73 lines
2.4 KiB
Markdown
73 lines
2.4 KiB
Markdown
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# Hyper
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Hyper is a separate HTTP library written in Rust. curl can be told to use this
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library as a backend to deal with HTTP.
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## Experimental!
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Hyper support in curl is considered **EXPERIMENTAL** until further notice. It
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needs to be explicitly enabled at build-time.
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Further development and tweaking of the Hyper backend support in curl happens
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in the master branch using pull-requests, just like ordinary changes.
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## Hyper version
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The C API for Hyper is brand new and is still under development.
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## build curl with hyper
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Using Rust 1.64.0 or later, build hyper and enable its C API like this:
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% git clone https://github.com/hyperium/hyper
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% cd hyper
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% RUSTFLAGS="--cfg hyper_unstable_ffi" cargo rustc --features client,http1,http2,ffi --crate-type cdylib
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Also, `--release` can be added for a release (optimized) build.
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Build curl to use hyper's C API:
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% git clone https://github.com/curl/curl
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% cd curl
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% autoreconf -fi
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% ./configure LDFLAGS="-Wl,-rpath,<hyper-dir>/target/debug -Wl,-rpath,<hyper-dir>/target/release" --with-openssl --with-hyper=<hyper-dir>
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% make
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# using Hyper internally
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Hyper is a low level HTTP transport library. curl itself provides all HTTP
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headers and Hyper provides all received headers back to curl.
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Therefore, most of the "header logic" in curl as in responding to and acting
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on specific input and output headers are done the same way in curl code.
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The API in Hyper delivers received HTTP headers as (cleaned up) name=value
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pairs, making it impossible for curl to know the exact byte representation
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over the wire with Hyper.
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## Limitations
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The hyper backend does not support
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- `CURLOPT_IGNORE_CONTENT_LENGTH`
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- `--raw` and disabling `CURLOPT_HTTP_TRANSFER_DECODING`
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- RTSP
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- hyper is much stricter about what HTTP header contents it allows
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- leading whitespace in first HTTP/1 response header
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- HTTP/0.9
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- HTTP/2 upgrade using HTTP:// URLs. Aka 'h2c'
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- HTTP/2 in general. Hyper has support for HTTP/2 but the curl side
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needs changes so that a `hyper_clientconn` can last for the duration
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of a connection. Probably this means turning the Hyper HTTP/2 backend
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into a connection filter.
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## Remaining issues
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This backend is still not feature complete with the native backend. Areas that
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still need attention and verification include:
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- multiplexed HTTP/2
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- h2 Upgrade:
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- receiving HTTP/1 trailers
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- sending HTTP/1 trailers
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