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🌱 kcp: enable websocket dialer with fallback to spdy #12902

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k8s-ci-robot merged 1 commit into from
Oct 28, 2025
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🌱 kcp: enable websocket dialer with fallback to spdy #12902

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11 changes: 11 additions & 0 deletions controlplane/kubeadm/internal/proxy/dial.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ import (
"github.com/pkg/errors"
corev1 "k8s.io/api/core/v1"
kerrors "k8s.io/apimachinery/pkg/util/errors"
"k8s.io/apimachinery/pkg/util/httpstream"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/portforward"
"k8s.io/client-go/transport/spdy"
Expand Down Expand Up @@ -108,6 +109,16 @@ func (d *Dialer) DialContext(ctx context.Context, _ string, addr string) (net.Co

dialer := spdy.NewDialer(d.upgrader, httpClient, "POST", req.URL())

// Configure websocket dialer and keep spdy as fallback
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@sbueringer sbueringer Oct 28, 2025

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Change looks easy enough. Any ideas on how I can validate if this is correct? (e.g. is there some prior art somewhere else?)

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@chrischdi chrischdi Oct 28, 2025

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I did via using tilt.

I added a breakpoint here for KCP accordingly to check if it uses websocket or does the fallback.

For v1.34: it did not do the fallback and successfully used websockets (verified via the dial method)

For v1.30 it did use the fallback / old code SPDY

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@sbueringer sbueringer Oct 28, 2025

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Thx!

For future reference, kubectl does something similar: https://github.com/kubernetes/kubernetes/blob/c3f15fd707a092e6cb7d96b84b81ada1f118d759/staging/src/k8s.io/kubectl/pkg/cmd/portforward/portforward.go#L144-L155

// Note: websockets are enabled per default starting with kubernetes 1.31.
tunnelingDialer, err := portforward.NewSPDYOverWebsocketDialer(req.URL(), d.proxy.KubeConfig)
if err != nil {
return nil, errors.Wrap(err, "error creating websocket tunneling dialer")
}
dialer = portforward.NewFallbackDialer(tunnelingDialer, dialer, func(err error) bool {
return httpstream.IsUpgradeFailure(err) || httpstream.IsHTTPSProxyError(err)
})

// Create a new connection from the dialer.
//
// Warning: Any early return should close this connection, otherwise we're going to leak them.
Expand Down