[Feature Request] Support h2c in vhost server

[sword-jin]

Describe the feature request

Like the title, we can enable h2c support in vhost server, there is a PR already

#4561

Describe alternatives you've considered

No response

Affected area

• Docs
• Installation
• Performance and Scalability
• Security
• User Experience
• Test and Release
• Developer Infrastructure
• Client Plugin
• Server Plugin
• Extensions
• Others

[sword-jin]

@fatedier I think it's safe to wrapper the handler with h2c if we don't want to introduce new optional parameter

[fatedier]

Could you provide relevant documentation or examples from other projects? Also, please add an end-to-end (e2e) test case to ensure existing functionality is not affected.

[sword-jin]

I see, I will write a e2e test case, I think we can see the real user case in the e2e case

[sword-jin]

I can't reprocude the bug when running all the components locally, this is my playground https://github.com/sword-jin/caddy-frp-grpc-streaming/blob/be0c28f7a1a0972a6103b8434d43f73ea51f9939/cmd/client/main.go#L46

sequenceDiagram
    autonumber
    actor B as Browser
    box Purple On Cloud
    participant C as Caddy
    participant FS as Frps
    end
    box Grey On Local
    participant FC as Frpc
    participant LS as LocalServer
    end
    
    B ->> C: request 443
    C ->> C: tls termination
    C ->> FS: reverse proxy to 8888
    FS ->>+ FC: notify the client new connection
    FC ->>- FS: new tcp connection
    FS ->> FC: forward request
    FC ->> LocalServer: forward request

Loading

This diagram Illuminates how a request reach out the local server. This repo trys to build the same worfklow, but fortunately it doesn't work.

In the playground, we use a mock certificate, and the client skip the validation

When the frps and caddy on real cloud with a real tls certificate, the client always gets stream error: internal: protocol error: no Grpc-Status trailer: unexpected EOF at https://github.com/sword-jin/caddy-frp-grpc-streaming/blob/be0c28f7a1a0972a6103b8434d43f73ea51f9939/cmd/client/main.go#L46-L48

Form the logs of caddy and frps and local server, the request has been handled successfully, the problem is the trailer header is missing.

What I did to fix is add a h2c layer in frp vhost server and use http2 transport

I check the frps's response, left is without h2c, right is with h2c, the difference is left doesn't have Trailer:Grpc-Status which cause the error