Handle custom kubelet port in agent tunnel

The kubelet port can be overridden by users; we shouldn't assume its always 10250

Signed-off-by: Brad Davidson <brad.davidson@rancher.com>

pkg/agent/tunnel/tunnel.go

@@ -7,7 +7,9 @@ import (
 	"net"
 	"os"
 	"reflect"
+	"strconv"
 	"sync"
+	"time"
 
 	"github.com/gorilla/websocket"
 	agentconfig "github.com/k3s-io/k3s/pkg/agent/config"
@@ -22,6 +24,7 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/fields"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/util/wait"
 	"k8s.io/apimachinery/pkg/watch"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/rest"
@@ -31,10 +34,11 @@ import (
 )
 
 type agentTunnel struct {
-	client kubernetes.Interface
-	cidrs  cidranger.Ranger
-	ports  map[string]bool
-	mode   string
+	client      kubernetes.Interface
+	cidrs       cidranger.Ranger
+	ports       map[string]bool
+	mode        string
+	kubeletPort string
 }
 
 // explicit interface check
@@ -85,6 +89,9 @@ func Setup(ctx context.Context, config *daemonconfig.Node, proxy proxy.Proxy) er
 		close(apiServerReady)
 	}()
 
+	// Allow the kubelet port, as published via our node object
+	go tunnel.setKubeletPort(ctx, apiServerReady)
+
 	switch tunnel.mode {
 	case daemonconfig.EgressSelectorModeCluster:
 		// In Cluster mode, we allow the cluster CIDRs, and any connections to the node's IPs for pods using host network.
@@ -135,6 +142,23 @@ func Setup(ctx context.Context, config *daemonconfig.Node, proxy proxy.Proxy) er
 	return nil
 }
 
+// setKubeletPort retrieves the configured kubelet port from our node object
+func (a *agentTunnel) setKubeletPort(ctx context.Context, apiServerReady <-chan struct{}) {
+	<-apiServerReady
+
+	wait.PollImmediateWithContext(ctx, time.Second, util.DefaultAPIServerReadyTimeout, func(ctx context.Context) (bool, error) {
+		nodeName := os.Getenv("NODE_NAME")
+		node, err := a.client.CoreV1().Nodes().Get(ctx, nodeName, metav1.GetOptions{})
+		if err != nil {
+			logrus.Debugf("Tunnel authorizer failed to get Kubelet Port: %v", err)
+			return false, nil
+		}
+		a.kubeletPort = strconv.FormatInt(int64(node.Status.DaemonEndpoints.KubeletEndpoint.Port), 10)
+		logrus.Infof("Tunnel authorizer set Kubelet Port %s", a.kubeletPort)
+		return true, nil
+	})
+}
+
 func (a *agentTunnel) clusterAuth(config *daemonconfig.Node) {
 	// In Cluster mode, we add static entries for the Node IPs and Cluster CIDRs
 	for _, ip := range config.AgentConfig.NodeIPs {
@@ -304,7 +328,7 @@ func (a *agentTunnel) authorized(ctx context.Context, proto, address string) boo
 	logrus.Debugf("Tunnel authorizer checking dial request for %s", address)
 	host, port, err := net.SplitHostPort(address)
 	if err == nil {
-		if proto == "tcp" && daemonconfig.KubeletReservedPorts[port] && (host == "127.0.0.1" || host == "::1") {
+		if a.isKubeletPort(proto, host, port) {
 			return true
 		}
 		if ip := net.ParseIP(host); ip != nil {
@@ -359,3 +383,8 @@ func (a *agentTunnel) connect(rootCtx context.Context, waitGroup *sync.WaitGroup
 
 	return cancel
 }
+
+// isKubeletPort returns true if the connection is to a reserved TCP port on a loopback address.
+func (a *agentTunnel) isKubeletPort(proto, host, port string) bool {
+	return proto == "tcp" && (host == "127.0.0.1" || host == "::1") && (port == a.kubeletPort || port == daemonconfig.StreamServerPort)
+}

pkg/daemons/config/types.go

@@ -32,16 +32,8 @@ const (
 	EgressSelectorModePod         = "pod"
 	CertificateRenewDays          = 90
 	StreamServerPort              = "10010"
-	KubeletPort                   = "10250"
 )
 
-// These ports can always be accessed via the tunnel server, at the loopback address.
-// Other addresses and ports are only accessible via the tunnel on newer agents, when used by a pod.
-var KubeletReservedPorts = map[string]bool{
-	StreamServerPort: true,
-	KubeletPort:      true,
-}
-
 type Node struct {
 	Docker                   bool
 	ContainerRuntimeEndpoint string

pkg/daemons/control/tunnel.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"net"
 	"net/http"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -77,15 +78,21 @@ type TunnelServer struct {
 var _ cidranger.RangerEntry = &tunnelEntry{}
 
 type tunnelEntry struct {
-	cidr     net.IPNet
-	nodeName string
-	node     bool
+	kubeletPort string
+	nodeName    string
+	cidr        net.IPNet
 }
 
 func (n *tunnelEntry) Network() net.IPNet {
 	return n.cidr
 }
 
+// Some ports can always be accessed via the tunnel server, at the loopback address.
+// Other addresses and ports are only accessible via the tunnel on newer agents, when used by a pod.
+func (n *tunnelEntry) IsReservedPort(port string) bool {
+	return n.kubeletPort != "" && (port == n.kubeletPort || port == config.StreamServerPort)
+}
+
 // ServeHTTP handles either CONNECT requests, or websocket requests to the remotedialer server
 func (t *TunnelServer) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
 	logrus.Debugf("Tunnel server handing %s %s request for %s from %s", req.Proto, req.Method, req.URL, req.RemoteAddr)
@@ -134,7 +141,8 @@ func (t *TunnelServer) onChangeNode(nodeName string, node *v1.Node) (*v1.Node, e
 						t.cidrs.Remove(*n)
 					} else {
 						logrus.Debugf("Tunnel server egress proxy updating Node %s IP %v", nodeName, n)
-						t.cidrs.Insert(&tunnelEntry{cidr: *n, nodeName: nodeName, node: true})
+						kubeletPort := strconv.FormatInt(int64(node.Status.DaemonEndpoints.KubeletEndpoint.Port), 10)
+						t.cidrs.Insert(&tunnelEntry{cidr: *n, nodeName: nodeName, kubeletPort: kubeletPort})
 					}
 				}
 			}
@@ -222,7 +230,7 @@ func (t *TunnelServer) dialBackend(ctx context.Context, addr string) (net.Conn,
 		if nets, err := t.cidrs.ContainingNetworks(ip); err == nil && len(nets) > 0 {
 			if n, ok := nets[0].(*tunnelEntry); ok {
 				nodeName = n.nodeName
-				if n.node && config.KubeletReservedPorts[port] {
+				if n.IsReservedPort(port) {
 					toKubelet = true
 					useTunnel = true
 				} else {