gRPC traffic is not mirrored when using the Linkerd service mesh

[bourquep]

Bug Description

When debugging a mirrored C# (.Net 8) micro service in Rider, breakpoints for incoming gRPC requests are not hit.

My service listens for HTTP requests on port 8080 and for gRPC requests on port 5000. I see that HTTP handlers are mirrored properly (well, at least the /healthz endpoint which is called periodically by the k8s probe). But the gRPC requests are not. Those gRPC requests actually come into the ingress (Contour/Envoy) as grpc-web requests, which are translated to gRPC by Envoy. Then, Envoy sends a meshed request to my service on port 5000.

Removing the Linkerd proxy from my mirrored pod fixes the issue (my breakpoints are hit)

Steps to Reproduce

1. Have a Contour ingress, injected with the Linkerd proxy
2. Have a gRPC service in a pod that is also injected by the Linkerd proxy
3. Use mirrord to mirror the service's traffic
4. Make a grpc-web call to the Contour ingress
5. Observe that the mirrored process doesn't receive the request
6. Remove the Linkerd proxy from the gRPC service pod
7. Make a grpc-web call to the Contour ingress
8. Observe that the mirrored process does receive the request

Backtrace

No response

Relevant Logs

No response

Your operating system and version

macOS 14.4.1 (23E224)

Local process

A C# (.Net 8) process

Local process version

No response

Additional Info

No response