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//! Module exposing structures relating to the reactor's view of a circuit's hops.
use super::{CircuitCmd, CloseStreamBehavior};
use crate::circuit::circhop::{
CircHopInbound, CircHopOutbound, HopSettings, ReactorStreamComponents, SendRelayCell,
};
use crate::client::reactor::circuit::path::PathEntry;
use crate::congestion::CongestionControl;
use crate::crypto::cell::HopNum;
use crate::memquota::StreamAccount;
use crate::stream::cmdcheck::AnyCmdChecker;
use crate::stream::flow_ctrl::state::WithSidechannelMitigations;
use crate::streammap::{self, StreamEntMut, StreamMap};
use crate::tunnel::TunnelScopedCircId;
use crate::util::tunnel_activity::TunnelActivity;
use crate::{Error, Result};
use futures::Stream;
use futures::stream::FuturesUnordered;
use smallvec::SmallVec;
use tor_cell::chancell::{BoxedCellBody, CircId};
use tor_cell::relaycell::flow_ctrl::{Xoff, Xon, XonKBpsEwma};
use tor_cell::relaycell::msg::AnyRelayMsg;
use tor_cell::relaycell::{
AnyRelayMsgOuter, RelayCellDecoder, RelayCellDecoderResult, RelayCellFormat, StreamId,
UnparsedRelayMsg,
use tor_rtcompat::DynTimeProvider;
use web_time_compat::Instant;
use safelog::sensitive as sv;
use tor_error::Bug;
use tracing::instrument;
use std::result::Result as StdResult;
use std::sync::{Arc, Mutex, MutexGuard};
use std::task::Poll;
#[cfg(test)]
use tor_cell::relaycell::msg::SendmeTag;
/// The "usual" number of hops in a [`CircHopList`].
///
/// This saves us a heap allocation when the number of hops is less than or equal to this value.
const NUM_HOPS: usize = 3;
/// Represents the reactor's view of a circuit's hop.
#[derive(Default)]
pub(crate) struct CircHopList {
/// The list of hops.
hops: SmallVec<[CircHop; NUM_HOPS]>,
}
impl CircHopList {
/// Return a reference to the hop corresponding to `hopnum`, if there is one.
pub(super) fn hop(&self, hopnum: HopNum) -> Option<&CircHop> {
self.hops.get(Into::<usize>::into(hopnum))
/// Return a mutable reference to the hop corresponding to `hopnum`, if there is one.
pub(super) fn get_mut(&mut self, hopnum: HopNum) -> Option<&mut CircHop> {
self.hops.get_mut(Into::<usize>::into(hopnum))
/// Append the specified hop.
pub(crate) fn push(&mut self, hop: CircHop) {
self.hops.push(hop);
/// Returns `true` if the list contains no [`CircHop`]s.
pub(crate) fn is_empty(&self) -> bool {
self.hops.is_empty()
/// Returns the number of hops in the list.
pub(crate) fn len(&self) -> usize {
self.hops.len()
/// Returns a [`Stream`] of [`CircuitCmd`] to poll from the main loop.
/// The iterator contains at most one [`CircuitCmd`] for each hop,
/// representing the instructions for handling the ready-item, if any,
/// of its highest priority stream.
/// IMPORTANT: this stream locks the stream map mutexes of each `CircHop`!
/// To avoid contention, never create more than one
/// [`ready_streams_iterator`](Self::ready_streams_iterator)
/// stream at a time!
/// This is cancellation-safe.
pub(in crate::client::reactor) fn ready_streams_iterator(
&self,
exclude: Option<HopNum>,
) -> impl Stream<Item = CircuitCmd> + use<> {
self.hops
.iter()
.enumerate()
.filter_map(|(i, hop)| {
let hop_num = HopNum::from(i as u8);
if exclude == Some(hop_num) {
// We must skip polling this hop
return None;
if !hop.ccontrol().can_send() {
// We can't send anything on this hop that counts towards SENDME windows.
//
// In theory we could send messages that don't count towards
// windows (like `RESOLVE`), and process end-of-stream
// events (to send an `END`), but it's probably not worth
// doing an O(N) iteration over flow-control-ready streams
// to see if that's the case.
// This *doesn't* block outgoing flow-control messages (e.g.
// SENDME), which are initiated via the control-message
// channel, handled above.
// TODO: Consider revisiting. OTOH some extra throttling when circuit-level
// congestion control has "bottomed out" might not be so bad, and the
// alternatives have complexity and/or performance costs.
let hop_map = Arc::clone(self.hops[i].stream_map());
Some(futures::future::poll_fn(move |cx| {
// Process an outbound message from the first ready stream on
// this hop. The stream map implements round robin scheduling to
// ensure fairness across streams.
// TODO: Consider looping here to process multiple ready
// streams. Need to be careful though to balance that with
// continuing to service incoming and control messages.
let mut hop_map = hop_map.lock().expect("lock poisoned");
let Some((sid, msg)) = hop_map.poll_ready_streams_iter(cx).next() else {
// No ready streams for this hop.
return Poll::Pending;
if msg.is_none() {
return Poll::Ready(CircuitCmd::CloseStream {
hop: hop_num,
sid,
behav: CloseStreamBehavior::default(),
reason: streammap::TerminateReason::StreamTargetClosed,
});
let msg = hop_map.take_ready_msg(sid).expect("msg disappeared");
#[allow(unused)] // unused in non-debug builds
let Some(StreamEntMut::Open(s)) = hop_map.get_mut(sid) else {
panic!("Stream {sid} disappeared");
debug_assert!(
s.can_send(&msg),
"Stream {sid} produced a message it can't send: {msg:?}"
);
let cell = SendRelayCell {
hop: Some(hop_num),
early: false,
cell: AnyRelayMsgOuter::new(Some(sid), msg),
Poll::Ready(CircuitCmd::Send(cell))
}))
})
.collect::<FuturesUnordered<_>>()
/// Remove all halfstreams that are expired at `now`.
pub(super) fn remove_expired_halfstreams(&mut self, now: Instant) {
for hop in self.hops.iter_mut() {
hop.stream_map()
.lock()
.expect("lock poisoned")
.remove_expired_halfstreams(now);
/// Returns true if there are any streams on this circuit
/// Important: this function locks the stream map of its each of the [`CircHop`]s
/// in this circuit, so it must **not** be called from any function where the
/// stream map lock is held (such as [`ready_streams_iterator`](Self::ready_streams_iterator).
pub(super) fn has_streams(&self) -> bool {
self.hops.iter().any(|hop| {
.n_open_streams()
> 0
/// Return the most active [`TunnelActivity`] for any hop on this `CircHopList`.
pub(crate) fn tunnel_activity(&self) -> TunnelActivity {
.map(|hop| {
.expect("Poisoned lock")
.tunnel_activity()
.max()
.unwrap_or_else(TunnelActivity::never_used)
/// Represents the reactor's view of a single hop.
pub(crate) struct CircHop {
/// The unique ID of the circuit. Used for logging.
unique_id: TunnelScopedCircId,
/// The Tor circuit identifier. Used for logging.
circ_id: CircId,
/// Hop number in the path.
hop_num: HopNum,
/// The inbound state of the hop.
/// Used for processing cells received from this hop.
inbound: CircHopInbound,
/// The outbound state of the hop.
/// Used for preparing cells to send to this hop.
outbound: CircHopOutbound,
impl CircHop {
/// Create a new hop.
pub(crate) fn new(
settings: &HopSettings,
) -> Self {
let relay_format = settings.relay_crypt_protocol().relay_cell_format();
let ccontrol = Arc::new(Mutex::new(CongestionControl::new(&settings.ccontrol)));
let inbound = CircHopInbound::new(RelayCellDecoder::new(relay_format), settings);
let outbound = CircHopOutbound::new(
ccontrol,
relay_format,
Arc::new(settings.flow_ctrl_params.clone()),
settings,
CircHop {
unique_id,
circ_id,
hop_num,
inbound,
outbound,
/// Start a stream. Creates an entry in the stream map with the given channels, and sends the
/// `message` to the provided hop.
pub(crate) fn begin_stream(
&mut self,
message: AnyRelayMsg,
time_prov: &DynTimeProvider,
cmd_checker: AnyCmdChecker,
memquota: &StreamAccount,
) -> Result<(SendRelayCell, StreamId, ReactorStreamComponents)> {
self.outbound.begin_stream(
Some(self.hop_num),
message,
time_prov,
cmd_checker,
memquota,
)
/// Close the stream associated with `id` because the stream was
/// dropped.
/// See [`CircHopOutbound::close_stream`].
pub(crate) fn close_stream(
id: StreamId,
message: CloseStreamBehavior,
why: streammap::TerminateReason,
expiry: Instant,
) -> Result<Option<SendRelayCell>> {
self.outbound.close_stream(
self.unique_id,
self.circ_id,
id,
why,
expiry,
/// Check if we should send an XON message.
/// If we should, then returns the XON message that should be sent.
#[instrument(level = "trace", skip_all)]
pub(crate) fn maybe_send_xon(
rate: XonKBpsEwma,
) -> Result<Option<Xon>> {
self.outbound.maybe_send_xon(rate, id)
/// Check if we should send an XOFF message.
/// If we should, then returns the XOFF message that should be sent.
pub(crate) fn maybe_send_xoff(&mut self, id: StreamId) -> Result<Option<Xoff>> {
self.outbound.maybe_send_xoff(id)
/// Return the format that is used for relay cells sent to this hop.
/// For the most part, this format isn't necessary to interact with a CircHop;
/// it becomes relevant when we are deciding _what_ we can encode for the hop.
pub(crate) fn relay_cell_format(&self) -> RelayCellFormat {
self.outbound.relay_cell_format()
/// Delegate to CongestionControl, for testing purposes
pub(crate) fn send_window_and_expected_tags(&self) -> (u32, Vec<SendmeTag>) {
self.outbound.send_window_and_expected_tags()
/// Return a mutable reference to our CongestionControl object.
pub(crate) fn ccontrol(&self) -> MutexGuard<'_, CongestionControl> {
self.outbound.ccontrol().lock().expect("poisoned lock")
/// Return a reference to our CircHopOutbound object.
pub(crate) fn outbound(&self) -> &CircHopOutbound {
&self.outbound
/// We're about to send `msg`.
/// See [`OpenStreamEnt::about_to_send`](crate::streammap::OpenStreamEnt::about_to_send).
// TODO prop340: This should take a cell or similar, not a message.
pub(crate) fn about_to_send(&mut self, stream_id: StreamId, msg: &AnyRelayMsg) -> Result<()> {
self.outbound
.about_to_send(self.unique_id, self.circ_id, stream_id, msg)
/// Add an entry to this map using the specified StreamId.
#[cfg(feature = "hs-service")]
pub(crate) fn add_ent_with_id(
stream_id: StreamId,
with_sidechannel_mitigations: WithSidechannelMitigations,
) -> Result<ReactorStreamComponents> {
self.outbound.add_ent_with_id(
stream_id,
with_sidechannel_mitigations,
/// Note that we received an END message (or other message indicating the end of
/// the stream) on the stream with `id`.
/// See [`StreamMap::ending_msg_received`](crate::streammap::StreamMap::ending_msg_received).
pub(crate) fn ending_msg_received(&self, stream_id: StreamId) -> Result<()> {
self.outbound.ending_msg_received(stream_id)
/// Parse a RELAY or RELAY_EARLY cell body.
/// Requires that the cryptographic checks on the message have already been
/// performed
pub(crate) fn decode(&mut self, cell: BoxedCellBody) -> Result<RelayCellDecoderResult> {
self.inbound.decode(cell)
/// Handle `msg`, delivering it to the stream with the specified `streamid` if appropriate.
/// Returns back the provided `msg`, if the message is an incoming stream request
/// that needs to be handled by the calling code.
// TODO: the above is a bit of a code smell -- we should try to avoid passing the msg
// back and forth like this.
pub(super) fn handle_msg(
hop_detail: &PathEntry,
cell_counts_toward_windows: bool,
streamid: StreamId,
msg: UnparsedRelayMsg,
now: Instant,
) -> Result<Option<UnparsedRelayMsg>> {
let possible_proto_violation_err = |streamid: StreamId| Error::UnknownStream {
src: sv(hop_detail.clone()),
streamid,
self.outbound.handle_msg(
possible_proto_violation_err,
cell_counts_toward_windows,
msg,
now,
/// Get the stream map of this hop.
pub(crate) fn stream_map(&self) -> &Arc<Mutex<StreamMap>> {
self.outbound.stream_map()
/// Set the stream map of this hop to `map`.
/// Returns an error if the existing stream map of the hop has any open stream.
pub(crate) fn set_stream_map(&mut self, map: Arc<Mutex<StreamMap>>) -> StdResult<(), Bug> {
self.outbound.set_stream_map(map)
/// Decrement the limit of outbound cells that may be sent to this hop; give
/// an error if it would reach zero.
pub(crate) fn decrement_outbound_cell_limit(&mut self) -> Result<()> {
self.outbound.decrement_cell_limit()
/// Decrement the limit of inbound cells that may be received from this hop; give
pub(crate) fn decrement_inbound_cell_limit(&mut self) -> Result<()> {
self.inbound.decrement_cell_limit()