feature: service_linux: Support systemd watchdog

dnscrypt-proxy/privilege_linux.go

@@ -47,7 +47,9 @@ func (proxy *Proxy) dropPrivilege(userStr string, fds []*os.File) {
 		dlog.Fatal(err)
 	}
 
-	ServiceManagerReadyNotify()
+	if err := ServiceManagerReadyNotify(); err != nil {
+		dlog.Fatal(err)
+	}
 
 	args = append(args, "-child")
 

dnscrypt-proxy/privilege_others.go

@@ -48,7 +48,9 @@ func (proxy *Proxy) dropPrivilege(userStr string, fds []*os.File) {
 		dlog.Fatal(err)
 	}
 
-	ServiceManagerReadyNotify()
+	if err := ServiceManagerReadyNotify(); err != nil {
+		dlog.Fatal(err)
+	}
 
 	args = append(args, "-child")
 

dnscrypt-proxy/proxy.go

@@ -166,7 +166,9 @@ func (proxy *Proxy) StartProxy() {
 	if liveServers > 0 {
 		dlog.Noticef("dnscrypt-proxy is ready - live servers: %d", liveServers)
 		if !proxy.child {
-			ServiceManagerReadyNotify()
+			if err := ServiceManagerReadyNotify(); err != nil {
+				dlog.Fatal(err)
+			}
 		}
 	} else if err != nil {
 		dlog.Error(err)

dnscrypt-proxy/service_android.go

@@ -6,5 +6,6 @@ func ServiceManagerStartNotify() error {
 	return nil
 }
 
-func ServiceManagerReadyNotify() {
+func ServiceManagerReadyNotify() error {
+	return nil
 }

dnscrypt-proxy/service_linux.go

@@ -2,13 +2,36 @@
 
 package main
 
-import "github.com/coreos/go-systemd/daemon"
+import (
+	"github.com/coreos/go-systemd/daemon"
+	clocksmith "github.com/jedisct1/go-clocksmith"
+)
 
 func ServiceManagerStartNotify() error {
 	daemon.SdNotify(false, "STATUS=Starting")
 	return nil
 }
 
-func ServiceManagerReadyNotify() {
+func ServiceManagerReadyNotify() error {
 	daemon.SdNotify(false, "READY=1")
+	return systemDWatchdog()
+}
+
+func systemDWatchdog() error {
+	watchdogFailureDelay, err := daemon.SdWatchdogEnabled(false)
+	if err != nil || watchdogFailureDelay == 0 {
+		return err
+	}
+	refreshInterval := watchdogFailureDelay / 3
+	go func() {
+		for {
+			// TODO There could be other checks this just
+			// checks program is not totally stuck and can
+			// run this goroutine
+			daemon.SdNotify(false, "WATCHDOG=1")
+			clocksmith.Sleep(refreshInterval)
+		}
+
+	}()
+	return nil
 }

dnscrypt-proxy/service_others.go

@@ -6,5 +6,6 @@ func ServiceManagerStartNotify() error {
 	return nil
 }
 
-func ServiceManagerReadyNotify() {
+func ServiceManagerReadyNotify() error {
+	return nil
 }

dnscrypt-proxy/service_windows.go

@@ -11,4 +11,6 @@ func ServiceManagerStartNotify() error {
 	return nil
 }
 
-func ServiceManagerReadyNotify() {}
+func ServiceManagerReadyNotify() error {
+	return nil
+}