[HttpClient] h2c support #36419
Description
Description
As far as I know it the HTTP Client component does not support HTTP/2 without TLS (aka. h2c). It could be useful for calling private endpoints without the need of certificate management but use the benefits of HTTP/2.
There are 2 methods to do it:
$ curl --http2 -I http://nghttp2.org
HTTP/1.1 101 Switching Protocols
Connection: Upgrade
Upgrade: h2c
HTTP/2 200
date: Fri, 10 Apr 2020 23:53:40 GMT
content-type: text/html
last-modified: Fri, 15 Nov 2019 14:36:38 GMT
etag: "5dceb7f6-19d8"
accept-ranges: bytes
content-length: 6616
x-backend-header-rtt: 0.001996
server: nghttpx
via: 2 nghttpx
alt-svc: h3-23=":4433"; ma=3600
x-frame-options: SAMEORIGIN
x-xss-protection: 1; mode=block
x-content-type-options: nosniff
$ curl --http2-prior-knowledge -I http://nghttp2.org
HTTP/2 200
date: Fri, 10 Apr 2020 23:53:42 GMT
content-type: text/html
last-modified: Fri, 15 Nov 2019 14:36:38 GMT
etag: "5dceb7f6-19d8"
accept-ranges: bytes
content-length: 6616
x-backend-header-rtt: 0.001454
server: nghttpx
via: 2 nghttpx
alt-svc: h3-23=":4433"; ma=3600
x-frame-options: SAMEORIGIN
x-xss-protection: 1; mode=block
x-content-type-options: nosniff
The php curl extension supports it via the CURL_HTTP_VERSION_2_PRIOR_KNOWLEDGE flag.