Traffic callout extension erroring out on gRPC backend on the loadbalancer

[varkey98]

I have a load balancer which has a grpc backend. When configuring traffic callout extension on that lb, the response data sent to my envoy (ext_proc_v3) server doesnt have `end_of_stream` set in the response data. This is what my server got for a single request:

2024/01/24 11:39:07 Started process
2024/01/24 11:39:07 Received stream
2024/01/24 11:39:07 request_headers:{headers:{headers:{key:":scheme"  raw_value:"https"}  headers:{key:":path"  raw_value:"/helloworld.Greeter/SayHello"}  headers:{key:":method"  raw_value:"POST"}  headers:{key:":authority"  raw_value:"35.212.139.253"}  headers:{key:"grpc-accept-encoding"  raw_value:"identity,deflate,gzip"}  headers:{key:"accept-encoding"  raw_value:"identity"}  headers:{key:"user-agent"  raw_value:"grpc-node-js/1.8.10"}  headers:{key:"content-type"  raw_value:"application/grpc"}  headers:{key:"x-forwarded-proto"  raw_value:"https"}  headers:{key:"via"  raw_value:"1.1 google"}  headers:{key:"x-forwarded-for"  raw_value:"49.207.211.218,35.212.139.253"}}}
2024/01/24 11:39:07 Received stream
2024/01/24 11:39:07 request_body:{body:"\x00\x00\x00\x00\x08\n\x06varkey"  end_of_stream:true}
2024/01/24 11:39:07 Received stream
2024/01/24 11:39:07 response_headers:{headers:{headers:{key:":status"  raw_value:"200"}  headers:{key:"content-type"  raw_value:"application/grpc"}}}
2024/01/24 11:39:07 Received stream
2024/01/24 11:39:07 response_body:{body:"\x00\x00\x00\x00\x0e\n\x0chello varkey"}

Ideally there should be `end_of_stream` set in response_body so that we can infer the request data has been completely sent over. This works fine for HTTP/1 backends, issue is with gRPC backend application