::BoxFuture, FutureExt, TryFutureExt};
+use tower::Service;
+
+use cuprate_blockchain::service::BlockchainReadHandle;
+use cuprate_p2p::block_downloader::{ChainSvcRequest, ChainSvcResponse};
+use cuprate_types::blockchain::{BlockchainReadRequest, BlockchainResponse};
+
+/// That service that allows retrieving the chain state to give to the P2P crates, so we can figure out
+/// what blocks we need.
+///
+/// This has a more minimal interface than [`BlockchainReadRequest`] to make using the p2p crates easier.
+#[derive(Clone)]
+pub struct ChainService(pub BlockchainReadHandle);
+
+impl Service<ChainSvcRequest> for ChainService {
+    type Response = ChainSvcResponse;
+    type Error = tower::BoxError;
+    type Future = BoxFuture<'static, Result<Self::Response, Self::Error>>;
+
+    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+        self.0.poll_ready(cx).map_err(Into::into)
+    }
+
+    fn call(&mut self, req: ChainSvcRequest) -> Self::Future {
+        let map_res = |res: BlockchainResponse| match res {
+            BlockchainResponse::CompactChainHistory {
+                block_ids,
+                cumulative_difficulty,
+            } => ChainSvcResponse::CompactHistory {
+                block_ids,
+                cumulative_difficulty,
+            },
+            BlockchainResponse::FindFirstUnknown(res) => ChainSvcResponse::FindFirstUnknown(res),
+            _ => unreachable!(),
+        };
+
+        match req {
+            ChainSvcRequest::CompactHistory => self
+                .0
+                .call(BlockchainReadRequest::CompactChainHistory)
+                .map_ok(map_res)
+                .map_err(Into::into)
+                .boxed(),
+            ChainSvcRequest::FindFirstUnknown(req) => self
+                .0
+                .call(BlockchainReadRequest::FindFirstUnknown(req))
+                .map_ok(map_res)
+                .map_err(Into::into)
+                .boxed(),
+            ChainSvcRequest::CumulativeDifficulty => self
+                .0
+                .call(BlockchainReadRequest::CompactChainHistory)
+                .map_ok(|res| {
+                    // TODO create a custom request instead of hijacking this one.
+                    // TODO: use the context cache.
+                    let BlockchainResponse::CompactChainHistory {
+                        cumulative_difficulty,
+                        ..
+                    } = res
+                    else {
+                        unreachable!()
+                    };
+
+                    ChainSvcResponse::CumulativeDifficulty(cumulative_difficulty)
+                })
+                .map_err(Into::into)
+                .boxed(),
+        }
+    }
+}

binaries/cuprated/src/blockchain/interface.rs

@@ -0,0 +1,161 @@
+//! The blockchain manager interface.
+//!
+//! This module contains all the functions to mutate the blockchain's state in any way, through the
+//! blockchain manager.
+use std::{
+    collections::{HashMap, HashSet},
+    sync::{LazyLock, Mutex, OnceLock},
+};
+
+use monero_serai::{block::Block, transaction::Transaction};
+use rayon::prelude::*;
+use tokio::sync::{mpsc, oneshot};
+use tower::{Service, ServiceExt};
+
+use cuprate_blockchain::service::BlockchainReadHandle;
+use cuprate_consensus::transactions::new_tx_verification_data;
+use cuprate_helper::cast::usize_to_u64;
+use cuprate_types::{
+    blockchain::{BlockchainReadRequest, BlockchainResponse},
+    Chain,
+};
+
+use crate::{
+    blockchain::manager::{BlockchainManagerCommand, IncomingBlockOk},
+    constants::PANIC_CRITICAL_SERVICE_ERROR,
+};
+
+/// The channel used to send [`BlockchainManagerCommand`]s to the blockchain manager.
+///
+/// This channel is initialized in [`init_blockchain_manager`](super::manager::init_blockchain_manager), the functions
+/// in this file document what happens if this is not initialized when they are called.
+pub(super) static COMMAND_TX: OnceLock<mpsc::Sender<BlockchainManagerCommand>> = OnceLock::new();
+
+/// An error that can be returned from [`handle_incoming_block`].
+#[derive(Debug, thiserror::Error)]
+pub enum IncomingBlockError {
+    /// Some transactions in the block were unknown.
+    ///
+    /// The inner values are the block hash and the indexes of the missing txs in the block.
+    #[error("Unknown transactions in block.")]
+    UnknownTransactions([u8; 32], Vec<u64>),
+    /// We are missing the block's parent.
+    #[error("The block has an unknown parent.")]
+    Orphan,
+    /// The block was invalid.
+    #[error(transparent)]
+    InvalidBlock(anyhow::Error),
+}
+
+/// Try to add a new block to the blockchain.
+///
+/// On success returns [`IncomingBlockOk`].
+///
+/// # Errors
+///
+/// This function will return an error if:
+///  - the block was invalid
+///  - we are missing transactions
+///  - the block's parent is unknown
+pub async fn handle_incoming_block(
+    block: Block,
+    given_txs: Vec<Transaction>,
+    blockchain_read_handle: &mut BlockchainReadHandle,
+) -> Result<IncomingBlockOk, IncomingBlockError> {
+    /// A [`HashSet`] of block hashes that the blockchain manager is currently handling.
+    ///
+    /// This lock prevents sending the same block to the blockchain manager from multiple connections
+    /// before one of them actually gets added to the chain, allowing peers to do other things.
+    ///
+    /// This is used over something like a dashmap as we expect a lot of collisions in a short amount of
+    /// time for new blocks, so we would lose the benefit of sharded locks. A dashmap is made up of `RwLocks`
+    /// which are also more expensive than `Mutex`s.
+    static BLOCKS_BEING_HANDLED: LazyLock<Mutex<HashSet<[u8; 32]>>> =
+        LazyLock::new(|| Mutex::new(HashSet::new()));
+    // FIXME: we should look in the tx-pool for txs when that is ready.
+
+    if !block_exists(block.header.previous, blockchain_read_handle)
+        .await
+        .expect(PANIC_CRITICAL_SERVICE_ERROR)
+    {
+        return Err(IncomingBlockError::Orphan);
+    }
+
+    let block_hash = block.hash();
+
+    if block_exists(block_hash, blockchain_read_handle)
+        .await
+        .expect(PANIC_CRITICAL_SERVICE_ERROR)
+    {
+        return Ok(IncomingBlockOk::AlreadyHave);
+    }
+
+    // TODO: remove this when we have a working tx-pool.
+    if given_txs.len() != block.transactions.len() {
+        return Err(IncomingBlockError::UnknownTransactions(
+            block_hash,
+            (0..usize_to_u64(block.transactions.len())).collect(),
+        ));
+    }
+
+    // TODO: check we actually got given the right txs.
+    let prepped_txs = given_txs
+        .into_par_iter()
+        .map(|tx| {
+            let tx = new_tx_verification_data(tx)?;
+            Ok((tx.tx_hash, tx))
+        })
+        .collect::<Result<_, anyhow::Error>>()
+        .map_err(IncomingBlockError::InvalidBlock)?;
+
+    let Some(incoming_block_tx) = COMMAND_TX.get() else {
+        // We could still be starting up the blockchain manager.
+        return Ok(IncomingBlockOk::NotReady);
+    };
+
+    // Add the blocks hash to the blocks being handled.
+    if !BLOCKS_BEING_HANDLED.lock().unwrap().insert(block_hash) {
+        // If another place is already adding this block then we can stop.
+        return Ok(IncomingBlockOk::AlreadyHave);
+    }
+
+    // From this point on we MUST not early return without removing the block hash from `BLOCKS_BEING_HANDLED`.
+
+    let (response_tx, response_rx) = oneshot::channel();
+
+    incoming_block_tx
+        .send(BlockchainManagerCommand::AddBlock {
+            block,
+            prepped_txs,
+            response_tx,
+        })
+        .await
+        .expect("TODO: don't actually panic here, an err means we are shutting down");
+
+    let res = response_rx
+        .await
+        .expect("The blockchain manager will always respond")
+        .map_err(IncomingBlockError::InvalidBlock);
+
+    // Remove the block hash from the blocks being handled.
+    BLOCKS_BEING_HANDLED.lock().unwrap().remove(&block_hash);
+
+    res
+}
+
+/// Check if we have a block with the given hash.
+async fn block_exists(
+    block_hash: [u8; 32],
+    blockchain_read_handle: &mut BlockchainReadHandle,
+) -> Result<bool, anyhow::Error> {
+    let BlockchainResponse::FindBlock(chain) = blockchain_read_handle
+        .ready()
+        .await?
+        .call(BlockchainReadRequest::FindBlock(block_hash))
+        .await?
+    else {
+        unreachable!();
+    };
+
+    Ok(chain.is_some())
+}

binaries/cuprated/src/blockchain/manager.rs

@@ -1 +1,143 @@
+use std::{collections::HashMap, sync::Arc};
 
+use futures::StreamExt;
+use monero_serai::block::Block;
+use tokio::sync::{mpsc, oneshot, Notify};
+use tower::{Service, ServiceExt};
+use tracing::error;
+
+use cuprate_blockchain::service::{BlockchainReadHandle, BlockchainWriteHandle};
+use cuprate_consensus::{
+    context::RawBlockChainContext, BlockChainContextRequest, BlockChainContextResponse,
+    BlockChainContextService, BlockVerifierService, ExtendedConsensusError, TxVerifierService,
+    VerifyBlockRequest, VerifyBlockResponse, VerifyTxRequest, VerifyTxResponse,
+};
+use cuprate_p2p::{
+    block_downloader::{BlockBatch, BlockDownloaderConfig},
+    BroadcastSvc, NetworkInterface,
+};
+use cuprate_p2p_core::ClearNet;
+use cuprate_types::{
+    blockchain::{BlockchainReadRequest, BlockchainResponse},
+    Chain, TransactionVerificationData,
+};
+
+use crate::{
+    blockchain::{
+        chain_service::ChainService,
+        interface::COMMAND_TX,
+        syncer,
+        types::{ConcreteBlockVerifierService, ConsensusBlockchainReadHandle},
+    },
+    constants::PANIC_CRITICAL_SERVICE_ERROR,
+};
+
+mod commands;
+mod handler;
+
+pub use commands::{BlockchainManagerCommand, IncomingBlockOk};
+
+/// Initialize the blockchain manager.
+///
+/// This function sets up the [`BlockchainManager`] and the [`syncer`] so that the functions in [`interface`](super::interface)
+/// can be called.
+pub async fn init_blockchain_manager(
+    clearnet_interface: NetworkInterface<ClearNet>,
+    blockchain_write_handle: BlockchainWriteHandle,
+    blockchain_read_handle: BlockchainReadHandle,
+    mut blockchain_context_service: BlockChainContextService,
+    block_verifier_service: ConcreteBlockVerifierService,
+    block_downloader_config: BlockDownloaderConfig,
+) {
+    // TODO: find good values for these size limits
+    let (batch_tx, batch_rx) = mpsc::channel(1);
+    let stop_current_block_downloader = Arc::new(Notify::new());
+    let (command_tx, command_rx) = mpsc::channel(3);
+
+    COMMAND_TX.set(command_tx).unwrap();
+
+    tokio::spawn(syncer::syncer(
+        blockchain_context_service.clone(),
+        ChainService(blockchain_read_handle.clone()),
+        clearnet_interface.clone(),
+        batch_tx,
+        Arc::clone(&stop_current_block_downloader),
+        block_downloader_config,
+    ));
+
+    let BlockChainContextResponse::Context(blockchain_context) = blockchain_context_service
+        .ready()
+        .await
+        .expect(PANIC_CRITICAL_SERVICE_ERROR)
+        .call(BlockChainContextRequest::GetContext)
+        .await
+        .expect(PANIC_CRITICAL_SERVICE_ERROR)
+    else {
+        unreachable!()
+    };
+
+    let manager = BlockchainManager {
+        blockchain_write_handle,
+        blockchain_read_handle,
+        blockchain_context_service,
+        cached_blockchain_context: blockchain_context.unchecked_blockchain_context().clone(),
+        block_verifier_service,
+        stop_current_block_downloader,
+        broadcast_svc: clearnet_interface.broadcast_svc(),
+    };
+
+    tokio::spawn(manager.run(batch_rx, command_rx));
+}
+
+/// The blockchain manager.
+///
+/// This handles all mutation of the blockchain, anything that changes the state of the blockchain must
+/// go through this.
+///
+/// Other parts of Cuprate can interface with this by using the functions in [`interface`](super::interface).
+pub struct BlockchainManager {
+    /// The [`BlockchainWriteHandle`], this is the _only_ part of Cuprate where a [`BlockchainWriteHandle`]
+    /// is held.
+    blockchain_write_handle: BlockchainWriteHandle,
+    /// A [`BlockchainReadHandle`].
+    blockchain_read_handle: BlockchainReadHandle,
+    // TODO: Improve the API of the cache service.
+    // TODO: rename the cache service -> `BlockchainContextService`.
+    /// The blockchain context cache, this caches the current state of the blockchain to quickly calculate/retrieve
+    /// values without needing to go to a [`BlockchainReadHandle`].
+    blockchain_context_service: BlockChainContextService,
+    /// A cached context representing the current state.
+    cached_blockchain_context: RawBlockChainContext,
+    /// The block verifier service, to verify incoming blocks.
+    block_verifier_service: ConcreteBlockVerifierService,
+    /// A [`Notify`] to tell the [syncer](syncer::syncer) that we want to cancel this current download
+    /// attempt.
+    stop_current_block_downloader: Arc<Notify>,
+    /// The broadcast service, to broadcast new blocks.
+    broadcast_svc: BroadcastSvc<ClearNet>,
+}
+
+impl BlockchainManager {
+    /// The [`BlockchainManager`] task.
+    pub async fn run(
+        mut self,
+        mut block_batch_rx: mpsc::Receiver<BlockBatch>,
+        mut command_rx: mpsc::Receiver<BlockchainManagerCommand>,
+    ) {
+        loop {
+            tokio::select! {
+                Some(batch) = block_batch_rx.recv() => {
+                    self.handle_incoming_block_batch(
+                        batch,
+                    ).await;
+                }
+                Some(incoming_command) = command_rx.recv() => {
+                    self.handle_command(incoming_command).await;
+                }
+                else => {
+                    todo!("TODO: exit the BC manager")
+                }
+            }
+        }
+    }
+}

binaries/cuprated/src/blockchain/manager/commands.rs

@@ -0,0 +1,32 @@
+//! This module contains the commands for the blockchain manager.
+use std::collections::HashMap;
+
+use monero_serai::block::Block;
+use tokio::sync::oneshot;
+
+use cuprate_types::TransactionVerificationData;
+
+/// The blockchain manager commands.
+pub enum BlockchainManagerCommand {
+    /// Attempt to add a new block to the blockchain.
+    AddBlock {
+        /// The [`Block`] to add.
+        block: Block,
+        /// All the transactions defined in [`Block::transactions`].
+        prepped_txs: HashMap<[u8; 32], TransactionVerificationData>,
+        /// The channel to send the response down.
+        response_tx: oneshot::Sender<Result<IncomingBlockOk, anyhow::Error>>,
+    },
+}
+
+/// The [`Ok`] response for an incoming block.
+pub enum IncomingBlockOk {
+    /// The block was added to the main-chain.
+    AddedToMainChain,
+    /// The blockchain manager is not ready yet.
+    NotReady,
+    /// The block was added to an alt-chain.
+    AddedToAltChain,
+    /// We already have the block.
+    AlreadyHave,
+}

binaries/cuprated/src/blockchain/manager/handler.rs

@@ -0,0 +1,484 @@
+//! The blockchain manager handler functions.
+use bytes::Bytes;
+use futures::{TryFutureExt, TryStreamExt};
+use monero_serai::{block::Block, transaction::Transaction};
+use rayon::prelude::*;
+use std::ops::ControlFlow;
+use std::{collections::HashMap, sync::Arc};
+use tower::{Service, ServiceExt};
+use tracing::info;
+
+use cuprate_blockchain::service::{BlockchainReadHandle, BlockchainWriteHandle};
+use cuprate_consensus::{
+    block::PreparedBlock, context::NewBlockData, transactions::new_tx_verification_data,
+    BlockChainContextRequest, BlockChainContextResponse, BlockVerifierService,
+    ExtendedConsensusError, VerifyBlockRequest, VerifyBlockResponse, VerifyTxRequest,
+    VerifyTxResponse,
+};
+use cuprate_helper::cast::usize_to_u64;
+use cuprate_p2p::{block_downloader::BlockBatch, constants::LONG_BAN, BroadcastRequest};
+use cuprate_types::{
+    blockchain::{BlockchainReadRequest, BlockchainResponse, BlockchainWriteRequest},
+    AltBlockInformation, HardFork, TransactionVerificationData, VerifiedBlockInformation,
+};
+
+use crate::blockchain::manager::commands::IncomingBlockOk;
+use crate::{
+    blockchain::{
+        manager::commands::BlockchainManagerCommand, types::ConsensusBlockchainReadHandle,
+    },
+    constants::PANIC_CRITICAL_SERVICE_ERROR,
+    signals::REORG_LOCK,
+};
+
+impl super::BlockchainManager {
+    /// Handle an incoming command from another part of Cuprate.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if any internal service returns an unexpected error that we cannot
+    /// recover from.
+    pub async fn handle_command(&mut self, command: BlockchainManagerCommand) {
+        match command {
+            BlockchainManagerCommand::AddBlock {
+                block,
+                prepped_txs,
+                response_tx,
+            } => {
+                let res = self.handle_incoming_block(block, prepped_txs).await;
+
+                drop(response_tx.send(res));
+            }
+        }
+    }
+
+    /// Broadcast a valid block to the network.
+    async fn broadcast_block(&mut self, block_bytes: Bytes, blockchain_height: usize) {
+        self.broadcast_svc
+            .ready()
+            .await
+            .expect("Broadcast service is Infallible.")
+            .call(BroadcastRequest::Block {
+                block_bytes,
+                current_blockchain_height: usize_to_u64(blockchain_height),
+            })
+            .await
+            .expect("Broadcast service is Infallible.");
+    }
+
+    /// Handle an incoming [`Block`].
+    ///
+    /// This function will route to [`Self::handle_incoming_alt_block`] if the block does not follow
+    /// the top of the main chain.
+    ///
+    /// Otherwise, this function will validate and add the block to the main chain.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if any internal service returns an unexpected error that we cannot
+    /// recover from.
+    pub async fn handle_incoming_block(
+        &mut self,
+        block: Block,
+        prepared_txs: HashMap<[u8; 32], TransactionVerificationData>,
+    ) -> Result<IncomingBlockOk, anyhow::Error> {
+        if block.header.previous != self.cached_blockchain_context.top_hash {
+            self.handle_incoming_alt_block(block, prepared_txs).await?;
+            return Ok(IncomingBlockOk::AddedToAltChain);
+        }
+
+        let VerifyBlockResponse::MainChain(verified_block) = self
+            .block_verifier_service
+            .ready()
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+            .call(VerifyBlockRequest::MainChain {
+                block,
+                prepared_txs,
+            })
+            .await?
+        else {
+            unreachable!();
+        };
+
+        let block_blob = Bytes::copy_from_slice(&verified_block.block_blob);
+        self.add_valid_block_to_main_chain(verified_block).await;
+
+        self.broadcast_block(block_blob, self.cached_blockchain_context.chain_height)
+            .await;
+
+        Ok(IncomingBlockOk::AddedToMainChain)
+    }
+
+    /// Handle an incoming [`BlockBatch`].
+    ///
+    /// This function will route to [`Self::handle_incoming_block_batch_main_chain`] or [`Self::handle_incoming_block_batch_alt_chain`]
+    /// depending on if the first block in the batch follows from the top of our chain.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if the batch is empty or if any internal service returns an unexpected
+    /// error that we cannot recover from or if the incoming batch contains no blocks.
+    pub async fn handle_incoming_block_batch(&mut self, batch: BlockBatch) {
+        let (first_block, _) = batch
+            .blocks
+            .first()
+            .expect("Block batch should not be empty");
+
+        if first_block.header.previous == self.cached_blockchain_context.top_hash {
+            self.handle_incoming_block_batch_main_chain(batch).await;
+        } else {
+            self.handle_incoming_block_batch_alt_chain(batch).await;
+        }
+    }
+
+    /// Handles an incoming [`BlockBatch`] that follows the main chain.
+    ///
+    /// This function will handle validating the blocks in the batch and adding them to the blockchain
+    /// database and context cache.
+    ///
+    /// This function will also handle banning the peer and canceling the block downloader if the
+    /// block is invalid.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if any internal service returns an unexpected error that we cannot
+    /// recover from or if the incoming batch contains no blocks.
+    async fn handle_incoming_block_batch_main_chain(&mut self, batch: BlockBatch) {
+        info!(
+            "Handling batch to main chain height: {}",
+            batch.blocks.first().unwrap().0.number().unwrap()
+        );
+
+        let batch_prep_res = self
+            .block_verifier_service
+            .ready()
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+            .call(VerifyBlockRequest::MainChainBatchPrepareBlocks {
+                blocks: batch.blocks,
+            })
+            .await;
+
+        let prepped_blocks = match batch_prep_res {
+            Ok(VerifyBlockResponse::MainChainBatchPrepped(prepped_blocks)) => prepped_blocks,
+            Err(_) => {
+                batch.peer_handle.ban_peer(LONG_BAN);
+                self.stop_current_block_downloader.notify_one();
+                return;
+            }
+            _ => unreachable!(),
+        };
+
+        for (block, txs) in prepped_blocks {
+            let verify_res = self
+                .block_verifier_service
+                .ready()
+                .await
+                .expect(PANIC_CRITICAL_SERVICE_ERROR)
+                .call(VerifyBlockRequest::MainChainPrepped { block, txs })
+                .await;
+
+            let verified_block = match verify_res {
+                Ok(VerifyBlockResponse::MainChain(verified_block)) => verified_block,
+                Err(_) => {
+                    batch.peer_handle.ban_peer(LONG_BAN);
+                    self.stop_current_block_downloader.notify_one();
+                    return;
+                }
+                _ => unreachable!(),
+            };
+
+            self.add_valid_block_to_main_chain(verified_block).await;
+        }
+    }
+
+    /// Handles an incoming [`BlockBatch`] that does not follow the main-chain.
+    ///
+    /// This function will handle validating the alt-blocks to add them to our cache and reorging the
+    /// chain if the alt-chain has a higher cumulative difficulty.
+    ///
+    /// This function will also handle banning the peer and canceling the block downloader if the
+    /// alt block is invalid or if a reorg fails.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if any internal service returns an unexpected error that we cannot
+    /// recover from.
+    async fn handle_incoming_block_batch_alt_chain(&mut self, mut batch: BlockBatch) {
+        // TODO: this needs testing (this whole section does but alt-blocks specifically).
+
+        let mut blocks = batch.blocks.into_iter();
+
+        while let Some((block, txs)) = blocks.next() {
+            // async blocks work as try blocks.
+            let res = async {
+                let txs = txs
+                    .into_par_iter()
+                    .map(|tx| {
+                        let tx = new_tx_verification_data(tx)?;
+                        Ok((tx.tx_hash, tx))
+                    })
+                    .collect::<Result<_, anyhow::Error>>()?;
+
+                let reorged = self.handle_incoming_alt_block(block, txs).await?;
+
+                Ok::<_, anyhow::Error>(reorged)
+            }
+            .await;
+
+            match res {
+                Err(e) => {
+                    batch.peer_handle.ban_peer(LONG_BAN);
+                    self.stop_current_block_downloader.notify_one();
+                    return;
+                }
+                Ok(AddAltBlock::Reorged) => {
+                    // Collect the remaining blocks and add them to the main chain instead.
+                    batch.blocks = blocks.collect();
+                    self.handle_incoming_block_batch_main_chain(batch).await;
+                    return;
+                }
+                // continue adding alt blocks.
+                Ok(AddAltBlock::Cached) => (),
+            }
+        }
+    }
+
+    /// Handles an incoming alt [`Block`].
+    ///
+    /// This function will do some pre-validation of the alt block, then if the cumulative difficulty
+    /// of the alt chain is higher than the main chain it will attempt a reorg otherwise it will add
+    /// the alt block to the alt block cache.
+    ///
+    /// # Errors
+    ///
+    /// This will return an [`Err`] if:
+    ///  - The alt block was invalid.
+    ///  - An attempt to reorg the chain failed.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if any internal service returns an unexpected error that we cannot
+    /// recover from.
+    async fn handle_incoming_alt_block(
+        &mut self,
+        block: Block,
+        prepared_txs: HashMap<[u8; 32], TransactionVerificationData>,
+    ) -> Result<AddAltBlock, anyhow::Error> {
+        let VerifyBlockResponse::AltChain(alt_block_info) = self
+            .block_verifier_service
+            .ready()
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+            .call(VerifyBlockRequest::AltChain {
+                block,
+                prepared_txs,
+            })
+            .await?
+        else {
+            unreachable!();
+        };
+
+        // TODO: check in consensus crate if alt block with this hash already exists.
+
+        // If this alt chain
+        if alt_block_info.cumulative_difficulty
+            > self.cached_blockchain_context.cumulative_difficulty
+        {
+            self.try_do_reorg(alt_block_info).await?;
+            return Ok(AddAltBlock::Reorged);
+        }
+
+        self.blockchain_write_handle
+            .ready()
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+            .call(BlockchainWriteRequest::WriteAltBlock(alt_block_info))
+            .await?;
+
+        Ok(AddAltBlock::Cached)
+    }
+
+    /// Attempt a re-org with the given top block of the alt-chain.
+    ///
+    /// This function will take a write lock on [`REORG_LOCK`] and then set up the blockchain database
+    /// and context cache to verify the alt-chain. It will then attempt to verify and add each block
+    /// in the alt-chain to the main-chain. Releasing the lock on [`REORG_LOCK`] when finished.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an [`Err`] if the re-org was unsuccessful, if this happens the chain
+    /// will be returned back into its state it was at when then function was called.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if any internal service returns an unexpected error that we cannot
+    /// recover from.
+    async fn try_do_reorg(
+        &mut self,
+        top_alt_block: AltBlockInformation,
+    ) -> Result<(), anyhow::Error> {
+        let _guard = REORG_LOCK.write().await;
+
+        let BlockchainResponse::AltBlocksInChain(mut alt_blocks) = self
+            .blockchain_read_handle
+            .ready()
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+            .call(BlockchainReadRequest::AltBlocksInChain(
+                top_alt_block.chain_id,
+            ))
+            .await?
+        else {
+            unreachable!();
+        };
+
+        alt_blocks.push(top_alt_block);
+
+        let split_height = alt_blocks[0].height;
+        let current_main_chain_height = self.cached_blockchain_context.chain_height;
+
+        let BlockchainResponse::PopBlocks(old_main_chain_id) = self
+            .blockchain_write_handle
+            .ready()
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+            .call(BlockchainWriteRequest::PopBlocks(
+                current_main_chain_height - split_height + 1,
+            ))
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+        else {
+            unreachable!();
+        };
+
+        self.blockchain_context_service
+            .ready()
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+            .call(BlockChainContextRequest::PopBlocks {
+                numb_blocks: current_main_chain_height - split_height + 1,
+            })
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR);
+
+        let reorg_res = self.verify_add_alt_blocks_to_main_chain(alt_blocks).await;
+
+        match reorg_res {
+            Ok(()) => Ok(()),
+            Err(e) => {
+                todo!("Reverse reorg")
+            }
+        }
+    }
+
+    /// Verify and add a list of [`AltBlockInformation`]s to the main-chain.
+    ///
+    /// This function assumes the first [`AltBlockInformation`] is the next block in the blockchain
+    /// for the blockchain database and the context cache, or in other words that the blockchain database
+    /// and context cache have already had the top blocks popped to where the alt-chain meets the main-chain.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an [`Err`] if the alt-blocks were invalid, in this case the re-org should
+    /// be aborted and the chain should be returned to its previous state.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if any internal service returns an unexpected error that we cannot
+    /// recover from.
+    async fn verify_add_alt_blocks_to_main_chain(
+        &mut self,
+        alt_blocks: Vec<AltBlockInformation>,
+    ) -> Result<(), anyhow::Error> {
+        for mut alt_block in alt_blocks {
+            let prepped_txs = alt_block
+                .txs
+                .drain(..)
+                .map(|tx| Ok(Arc::new(tx.try_into()?)))
+                .collect::<Result<_, anyhow::Error>>()?;
+
+            let prepped_block = PreparedBlock::new_alt_block(alt_block)?;
+
+            let VerifyBlockResponse::MainChain(verified_block) = self
+                .block_verifier_service
+                .ready()
+                .await
+                .expect(PANIC_CRITICAL_SERVICE_ERROR)
+                .call(VerifyBlockRequest::MainChainPrepped {
+                    block: prepped_block,
+                    txs: prepped_txs,
+                })
+                .await?
+            else {
+                unreachable!();
+            };
+
+            self.add_valid_block_to_main_chain(verified_block).await;
+        }
+
+        Ok(())
+    }
+
+    /// Adds a [`VerifiedBlockInformation`] to the main-chain.
+    ///
+    /// This function will update the blockchain database and the context cache, it will also
+    /// update [`Self::cached_blockchain_context`].
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if any internal service returns an unexpected error that we cannot
+    /// recover from.
+    pub async fn add_valid_block_to_main_chain(
+        &mut self,
+        verified_block: VerifiedBlockInformation,
+    ) {
+        self.blockchain_context_service
+            .ready()
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+            .call(BlockChainContextRequest::Update(NewBlockData {
+                block_hash: verified_block.block_hash,
+                height: verified_block.height,
+                timestamp: verified_block.block.header.timestamp,
+                weight: verified_block.weight,
+                long_term_weight: verified_block.long_term_weight,
+                generated_coins: verified_block.generated_coins,
+                vote: HardFork::from_vote(verified_block.block.header.hardfork_signal),
+                cumulative_difficulty: verified_block.cumulative_difficulty,
+            }))
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR);
+
+        self.blockchain_write_handle
+            .ready()
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+            .call(BlockchainWriteRequest::WriteBlock(verified_block))
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR);
+
+        let BlockChainContextResponse::Context(blockchain_context) = self
+            .blockchain_context_service
+            .ready()
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+            .call(BlockChainContextRequest::GetContext)
+            .await
+            .expect(PANIC_CRITICAL_SERVICE_ERROR)
+        else {
+            unreachable!();
+        };
+
+        self.cached_blockchain_context = blockchain_context.unchecked_blockchain_context().clone();
+    }
+}
+
+/// The result from successfully adding an alt-block.
+enum AddAltBlock {
+    /// The alt-block was cached.
+    Cached,
+    /// The chain was reorged.
+    Reorged,
+}

binaries/cuprated/src/blockchain/syncer.rs

@@ -1 +1,143 @@
+// FIXME: This whole module is not great and should be rewritten when the PeerSet is made.
+use std::{pin::pin, sync::Arc, time::Duration};
 
+use futures::StreamExt;
+use tokio::time::interval;
+use tokio::{
+    sync::{mpsc, Notify},
+    time::sleep,
+};
+use tower::{Service, ServiceExt};
+use tracing::instrument;
+
+use cuprate_consensus::{BlockChainContext, BlockChainContextRequest, BlockChainContextResponse};
+use cuprate_p2p::{
+    block_downloader::{BlockBatch, BlockDownloaderConfig, ChainSvcRequest, ChainSvcResponse},
+    NetworkInterface,
+};
+use cuprate_p2p_core::ClearNet;
+
+const CHECK_SYNC_FREQUENCY: Duration = Duration::from_secs(30);
+
+/// An error returned from the [`syncer`].
+#[derive(Debug, thiserror::Error)]
+pub enum SyncerError {
+    #[error("Incoming block channel closed.")]
+    IncomingBlockChannelClosed,
+    #[error("One of our services returned an error: {0}.")]
+    ServiceError(#[from] tower::BoxError),
+}
+
+/// The syncer tasks that makes sure we are fully synchronised with our connected peers.
+#[expect(
+    clippy::significant_drop_tightening,
+    reason = "Client pool which will be removed"
+)]
+#[instrument(level = "debug", skip_all)]
+pub async fn syncer<C, CN>(
+    mut context_svc: C,
+    our_chain: CN,
+    clearnet_interface: NetworkInterface<ClearNet>,
+    incoming_block_batch_tx: mpsc::Sender<BlockBatch>,
+    stop_current_block_downloader: Arc<Notify>,
+    block_downloader_config: BlockDownloaderConfig,
+) -> Result<(), SyncerError>
+where
+    C: Service<
+        BlockChainContextRequest,
+        Response = BlockChainContextResponse,
+        Error = tower::BoxError,
+    >,
+    C::Future: Send + 'static,
+    CN: Service<ChainSvcRequest, Response = ChainSvcResponse, Error = tower::BoxError>
+        + Clone
+        + Send
+        + 'static,
+    CN::Future: Send + 'static,
+{
+    tracing::info!("Starting blockchain syncer");
+
+    let mut check_sync_interval = interval(CHECK_SYNC_FREQUENCY);
+
+    let BlockChainContextResponse::Context(mut blockchain_ctx) = context_svc
+        .ready()
+        .await?
+        .call(BlockChainContextRequest::GetContext)
+        .await?
+    else {
+        unreachable!();
+    };
+
+    let client_pool = clearnet_interface.client_pool();
+
+    tracing::debug!("Waiting for new sync info in top sync channel");
+
+    loop {
+        check_sync_interval.tick().await;
+
+        tracing::trace!("Checking connected peers to see if we are behind",);
+
+        check_update_blockchain_context(&mut context_svc, &mut blockchain_ctx).await?;
+        let raw_blockchain_context = blockchain_ctx.unchecked_blockchain_context();
+
+        if !client_pool.contains_client_with_more_cumulative_difficulty(
+            raw_blockchain_context.cumulative_difficulty,
+        ) {
+            continue;
+        }
+
+        tracing::debug!(
+            "We are behind peers claimed cumulative difficulty, starting block downloader"
+        );
+        let mut block_batch_stream =
+            clearnet_interface.block_downloader(our_chain.clone(), block_downloader_config);
+
+        loop {
+            tokio::select! {
+                () = stop_current_block_downloader.notified() => {
+                    tracing::info!("Stopping block downloader");
+                    break;
+                }
+                batch = block_batch_stream.next() => {
+                    let Some(batch) = batch else {
+                        break;
+                    };
+
+                    tracing::debug!("Got batch, len: {}", batch.blocks.len());
+                    if incoming_block_batch_tx.send(batch).await.is_err() {
+                        return Err(SyncerError::IncomingBlockChannelClosed);
+                    }
+                }
+            }
+        }
+    }
+}
+
+/// Checks if we should update the given [`BlockChainContext`] and updates it if needed.
+async fn check_update_blockchain_context<C>(
+    context_svc: C,
+    old_context: &mut BlockChainContext,
+) -> Result<(), tower::BoxError>
+where
+    C: Service<
+        BlockChainContextRequest,
+        Response = BlockChainContextResponse,
+        Error = tower::BoxError,
+    >,
+    C::Future: Send + 'static,
+{
+    if old_context.blockchain_context().is_ok() {
+        return Ok(());
+    }
+
+    let BlockChainContextResponse::Context(ctx) = context_svc
+        .oneshot(BlockChainContextRequest::GetContext)
+        .await?
+    else {
+        unreachable!();
+    };
+
+    *old_context = ctx;
+
+    Ok(())
+}

binaries/cuprated/src/blockchain/types.rs

@@ -0,0 +1,24 @@
+use std::task::{Context, Poll};
+
+use futures::future::BoxFuture;
+use futures::{FutureExt, TryFutureExt};
+use tower::{util::MapErr, Service};
+
+use cuprate_blockchain::{cuprate_database::RuntimeError, service::BlockchainReadHandle};
+use cuprate_consensus::{BlockChainContextService, BlockVerifierService, TxVerifierService};
+use cuprate_p2p::block_downloader::{ChainSvcRequest, ChainSvcResponse};
+use cuprate_types::blockchain::{BlockchainReadRequest, BlockchainResponse};
+
+/// The [`BlockVerifierService`] with all generic types defined.
+pub type ConcreteBlockVerifierService = BlockVerifierService<
+    BlockChainContextService,
+    ConcreteTxVerifierService,
+    ConsensusBlockchainReadHandle,
+>;
+
+/// The [`TxVerifierService`] with all generic types defined.
+pub type ConcreteTxVerifierService = TxVerifierService<ConsensusBlockchainReadHandle>;
+
+/// The [`BlockchainReadHandle`] with the [`tower::Service::Error`] mapped to conform to what the consensus crate requires.
+pub type ConsensusBlockchainReadHandle =
+    MapErr<BlockchainReadHandle, fn(RuntimeError) -> tower::BoxError>;

binaries/cuprated/src/constants.rs

@@ -14,6 +14,10 @@ pub const VERSION_BUILD: &str = if cfg!(debug_assertions) {
     formatcp!("{VERSION}-release")
 };
 
+/// The panic message used when cuprated encounters a critical service error.
+pub const PANIC_CRITICAL_SERVICE_ERROR: &str =
+    "A service critical to Cuprate's function returned an unexpected error.";
+
 #[cfg(test)]
 mod test {
     use super::*;

binaries/cuprated/src/main.rs

@@ -16,6 +16,7 @@ mod config;
 mod constants;
 mod p2p;
 mod rpc;
+mod signals;
 mod statics;
 mod txpool;
 

binaries/cuprated/src/p2p.rs

@@ -2,4 +2,4 @@
 //!
 //! Will handle initiating the P2P and contains a protocol request handler.
 
-mod request_handler;
+pub mod request_handler;

binaries/cuprated/src/signals.rs

@@ -0,0 +1,12 @@
+//! Signals for Cuprate state used throughout the binary.
+
+use tokio::sync::RwLock;
+
+/// Reorg lock.
+///
+/// A [`RwLock`] where a write lock is taken during a reorg and a read lock can be taken
+/// for any operation which must complete without a reorg happening.
+///
+/// Currently, the only operation that needs to take a read lock is adding txs to the tx-pool,
+/// this can potentially be removed in the future, see: <https://github.com/Cuprate/cuprate/issues/305>
+pub static REORG_LOCK: RwLock<()> = RwLock::const_new(());

consensus/src/block.rs

@@ -123,7 +123,7 @@ impl PreparedBlock {
     ///
     /// The randomX VM must be Some if RX is needed or this will panic.
     /// The randomX VM must also be initialised with the correct seed.
-    fn new<R: RandomX>(block: Block, randomx_vm: Option<&R>) -> Result<Self, ConsensusError> {
+    pub fn new<R: RandomX>(block: Block, randomx_vm: Option<&R>) -> Result<Self, ConsensusError> {
         let (hf_version, hf_vote) = HardFork::from_block_header(&block.header)
             .map_err(|_| BlockError::HardForkError(HardForkError::HardForkUnknown))?;
 
@@ -180,6 +180,20 @@ impl PreparedBlock {
             block: block.block,
         })
     }
+
+    /// Creates a new [`PreparedBlock`] from an [`AltBlockInformation`].
+    pub fn new_alt_block(block: AltBlockInformation) -> Result<Self, ConsensusError> {
+        Ok(Self {
+            block_blob: block.block_blob,
+            hf_vote: HardFork::from_version(block.block.header.hardfork_version)
+                .map_err(|_| BlockError::HardForkError(HardForkError::HardForkUnknown))?,
+            hf_version: HardFork::from_vote(block.block.header.hardfork_signal),
+            block_hash: block.block_hash,
+            pow_hash: block.pow_hash,
+            miner_tx_weight: block.block.miner_transaction.weight(),
+            block: block.block,
+        })
+    }
 }
 
 /// A request to verify a block.
@@ -246,7 +260,7 @@ where
         + Clone
         + Send
         + 'static,
-    D: Database + Clone + Send + Sync + 'static,
+    D: Database + Clone + Send + 'static,
     D::Future: Send + 'static,
 {
     /// Creates a new block verifier.
@@ -276,7 +290,7 @@ where
         + 'static,
     TxV::Future: Send + 'static,
 
-    D: Database + Clone + Send + Sync + 'static,
+    D: Database + Clone + Send + 'static,
     D::Future: Send + 'static,
 {
     type Response = VerifyBlockResponse;

consensus/src/lib.rs

@@ -37,6 +37,7 @@ pub use context::{
 pub use transactions::{TxVerifierService, VerifyTxRequest, VerifyTxResponse};
 
 // re-export.
+pub use cuprate_consensus_rules::genesis::generate_genesis_block;
 pub use cuprate_types::{
     blockchain::{BlockchainReadRequest, BlockchainResponse},
     HardFork,
@@ -64,17 +65,13 @@ pub enum ExtendedConsensusError {
 }
 
 /// Initialize the 2 verifier [`tower::Service`]s (block and transaction).
-#[expect(clippy::type_complexity)]
 pub fn initialize_verifier<D, Ctx>(
     database: D,
     ctx_svc: Ctx,
-) -> Result<
-    (
-        BlockVerifierService<Ctx, TxVerifierService<D>, D>,
-        TxVerifierService<D>,
-    ),
-    ConsensusError,
->
+) -> (
+    BlockVerifierService<Ctx, TxVerifierService<D>, D>,
+    TxVerifierService<D>,
+)
 where
     D: Database + Clone + Send + Sync + 'static,
     D::Future: Send + 'static,
@@ -90,7 +87,7 @@ where
 {
     let tx_svc = TxVerifierService::new(database.clone());
     let block_svc = BlockVerifierService::new(ctx_svc, tx_svc.clone(), database);
-    Ok((block_svc, tx_svc))
+    (block_svc, tx_svc)
 }
 
 use __private::Database;

p2p/p2p-core/src/lib.rs

@@ -89,6 +89,7 @@ pub use protocol::*;
 use services::*;
 //re-export
 pub use cuprate_helper::network::Network;
+pub use cuprate_wire::CoreSyncData;
 
 /// The direction of a connection.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]

p2p/p2p/src/block_downloader.rs

@@ -1,6 +1,6 @@
 //! # Block Downloader
 //!
-//! This module contains the [`BlockDownloader`], which finds a chain to
+//! This module contains the block downloader, which finds a chain to
 //! download from our connected peers and downloads it. See the actual
 //! `struct` documentation for implementation details.
 //!

p2p/p2p/src/client_pool.rs

@@ -153,6 +153,18 @@ impl<N: NetworkZone> ClientPool<N> {
 
         self.borrow_clients(&peers).collect()
     }
+
+    /// Checks all clients in the pool checking if any claim a higher cumulative difficulty than the
+    /// amount specified.
+    pub fn contains_client_with_more_cumulative_difficulty(
+        &self,
+        cumulative_difficulty: u128,
+    ) -> bool {
+        self.clients.iter().any(|element| {
+            let sync_data = element.value().info.core_sync_data.lock().unwrap();
+            sync_data.cumulative_difficulty() > cumulative_difficulty
+        })
+    }
 }
 
 mod sealed {

p2p/p2p/src/config.rs

@@ -1,8 +1,9 @@
-use cuprate_address_book::AddressBookConfig;
 use cuprate_helper::network::Network;
 use cuprate_p2p_core::NetworkZone;
 use cuprate_wire::{common::PeerSupportFlags, BasicNodeData};
 
+pub use cuprate_address_book::AddressBookConfig;
+
 /// P2P config.
 #[derive(Clone, Debug)]
 pub struct P2PConfig<N: NetworkZone> {

p2p/p2p/src/constants.rs

@@ -16,14 +16,13 @@ pub(crate) const MAX_SEED_CONNECTIONS: usize = 3;
 pub(crate) const OUTBOUND_CONNECTION_ATTEMPT_TIMEOUT: Duration = Duration::from_secs(5);
 
 /// The durations of a short ban.
-#[cfg_attr(not(test), expect(dead_code))]
-pub(crate) const SHORT_BAN: Duration = Duration::from_secs(60 * 10);
+pub const SHORT_BAN: Duration = Duration::from_secs(60 * 10);
 
 /// The durations of a medium ban.
-pub(crate) const MEDIUM_BAN: Duration = Duration::from_secs(60 * 60 * 24);
+pub const MEDIUM_BAN: Duration = Duration::from_secs(60 * 60 * 24);
 
 /// The durations of a long ban.
-pub(crate) const LONG_BAN: Duration = Duration::from_secs(60 * 60 * 24 * 7);
+pub const LONG_BAN: Duration = Duration::from_secs(60 * 60 * 24 * 7);
 
 /// The default amount of time between inbound diffusion flushes.
 pub(crate) const DIFFUSION_FLUSH_AVERAGE_SECONDS_INBOUND: Duration = Duration::from_secs(5);

p2p/p2p/src/lib.rs

@@ -12,23 +12,21 @@ use tracing::{instrument, Instrument, Span};
 use cuprate_async_buffer::BufferStream;
 use cuprate_p2p_core::{
     client::Connector,
-    client::InternalPeerID,
     services::{AddressBookRequest, AddressBookResponse},
     CoreSyncSvc, NetworkZone, ProtocolRequestHandlerMaker,
 };
 
-mod block_downloader;
+pub mod block_downloader;
 mod broadcast;
 mod client_pool;
 pub mod config;
 pub mod connection_maintainer;
-mod constants;
+pub mod constants;
 mod inbound_server;
 
 use block_downloader::{BlockBatch, BlockDownloaderConfig, ChainSvcRequest, ChainSvcResponse};
 pub use broadcast::{BroadcastRequest, BroadcastSvc};
-use client_pool::ClientPoolDropGuard;
-pub use config::P2PConfig;
+pub use config::{AddressBookConfig, P2PConfig};
 use connection_maintainer::MakeConnectionRequest;
 
 /// Initializes the P2P [`NetworkInterface`] for a specific [`NetworkZone`].
@@ -174,9 +172,8 @@ impl<N: NetworkZone> NetworkInterface<N> {
         self.address_book.clone()
     }
 
-    /// Pulls a client from the client pool, returning it in a guard that will return it there when it's
-    /// dropped.
-    pub fn borrow_client(&self, peer: &InternalPeerID<N::Addr>) -> Option<ClientPoolDropGuard<N>> {
-        self.pool.borrow_client(peer)
+    /// Borrows the `ClientPool`, for access to connected peers.
+    pub const fn client_pool(&self) -> &Arc<client_pool::ClientPool<N>> {
+        &self.pool
     }
 }