feat: Add --timesync flag for guest clock synchronization

Add a --timesync option which uses vsock to send host time to
qemu-guest-agent running in the guest on VM suspend/resume.

Uses IOKit's power management APIs to detect system sleep/wake
events. Since the official iokit-sys crate is incomplete, a
custom fork is required.

This also maintains feature parity between krunkit and vfkit.

Assisted by: Claude (Anthropic AI)

Signed-off-by: Gunjan Vyas <vyasgun20@gmail.com>

Co-authored-by: Tyler Fanelli <tfanelli@redhat.com>

Author: vyasgun

Cargo.lock

@@ -16,3 +16,5 @@ sysinfo = "0.31.4"
 log = "0.4.0"
 env_logger = "0.11.8"
 regex = "1.11.1"
+core-foundation = "0.10.1"
+objc2-io-kit = "0.3.2"

Cargo.toml

@@ -63,6 +63,10 @@ pub struct Args {
     /// Firmware path.
     #[arg(long, short)]
     pub firmware_path: Option<PathBuf>,
+
+    /// Vsock port for timesync
+    #[arg(long = "timesync")]
+    pub timesync: Option<u32>,
 }
 
 /// Parse the input string into a hash map of key value pairs, associating the argument with its

src/cmdline.rs

@@ -16,6 +16,8 @@ use std::{
     io,
 };
 
+use crate::timesync::timesync_listener;
+use crate::virtio::{VsockAction, VsockConfig};
 use anyhow::{anyhow, Context};
 use env_logger::{Builder, Env, Target};
 
@@ -191,6 +193,19 @@ impl TryFrom<Args> for KrunContext {
             }
         }
 
+        if let Some(timesync_port) = args.timesync {
+            let vsock_config = VsockConfig {
+                port: timesync_port,
+                socket_url: PathBuf::from(format!(
+                    "/tmp/krunkit_timesync_{}.sock",
+                    std::process::id()
+                )),
+                action: VsockAction::Connect,
+            };
+            unsafe { vsock_config.krun_ctx_set(id)? }
+            thread::spawn(move || timesync_listener(vsock_config));
+        }
+
         Ok(Self { id, args })
     }
 }

src/context.rs

@@ -5,6 +5,7 @@
 mod cmdline;
 mod context;
 mod status;
+mod timesync;
 mod virtio;
 
 use cmdline::Args;

src/main.rs

@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::virtio::VsockConfig;
+use std::io::{BufRead, BufReader, Write};
+use std::os::unix::net::UnixStream;
+use std::path::PathBuf;
+use std::time::SystemTime;
+use std::time::UNIX_EPOCH;
+
+use core_foundation::runloop::{
+    kCFRunLoopCommonModes, CFRunLoopAddSource, CFRunLoopGetCurrent, CFRunLoopRun, __CFRunLoopSource,
+};
+use objc2_io_kit::{
+    io_object_t, io_service_t, kIOMessageSystemHasPoweredOn, kIOMessageSystemWillPowerOn,
+    kIOMessageSystemWillSleep, IONotificationPort, IORegisterForSystemPower,
+};
+use std::{
+    ffi::c_void,
+    sync::mpsc::{channel, Receiver, Sender},
+};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Activity {
+    Sleep,
+    Wake,
+}
+
+#[allow(non_upper_case_globals)]
+extern "C-unwind" fn power_callback(
+    refcon: *mut c_void,
+    _service: io_service_t,
+    message_type: u32,
+    _message_argument: *mut c_void,
+) {
+    let tx = unsafe { &*(refcon as *mut Sender<Activity>) };
+    log::debug!("Power callback called: {:X?}", message_type);
+    let activity = match message_type {
+        kIOMessageSystemWillSleep => Some(Activity::Sleep),
+        kIOMessageSystemWillPowerOn | kIOMessageSystemHasPoweredOn => Some(Activity::Wake),
+        _ => {
+            log::debug!("Unknown message type: {:X?}", message_type);
+            None
+        }
+    };
+    if let Some(activity) = activity {
+        if let Err(e) = tx.send(activity) {
+            log::error!("Failed to send activity: {e}");
+        }
+    }
+}
+
+pub fn start_power_monitor() -> Receiver<Activity> {
+    let (tx, rx) = channel::<Activity>();
+    std::thread::spawn(move || unsafe {
+        let tx_ptr = Box::into_raw(Box::new(tx));
+        let mut notifier_port: *mut IONotificationPort = std::ptr::null_mut();
+        let mut notifier_object: io_object_t = 0;
+
+        let root_port = IORegisterForSystemPower(
+            tx_ptr as *mut c_void,
+            &mut notifier_port,
+            Some(power_callback),
+            &mut notifier_object,
+        );
+        if root_port == 0 {
+            log::error!("Failed to register for system power notifications");
+            return;
+        }
+        let run_loop_source = IONotificationPort::run_loop_source(notifier_port).unwrap();
+        CFRunLoopAddSource(
+            CFRunLoopGetCurrent(),
+            std::ptr::from_ref(&*run_loop_source) as *mut __CFRunLoopSource,
+            kCFRunLoopCommonModes,
+        );
+        CFRunLoopRun();
+    });
+    rx
+}
+
+fn sync_time(socket_url: PathBuf) {
+    let mut stream = match UnixStream::connect(&socket_url) {
+        Ok(stream) => stream,
+        Err(e) => {
+            log::error!(
+                "Failed to connect to timesync socket {:?}: {}",
+                socket_url,
+                e
+            );
+            return;
+        }
+    };
+
+    let time_ns = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap()
+        .as_nanos();
+    let cmd =
+        format!("{{\"execute\": \"guest-set-time\", \"arguments\":{{\"time\": {time_ns}}}}}\n");
+
+    if let Err(e) = stream.write_all(cmd.as_bytes()) {
+        log::error!("Failed to write to timesync socket: {}", e);
+        return;
+    }
+
+    let mut reader = BufReader::new(&stream);
+    let mut response = String::new();
+    match reader.read_line(&mut response) {
+        Ok(_) => {
+            log::info!("Time synced to {time_ns}");
+        }
+        Err(e) => {
+            log::error!("Failed to read qemu-guest-agent response: {e}");
+        }
+    }
+}
+
+pub fn timesync_listener(vsock_config: VsockConfig) {
+    let rx = start_power_monitor();
+    for activity in rx {
+        match activity {
+            Activity::Sleep => {
+                log::debug!("System is going to sleep");
+            }
+            Activity::Wake => {
+                log::debug!("System is waking up. Syncing time...");
+                sync_time(vsock_config.socket_url.clone());
+            }
+        }
+    }
+}