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// Copyright 2023 litep2p developers
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//! Notification protocol implementation.
use crate::{
error::Error,
executor::Executor,
protocol::{
self,
notification::{
connection::Connection,
handle::NotificationEventHandle,
negotiation::{HandshakeEvent, HandshakeService},
types::NotificationCommand,
},
TransportEvent, TransportService,
},
substream::Substream,
types::{protocol::ProtocolName, SubstreamId},
PeerId, DEFAULT_CHANNEL_SIZE,
};
use bytes::BytesMut;
use futures::{future::BoxFuture, stream::FuturesUnordered, StreamExt};
use multiaddr::Multiaddr;
use tokio::sync::{
mpsc::{channel, Receiver, Sender},
oneshot,
};
use std::{collections::HashMap, sync::Arc, time::Duration};
pub use config::{Config, ConfigBuilder};
pub use handle::{NotificationHandle, NotificationSink};
pub use types::{Direction, NotificationError, NotificationEvent, ValidationResult};
mod config;
mod connection;
mod handle;
mod negotiation;
mod types;
#[cfg(test)]
mod tests;
/// Logging target for the file.
const LOG_TARGET: &str = "litep2p::notification";
/// Connection state.
///
/// Used to track transport level connectivity state when there is a pending validation.
/// See [`PeerState::PendingValidation.`] for more details.
#[derive(Debug, PartialEq, Eq)]
enum ConnectionState {
/// There is a active, transport-level connection open to the peer.
Open,
/// There is no transport-level connection open to the peer.
Closed,
}
/// Inbound substream state.
#[derive(Debug)]
enum InboundState {
/// Substream is closed.
Closed,
/// Handshake is being read from the remote node.
ReadingHandshake,
/// Substream and its handshake are being validated by the user protocol.
Validating {
/// Inbound substream.
inbound: Substream,
},
/// Handshake is being sent to the remote node.
SendingHandshake,
/// Substream is open.
Open {
/// Inbound substream.
inbound: Substream,
},
}
/// Outbound substream state.
#[derive(Debug)]
enum OutboundState {
/// Substream is closed.
Closed,
/// Outbound substream initiated.
OutboundInitiated {
/// Substream ID.
substream: SubstreamId,
},
/// Substream is in the state of being negotiated.
///
/// This process entails sending local node's handshake and reading back the remote node's
/// handshake if they've accepted the substream or detecting that the substream was closed
/// in case the substream was rejected.
Negotiating,
/// Substream is open.
Open {
/// Received handshake.
handshake: Vec<u8>,
/// Outbound substream.
outbound: Substream,
},
}
impl OutboundState {
/// Get pending outboud substream ID, if it exists.
fn pending_open(&self) -> Option<SubstreamId> {
match &self {
OutboundState::OutboundInitiated { substream } => Some(*substream),
_ => None,
}
}
}
#[derive(Debug)]
enum PeerState {
/// Peer state is poisoned due to invalid state transition.
Poisoned,
/// Validation for an inbound substream is still pending.
///
/// In order to enforce valid state transitions, `NotificationProtocol` keeps track of pending
/// validations across connectivity events (open/closed) and enforces that no activity happens
/// for any peer that is still awaiting validation for their inbound substream.
///
/// If connection closes while the substream is being validated, instead of removing peer from
/// `peers`, the peer state is set as `ValidationPending` which indicates to the state machine
/// that a response for a inbound substream is pending validation. The substream itself will be
/// dead by the time validation is received if the peer state is `ValidationPending` since the
/// substream was part of a previous, now-closed substream but this state allows
/// `NotificationProtocol` to enforce correct state transitions by, e.g., rejecting new inbound
/// substream while a previous substream is still being validated or rejecting outbound
/// substreams on new connections if that same condition holds.
ValidationPending {
/// What is current connectivity state of the peer.
///
/// If `state` is `ConnectionState::Closed` when the validation is finally received, peer
/// is removed from `peer` and if the `state` is `ConnectionState::Open`, peer is moved to
/// state `PeerState::Closed` and user is allowed to retry opening an outbound substream.
state: ConnectionState,
},
/// Connection to peer is closed.
Closed {
/// Connection might have been closed while there was an outbound substream still pending.
///
/// To handle this state transition correctly in case the substream opens after the
/// connection is considered closed, store the `SubstreamId` to that it can be verified in
/// case the substream ever opens.
pending_open: Option<SubstreamId>,
},
/// Peer is being dialed in order to open an outbound substream to them.
Dialing,
/// Outbound substream initiated.
OutboundInitiated {
/// Substream ID.
substream: SubstreamId,
},
/// Substream is being validated.
Validating {
/// Protocol.
protocol: ProtocolName,
/// Fallback protocol, if the substream was negotiated using a fallback name.
fallback: Option<ProtocolName>,
/// Outbound protocol state.
outbound: OutboundState,
/// Inbound protocol state.
inbound: InboundState,
/// Direction.
direction: Direction,
},
/// Notification stream has been opened.
Open {
/// `Oneshot::Sender` for shutting down the connection.
shutdown: oneshot::Sender<()>,
},
}
/// Peer context.
#[derive(Debug)]
struct PeerContext {
/// Peer state.
state: PeerState,
}
impl PeerContext {
/// Create new [`PeerContext`].
fn new() -> Self {
Self {
state: PeerState::Closed { pending_open: None },
}
}
}
pub(crate) struct NotificationProtocol {
/// Transport service.
service: TransportService,
/// Protocol.
protocol: ProtocolName,
/// Auto accept inbound substream if the outbound substream was initiated by the local node.
auto_accept: bool,
/// TX channel passed to the protocol used for sending events.
event_handle: NotificationEventHandle,
/// TX channel for sending shut down notifications from connection handlers to
/// [`NotificationProtocol`].
shutdown_tx: Sender<PeerId>,
/// RX channel for receiving shutdown notifications from the connection handlers.
shutdown_rx: Receiver<PeerId>,
/// RX channel passed to the protocol used for receiving commands.
command_rx: Receiver<NotificationCommand>,
/// TX channel given to connection handlers for sending notifications.
notif_tx: Sender<(PeerId, BytesMut)>,
/// Connected peers.
peers: HashMap<PeerId, PeerContext>,
/// Pending outboudn substreams.
pending_outbound: HashMap<SubstreamId, PeerId>,
/// Handshaking service which reads and writes the handshakes to inbound
/// and outbound substreams asynchronously.
negotiation: HandshakeService,
/// Synchronous channel size.
sync_channel_size: usize,
/// Asynchronous channel size.
async_channel_size: usize,
/// Executor for connection handlers.
executor: Arc<dyn Executor>,
/// Pending substream validations.
pending_validations: FuturesUnordered<BoxFuture<'static, (PeerId, ValidationResult)>>,
/// Timers for pending outbound substreams.
timers: FuturesUnordered<BoxFuture<'static, PeerId>>,
/// Should `NotificationProtocol` attempt to dial the peer.
should_dial: bool,
}
impl NotificationProtocol {
pub(crate) fn new(
service: TransportService,
config: Config,
executor: Arc<dyn Executor>,
) -> Self {
let (shutdown_tx, shutdown_rx) = channel(DEFAULT_CHANNEL_SIZE);
Self {
service,
shutdown_tx,
shutdown_rx,
executor,
peers: HashMap::new(),
protocol: config.protocol_name,
auto_accept: config.auto_accept,
pending_validations: FuturesUnordered::new(),
timers: FuturesUnordered::new(),
event_handle: NotificationEventHandle::new(config.event_tx),
notif_tx: config.notif_tx,
command_rx: config.command_rx,
pending_outbound: HashMap::new(),
negotiation: HandshakeService::new(config.handshake),
sync_channel_size: config.sync_channel_size,
async_channel_size: config.async_channel_size,
should_dial: config.should_dial,
}
}
/// Connection established to remote node.
///
/// If the peer already exists, the only valid state for it is `Dialing` as it indicates that
/// the user tried to open a substream to a peer who was not connected to local node.
///
/// Any other state indicates that there's an error in the state transition logic.
async fn on_connection_established(&mut self, peer: PeerId) -> crate::Result<()> {
tracing::trace!(target: LOG_TARGET, ?peer, protocol = %self.protocol, "connection established");
let Some(context) = self.peers.get_mut(&peer) else {
self.peers.insert(peer, PeerContext::new());
return Ok(());
};
match std::mem::replace(&mut context.state, PeerState::Poisoned) {
PeerState::Dialing => {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"dial succeeded, open substream to peer",
);
context.state = PeerState::Closed { pending_open: None };
self.on_open_substream(peer).await
}
// connection established but validation is still pending
//
// update the connection state so that `NotificationProtocol` can proceed
// to correct state after the validation result has beern received
PeerState::ValidationPending { state } => {
debug_assert_eq!(state, ConnectionState::Closed);
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"new connection established while validation still pending",
);
context.state = PeerState::ValidationPending {
state: ConnectionState::Open,
};
Ok(())
}
state => {
tracing::error!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?state,
"state mismatch: peer already exists",
);
debug_assert!(false);
Err(Error::PeerAlreadyExists(peer))
}
}
}
/// Connection closed to remote node.
///
/// If the connection was considered open (both substreams were open), user is notified that
/// the notification stream was closed.
///
/// If the connection was still in progress (either substream was not fully open), the user is
/// reported about it only if they had opened an outbound substream (outbound is either fully
/// open, it had been initiated or the substream was under negotiation).
async fn on_connection_closed(&mut self, peer: PeerId) -> crate::Result<()> {
tracing::trace!(target: LOG_TARGET, ?peer, protocol = %self.protocol, "connection closed");
let Some(context) = self.peers.remove(&peer) else {
tracing::error!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"state mismatch: peer doesn't exist",
);
debug_assert!(false);
return Err(Error::PeerDoesntExist(peer));
};
// clean up all pending state for the peer
self.negotiation.remove_outbound(&peer);
self.negotiation.remove_inbound(&peer);
match context.state {
// outbound initiated, report open failure to peer
PeerState::OutboundInitiated { .. } => {
self.event_handle
.report_notification_stream_open_failure(peer, NotificationError::Rejected)
.await;
}
// substream fully open, report that the notification stream is closed
PeerState::Open { shutdown } => {
let _ = shutdown.send(());
}
// if the substream was being validated, user must be notified that the substream is
// now considered rejected if they had been made aware of the existence of the pending
// connection
PeerState::Validating {
outbound, inbound, ..
} => {
match (outbound, inbound) {
// substream was being validated by the protocol when the connection was closed
(OutboundState::Closed, InboundState::Validating { .. }) => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"connection closed while validation pending",
);
self.peers.insert(
peer,
PeerContext {
state: PeerState::ValidationPending {
state: ConnectionState::Closed,
},
},
);
}
// user either initiated an outbound substream or an outbound substream was
// opened/being opened as a result of an accepted inbound substream but was not
// yet fully open
//
// to have consistent state tracking in the user protocol, substream rejection
// must be reported to the user
(
OutboundState::OutboundInitiated { .. }
| OutboundState::Negotiating
| OutboundState::Open { .. },
_,
) => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"connection closed outbound substream under negotiation",
);
self.event_handle
.report_notification_stream_open_failure(
peer,
NotificationError::Rejected,
)
.await;
}
(_, _) => {}
}
}
// pending validations must be tracked across connection open/close events
PeerState::ValidationPending { .. } => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"validation pending while connection closed",
);
self.peers.insert(
peer,
PeerContext {
state: PeerState::ValidationPending {
state: ConnectionState::Closed,
},
},
);
}
_ => {}
}
Ok(())
}
/// Local node opened a substream to remote node.
///
/// The connection can be in three different states:
/// - this is the first substream that was opened and thus the connection was initiated by the
/// local node
/// - this is a response to a previously received inbound substream which the local node
/// accepted and as a result, opened its own substream
/// - local and remote nodes opened substreams at the same time
///
/// In the first case, the local node's handshake is sent to remote node and the substream is
/// polled in the background until they either send their handshake or close the substream.
///
/// For the second case, the connection was initiated by the remote node and the substream was
/// accepted by the local node which initiated an outbound substream to the remote node.
/// The only valid states for this case are [`InboundState::Open`],
/// and [`InboundState::SendingHandshake`] as they imply
/// that the inbound substream have been accepted by the local node and this opened outbound
/// substream is a result of a valid state transition.
///
/// For the third case, if the nodes have opened substreams at the same time, the outbound state
/// must be [`OutboundState::OutboundInitiated`] to ascertain that the an outbound substream was
/// actually opened. Any other state would be a state mismatch and would mean that the
/// connection is opening substreams without the permission of the protocol handler.
async fn on_outbound_substream(
&mut self,
protocol: ProtocolName,
fallback: Option<ProtocolName>,
peer: PeerId,
substream_id: SubstreamId,
outbound: Substream,
) -> crate::Result<()> {
tracing::debug!(
target: LOG_TARGET,
?peer,
?protocol,
?substream_id,
"handle outbound substream",
);
// peer must exist since an outbound substream was received from them
let context = self.peers.get_mut(&peer).expect("peer to exist");
let pending_peer = self.pending_outbound.remove(&substream_id);
match std::mem::replace(&mut context.state, PeerState::Poisoned) {
// the connection was initiated by the local node, send handshake to remote and wait to
// receive their handshake back
PeerState::OutboundInitiated { substream } => {
debug_assert!(substream == substream_id);
debug_assert!(pending_peer == Some(peer));
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?fallback,
?substream_id,
"negotiate outbound protocol",
);
self.negotiation.negotiate_outbound(peer, outbound);
context.state = PeerState::Validating {
protocol,
fallback,
inbound: InboundState::Closed,
outbound: OutboundState::Negotiating,
direction: Direction::Outbound,
};
}
PeerState::Validating {
protocol,
fallback,
inbound,
direction,
outbound: outbound_state,
} => {
// the inbound substream has been accepted by the local node since the handshake has
// been read and the local handshake has either already been sent or
// it's in the process of being sent.
match inbound {
InboundState::SendingHandshake | InboundState::Open { .. } => {
context.state = PeerState::Validating {
protocol,
fallback,
inbound,
direction,
outbound: OutboundState::Negotiating,
};
self.negotiation.negotiate_outbound(peer, outbound);
}
// nodes have opened substreams at the same time
inbound_state => match outbound_state {
OutboundState::OutboundInitiated { substream } => {
debug_assert!(substream == substream_id);
context.state = PeerState::Validating {
protocol,
fallback,
direction,
inbound: inbound_state,
outbound: OutboundState::Negotiating,
};
self.negotiation.negotiate_outbound(peer, outbound);
}
// invalid state: more than one outbound substream has been opened
inner_state => {
tracing::error!(
target: LOG_TARGET,
?peer,
%protocol,
?substream_id,
?inbound_state,
?inner_state,
"invalid state, expected `OutboundInitiated`",
);
let _ = outbound.close().await;
debug_assert!(false);
}
},
}
}
// the connection may have been closed while an outbound substream was pending
// if the outbound substream was initiated successfully, close it and reset
// `pending_open`
PeerState::Closed { pending_open } if pending_open == Some(substream_id) => {
let _ = outbound.close().await;
context.state = PeerState::Closed { pending_open: None };
}
state => {
tracing::error!(
target: LOG_TARGET,
?peer,
%protocol,
?substream_id,
?state,
"invalid state: more than one outbound substream opened",
);
let _ = outbound.close().await;
debug_assert!(false);
}
}
Ok(())
}
/// Remote opened a substream to local node.
///
/// The peer can be in four different states for the inbound substream to be considered valid:
/// - the connection is closed
/// - conneection is open but substream validation from a previous connection is still pending
/// - outbound substream has been opened but not yet acknowledged by the remote peer
/// - outbound substream has been opened and acknowledged by the remote peer and it's being
/// negotiated
///
/// If remote opened more than one substream, the new substream is simply discarded.
async fn on_inbound_substream(
&mut self,
protocol: ProtocolName,
fallback: Option<ProtocolName>,
peer: PeerId,
substream: Substream,
) -> crate::Result<()> {
// peer must exist since an inbound substream was received from them
let context = self.peers.get_mut(&peer).expect("peer to exist");
tracing::debug!(
target: LOG_TARGET,
?peer,
%protocol,
?fallback,
state = ?context.state,
"handle inbound substream",
);
match std::mem::replace(&mut context.state, PeerState::Poisoned) {
// inbound substream of a previous connection is still pending validation,
// reject any new inbound substreams until an answer is heard from the user
state @ PeerState::ValidationPending { .. } => {
tracing::debug!(
target: LOG_TARGET,
?peer,
%protocol,
?fallback,
?state,
"validation for previous substream still pending",
);
let _ = substream.close().await;
context.state = state;
}
// outbound substream for previous connection still pending, reject inbound substream
// and wait for the outbound substream state to conclude as either succeeded or failed
// before accepting any inbound substreams.
PeerState::Closed {
pending_open: Some(substream_id),
} => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"received inbound substream while outbound substream opening, rejecting",
);
let _ = substream.close().await;
context.state = PeerState::Closed {
pending_open: Some(substream_id),
};
}
// the peer state is closed so this is a fresh inbound substream.
PeerState::Closed { pending_open: None } => {
self.negotiation.read_handshake(peer, substream);
context.state = PeerState::Validating {
protocol,
fallback,
direction: Direction::Inbound,
inbound: InboundState::ReadingHandshake,
outbound: OutboundState::Closed,
};
}
// if the connection is under validation (so an outbound substream has been opened and
// it's still pending or under negotiation), the only valid state for the
// inbound state is closed as it indicates that there isn't an inbound substream yet for
// the remote node duplicate substreams are prohibited.
PeerState::Validating {
protocol,
fallback,
outbound,
direction,
inbound: InboundState::Closed,
} => {
self.negotiation.read_handshake(peer, substream);
context.state = PeerState::Validating {
protocol,
fallback,
outbound,
direction,
inbound: InboundState::ReadingHandshake,
};
}
// outbound substream may have been initiated by the local node while a remote node also
// opened a substream roughly at the same time
PeerState::OutboundInitiated {
substream: outbound,
} => {
self.negotiation.read_handshake(peer, substream);
context.state = PeerState::Validating {
protocol,
fallback,
direction: Direction::Outbound,
outbound: OutboundState::OutboundInitiated {
substream: outbound,
},
inbound: InboundState::ReadingHandshake,
};
}
// new inbound substream opend while validation for the previous substream was still
// pending
//
// the old substream can be considered dead because remote wouldn't open a new substream
// to us unless they had discarded the previous substream.
//
// set peer state to `ValidationPending` to indicate that the peer is "blocked" until a
// validation for the substream is heard, blocking any further activity for
// the connection and once the validation is received and in case the
// substream is accepted, it will be reported as open failure to to the peer
// because the states have gone out of sync.
PeerState::Validating {
outbound: OutboundState::Closed,
inbound:
InboundState::Validating {
inbound: pending_substream,
},
..
} => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"remote opened substream while previous was still pending, connection failed",
);
let _ = substream.close().await;
let _ = pending_substream.close().await;
context.state = PeerState::ValidationPending {
state: ConnectionState::Open,
};
}
// remote opened another inbound substream, close it and otherwise ignore the event
// as this is a non-serious protocol violation.
state => {
tracing::debug!(
target: LOG_TARGET,
?peer,
%protocol,
?fallback,
?state,
"remote opened more than one inbound substreams, discarding",
);
let _ = substream.close().await;
context.state = state;
}
}
Ok(())
}
/// Failed to open substream to remote node.
///
/// If the substream was initiated by the local node, it must be reported that the substream
/// failed to open. Otherwise the peer state can silently be converted to `Closed`.
async fn on_substream_open_failure(&mut self, substream_id: SubstreamId, error: Error) {
tracing::debug!(
target: LOG_TARGET,
protocol = %self.protocol,
?substream_id,
?error,
"failed to open substream"
);
let Some(peer) = self.pending_outbound.remove(&substream_id) else {
tracing::warn!(
target: LOG_TARGET,
protocol = %self.protocol,
?substream_id,
"pending outbound substream doesn't exist",
);
debug_assert!(false);
return;
};
// peer must exist since an outbound substream failure was received from them
let Some(context) = self.peers.get_mut(&peer) else {
tracing::warn!(target: LOG_TARGET, ?peer, "peer doesn't exist");
debug_assert!(false);
return;
};
match &mut context.state {
PeerState::OutboundInitiated { .. } => {
context.state = PeerState::Closed { pending_open: None };
self.event_handle
.report_notification_stream_open_failure(peer, NotificationError::Rejected)
.await;
}
// if the substream was accepted by the local node and as a result, an outbound
// substream was accepted as a result this should not be reported to local node
PeerState::Validating { outbound, .. } => {
self.negotiation.remove_inbound(&peer);
self.negotiation.remove_outbound(&peer);
let pending_open = match outbound {
OutboundState::Closed => None,
OutboundState::OutboundInitiated { substream } => {
self.event_handle
.report_notification_stream_open_failure(
peer,
NotificationError::Rejected,
)
.await;
Some(*substream)
}
OutboundState::Negotiating | OutboundState::Open { .. } => {
self.event_handle
.report_notification_stream_open_failure(
peer,
NotificationError::Rejected,
)
.await;
None
}
};
context.state = PeerState::Closed { pending_open };
}
PeerState::Closed { pending_open } => {
tracing::debug!(
target: LOG_TARGET,
protocol = %self.protocol,
?substream_id,
"substream open failure for a closed connection",
);
debug_assert_eq!(pending_open, &Some(substream_id));
context.state = PeerState::Closed { pending_open: None };
}
state => {
tracing::warn!(
target: LOG_TARGET,
protocol = %self.protocol,
?substream_id,
?state,
"invalid state for outbound substream open failure",
);
context.state = PeerState::Closed { pending_open: None };
debug_assert!(false);
}
}
}
/// Open substream to remote `peer`.
///
/// Outbound substream can opened only if the `PeerState` is `Closed`.
/// By forcing the substream to be opened only if the state is currently closed,
/// `NotificationProtocol` can enfore more predictable state transitions.
///
/// Other states either imply an invalid state transition ([`PeerState::Open`]) or that an
/// inbound substream has already been received and its currently being validated by the user.
async fn on_open_substream(&mut self, peer: PeerId) -> crate::Result<()> {
tracing::trace!(target: LOG_TARGET, ?peer, protocol = %self.protocol, "open substream");
let Some(context) = self.peers.get_mut(&peer) else {
if !self.should_dial {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"connection to peer not open and dialing disabled",
);
self.event_handle
.report_notification_stream_open_failure(peer, NotificationError::DialFailure)
.await;
return Ok(());
}
match self.service.dial(&peer) {
Err(error) => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?error,
"failed to dial peer",
);
self.event_handle
.report_notification_stream_open_failure(
peer,
NotificationError::DialFailure,
)
.await;
return Err(error);
}
Ok(()) => {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"started to dial peer",
);
self.peers.insert(
peer,
PeerContext {
state: PeerState::Dialing,
},
);
return Ok(());
}
}
};
match context.state {
// protocol can only request a new outbound substream to be opened if the state is
// `Closed` other states imply that it's already open
PeerState::Closed {
pending_open: Some(substream_id),
} => {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?substream_id,
"outbound substream opening, reusing pending open substream",
);
self.pending_outbound.insert(substream_id, peer);
context.state = PeerState::OutboundInitiated {
substream: substream_id,
};
}
PeerState::Closed { .. } => match self.service.open_substream(peer) {
Ok(substream_id) => {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?substream_id,
"outbound substream opening",
);
self.pending_outbound.insert(substream_id, peer);
context.state = PeerState::OutboundInitiated {
substream: substream_id,
};
}
Err(error) => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?error,
"failed to open substream",
);
self.event_handle
.report_notification_stream_open_failure(
peer,
NotificationError::NoConnection,
)
.await;
context.state = PeerState::Closed { pending_open: None };
}
},
// while a validation is pending for an inbound substream, user is not allowed to open
// any outbound substreams until the old inbond substream is either accepted or rejected
PeerState::ValidationPending { .. } => {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"validation still pending, rejecting outbound substream request",
);
self.event_handle
.report_notification_stream_open_failure(
peer,
NotificationError::ValidationPending,
)
.await;
}
_ => {}
}
Ok(())
}
/// Close substream to remote `peer`.
///
/// This function can only be called if the substream was actually open, any other state is
/// unreachable as the user is unable to emit this command to [`NotificationProtocol`] unless
/// the connection has been fully opened.
async fn on_close_substream(&mut self, peer: PeerId) {
tracing::debug!(target: LOG_TARGET, ?peer, protocol = %self.protocol, "close substream");
let Some(context) = self.peers.get_mut(&peer) else {
tracing::debug!(target: LOG_TARGET, ?peer, "peer doesn't exist");
return;
};
match std::mem::replace(&mut context.state, PeerState::Poisoned) {
PeerState::Open { shutdown } => {
let _ = shutdown.send(());
context.state = PeerState::Closed { pending_open: None };
}
state => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?state,
"substream already closed",
);
context.state = state;
}
}
}
/// Handle validation result.
///
/// The validation result binary (accept/reject). If the node is rejected, the substreams are
/// discarded and state is set to `PeerState::Closed`. If there was an outbound substream in
/// progress while the connection was rejected by the user, the oubound state is discarded,
/// except for the substream ID of the substream which is kept for later use, in case the
/// substream happens to open.
///
/// If the node is accepted and there is no outbound substream to them open yet, a new substream
/// is opened and once it opens, the local handshake will be sent to the remote peer and if
/// they also accept the substream the connection is considered fully open.
async fn on_validation_result(
&mut self,
peer: PeerId,
result: ValidationResult,
) -> crate::Result<()> {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?result,
"handle validation result",
);
let Some(context) = self.peers.get_mut(&peer) else {
tracing::debug!(target: LOG_TARGET, ?peer, "peer doesn't exist");
return Err(Error::PeerDoesntExist(peer));
};
match std::mem::replace(&mut context.state, PeerState::Poisoned) {
PeerState::Validating {
protocol,
fallback,
outbound,
direction,
inbound: InboundState::Validating { inbound },
} => match result {
// substream was rejected by the local node, if an outbound substream was under
// negotation, discard that data and if an outbound substream was
// initiated, save the `SubstreamId` of that substream and later if the substream
// is opened, the state can be corrected to `pending_open: None`.
ValidationResult::Reject => {
let _ = inbound.close().await;
self.negotiation.remove_outbound(&peer);
self.negotiation.remove_inbound(&peer);
context.state = PeerState::Closed {
pending_open: outbound.pending_open(),
};
Ok(())
}
ValidationResult::Accept => match outbound {
// no outbound substream exists so initiate a new substream open and send the
// local handshake to remote node, indicating that the
// connection was accepted by the local node
OutboundState::Closed => match self.service.open_substream(peer) {
Ok(substream) => {
self.negotiation.send_handshake(peer, inbound);
self.pending_outbound.insert(substream, peer);
context.state = PeerState::Validating {
protocol,
fallback,
direction,
inbound: InboundState::SendingHandshake,
outbound: OutboundState::OutboundInitiated { substream },
};
Ok(())
}
// failed to open outbound substream after accepting an inbound substream
//
// since the user was notified of this substream and they accepted it,
// they expecting some kind of answer (open success/failure).
//
// report to user that the substream failed to open so they can track the
// state transitions of the peer correctly
Err(error) => {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?result,
?error,
"failed to open outbound substream for accepted substream",
);
let _ = inbound.close().await;
context.state = PeerState::Closed { pending_open: None };
self.event_handle
.report_notification_stream_open_failure(
peer,
NotificationError::Rejected,
)
.await;
Err(error)
}
},
// here the state is one of `OutboundState::{OutboundInitiated, Negotiating,
// Open}` so that state can be safely ignored and all that
// has to be done is to send the local handshake to remote
// node to indicate that the connection was accepted.
_ => {
self.negotiation.send_handshake(peer, inbound);
context.state = PeerState::Validating {
protocol,
fallback,
direction,
inbound: InboundState::SendingHandshake,
outbound,
};
Ok(())
}
},
},
// validation result received for an inbound substream which is now considered dead
// because while the substream was being validated, the connection had closed.
//
// if the substream was rejected and there is no active connection to the peer,
// just remove the peer from `peers` without informing user
//
// if the substream was accepted, the user must be informed that the substream failed to
// open. Depending on whether there is currently a connection open to the peer, either
// report `Rejected`/`NoConnection` and let the user try again.
PeerState::ValidationPending { state } => {
if let Some(error) = match state {
ConnectionState::Open => {
context.state = PeerState::Closed { pending_open: None };
std::matches!(result, ValidationResult::Accept)
.then_some(NotificationError::Rejected)
}
ConnectionState::Closed => {
self.peers.remove(&peer);
std::matches!(result, ValidationResult::Accept)
.then_some(NotificationError::NoConnection)
}
} {
self.event_handle.report_notification_stream_open_failure(peer, error).await;
}
Ok(())
}
// if the user incorrectly send a validation result for a peer that doesn't require
// validation, set state back to what it was and ignore the event
//
// the user protocol may send a stale validation result not because of a programming
// error but because it has a backlock of unhandled events, with one event potentially
// nullifying the need for substream validation, and is just temporarily out of sync
// with `NotificationProtocol`
state => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?state,
"validation result received for peer that doesn't require validation",
);
context.state = state;
Ok(())
}
}
}
/// Handle handshake event.
///
/// There are three different handshake event types:
/// - outbound substream negotiated
/// - inbound substream negotiated
/// - substream negotiation error
///
/// Neither outbound nor inbound substream negotiated automatically means that the connection is
/// considered open as both substreams must be fully negotiated for that to be the case. That is
/// why the peer state for inbound and outbound are set separately and at the end of the
/// function is the collective state of the substreams checked and if both substreams are
/// negotiated, the user informed that the connection is open.
///
/// If the negotiation fails, the user may have to be informed of that. Outbound substream
/// failure always results in user getting notified since the existence of an outbound substream
/// means that the user has either initiated an outbound substreams or has accepted an inbound
/// substreams, resulting in an outbound substreams.
///
/// Negotiation failure for inbound substreams which are in the state
/// [`InboundState::ReadingHandshake`] don't result in any notification because while the
/// handshake is being read from the substream, the user is oblivious to the fact that an
/// inbound substream has even been received.
async fn on_handshake_event(&mut self, peer: PeerId, event: HandshakeEvent) {
let Some(context) = self.peers.get_mut(&peer) else {
tracing::error!(target: LOG_TARGET, "invalid state: negotiation event received but peer doesn't exist");
debug_assert!(false);
return;
};
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?event,
"handle handshake event",
);
match event {
// either an inbound or outbound substream has been negotiated successfully
HandshakeEvent::Negotiated {
peer,
handshake,
substream,
direction,
} => match direction {
// outbound substream was negotiated, the only valid state for peer is `Validating`
// and only valid state for `OutboundState` is `Negotiating`
negotiation::Direction::Outbound => {
self.negotiation.remove_outbound(&peer);
match std::mem::replace(&mut context.state, PeerState::Poisoned) {
PeerState::Validating {
protocol,
fallback,
direction,
outbound: OutboundState::Negotiating,
inbound,
} => {
context.state = PeerState::Validating {
protocol,
fallback,
direction,
outbound: OutboundState::Open {
handshake,
outbound: substream,
},
inbound,
};
}
state => {
tracing::warn!(
target: LOG_TARGET,
?peer,
?state,
"outbound substream negotiated but peer has invalid state",
);
debug_assert!(false);
}
}
}
// inbound negotiation event completed
//
// the negotiation event can be on of two different types:
// - remote handshake was read from the substream
// - local handshake has been sent to remote node
//
// For the first case, the substream has to be validated by the local node.
// This means reporting the protocol name, potential negotiated fallback and the
// handshake. Local node will then either accept or reject the substream which is
// handled by [`NotificationProtocol::on_validation_result()`]. Compared to
// Substrate, litep2p requires both peers to validate the inbound handshake to allow
// more complex connection validation. If this is not necessary and the protocol
// wishes to auto-accept the inbound substreams that are a result of
// an outbound substream already accepted by the remote node, the
// substream validation is skipped and the local handshake is sent
// right away.
//
// For the second case, the local handshake was sent to remote node successfully and
// the inbound substream is considered open and if the outbound
// substream is open as well, the connection is fully open.
//
// Only valid states for [`InboundState`] are [`InboundState::ReadingHandshake`] and
// [`InboundState::SendingHandshake`] because otherwise the inbound
// substream cannot be in [`HandshakeService`](super::negotiation::HandshakeService)
// unless there is a logic bug in the state machine.
negotiation::Direction::Inbound => {
self.negotiation.remove_inbound(&peer);
match std::mem::replace(&mut context.state, PeerState::Poisoned) {
PeerState::Validating {
protocol,
fallback,
direction,
outbound,
inbound: InboundState::ReadingHandshake,
} => {
if !std::matches!(outbound, OutboundState::Closed) && self.auto_accept {
tracing::trace!(
target: LOG_TARGET,
?peer,
%protocol,
?fallback,
?direction,
?outbound,
"auto-accept inbound substream",
);
self.negotiation.send_handshake(peer, substream);
context.state = PeerState::Validating {
protocol,
fallback,
direction,
inbound: InboundState::SendingHandshake,
outbound,
};
return;
}
tracing::trace!(
target: LOG_TARGET,
?peer,
%protocol,
?fallback,
?outbound,
"send inbound protocol for validation",
);
context.state = PeerState::Validating {
protocol: protocol.clone(),
fallback: fallback.clone(),
inbound: InboundState::Validating { inbound: substream },
outbound,
direction,
};
let (tx, rx) = oneshot::channel();
self.pending_validations.push(Box::pin(async move {
match rx.await {
Ok(ValidationResult::Accept) =>
(peer, ValidationResult::Accept),
_ => (peer, ValidationResult::Reject),
}
}));
self.event_handle
.report_inbound_substream(protocol, fallback, peer, handshake, tx)
.await;
}
PeerState::Validating {
protocol,
fallback,
direction,
inbound: InboundState::SendingHandshake,
outbound,
} => {
tracing::trace!(
target: LOG_TARGET,
?peer,
%protocol,
?fallback,
"inbound substream negotiated, waiting for outbound substream to complete",
);
context.state = PeerState::Validating {
protocol: protocol.clone(),
fallback: fallback.clone(),
inbound: InboundState::Open { inbound: substream },
outbound,
direction,
};
}
_state => debug_assert!(false),
}
}
},
// error occurred during negotiation, eitehr for inbound or outbound substream
// user is notified of the error only if they've either initiated an outbound substream
// or if they accepted an inbound substream and as a result initiated an outbound
// substream.
HandshakeEvent::NegotiationError { peer, direction } => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?direction,
state = ?context.state,
"failed to negotiate substream",
);
let _ = self.negotiation.remove_outbound(&peer);
let _ = self.negotiation.remove_inbound(&peer);
// if an outbound substream had been initiated (whatever its state is), it means
// that the user knows about the connection and must be notified that it failed to
// negotiate.
match std::mem::replace(&mut context.state, PeerState::Poisoned) {
PeerState::Validating { outbound, .. } => {
context.state = PeerState::Closed {
pending_open: outbound.pending_open(),
};
// notify user if the outbound substream is not considered closed
if !std::matches!(outbound, OutboundState::Closed) {
return self
.event_handle
.report_notification_stream_open_failure(
peer,
NotificationError::Rejected,
)
.await;
}
}
_state => debug_assert!(false),
}
}
}
// if both inbound and outbound substreams are considered open, notify the user that
// a notification stream has been opened and set up for sending and receiving
// notifications to and from remote node
match std::mem::replace(&mut context.state, PeerState::Poisoned) {
PeerState::Validating {
protocol,
fallback,
direction,
outbound:
OutboundState::Open {
handshake,
outbound,
},
inbound: InboundState::Open { inbound },
} => {
tracing::debug!(
target: LOG_TARGET,
?peer,
%protocol,
?fallback,
"notification stream opened",
);
let (async_tx, async_rx) = channel(self.async_channel_size);
let (sync_tx, sync_rx) = channel(self.sync_channel_size);
let sink = NotificationSink::new(peer, sync_tx, async_tx);
// start connection handler for the peer which only deals with sending/receiving
// notifications
//
// the connection handler must be started only after the newly opened notification
// substream is reported to user because the connection handler
// might exit immediately after being started if remote closed the connection.
//
// if the order of events (open & close) is not ensured to be correct, the code
// handling the connectivity logic on the `NotificationHandle` side
// might get confused about the current state of the connection.
let shutdown_tx = self.shutdown_tx.clone();
let (connection, shutdown) = Connection::new(
peer,
inbound,
outbound,
self.event_handle.clone(),
shutdown_tx.clone(),
self.notif_tx.clone(),
async_rx,
sync_rx,
);
context.state = PeerState::Open { shutdown };
self.event_handle
.report_notification_stream_opened(
protocol, fallback, direction, peer, handshake, sink,
)
.await;
self.executor.run(Box::pin(async move {
connection.start().await;
}));
}
state => {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?state,
"validation for substream still pending",
);
self.timers.push(Box::pin(async move {
futures_timer::Delay::new(Duration::from_secs(5)).await;
peer
}));
context.state = state;
}
}
}
/// Handle dial failure.
async fn on_dial_failure(&mut self, peer: PeerId, address: Multiaddr) {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?address,
"handle dial failure",
);
let Some(context) = self.peers.remove(&peer) else {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?address,
"dial failure for an unknown peer",
);
return;
};
match context.state {
PeerState::Dialing => {
tracing::debug!(target: LOG_TARGET, ?peer, protocol = %self.protocol, ?address, "failed to dial peer");
self.event_handle
.report_notification_stream_open_failure(peer, NotificationError::DialFailure)
.await;
}
state => {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?state,
"dial failure for peer that's not being dialed",
);
self.peers.insert(peer, PeerContext { state });
}
}
}
/// Handle next notification event.
async fn next_event(&mut self) {
// biased select is used because the substream events must be prioritized above other events
// that is because a closed substream is detected by either `substreams` or `negotiation`
// and if that event is not handled with priority but, e.g., inbound substream is
// handled before, it can create a situation where the state machine gets confused
// about the peer's state.
tokio::select! {
biased;
event = self.negotiation.next(), if !self.negotiation.is_empty() => {
let (peer, event) = event.expect("`HandshakeService` to return `Some(..)`");
self.on_handshake_event(peer, event).await;
}
event = self.shutdown_rx.recv() => match event {
None => (),
Some(peer) => {
if let Some(context) = self.peers.get_mut(&peer) {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"notification stream to peer closed",
);
context.state = PeerState::Closed { pending_open: None };
}
}
},
// TODO: this could be combined with `Negotiation`
peer = self.timers.next(), if !self.timers.is_empty() => match peer {
Some(peer) => {
match self.peers.get_mut(&peer) {
Some(context) => match std::mem::replace(&mut context.state, PeerState::Poisoned) {
PeerState::Validating {
outbound: OutboundState::Open { outbound, .. },
inbound: InboundState::Closed,
..
} => {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"peer didn't answer in 10 seconds, canceling substream and closing connection",
);
context.state = PeerState::Closed { pending_open: None };
let _ = outbound.close().await;
self.event_handle
.report_notification_stream_open_failure(peer, NotificationError::Rejected)
.await;
// NOTE: this is used to work around an issue in Substrate where the protocol
// is not notified if an inbound substream is closed. That indicates that remote
// wishes the close the connection but `Notifications` still keeps the substream state
// as `Open` until the outbound substream is closed (even though the outbound substream
// is also closed at that point). This causes a further issue: inbound substreams
// are automatically opened when state is `Open`, even if the inbound substream belongs
// to a new "connection" (pair of substreams).
//
// basically what happens (from Substrate's PoV) is there are pair of substreams (`inbound1`, `outbound1`),
// litep2p closes both substreams so both `inbound1` and outbound1 become non-readable/writable.
// Substrate doesn't detect this an instead only marks `inbound1` is closed while still keeping
// the (now-closed) `outbound1` active and it will be detected closed only when Substrate tries to
// write something into that substream. If now litep2p tries to open a new connection to Substrate,
// the outbound substream from litep2p's PoV will be automatically accepted (https://github.com/paritytech/polkadot-sdk/blob/59b2661444de2a25f2125a831bd786035a9fac4b/substrate/client/network/src/protocol/notifications/handler.rs#L544-L556)
// but since Substrate thinks `outbound1` is still active, it won't open a new outbound substream
// and it ends up having (`inbound2`, `outbound1`) as its pair of substreams which doens't make sense.
//
// since litep2p is expecting to receive an inbound substream from Substrate and never receives it,
// it basically can't make progress with the substream open request because litep2p can't force Substrate
// to detect that `outbound1` is closed. Easiest (and very hacky at the same time) way to reset the substream
// state is to close the connection. This is not an appropriate way to fix the issue and causes issues with,
// e.g., smoldot which at the time of writing this doesn't support the transaction protocol. The only way to fix
// this cleanly is to make Substrate detect closed substreams correctly.
if let Err(error) = self.service.force_close(peer) {
tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?error,
"failed to force close connection",
);
}
}
state => {
tracing::trace!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
?state,
"ignore expired timer for peer",
);
context.state = state;
}
}
None => tracing::debug!(
target: LOG_TARGET,
?peer,
protocol = %self.protocol,
"peer doesn't exist anymore",
),
}
}
None => (),
},
event = self.service.next() => match event {
Some(TransportEvent::ConnectionEstablished { peer, .. }) => {
if let Err(error) = self.on_connection_established(peer).await {
tracing::debug!(
target: LOG_TARGET,
?peer,
?error,
"failed to register peer",
);
}
}
Some(TransportEvent::ConnectionClosed { peer }) => {
if let Err(error) = self.on_connection_closed(peer).await {
tracing::debug!(
target: LOG_TARGET,
?peer,
?error,
"failed to disconnect peer",
);
}
}
Some(TransportEvent::SubstreamOpened {
peer,
substream,
direction,
protocol,
fallback,
}) => match direction {
protocol::Direction::Inbound => {
if let Err(error) = self.on_inbound_substream(protocol, fallback, peer, substream).await {
tracing::debug!(
target: LOG_TARGET,
?peer,
?error,
"failed to handle inbound substream",
);
}
}
protocol::Direction::Outbound(substream_id) => {
if let Err(error) = self
.on_outbound_substream(protocol, fallback, peer, substream_id, substream)
.await
{
tracing::debug!(
target: LOG_TARGET,
?peer,
?error,
"failed to handle outbound substream",
);
}
}
},
Some(TransportEvent::SubstreamOpenFailure { substream, error }) => {
self.on_substream_open_failure(substream, error).await;
}
Some(TransportEvent::DialFailure { peer, address }) => self.on_dial_failure(peer, address).await,
None => (),
},
result = self.pending_validations.select_next_some(), if !self.pending_validations.is_empty() => {
if let Err(error) = self.on_validation_result(result.0, result.1).await {
tracing::debug!(
target: LOG_TARGET,
peer = ?result.0,
result = ?result.1,
?error,
"failed to handle validation result",
);
}
}
command = self.command_rx.recv() => match command {
None => {
tracing::debug!(target: LOG_TARGET, "user protocol has exited, exiting");
}
Some(command) => match command {
NotificationCommand::OpenSubstream { peers } => {
for peer in peers {
if let Err(error) = self.on_open_substream(peer).await {
tracing::debug!(
target: LOG_TARGET,
?peer,
?error,
"failed to open substream",
);
}
}
}
NotificationCommand::CloseSubstream { peers } => {
for peer in peers {
self.on_close_substream(peer).await;
}
}
NotificationCommand::ForceClose { peer } => {
let _ = self.service.force_close(peer);
}
}
},
}
}
/// Start [`NotificationProtocol`] event loop.
pub(crate) async fn run(mut self) {
tracing::debug!(target: LOG_TARGET, "starting notification event loop");
loop {
self.next_event().await;
}
}
}