try so_timestamp on macos

src/raw_socket.rs

@@ -16,6 +16,8 @@ use crate::{
 mod freebsd;
 #[cfg(target_os = "linux")]
 mod linux;
+#[cfg(target_os = "macos")]
+mod macos;
 
 // A struct providing safe wrappers around various socket api calls
 #[derive(Debug, Hash)]

src/raw_socket/macos.rs

@@ -0,0 +1,35 @@
+use crate::cerr;
+
+use super::RawSocket;
+
+impl RawSocket {
+    pub(crate) fn so_timestamp(&self, options: u32) -> std::io::Result<()> {
+        // Documentation on the timestamping calls:
+        //
+        // - linux: https://www.kernel.org/doc/Documentation/networking/timestamping.txt
+        // - freebsd: https://man.freebsd.org/cgi/man.cgi?setsockopt
+        //
+        // SAFETY:
+        //
+        // - the socket is provided by (safe) rust, and will outlive the call
+        // - method is guaranteed to be a valid "name" argument
+        // - the options pointer outlives the call
+        // - the `option_len` corresponds with the options pointer
+        //
+        // Only some bits are valid to set in `options`, but setting invalid bits is
+        // perfectly safe
+        //
+        // > Setting other bit returns EINVAL and does not change the current state.
+        unsafe {
+            cerr(libc::setsockopt(
+                self.fd,
+                libc::SOL_SOCKET,
+                libc::SO_TIMESTAMP,
+                &options as *const _ as *const libc::c_void,
+                std::mem::size_of_val(&options) as libc::socklen_t,
+            ))
+        }?;
+
+        Ok(())
+    }
+}

src/socket.rs

@@ -9,19 +9,23 @@ use crate::{
     raw_socket::RawSocket,
 };
 
-#[cfg(not(any(target_os = "linux", target_os = "freebsd")))]
+#[cfg(not(any(target_os = "linux", target_os = "freebsd", target_os = "macos")))]
 mod fallback;
 #[cfg(target_os = "freebsd")]
 mod freebsd;
 #[cfg(target_os = "linux")]
 mod linux;
+#[cfg(target_os = "macos")]
+mod macos;
 
-#[cfg(not(any(target_os = "linux", target_os = "freebsd")))]
+#[cfg(not(any(target_os = "linux", target_os = "freebsd", target_os = "macos")))]
 use self::fallback::*;
 #[cfg(target_os = "freebsd")]
 use self::freebsd::*;
 #[cfg(target_os = "linux")]
 pub use self::linux::*;
+#[cfg(target_os = "macos")]
+use self::macos::*;
 
 #[derive(Debug, Clone, Copy, Eq, PartialEq, PartialOrd, Ord, Hash, Default)]
 pub struct Timestamp {
@@ -30,7 +34,7 @@ pub struct Timestamp {
 }
 
 impl Timestamp {
-    #[cfg_attr(target_os = "macos", unused)] // macos does not do nanoseconds
+    #[cfg_attr(target_os = "macos", allow(unused))] // macos does not do nanoseconds
     pub(crate) fn from_timespec(timespec: libc::timespec) -> Self {
         Self {
             seconds: timespec.tv_sec as _,

src/socket/macos.rs

@@ -0,0 +1,14 @@
+use crate::raw_socket::RawSocket;
+
+use super::InterfaceTimestampMode;
+
+pub(super) fn configure_timestamping(
+    socket: &RawSocket,
+    mode: InterfaceTimestampMode,
+) -> std::io::Result<()> {
+    match mode {
+        InterfaceTimestampMode::None => Ok(()),
+        InterfaceTimestampMode::SoftwareRecv => socket.so_timestamp(1),
+        _ => Err(std::io::ErrorKind::Unsupported.into()),
+    }
+}