patched h2 for impit

This is a patched version of h2 for the impit project.

More information about this crate can be found in the crate documentation.

impit: SETTINGS knobs

Two environment variables change the first SETTINGS frame a client connection sends, so impit can send the same settings as a real browser:

• IMPIT_H2_OMIT_SETTINGS: comma-separated setting ids to leave out of that frame. Only 2 (ENABLE_PUSH), 5 (MAX_FRAME_SIZE) and 6 (MAX_HEADER_LIST_SIZE) are honoured; other ids are ignored.
• IMPIT_H2_NO_RFC7540_PRIORITIES: 0 or 1 adds setting 9 (SETTINGS_NO_RFC7540_PRIORITIES, RFC 9218) with that value; anything else is ignored.

Only that frame changes: h2 keeps enforcing the limits set on the client Builder. Unset or empty, the variables change nothing.

One thing follows from the frame: with 2 left out, the server may push. h2 still has push disabled, so it refuses each pushed stream with RST_STREAM REFUSED_STREAM, and the connection and the request carry on (with ENABLE_PUSH sent, a push is still a connection error). Each refusal counts toward the connection's limit on local resets (max_local_error_reset_streams, 1024 by default), as upstream h2 counts its own refusals since hyperium#966. Beyond that limit, the connection ends with GOAWAY ENHANCE_YOUR_CALM.

The variables are process-wide and are read when a client connection starts. The older IMPIT_H2_PSEUDOHEADERS_ORDER (read in src/frame/headers.rs each time h2 encodes a header block) sets the pseudo-header order: a comma-separated list naming all six, :method,:scheme,:authority,:path,:protocol,:status when unset; a missing or unknown name panics.

Features

• Client and server HTTP/2 implementation.
• Implements the full HTTP/2 specification.
• Passes h2spec.
• Focus on performance and correctness.
• Built on Tokio.

Non goals

This crate is intended to only be an implementation of the HTTP/2 specification. It does not handle:

• Managing TCP connections
• HTTP 1.0 upgrade
• TLS
• Any feature not described by the HTTP/2 specification.

This crate is now used by hyper, which will provide all of these features.

Usage

To use h2, first add this to your Cargo.toml:

[dependencies]
h2 = "0.4"

Next, add this to your crate:

extern crate h2;

use h2::server::Connection;

fn main() {
    // ...
}

FAQ

Is this an embedded Java SQL database engine?

No.