424 lines
17 KiB
Rust
424 lines
17 KiB
Rust
//! The inbound service handles requests from Zebra's peers.
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//!
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//! It downloads and verifies gossiped blocks and mempool transactions,
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//! when Zebra is close to the chain tip.
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//!
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//! It also responds to peer requests for blocks, transactions, and peer addresses.
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use std::{
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future::Future,
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pin::Pin,
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sync::Arc,
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task::{Context, Poll},
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};
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use chrono::Utc;
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use futures::{
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future::{FutureExt, TryFutureExt},
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stream::Stream,
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};
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use tokio::sync::oneshot::{self, error::TryRecvError};
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use tower::{buffer::Buffer, timeout::Timeout, util::BoxService, Service, ServiceExt};
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use zebra_network as zn;
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use zebra_state as zs;
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use zebra_chain::block::{self, Block};
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use zebra_consensus::chain::VerifyChainError;
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use zebra_network::{constants::MAX_ADDRS_IN_MESSAGE, AddressBook};
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// Re-use the syncer timeouts for consistency.
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use super::{
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mempool, mempool as mp,
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sync::{BLOCK_DOWNLOAD_TIMEOUT, BLOCK_VERIFY_TIMEOUT},
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};
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mod downloads;
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#[cfg(test)]
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mod tests;
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use downloads::Downloads as BlockDownloads;
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/// A security parameter to return only 1/3 of available addresses as a
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/// response to a `Peers` request.
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const FRAC_OF_AVAILABLE_ADDRESS: f64 = 1. / 3.;
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type BlockDownloadPeerSet =
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Buffer<BoxService<zn::Request, zn::Response, zn::BoxError>, zn::Request>;
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type State = Buffer<BoxService<zs::Request, zs::Response, zs::BoxError>, zs::Request>;
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type Mempool = Buffer<BoxService<mp::Request, mp::Response, mp::BoxError>, mp::Request>;
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type BlockVerifier = Buffer<BoxService<Arc<Block>, block::Hash, VerifyChainError>, Arc<Block>>;
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type GossipedBlockDownloads =
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BlockDownloads<Timeout<BlockDownloadPeerSet>, Timeout<BlockVerifier>, State>;
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/// The services used by the [`Inbound`] service.
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pub struct InboundSetupData {
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/// A shared list of peer addresses.
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pub address_book: Arc<std::sync::Mutex<AddressBook>>,
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/// A service that can be used to download gossiped blocks.
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pub block_download_peer_set: BlockDownloadPeerSet,
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/// A service that verifies downloaded blocks.
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///
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/// Given to `Inbound.block_downloads` after the required services are set up.
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pub block_verifier: BlockVerifier,
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/// A service that manages transactions in the memory pool.
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pub mempool: Mempool,
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/// A service that manages cached blockchain state.
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pub state: State,
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}
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/// Tracks the internal state of the [`Inbound`] service during setup.
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pub enum Setup {
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/// Waiting for service setup to complete.
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///
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/// All requests are ignored.
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Pending {
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/// A oneshot channel used to receive required services,
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/// after they are set up.
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setup: oneshot::Receiver<InboundSetupData>,
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},
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/// Setup is complete.
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///
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/// All requests are answered.
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Initialized {
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/// A shared list of peer addresses.
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address_book: Arc<std::sync::Mutex<zn::AddressBook>>,
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/// A `futures::Stream` that downloads and verifies gossiped blocks.
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block_downloads: Pin<Box<GossipedBlockDownloads>>,
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/// A service that manages transactions in the memory pool.
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mempool: Mempool,
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/// A service that manages cached blockchain state.
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state: State,
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},
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/// Temporary state used in the inbound service's internal initialization code.
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///
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/// If this state occurs outside the service initialization code, the service panics.
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FailedInit,
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/// Setup failed, because the setup channel permanently failed.
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/// The service keeps returning readiness errors for every request.
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FailedRecv {
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/// The original channel error.
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error: SharedRecvError,
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},
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}
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/// A wrapper around `Arc<TryRecvError>` that implements `Error`.
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#[derive(thiserror::Error, Debug, Clone)]
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#[error(transparent)]
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pub struct SharedRecvError(Arc<TryRecvError>);
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impl From<TryRecvError> for SharedRecvError {
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fn from(source: TryRecvError) -> Self {
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Self(Arc::new(source))
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}
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}
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/// Uses the node state to respond to inbound peer requests.
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///
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/// This service, wrapped in appropriate middleware, is passed to
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/// `zebra_network::init` to respond to inbound peer requests.
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///
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/// The `Inbound` service is responsible for:
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///
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/// - supplying network data like peer addresses to other nodes;
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/// - supplying chain data like blocks to other nodes;
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/// - supplying mempool transactions to other nodes;
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/// - receiving gossiped transactions; and
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/// - receiving gossiped blocks.
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///
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/// Because the `Inbound` service is responsible for participating in the gossip
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/// protocols used for transaction and block diffusion, there is a potential
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/// overlap with the `ChainSync` and `Mempool` components.
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///
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/// The division of responsibility is that:
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///
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/// The `ChainSync` and `Mempool` components are *internally driven*,
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/// periodically polling the network to check for new blocks or transactions.
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///
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/// The `Inbound` service is *externally driven*, responding to block gossip
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/// by attempting to download and validate advertised blocks.
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///
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/// Gossiped transactions are forwarded to the mempool downloader,
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/// which unifies polled and gossiped transactions into a single download list.
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pub struct Inbound {
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/// Provides service dependencies, if they are available.
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///
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/// Some services are unavailable until Zebra has completed setup.
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setup: Setup,
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}
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impl Inbound {
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/// Create a new inbound service.
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///
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/// Dependent services are sent via the `setup` channel after initialization.
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pub fn new(setup: oneshot::Receiver<InboundSetupData>) -> Inbound {
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Inbound {
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setup: Setup::Pending { setup },
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}
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}
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/// Remove `self.setup`, temporarily replacing it with an invalid state.
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fn take_setup(&mut self) -> Setup {
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let mut setup = Setup::FailedInit;
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std::mem::swap(&mut self.setup, &mut setup);
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setup
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}
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}
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impl Service<zn::Request> for Inbound {
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type Response = zn::Response;
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type Error = zn::BoxError;
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type Future =
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Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send + 'static>>;
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fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
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// Check whether the setup is finished, but don't wait for it to
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// become ready before reporting readiness. We expect to get it "soon",
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// and reporting unreadiness might cause unwanted load-shedding, since
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// the load-shed middleware is unable to distinguish being unready due
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// to load from being unready while waiting on setup.
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// Every setup variant handler must provide a result
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let result;
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self.setup = match self.take_setup() {
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Setup::Pending { mut setup } => match setup.try_recv() {
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Ok(setup_data) => {
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let InboundSetupData {
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address_book,
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block_download_peer_set,
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block_verifier,
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mempool,
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state,
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} = setup_data;
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let block_downloads = Box::pin(BlockDownloads::new(
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Timeout::new(block_download_peer_set.clone(), BLOCK_DOWNLOAD_TIMEOUT),
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Timeout::new(block_verifier, BLOCK_VERIFY_TIMEOUT),
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state.clone(),
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));
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result = Ok(());
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Setup::Initialized {
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address_book,
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block_downloads,
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mempool,
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state,
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}
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}
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Err(TryRecvError::Empty) => {
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// There's no setup data yet, so keep waiting for it
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result = Ok(());
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Setup::Pending { setup }
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}
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Err(error @ TryRecvError::Closed) => {
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// Mark the service as failed, because setup failed
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error!(?error, "inbound setup failed");
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let error: SharedRecvError = error.into();
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result = Err(error.clone().into());
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Setup::FailedRecv { error }
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}
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},
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// Make sure previous setups were left in a valid state
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Setup::FailedInit => unreachable!("incomplete previous Inbound initialization"),
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// If setup failed, report service failure
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Setup::FailedRecv { error } => {
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result = Err(error.clone().into());
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Setup::FailedRecv { error }
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}
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// Clean up completed download tasks, ignoring their results
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Setup::Initialized {
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address_book,
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mut block_downloads,
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mempool,
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state,
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} => {
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while let Poll::Ready(Some(_)) = block_downloads.as_mut().poll_next(cx) {}
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result = Ok(());
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Setup::Initialized {
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address_book,
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block_downloads,
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mempool,
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state,
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}
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}
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};
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// Make sure we're leaving the setup in a valid state
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if matches!(self.setup, Setup::FailedInit) {
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unreachable!("incomplete Inbound initialization after poll_ready state handling");
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}
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// TODO:
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// * do we want to propagate backpressure from the download queue or its outbound network?
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// currently, the download queue waits for the outbound network in the download future,
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// and drops new requests after it reaches a hard-coded limit. This is the
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// "load shed directly" pattern from #1618.
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// * currently, the state service is always ready, unless its buffer is full.
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// So we might also want to propagate backpressure from its buffer.
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// * poll_ready needs to be implemented carefully, to avoid hangs or deadlocks.
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// See #1593 for details.
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Poll::Ready(result)
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}
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/// Call the inbound service.
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///
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/// Errors indicate that the peer has done something wrong or unexpected,
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/// and will cause callers to disconnect from the remote peer.
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#[instrument(name = "inbound", skip(self, req))]
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fn call(&mut self, req: zn::Request) -> Self::Future {
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let (address_book, block_downloads, mempool, state) = match &mut self.setup {
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Setup::Initialized {
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address_book,
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block_downloads,
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mempool,
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state,
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} => (address_book, block_downloads, mempool, state),
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_ => {
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debug!("ignoring request from remote peer during setup");
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return async { Ok(zn::Response::Nil) }.boxed();
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}
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};
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match req {
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zn::Request::Peers => {
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// # Security
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//
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// We truncate the list to not reveal our entire peer set in one call.
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// But we don't monitor repeated requests and the results are shuffled,
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// a crawler could just send repeated queries and get the full list.
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//
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// # Correctness
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//
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// Briefly hold the address book threaded mutex while
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// cloning the address book. Then sanitize after releasing
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// the lock.
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let peers = address_book.lock().unwrap().clone();
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// Correctness: get the current time after acquiring the address book lock.
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let now = Utc::now();
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// Send a sanitized response
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let mut peers = peers.sanitized(now);
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// Truncate the list
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let truncate_at = MAX_ADDRS_IN_MESSAGE
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.min((peers.len() as f64 * FRAC_OF_AVAILABLE_ADDRESS).ceil() as usize);
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peers.truncate(truncate_at);
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if !peers.is_empty() {
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async { Ok(zn::Response::Peers(peers)) }.boxed()
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} else {
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info!("ignoring `Peers` request from remote peer because our address book is empty");
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async { Ok(zn::Response::Nil) }.boxed()
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}
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}
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zn::Request::BlocksByHash(hashes) => {
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// Correctness:
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//
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// We can't use `call_all` here, because it can hold one buffer slot per concurrent
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// future, until the `CallAll` struct is dropped. We can't hold those slots in this
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// future because:
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// * we're not sure when the returned future will complete, and
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// * we don't limit how many returned futures can be concurrently running
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// https://github.com/tower-rs/tower/blob/master/tower/src/util/call_all/common.rs#L112
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use futures::stream::TryStreamExt;
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hashes
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.into_iter()
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.map(|hash| zs::Request::Block(hash.into()))
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.map(|request| state.clone().oneshot(request))
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.collect::<futures::stream::FuturesOrdered<_>>()
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.try_filter_map(|response| async move {
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Ok(match response {
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zs::Response::Block(Some(block)) => Some(block),
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// `zcashd` ignores missing blocks in GetData responses,
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// rather than including them in a trailing `NotFound`
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// message
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zs::Response::Block(None) => None,
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_ => unreachable!("wrong response from state"),
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})
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})
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.try_collect::<Vec<_>>()
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.map_ok(|blocks| {
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if blocks.is_empty() {
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zn::Response::Nil
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} else {
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zn::Response::Blocks(blocks)
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}
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})
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.boxed()
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}
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zn::Request::TransactionsById(transactions) => {
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let request = mempool::Request::TransactionsById(transactions);
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mempool.clone().oneshot(request).map_ok(|resp| match resp {
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mempool::Response::Transactions(transactions) if transactions.is_empty() => zn::Response::Nil,
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mempool::Response::Transactions(transactions) => zn::Response::Transactions(transactions),
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_ => unreachable!("Mempool component should always respond to a `TransactionsById` request with a `Transactions` response"),
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})
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.boxed()
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}
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zn::Request::FindBlocks { known_blocks, stop } => {
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let request = zs::Request::FindBlockHashes { known_blocks, stop };
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state.clone().oneshot(request).map_ok(|resp| match resp {
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zs::Response::BlockHashes(hashes) if hashes.is_empty() => zn::Response::Nil,
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zs::Response::BlockHashes(hashes) => zn::Response::BlockHashes(hashes),
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_ => unreachable!("zebra-state should always respond to a `FindBlockHashes` request with a `BlockHashes` response"),
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})
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.boxed()
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}
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zn::Request::FindHeaders { known_blocks, stop } => {
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let request = zs::Request::FindBlockHeaders { known_blocks, stop };
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state.clone().oneshot(request).map_ok(|resp| match resp {
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zs::Response::BlockHeaders(headers) if headers.is_empty() => zn::Response::Nil,
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zs::Response::BlockHeaders(headers) => zn::Response::BlockHeaders(headers),
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_ => unreachable!("zebra-state should always respond to a `FindBlockHeaders` request with a `BlockHeaders` response"),
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})
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.boxed()
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}
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zn::Request::PushTransaction(transaction) => {
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mempool
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.clone()
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.oneshot(mempool::Request::Queue(vec![transaction.into()]))
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// The response just indicates if processing was queued or not; ignore it
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.map_ok(|_resp| zn::Response::Nil)
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.boxed()
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}
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zn::Request::AdvertiseTransactionIds(transactions) => {
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let transactions = transactions.into_iter().map(Into::into).collect();
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mempool
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.clone()
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.oneshot(mempool::Request::Queue(transactions))
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// The response just indicates if processing was queued or not; ignore it
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.map_ok(|_resp| zn::Response::Nil)
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.boxed()
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}
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zn::Request::AdvertiseBlock(hash) => {
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block_downloads.download_and_verify(hash);
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async { Ok(zn::Response::Nil) }.boxed()
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}
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zn::Request::MempoolTransactionIds => {
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mempool.clone().oneshot(mempool::Request::TransactionIds).map_ok(|resp| match resp {
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mempool::Response::TransactionIds(transaction_ids) if transaction_ids.is_empty() => zn::Response::Nil,
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mempool::Response::TransactionIds(transaction_ids) => zn::Response::TransactionIds(transaction_ids.into_iter().collect()),
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_ => unreachable!("Mempool component should always respond to a `TransactionIds` request with a `TransactionIds` response"),
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})
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.boxed()
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}
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zn::Request::Ping(_) => {
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unreachable!("ping requests are handled internally");
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}
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}
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}
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}
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