RFC: virtual (overlay) system clock

docs/man/statime.toml.5.md

@@ -41,6 +41,9 @@ will be indicated by each configuration setting shown.
 `path-trace` = *bool*
 :   The instance uses the path trace option. This allows detecting clock loops when enabled on all instances in the network.
 
+`virtual-system-clock` = *bool* (**false**)
+:   Use a virtual overlay clock instead of adjusting the system clock.
+
 ## `[[port]]`
 
 `interface` = *interface name*

docs/precompiled/man/statime.8

@@ -1,4 +1,4 @@
-.\" Automatically generated by Pandoc 3.2
+.\" Automatically generated by Pandoc 3.4
 .\"
 .TH "STATIME" "8" "" "statime 0.2.1" "statime"
 .SH NAME

docs/precompiled/man/statime.toml.5

@@ -1,4 +1,4 @@
-.\" Automatically generated by Pandoc 3.2
+.\" Automatically generated by Pandoc 3.4
 .\"
 .TH "STATIME.TOML" "5" "" "statime 0.2.1" "statime"
 .SH NAME
@@ -42,6 +42,9 @@ A tie breaker for the best master clock algorithm in the range
 A tie breaker for the best master clock algorithm in the range
 \f[CR]0..256\f[R].
 \f[CR]0\f[R] being highest priority an \f[CR]255\f[R] the lowest.
+.TP
+\f[CR]virtual\-system\-clock\f[R] = \f[I]bool\f[R] (\f[B]false\f[R])
+Use a virtual overlay clock instead of adjusting the system clock.
 .SS \f[CR][[port]]\f[R]
 .TP
 \f[CR]interface\f[R] = \f[I]interface name\f[R]

statime-linux/src/clock/mod.rs

@@ -6,7 +6,7 @@ use clock_steering::{unix::UnixClock, TimeOffset};
 use statime::{
     config::{LeapIndicator, TimePropertiesDS},
     time::{Duration, Time},
-    Clock,
+    Clock, OverlayClock, SharedClock,
 };
 
 #[derive(Debug, Clone)]
@@ -172,3 +172,29 @@ impl Clock for LinuxClock {
 pub fn libc_timespec_into_instant(spec: libc::timespec) -> Time {
     Time::from_fixed_nanos(spec.tv_sec as i128 * 1_000_000_000i128 + spec.tv_nsec as i128)
 }
+
+pub trait PortTimestampToTime {
+    fn port_timestamp_to_time(&self, ts: timestamped_socket::socket::Timestamp) -> Time;
+}
+
+impl PortTimestampToTime for LinuxClock {
+    fn port_timestamp_to_time(&self, mut ts: timestamped_socket::socket::Timestamp) -> Time {
+        // get_tai gives zero if this is a hardware clock, and the needed
+        // correction when this port uses software timestamping
+        ts.seconds += self.get_tai_offset().expect("Unable to get tai offset") as libc::time_t;
+        Time::from_fixed_nanos(ts.seconds as i128 * 1_000_000_000i128 + ts.nanos as i128)
+    }
+}
+
+impl PortTimestampToTime for OverlayClock<LinuxClock> {
+    fn port_timestamp_to_time(&self, ts: timestamped_socket::socket::Timestamp) -> Time {
+        let roclock_time = self.underlying().port_timestamp_to_time(ts);
+        self.time_from_underlying(roclock_time)
+    }
+}
+
+impl PortTimestampToTime for SharedClock<OverlayClock<LinuxClock>> {
+    fn port_timestamp_to_time(&self, ts: timestamped_socket::socket::Timestamp) -> Time {
+        self.0.lock().unwrap().port_timestamp_to_time(ts)
+    }
+}

statime-linux/src/config/mod.rs

@@ -36,6 +36,8 @@ pub struct Config {
     pub ports: Vec<PortConfig>,
     #[serde(default)]
     pub observability: ObservabilityConfig,
+    #[serde(default)]
+    pub virtual_system_clock: bool,
 }
 
 #[derive(Deserialize, Debug, Clone, PartialEq, Eq)]
@@ -285,6 +287,7 @@ interface = "enp0s31f6"
             path_trace: false,
             ports: vec![expected_port],
             observability: ObservabilityConfig::default(),
+            virtual_system_clock: false,
         };
 
         let actual = toml::from_str(MINIMAL_CONFIG).unwrap();