How to use HTTP/2's pushing features with curl?

Question

I have been looking into ways to use HTTP/2's pushing features, in order to reduce the number of issued GET requests and the average perceived delay in specific client-server implementations. The existing client heavily relies on the use of curl to issue GET requests, and I need to be able to reuse the current implementation. Recent versions of curl provide support for HTTP/2, relying on the underlying nghttp2 module. Using the existing nghttp2 server:

nghttpd -d /var/www/html/ 3000 local.key local.crt

both nghttp and curl can be used to get an example text file's content:

nghttp https://localhost:3000/text.txt
This is some sample text.

curl https://localhost:3000/text.txt -k --http2
This is some sample text.

Using nghttp2's pushing feature however, where another text file is pushed along:

nghttpd -d /var/www/html/ -p/text.txt=/text2.txt 3000 local.key local.crt

curl seems not capable of dealing with the pushed resource:

nghttp https://localhost:3000/bbb/text.txt
This is some sample text.
This is some sample text as well.

curl https://localhost:3000/text.txt -k --http2 -v
...
* nghttp2_session_mem_recv() returns 268
* before_frame_send() was called
* on_frame_send() was called
* on_stream_close() was called, error_code = 1
* before_frame_send() was called
* on_frame_send() was called
* on_stream_close() was called, error_code = 1
* Connection #0 to host localhost left intact

Indeed, at server side, two resets are received for the two opened streams:

[id=1] [331.593] recv RST_STREAM frame <length=4, flags=0x00, stream_id=1>
      (error_code=PROTOCOL_ERROR(0x01))
[id=1] [331.594] recv RST_STREAM frame <length=4, flags=0x00, stream_id=2>
      (error_code=PROTOCOL_ERROR(0x01))
[id=1] [331.594] closed

Is there a way to use curl with the HTTP/2 pushing features?

Linebreeding

Answer 1

curl (the command line tool) doesn't support HTTP/2 push (yet).

You can only make use of it when doing HTTP/2 with libcurl and not the command line tool.

Dipsomaniac

Does curl support the HTTP/2 push as of today? – Ginetteginevra

@ldclakmal I think it does: curl.se/docs/http2.html I confirm on some of my installations (7.52.1 on a pi3) that it also fetches pushed resources. On some others though it doesn't (e.g 7.68.0 on Ubuntu 20, or 7.76.0 on windows) so I'm not sure what is going on there. – Cataplasm

curl, the command line tool, still does not support HTTP/2 push. – Dipsomaniac

And how about alternative with command line? – Reseda

Does curl support the HTTP/2 push as of today? – Jagannath