feat: support portforwarding over websocket (#2894)

* feat: support portforwarding over websocket

* replicating kubectl implementation

* update readme

README.md

@@ -563,6 +563,13 @@ In order to surface hotkeys globally please follow these steps:
 
 ---
 
+## Port Forwarding over websockets
+
+K9s follows `kubectl` feature flag environment variables to enable/disable port-forwarding over websockets. (default enabled in >1.30)
+To disable Websocket support, set `KUBECTL_PORT_FORWARD_WEBSOCKETS=false`
+
+---
+
 ## FastForwards
 
 As of v0.25.0, you can leverage the `FastForwards` feature to tell K9s how to default port-forwards. In situations where you are dealing with multiple containers or containers exposing multiple ports, it can be cumbersome to specify the desired port-forward from the dialog as in most cases, you already know which container/port tuple you desire. For these use cases, you can now annotate your manifests with the following annotations:

internal/dao/port_forwarder.go

@@ -18,10 +18,12 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/runtime/serializer"
+	"k8s.io/apimachinery/pkg/util/httpstream"
 	"k8s.io/cli-runtime/pkg/genericclioptions"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/portforward"
 	"k8s.io/client-go/transport/spdy"
+	cmdutil "k8s.io/kubectl/pkg/cmd/util"
 )
 
 const defaultTimeout = 30 * time.Second
@@ -181,6 +183,18 @@ func (p *PortForwarder) forwardPorts(method string, url *url.URL, addr, portMap
 	}
 	dialer := spdy.NewDialer(upgrader, &http.Client{Transport: transport, Timeout: defaultTimeout}, method, url)
 
+	if !cmdutil.PortForwardWebsockets.IsDisabled() {
+		tunnelingDialer, err := portforward.NewSPDYOverWebsocketDialer(url, cfg)
+		if err != nil {
+			return nil, err
+		}
+
+		// First attempt tunneling (websocket) dialer, then fallback to spdy dialer.
+		dialer = portforward.NewFallbackDialer(tunnelingDialer, dialer, func(err error) bool {
+			return httpstream.IsUpgradeFailure(err) || httpstream.IsHTTPSProxyError(err)
+		})
+	}
+
 	return portforward.NewOnAddresses(dialer, []string{addr}, []string{portMap}, p.stopChan, p.readyChan, p.Out, p.ErrOut)
 }