is it able to sniff connections established before grpcudmp launch?

[jizhilong]

Hi dear maintainer, My experiment shows the following 2 cases:

1. launch grpcdump, then launch a grpc client and invoke a grpc call -> The request/response is dumped to the console.
2. launch a grpc client and invoking grpc calls(unary call) regularly, then launch grpcdump -> No request/response is dumped to the console.

so the question in this issue title arises. If the answer is negative, is it possible to support sniff established connections in the future?

[jizhilong]

After some digging into grpcdump and gopacket, I realized the main blocker is hpack-as headers in HTTP2 are compressed with hpack, it's not possible to sniff their actual content if we skip the initial requests in which the compression tables were established.

[jschwinger233]

I've written my version of grpcdump to workaround this issue, have a try: https://github.com/jschwinger233/grpcdump