Merge 7b023a3e8e into 951173ba19

Fixes #74 - When the device is unable to connect to the time servers, it
was looping every two seconds.  This lead to unecessary processing, and
if the device was able to connect to DNS but not the time servers, it
was causing undue load on the DNS server as well.

network.go

@@ -13,6 +13,8 @@ import (
 	"github.com/vishvananda/netlink/nl"
 )
 
+var mDNSConn *mdns.Conn
+
 var networkState struct {
 	Up   bool
 	IPv4 string
@@ -91,13 +93,26 @@ func checkNetworkState() {
 	}
 
 	if newState != networkState {
-		networkState = newState
 		fmt.Println("network state changed")
+		//restart MDNS
+		startMDNS()
+		networkState = newState
 		requestDisplayUpdate()
 	}
 }
 
 func startMDNS() error {
+	//If server was previously running, stop it
+	if mDNSConn != nil {
+		fmt.Printf("Stopping mDNS server\n")
+		err := mDNSConn.Close()
+		if err != nil {
+			fmt.Printf("failed to stop mDNS server: %v\n", err)
+		}
+	}
+
+	//Start a new server
+	fmt.Printf("Starting mDNS server on jetkvm.local\n")
 	addr4, err := net.ResolveUDPAddr("udp4", mdns.DefaultAddressIPv4)
 	if err != nil {
 		return err
@@ -118,10 +133,11 @@ func startMDNS() error {
 		return err
 	}
 
-	_, err = mdns.Server(ipv4.NewPacketConn(l4), ipv6.NewPacketConn(l6), &mdns.Config{
+	mDNSConn, err = mdns.Server(ipv4.NewPacketConn(l4), ipv6.NewPacketConn(l6), &mdns.Config{
 		LocalNames: []string{"jetkvm.local"}, //TODO: make it configurable
 	})
 	if err != nil {
+		mDNSConn = nil
 		return err
 	}
 	//defer server.Close()
@@ -157,7 +173,6 @@ func init() {
 			}
 		}
 	}()
-	fmt.Println("Starting mDNS server")
 	err := startMDNS()
 	if err != nil {
 		fmt.Println("failed to run mDNS: %v", err)

ntp.go

@@ -20,6 +20,8 @@ func TimeSyncLoop() {
 		err := SyncSystemTime()
 		if err != nil {
 			log.Printf("Failed to sync system time: %v", err)
+			// Sync failed for all 4 endpoints, likely network issue, wait for 1 hour before retrying
+			time.Sleep(1 * time.Hour)
 			continue
 		}
 		log.Printf("Time sync successful, now is: %v, time taken: %v", time.Now(), time.Since(start))