Create port allocator, based on IP allocator mechanism

Including some refactoring of IP allocator

cmd/kube-apiserver/app/server.go

@@ -86,6 +86,7 @@ type APIServer struct {
 	CorsAllowedOriginList      util.StringList
 	AllowPrivileged            bool
 	PortalNet                  util.IPNet // TODO: make this a list
+	ServiceNodePorts           util.PortRange
 	EnableLogsSupport          bool
 	MasterServiceNamespace     string
 	RuntimeConfig              util.ConfigurationMap
@@ -183,6 +184,7 @@ func (s *APIServer) AddFlags(fs *pflag.FlagSet) {
 	fs.Var(&s.CorsAllowedOriginList, "cors-allowed-origins", "List of allowed origins for CORS, comma separated.  An allowed origin can be a regular expression to support subdomain matching.  If this list is empty CORS will not be enabled.")
 	fs.BoolVar(&s.AllowPrivileged, "allow-privileged", s.AllowPrivileged, "If true, allow privileged containers.")
 	fs.Var(&s.PortalNet, "portal-net", "A CIDR notation IP range from which to assign portal IPs. This must not overlap with any IP ranges assigned to nodes for pods.")
+	fs.Var(&s.ServiceNodePorts, "service-node-ports", "A port range to reserve for services with NodePort visibility.  Example: '30000-32767'.  Inclusive at both ends of the range.")
 	fs.StringVar(&s.MasterServiceNamespace, "master-service-namespace", s.MasterServiceNamespace, "The namespace from which the kubernetes master services should be injected into pods")
 	fs.Var(&s.RuntimeConfig, "runtime-config", "A set of key=value pairs that describe runtime configuration that may be passed to the apiserver. api/<version> key can be used to turn on/off specific api versions. api/all and api/legacy are special keys to control all and legacy api versions respectively.")
 	client.BindKubeletClientConfigFlags(fs, &s.KubeletConfig)