Fix IPv6 primary node-ip handling

I should have caught `[]string{cfg.NodeIP}[0]` and `[]string{envInfo.NodeIP.String()}[0]` in code review...

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

pkg/agent/config/config.go

@@ -370,10 +370,9 @@ func get(ctx context.Context, envInfo *cmds.Agent, proxy proxy.Proxy) (*config.N
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to retrieve configuration from server")
 	}
-
 	// If the supervisor and externally-facing apiserver are not on the same port, tell the proxy where to find the apiserver.
 	if controlConfig.SupervisorPort != controlConfig.HTTPSPort {
-		isIPv6 := utilsnet.IsIPv6(net.ParseIP([]string{envInfo.NodeIP.String()}[0]))
+		isIPv6 := utilsnet.IsIPv6(net.ParseIP(util.GetFirstValidIPString(envInfo.NodeIP)))
 		if err := proxy.SetAPIServerPort(controlConfig.HTTPSPort, isIPv6); err != nil {
 			return nil, errors.Wrapf(err, "failed to set apiserver port to %d", controlConfig.HTTPSPort)
 		}

pkg/agent/run.go

@@ -322,7 +322,7 @@ func createProxyAndValidateToken(ctx context.Context, cfg *cmds.Agent) (proxy.Pr
 	if err := os.MkdirAll(agentDir, 0700); err != nil {
 		return nil, err
 	}
-	isIPv6 := utilsnet.IsIPv6(net.ParseIP([]string{cfg.NodeIP.String()}[0]))
+	isIPv6 := utilsnet.IsIPv6(net.ParseIP(util.GetFirstValidIPString(cfg.NodeIP)))
 
 	proxy, err := proxy.NewSupervisorProxy(ctx, !cfg.DisableLoadBalancer, agentDir, cfg.ServerURL, cfg.LBServerPort, isIPv6)
 	if err != nil {

pkg/daemons/agent/agent_linux.go

@@ -34,8 +34,7 @@ func createRootlessConfig(argsMap map[string]string, controllers map[string]bool
 
 func kubeProxyArgs(cfg *config.Agent) map[string]string {
 	bindAddress := "127.0.0.1"
-	isIPv6 := utilsnet.IsIPv6(net.ParseIP([]string{cfg.NodeIP}[0]))
-	if isIPv6 {
+	if utilsnet.IsIPv6(net.ParseIP(cfg.NodeIP)) {
 		bindAddress = "::1"
 	}
 	argsMap := map[string]string{
@@ -67,8 +66,7 @@ func kubeProxyArgs(cfg *config.Agent) map[string]string {
 
 func kubeletArgs(cfg *config.Agent) map[string]string {
 	bindAddress := "127.0.0.1"
-	isIPv6 := utilsnet.IsIPv6(net.ParseIP([]string{cfg.NodeIP}[0]))
-	if isIPv6 {
+	if utilsnet.IsIPv6(net.ParseIP(cfg.NodeIP)) {
 		bindAddress = "::1"
 	}
 	argsMap := map[string]string{

pkg/daemons/agent/agent_windows.go

@@ -4,6 +4,7 @@
 package agent
 
 import (
+	"net"
 	"os"
 	"path/filepath"
 	"strings"
@@ -11,8 +12,8 @@ import (
 	"github.com/k3s-io/k3s/pkg/daemons/config"
 	"github.com/k3s-io/k3s/pkg/util"
 	"github.com/sirupsen/logrus"
-	"k8s.io/apimachinery/pkg/util/net"
 	"k8s.io/kubernetes/pkg/kubeapiserver/authorizer/modes"
+	utilsnet "k8s.io/utils/net"
 )
 
 const (
@@ -21,8 +22,7 @@ const (
 
 func kubeProxyArgs(cfg *config.Agent) map[string]string {
 	bindAddress := "127.0.0.1"
-	_, IPv6only, _ := util.GetFirstString([]string{cfg.NodeIP})
-	if IPv6only {
+	if utilsnet.IsIPv6(net.ParseIP(cfg.NodeIP)) {
 		bindAddress = "::1"
 	}
 	argsMap := map[string]string{
@@ -95,9 +95,22 @@ func kubeletArgs(cfg *config.Agent) map[string]string {
 	if cfg.NodeName != "" {
 		argsMap["hostname-override"] = cfg.NodeName
 	}
-	defaultIP, err := net.ChooseHostInterface()
-	if err != nil || defaultIP.String() != cfg.NodeIP {
-		argsMap["node-ip"] = cfg.NodeIP
+
+	// If the embedded CCM is disabled, don't assume that dual-stack node IPs are safe.
+	// When using an external CCM, the user wants dual-stack node IPs, they will need to set the node-ip kubelet arg directly.
+	// This should be fine since most cloud providers have their own way of finding node IPs that doesn't depend on the kubelet
+	// setting them.
+	if cfg.DisableCCM {
+		dualStack, err := utilsnet.IsDualStackIPs(cfg.NodeIPs)
+		if err == nil && !dualStack {
+			argsMap["node-ip"] = cfg.NodeIP
+		}
+	} else {
+		// Cluster is using the embedded CCM, we know that the feature-gate will be enabled there as well.
+		argsMap["feature-gates"] = util.AddFeatureGate(argsMap["feature-gates"], "CloudDualStackNodeIPs=true")
+		if nodeIPs := util.JoinIPs(cfg.NodeIPs); nodeIPs != "" {
+			argsMap["node-ip"] = util.JoinIPs(cfg.NodeIPs)
+		}
 	}
 
 	argsMap["node-labels"] = strings.Join(cfg.NodeLabels, ",")