feat(systemd): Support reloading

Signed-off-by: Steffen Vogel <post@steffenvogel.de>

pkg/daemon/daemon.go

@@ -7,6 +7,7 @@ import (
 	"errors"
 	"fmt"
 	"strings"
+	"time"
 
 	"go.uber.org/zap"
 	"golang.zx2c4.com/wireguard/wgctrl"
@@ -108,7 +109,7 @@ func (d *Daemon) Start() error {
 		return fmt.Errorf("initial sync failed: %w", err)
 	}
 
-	signals := osx.SetupSignals(osx.SigUpdate)
+	signals := osx.SetupSignals(osx.SigUpdate, osx.SigReload)
 
 	wdt, err := d.watchdogTicker()
 	if err != nil && !errors.Is(err, errNotSupported) {
@@ -129,6 +130,12 @@ out:
 				if err := d.Sync(); err != nil {
 					d.logger.Error("Failed to synchronize interfaces", zap.Error(err))
 				}
+
+			case osx.SigReload:
+				if err := d.reload(); err != nil {
+					return err
+				}
+
 			default:
 				break out
 			}
@@ -276,6 +283,22 @@ func (d *Daemon) watchdogTicker() (<-chan time.Time, error) {
 	return time.NewTicker(wdInterval / 2).C, nil
 }
 
+func (d *Daemon) reload() error {
+	if err := d.setState(StateReloading); err != nil {
+		return fmt.Errorf("failed transition state: %w", err)
+	}
+
+	if _, err := d.Config.ReloadAllSources(); err != nil {
+		d.logger.Error("Failed to reload config", zap.Error(err))
+	}
+
+	if err := d.setState(StateReady); err != nil {
+		return fmt.Errorf("failed transition state: %w", err)
+	}
+
+	return nil
+}
+
 func (d *Daemon) setState(s State) error {
 	d.state = s
 
@@ -308,6 +331,18 @@ func (d *Daemon) setState(s State) error {
 func (d *Daemon) notify(notify string) error {
 	notifyMessages := []string{notify}
 
+	if notify == systemd.NotifyReloading {
+		now, err := osx.GetClockMonotonic()
+		if err != nil {
+			return fmt.Errorf("failed to get monotonic clock: %w", err)
+		}
+
+		notifyMessages = append(notifyMessages,
+			fmt.Sprintf("MONOTONIC_USEC=%d", now.UnixMicro()))
+
+		d.logger.DebugV(5, "Notifying systemd", zap.Strings("message", notifyMessages))
+	}
+
 	if _, err := systemd.Notify(false, strings.Join(notifyMessages, "\n")); err != nil {
 		return err
 	}

pkg/os/clock_linux.go

@@ -0,0 +1,22 @@
+// SPDX-FileCopyrightText: 2023-2024 Steffen Vogel <post@steffenvogel.de>
+// SPDX-License-Identifier: Apache-2.0
+
+package os
+
+import (
+	"syscall"
+	"time"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// GetClockMonotonic returns the current time from the CLOCK_MONOTONIC clock.
+func GetClockMonotonic() (t time.Time, err error) {
+	var ts syscall.Timespec
+	if _, _, err := syscall.Syscall(syscall.SYS_CLOCK_GETTIME, unix.CLOCK_MONOTONIC, uintptr(unsafe.Pointer(&ts)), 0); err != 0 {
+		return time.Time{}, err
+	}
+
+	return time.Unix(int64(ts.Sec), int64(ts.Nsec)), nil //nolint:unconvert
+}

pkg/os/clock_others.go

@@ -0,0 +1,15 @@
+// SPDX-FileCopyrightText: 2023-2024 Steffen Vogel <post@steffenvogel.de>
+// SPDX-License-Identifier: Apache-2.0
+
+//go:build !linux
+
+package os
+
+import (
+	"time"
+)
+
+// GetClockMonotonic returns the current time from the CLOCK_MONOTONIC clock.
+func GetClockMonotonic() (t time.Time, err error) {
+	return time.Now(), nil
+}

pkg/os/signal_others.go

@@ -11,4 +11,5 @@ import (
 
 const (
 	SigUpdate = unix.SIGUSR1
+	SigReload = unix.SIGHUP
 )

pkg/os/signal_windows.go

@@ -11,4 +11,5 @@ import (
 
 const (
 	SigUpdate = syscall.Signal(-1) // not supported
+	SigReload = syscall.Signal(-2) // not supported
 )