feat(measurement): implement ICMP measurement engine

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),