feat(measurement): implement ICMP measurement engine

src/main.rs

@@ -22,6 +22,10 @@ mod time;
 mod util;
 
 use crate::baseliner::Baseliner;
+use crate::measurement::icmp::{IcmpBinding, IcmpEngine};
+use crate::measurement::model::{
+    MeasurementSource, MeasurementStream, MeasurementStreamId, ProbeSchedule,
+};
 use crate::metrics::{Metric, Metrics, MetricsSender};
 use crate::pinger::{InFlightProbeCache, PingListener, PingSender};
 use crate::pinger_icmp::{PingerICMPEchoListener, PingerICMPEchoSender};
@@ -34,7 +38,7 @@ use crate::settings::Settings;
 use ::log::{info, warn};
 use flume::RecvTimeoutError;
 use std::collections::HashMap;
-use std::net::IpAddr;
+use std::net::{IpAddr, Ipv4Addr};
 use std::str::FromStr;
 use std::sync::atomic::{AtomicBool, AtomicU32, Ordering};
 use std::sync::{Arc, Mutex, RwLock};
@@ -246,6 +250,22 @@ fn run(settings: &Settings) -> anyhow::Result<()> {
     let start_time = Instant::now();
     let probe_id = probe_identifier();
 
+    let (ie_txt, _) = flume::unbounded();
+    let (binding_tx, binding_rx) = flume::unbounded();
+    let engine = IcmpEngine::new(start_time, &settings.network, ie_txt, binding_rx)?;
+    binding_tx.send(vec![IcmpBinding::new(
+        MeasurementStream {
+            id: MeasurementStreamId(0),
+            peer: IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
+            source: MeasurementSource::IcmpEcho,
+        },
+        ProbeSchedule {
+            period: Duration::from_secs(1),
+            offset: Duration::from_secs(0),
+        },
+    )])?;
+    engine.run()?;
+
     let ReflectorSetup {
         peers: reflector_peers,
         pool: reflector_pool,

src/measurement/icmp.rs

@@ -0,0 +1,543 @@
+use std::{
+    collections::{HashMap, HashSet},
+    io,
+    net::IpAddr,
+    sync::{Arc, Mutex, atomic::Ordering},
+    thread,
+    time::{Duration, Instant, SystemTime},
+};
+
+use flume::{Receiver, RecvTimeoutError, Sender};
+use icmp_socket2::{
+    IcmpSocket, IcmpSocket4, Icmpv4Message, Icmpv4Packet,
+    packet::{IcmpPacketBuildError, WithEchoRequest, WithTimestampRequest},
+};
+use thiserror::Error;
+
+use crate::{
+    SHUTDOWN,
+    measurement::model::{
+        MeasurementEvent, MeasurementLoss, MeasurementObservation, MeasurementSource,
+        MeasurementStream, MeasurementStreamId, OneWayClock, OneWayLatency, ProbeSchedule,
+        SignedDuration,
+    },
+    settings::NetworkSettings,
+    time::{ClockSample, Realtime},
+};
+
+pub struct IcmpBinding {
+    pub stream: MeasurementStream,
+    pub schedule: ProbeSchedule,
+
+    next_probe_at: Instant,
+}
+
+impl IcmpBinding {
+    pub fn new(stream: MeasurementStream, schedule: ProbeSchedule) -> Self {
+        Self {
+            stream,
+            schedule,
+            next_probe_at: Instant::now(),
+        }
+    }
+}
+
+#[derive(Debug, Error)]
+pub enum IcmpError {
+    #[error("I/O error")]
+    Io(#[from] io::Error),
+
+    #[error("failed to build ICMP packet")]
+    PacketBuild(#[from] IcmpPacketBuildError),
+
+    #[error("invalid ICMP packet: {0}")]
+    InvalidPacket(String),
+
+    #[error("unsupported measurement source: {0:?}")]
+    UnsupportedSource(MeasurementSource),
+
+    #[error("probe interval must be non-zero for stream {0:?}")]
+    InvalidInterval(MeasurementStreamId),
+
+    #[error("probe offset must be less than the period for stream {0:?}")]
+    InvalidOffset(MeasurementStreamId),
+
+    #[error(
+        "no matching probe found for peer {:?}, source: {:?}, sequence: {}",
+        .0.0,
+        .0.1,
+        .0.2
+    )]
+    NoMatchingProbe(InFlightProbeKey),
+
+    #[error("wrong identifier: expected {expected}, found {found}")]
+    WrongIdentifier { expected: u16, found: u16 },
+
+    #[error("unsupported ICMP peer address: {0}")]
+    UnsupportedPeer(IpAddr),
+
+    #[error("event channel closed")]
+    EventChannelClosed,
+}
+
+#[derive(Debug, Clone, Copy)]
+struct InFlightProbe {
+    stream: MeasurementStream,
+    sent_at: Instant,
+}
+
+type InFlightProbeKey = (IpAddr, MeasurementSource, u16);
+type InFlightProbes = Mutex<HashMap<InFlightProbeKey, InFlightProbe>>;
+
+struct IcmpSender {
+    socket: IcmpSocket4,
+    identifier: u16,
+    next_sequence: u16,
+    bindings: HashMap<MeasurementStreamId, IcmpBinding>,
+    inflight: Arc<InFlightProbes>,
+    origin: Instant,
+    binding_rx: Receiver<Vec<IcmpBinding>>,
+}
+
+struct IcmpReceiver {
+    socket: IcmpSocket4,
+    identifier: u16,
+    inflight: Arc<InFlightProbes>,
+    observation_tx: Sender<MeasurementEvent>,
+}
+
+pub struct IcmpEngine {
+    sender: IcmpSender,
+    receiver: IcmpReceiver,
+}
+
+impl IcmpEngine {
+    pub fn new(
+        origin: Instant,
+        #[allow(unused)] settings: &NetworkSettings,
+        observation_tx: Sender<MeasurementEvent>,
+        binding_rx: Receiver<Vec<IcmpBinding>>,
+    ) -> Result<Self, IcmpError> {
+        #[allow(unused_mut)]
+        let mut rx_socket = IcmpSocket4::new()?;
+
+        #[cfg(any(target_os = "android", target_os = "fuchsia", target_os = "linux"))]
+        if let Some(device) = &settings.measurement_bind_device {
+            IcmpSocket::bind_device(&mut rx_socket, device)?;
+        }
+
+        #[cfg(any(target_os = "android", target_os = "fuchsia", target_os = "linux"))]
+        if let Some(mark) = settings.measurement_mark {
+            IcmpSocket::set_mark(&mut rx_socket, mark)?;
+        }
+
+        #[cfg(target_os = "freebsd")]
+        if let Some(fib) = settings.measurement_fib {
+            IcmpSocket::set_fib(&mut rx_socket, fib)?;
+        }
+
+        rx_socket.enable_receive_metadata()?;
+        let tx_socket = rx_socket.try_clone()?;
+        let identifier = (std::process::id() & 0xffff) as u16;
+        let inflight: Arc<InFlightProbes> = Arc::new(Mutex::new(HashMap::new()));
+
+        Ok(Self {
+            sender: IcmpSender {
+                socket: tx_socket,
+                identifier,
+                next_sequence: 0,
+                bindings: HashMap::new(),
+                inflight: Arc::clone(&inflight),
+                origin,
+                binding_rx,
+            },
+            receiver: IcmpReceiver {
+                socket: rx_socket,
+                identifier,
+                inflight,
+                observation_tx,
+            },
+        })
+    }
+
+    pub fn run(self) -> Result<(), IcmpError> {
+        let Self { sender, receiver } = self;
+
+        let sender_handle = thread::spawn(move || {
+            let result = sender.run();
+            SHUTDOWN.store(true, Ordering::Relaxed);
+            result
+        });
+        let sender_thread = sender_handle.thread().clone();
+
+        let receiver_handle = thread::spawn(move || {
+            let result = receiver.run();
+            SHUTDOWN.store(true, Ordering::Relaxed);
+            sender_thread.unpark();
+            result
+        });
+
+        let sender_result = sender_handle.join().expect("ICMP sender thread panicked");
+
+        SHUTDOWN.store(true, Ordering::Relaxed);
+
+        let receiver_result = receiver_handle
+            .join()
+            .expect("ICMP receiver thread panicked");
+
+        sender_result?;
+        receiver_result?;
+
+        Ok(())
+    }
+}
+
+impl IcmpSender {
+    fn set_bindings(&mut self, desired: Vec<IcmpBinding>) -> Result<(), IcmpError> {
+        // Validate the complete desired state before mutating anything.
+        for binding in &desired {
+            if binding.schedule.period.is_zero() {
+                return Err(IcmpError::InvalidInterval(binding.stream.id));
+            }
+
+            if binding.schedule.offset >= binding.schedule.period {
+                return Err(IcmpError::InvalidOffset(binding.stream.id));
+            }
+
+            if !matches!(
+                binding.stream.source,
+                MeasurementSource::IcmpEcho | MeasurementSource::IcmpTimestamp
+            ) {
+                return Err(IcmpError::UnsupportedSource(binding.stream.source));
+            }
+        }
+
+        let now = Instant::now();
+        let desired_ids = desired
+            .iter()
+            .map(|binding| binding.stream.id)
+            .collect::<HashSet<_>>();
+
+        // Remove bindings that are no longer desired.
+        self.bindings.retain(|id, _| desired_ids.contains(id));
+
+        for desired in desired {
+            match self.bindings.get_mut(&desired.stream.id) {
+                Some(current) if current.schedule == desired.schedule => {
+                    // Same schedule, so leave next_probe_at alone.
+                    current.stream = desired.stream;
+                }
+
+                Some(current) => {
+                    // Same stream, but its schedule changed. Rejoin the new grid.
+                    current.stream = desired.stream;
+                    current.schedule = desired.schedule;
+                    current.next_probe_at = desired.schedule.next_probe_at(self.origin, now);
+                }
+
+                None => {
+                    // New stream. Join its configured schedule at the next
+                    // occurrence after now.
+                    let mut binding = desired;
+                    binding.next_probe_at = binding.schedule.next_probe_at(self.origin, now);
+
+                    self.bindings.insert(binding.stream.id, binding);
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    fn run(mut self) -> Result<(), IcmpError> {
+        while !SHUTDOWN.load(Ordering::Relaxed) {
+            let deadline = self.next_deadline();
+
+            match deadline {
+                Some(deadline) => match self.binding_rx.recv_deadline(deadline) {
+                    Ok(bindings) => {
+                        self.set_bindings(bindings)?;
+                    }
+
+                    Err(RecvTimeoutError::Timeout) => {
+                        self.send_due_probes(Instant::now())?;
+                    }
+
+                    Err(RecvTimeoutError::Disconnected) => {
+                        break;
+                    }
+                },
+
+                None => {
+                    // Nothing scheduled. Don't exit.
+                    // Just sleep until configuration arrives.
+                    let bindings = self
+                        .binding_rx
+                        .recv()
+                        .map_err(|_| IcmpError::EventChannelClosed)?;
+                    self.set_bindings(bindings)?;
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    fn send_due_probes(&mut self, now: Instant) -> Result<(), IcmpError> {
+        let due = self
+            .bindings
+            .iter()
+            .filter_map(|(&stream_id, binding)| (binding.next_probe_at <= now).then_some(stream_id))
+            .collect::<Vec<_>>();
+
+        for stream_id in due {
+            self.send_probe(stream_id)?;
+
+            let binding = self
+                .bindings
+                .get_mut(&stream_id)
+                .expect("due binding disappeared");
+
+            while binding.next_probe_at <= now {
+                binding.next_probe_at += binding.schedule.period;
+            }
+        }
+
+        Ok(())
+    }
+
+    fn send_probe(&mut self, stream_id: MeasurementStreamId) -> Result<(), IcmpError> {
+        let stream = self
+            .bindings
+            .get(&stream_id)
+            .expect("binding disappeared")
+            .stream;
+
+        let IpAddr::V4(peer) = stream.peer else {
+            return Err(IcmpError::UnsupportedPeer(stream.peer));
+        };
+
+        let sequence = self.next_sequence;
+        self.next_sequence = self.next_sequence.wrapping_add(1);
+
+        let packet = match stream.source {
+            MeasurementSource::IcmpEcho => {
+                Icmpv4Packet::with_echo_request(self.identifier, sequence, Vec::new())?
+            }
+            MeasurementSource::IcmpTimestamp => {
+                let originate = ClockSample::<Realtime>::now().as_time_since_midnight() as u32;
+                Icmpv4Packet::with_timestamp_request(self.identifier, sequence, originate, 0, 0)?
+            }
+            source => return Err(IcmpError::UnsupportedSource(source)),
+        };
+
+        let sent_at = Instant::now();
+        let key = (stream.peer, stream.source, sequence);
+        let mut inflight = self.inflight.lock().expect("ICMP inflight mutex poisoned");
+        inflight.insert(key, InFlightProbe { stream, sent_at });
+
+        if let Err(err) = self.socket.send_to(peer, packet) {
+            return Err(err.into());
+        }
+
+        Ok(())
+    }
+
+    fn next_deadline(&self) -> Option<Instant> {
+        self.bindings
+            .values()
+            .map(|binding| binding.next_probe_at)
+            .min()
+    }
+}
+
+impl IcmpReceiver {
+    fn run(mut self) -> Result<(), IcmpError> {
+        const RECEIVE_TIMEOUT: Duration = Duration::from_millis(50);
+        const HOUSEKEEPING_INTERVAL: Duration = Duration::from_millis(500);
+
+        self.socket.set_timeout(Some(RECEIVE_TIMEOUT));
+
+        let mut next_housekeeping = Instant::now() + HOUSEKEEPING_INTERVAL;
+
+        while !SHUTDOWN.load(Ordering::Relaxed) {
+            match self.socket.rcv_from_with_meta() {
+                Ok(result) => {
+                    match self.handle_reply(
+                        result.packet,
+                        result.peer.as_socket().unwrap().ip(),
+                        result.received_at,
+                        result.kernel_rx_timestamp,
+                    ) {
+                        Ok(observation) => {
+                            self.observation_tx
+                                .send(MeasurementEvent::Observation(observation))
+                                .map_err(|_| IcmpError::EventChannelClosed)?;
+                        }
+                        Err(
+                            IcmpError::WrongIdentifier { .. }
+                            | IcmpError::NoMatchingProbe { .. }
+                            | IcmpError::InvalidPacket(_),
+                        ) => {
+                            // Not one of ours, malformed, or a late reply.
+                        }
+                        Err(err) => return Err(err),
+                    }
+                }
+                Err(err)
+                    if matches!(
+                        err.kind(),
+                        io::ErrorKind::WouldBlock | io::ErrorKind::TimedOut
+                    ) => {}
+                Err(err) => return Err(err.into()),
+            }
+
+            let now = Instant::now();
+
+            if now >= next_housekeeping {
+                self.expire_inflight(now)?;
+                next_housekeeping = now + HOUSEKEEPING_INTERVAL;
+            }
+        }
+
+        Ok(())
+    }
+
+    fn handle_reply(
+        &mut self,
+        packet: Icmpv4Packet,
+        peer: IpAddr,
+        observed_at: Instant,
+        kernel_rx_timestamp: Option<SystemTime>,
+    ) -> Result<MeasurementObservation, IcmpError> {
+        match packet.message {
+            Icmpv4Message::EchoReply {
+                identifier,
+                sequence,
+                ..
+            } => {
+                if identifier != self.identifier {
+                    return Err(IcmpError::WrongIdentifier {
+                        expected: self.identifier,
+                        found: identifier,
+                    });
+                }
+
+                let key = (peer, MeasurementSource::IcmpEcho, sequence);
+                let probe = {
+                    let mut inflight = self.inflight.lock().expect("ICMP inflight mutex poisoned");
+
+                    inflight
+                        .remove(&key)
+                        .ok_or(IcmpError::NoMatchingProbe(key))?
+                };
+
+                Ok(MeasurementObservation {
+                    stream: probe.stream,
+                    started_at: probe.sent_at,
+                    observed_at,
+                    one_way: None,
+                })
+            }
+            Icmpv4Message::TimestampReply {
+                identifier,
+                sequence,
+                originate,
+                receive,
+                transmit,
+            } => {
+                const NON_STANDARD_TIMESTAMP: u32 = 1 << 31;
+
+                if identifier != self.identifier {
+                    return Err(IcmpError::WrongIdentifier {
+                        expected: self.identifier,
+                        found: identifier,
+                    });
+                }
+
+                if receive & NON_STANDARD_TIMESTAMP != 0 || transmit & NON_STANDARD_TIMESTAMP != 0 {
+                    return Err(IcmpError::InvalidPacket(
+                        "non-standard RFC 792 timestamp".into(),
+                    ));
+                }
+
+                let key = (peer, MeasurementSource::IcmpTimestamp, sequence);
+                let probe = {
+                    let mut inflight = self.inflight.lock().expect("ICMP inflight mutex poisoned");
+
+                    inflight
+                        .remove(&key)
+                        .ok_or(IcmpError::NoMatchingProbe(key))?
+                };
+
+                let now_ms = if let Some(timestamp) = kernel_rx_timestamp {
+                    ClockSample::<Realtime>::from(timestamp).as_time_since_midnight()
+                } else {
+                    ClockSample::<Realtime>::now().as_time_since_midnight()
+                };
+
+                let uplink_ms = timestamp_delta(receive as i64, originate as i64);
+                let downlink_ms = timestamp_delta(now_ms, transmit as i64);
+
+                Ok(MeasurementObservation {
+                    stream: probe.stream,
+                    started_at: probe.sent_at,
+                    observed_at,
+                    one_way: Some(OneWayLatency {
+                        uplink: SignedDuration::from_millis(uplink_ms),
+                        downlink: SignedDuration::from_millis(downlink_ms),
+                        clock: OneWayClock::Uncalibrated,
+                    }),
+                })
+            }
+            _ => Err(IcmpError::InvalidPacket(
+                "unsupported ICMP message type".to_string(),
+            )),
+        }
+    }
+
+    fn expire_inflight(&self, now: Instant) -> Result<(), IcmpError> {
+        const PROBE_TIMEOUT: Duration = Duration::from_secs(2);
+
+        let expired = {
+            let mut inflight = self.inflight.lock().expect("ICMP inflight mutex poisoned");
+            let mut expired = Vec::new();
+
+            inflight.retain(|_, probe| {
+                if now.saturating_duration_since(probe.sent_at) >= PROBE_TIMEOUT {
+                    expired.push(*probe);
+                    false
+                } else {
+                    true
+                }
+            });
+
+            expired
+        };
+
+        for probe in expired {
+            self.observation_tx
+                .send(MeasurementEvent::Loss(MeasurementLoss {
+                    stream: probe.stream,
+                    started_at: probe.sent_at,
+                    detected_at: now,
+                }))
+                .map_err(|_| IcmpError::EventChannelClosed)?;
+        }
+
+        Ok(())
+    }
+}
+
+const MS_PER_DAY: i64 = 86_400_000;
+
+fn timestamp_delta(later: i64, earlier: i64) -> i64 {
+    let delta = later - earlier;
+    if delta < -MS_PER_DAY / 2 {
+        delta + MS_PER_DAY
+    } else if delta > MS_PER_DAY / 2 {
+        delta - MS_PER_DAY
+    } else {
+        delta
+    }
+}

src/measurement/mod.rs

@@ -1,2 +1,2 @@
-mod icmp;
+pub(crate) mod icmp;
-mod model;
+pub(crate) mod model;

src/measurement/model.rs

@@ -6,6 +6,7 @@ use std::{
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct MeasurementStreamId(pub u64);
 
+#[allow(dead_code)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum MeasurementSource {
     IcmpEcho,
@@ -22,17 +23,54 @@ pub struct MeasurementStream {
     pub source: MeasurementSource,
 }
 
+#[allow(dead_code)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum OneWayClock {
     Uncalibrated,
     Calibrated,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct ProbeSchedule {
+    pub period: Duration,
+    pub offset: Duration,
+}
+
+impl ProbeSchedule {
+    pub(crate) fn next_probe_at(&self, origin: Instant, now: Instant) -> Instant {
+        const NANOS_PER_SEC: u128 = 1_000_000_000;
+
+        let first = origin + self.offset;
+
+        if now < first {
+            return first;
+        }
+
+        let elapsed_ns = now.duration_since(first).as_nanos();
+        let period_ns = self.period.as_nanos();
+        let remainder = elapsed_ns % period_ns;
+
+        let until_next = if remainder == 0 {
+            period_ns
+        } else {
+            period_ns - remainder
+        };
+
+        let until_next = Duration::new(
+            (until_next / NANOS_PER_SEC) as u64,
+            (until_next % NANOS_PER_SEC) as u32,
+        );
+
+        now + until_next
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 pub struct SignedDuration {
     nanos: i64,
 }
 
+#[allow(dead_code)]
 impl SignedDuration {
     pub const fn from_nanos(nanos: i64) -> Self {
         Self { nanos }
@@ -60,6 +98,7 @@ pub struct OneWayLatency {
     pub clock: OneWayClock,
 }
 
+#[allow(dead_code)]
 #[derive(Debug, Clone, Copy)]
 pub struct MeasurementObservation {
     pub stream: MeasurementStream,
@@ -74,6 +113,7 @@ pub struct MeasurementObservation {
     pub one_way: Option<OneWayLatency>,
 }
 
+#[allow(dead_code)]
 impl MeasurementObservation {
     pub fn rtt(&self) -> Duration {
         self.observed_at.duration_since(self.started_at)
@@ -84,12 +124,14 @@ impl MeasurementObservation {
     }
 }
 
+#[allow(dead_code)]
 pub struct MeasurementLoss {
     pub stream: MeasurementStream,
     pub started_at: Instant,
     pub detected_at: Instant,
 }
 
+#[allow(dead_code)]
 pub enum MeasurementEvent {
     Observation(MeasurementObservation),
     Loss(MeasurementLoss),

src/settings/mod.rs

@@ -219,8 +219,11 @@ pub(crate) struct NetworkSettings {
     #[serde(default = "default_min_percent")]
     pub(crate) upload_min_percent: f64,
 
+    #[allow(dead_code)]
     pub(crate) measurement_bind_device: Option<String>,
+    #[allow(dead_code)]
     pub(crate) measurement_mark: Option<u32>,
+    #[allow(dead_code)]
     pub(crate) measurement_fib: Option<u32>,
 }