Use the correct NTP dhcp4 option

cmd/dhcp4d/dhcp4d.go

@@ -266,6 +266,7 @@ func newSrv(permDir string) (*srv, error) {
 	if err != nil {
 		return nil, err
 	}
+	serverIP = serverIP.To4()
 	var domainSearch []byte
 	domainSearch, err = dhcp4d.CompressNames("lan.", *domain)
 	if err != nil {
@@ -275,7 +276,7 @@ func newSrv(permDir string) (*srv, error) {
 		dhcp4.OptionSubnetMask:                 []byte{255, 255, 255, 0},
 		dhcp4.OptionRouter:                     []byte(serverIP),
 		dhcp4.OptionDomainNameServer:           []byte(serverIP),
-		dhcp4.OptionTimeServer:       []byte(serverIP),
+		dhcp4.OptionNetworkTimeProtocolServers: []byte(serverIP),
 		dhcp4.OptionDomainName:                 []byte(*domain),
 		dhcp4.OptionDomainSearch:               domainSearch,
 	}