Based on #14135, implement TLSv1.3 earlydata support for the curl
command line, libcurl and its implementation in GnuTLS.
If a known TLS session announces early data support, and the feature is
enabled *and* it is not a "connect-only" transfer, delay the TLS
handshake until the first request is being sent.
- Add --tls-earldata as new boolean command line option for curl.
- Add CURLSSLOPT_EARLYDATA to libcurl to enable use of the feature.
- Add CURLINFO_EARLYDATA_SENT_T to libcurl, reporting the amount of
bytes sent and accepted/rejected by the server.
Implementation details:
- store the ALPN protocol selected at the SSL session.
- When reusing the session and enabling earlydata, use exactly
that ALPN protocol for negoptiation with the server. When the
sessions ALPN does not match the connections ALPN, earlydata
will not be enabled.
- Check that the server selected the correct ALPN protocol for
an earlydata connect. If the server does not confirm or reports
something different, the connect fails.
- HTTP/2: delay sending the initial SETTINGS frames during connect,
if not connect-only.
Verification:
- add test_02_32 to verify earlydata GET with nghttpx.
- add test_07_70 to verify earlydata PUT with nghttpx.
- add support in 'hx-download', 'hx-upload' clients for the feature
Assisted-by: ad-chaos on github
Closes#15211
962097b8dd