Force SSL for all connections if user enabled `SSL`

[leoncamel]

Is your feature request related to a problem? (你需要的功能是否与某个问题有关?)

NO

Describe the solution you'd like (描述你期望的解决方法)

In the case we enable SSL, the common sense is we force every client to use SSL/TLS connection for security reason. But, In the current implementation, client can connect in both plain-text and SSL/TLS.

As defined in gobal.h and global.cpp, the protocol name is "h2". But, in the RFC9113: HTTP/2
. The "h2" protocol explained as the following:

- The string "h2" identifies the protocol where HTTP/2 uses Transport Layer Security (TLS); 

- The "h2c" string was previously used as a token for use in the HTTP Upgrade mechanism's Upgrade header field ([Section 7.8](https://www.rfc-editor.org/rfc/rfc9110#section-7.8) of [[HTTP](https://www.rfc-editor.org/rfc/rfc9113.html#RFC9110)]). This usage was never widely deployed and is deprecated by this document. The same applies to the HTTP2-Settings header field, which was used with the upgrade to "h2c".

So, we just want a feature to complaint to protocol definition: force all client connections to use SSL/TLS if user explicitly enabled ssl.

Describe alternatives you've considered (描述你想到的折衷方案)

Additional context/screenshots (更多上下文/截图)

• https://www.rfc-editor.org/rfc/rfc9113.html

[leoncamel]

As we investigate the function DetectSSLState, it will auto-detect the first packet to enable SSL or not.

This seems cool feature for both plain-text & SSL/TLS connections. But, in case use want use ssl-only connections, is there any method we can do that?

Thanks, for any suggestion.

[infdahai]

Maybe after accepting the SSL connection for the first time, it can switche the flag and rejects the plain text. just add a flag to socket with forcing the ssl conn.

[chenBright]

bRPC already supports the feature, close the issue.