Implement HTTP CONNECT for HTTP/2

[jmcc0nn3ll]

migrated from Bugzilla #481459
status NEW severity enhancement in component http2 for 9.3.x
Reported in version 9.3.5 on platform PC
Assigned to: Simone Bordet

On 2015-11-04 16:48:22 -0500, Simone Bordet wrote:

https://tools.ietf.org/html/rfc7540#section-8.3

On 2016-01-07 15:18:18 -0500, Simone Bordet wrote:

See also https://tools.ietf.org/html/rfc7639

[sbordet]

The issue is more complicated than initially thought.

After discussion with @gregw, need to check whether browsers already support it.
If so, then we need at least to have the server side working.

For the server side, the idea is that we change the HTTP parser to consider a CONNECT request to have an infinite request content, rather than being considered a request without content.
Similarly, it will have an infinite response content.
Then, ConnectHandler needs to be changed in a way that it reads content either via the request's InputStream or via the transport directly. In this way, the transport does the un-framing, so that the HTTP/1.1 transport does not do any un-framing (it will consider the request content to be delimited by EOF), while the HTTP/2 transport does the DATA un-framing (i.e. receives a DATA frame and passes its payload to the application - in this case to the ConnectHandler).
Similarly, ConnectHandler will receive content from the server and then either write it via the response OutputStream or directly via the transport, so that the HTTP/1.1 transport will just send the bytes as is, while the HTTP/2 transport will frame the bytes into DATA frames.

On the client side, things may be even more complicated. We would need to support mixed modes where the client needs to talk HTTP/2 to the forward proxy, but HTTP/1.1 to the server, or viceversa.
This hints for the client to support the transport dynamically, e.g. to choose the transport based on the ALPN protocol.