curl_setopt($ch,CURLOPT_HTTP_VERSION,CURL_HTTP_VERSION_2_0) does not honored when the CURLOPT_PROXY is combined

Description

The following code:

<?php
set_time_limit(100);
function test1(){
$ch=curl_init();
curl_setopt($ch,CURLOPT_URL,'https://ftp.mozilla.org/');
curl_setopt($ch,CURLOPT_SSL_VERIFYPEER,false);
curl_setopt($ch,CURLOPT_HTTP_VERSION,CURL_HTTP_VERSION_2_0);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
curl_setopt($ch,CURLOPT_HEADER,false);
curl_setopt($ch,CURLOPT_HTTPPROXYTUNNEL,true);
curl_setopt($ch,CURLOPT_PROXY,'127.0.0.1:8888');// SOCKS5H
curl_setopt($ch,CURLOPT_PROXYTYPE,CURLPROXY_SOCKS5_HOSTNAME);
curl_setopt($ch,CURLOPT_POST,true);
curl_setopt($ch,CURLOPT_POSTFIELDS,http_build_query(['test'=>1]));
curl_setopt($ch,CURLOPT_HTTPHEADER,['Content-Type: application/x-www-form-urlencoded']);
curl_setopt($ch,CURLOPT_VERBOSE,true);
return curl_exec($ch);
}
function test2(){
$ch=curl_init();
curl_setopt($ch,CURLOPT_URL,'https://ftp.mozilla.org/');
curl_setopt($ch,CURLOPT_SSL_VERIFYPEER,false);
curl_setopt($ch,CURLOPT_HTTP_VERSION,CURL_HTTP_VERSION_2_0);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
curl_setopt($ch,CURLOPT_HEADER,false);
// no proxy
curl_setopt($ch,CURLOPT_POST,true);
curl_setopt($ch,CURLOPT_POSTFIELDS,http_build_query(['test'=>1]));
curl_setopt($ch,CURLOPT_HTTPHEADER,['Content-Type: application/x-www-form-urlencoded']);
curl_setopt($ch,CURLOPT_VERBOSE,true);
return curl_exec($ch);
}
var_dump(test1());
var_dump(test2());

Resulted in this output:

*   Trying 127.0.0.1:8888...
* SOCKS5 connect to ftp.mozilla.org:443 (remotely resolved)
* SOCKS5 request granted.
* Connected to 127.0.0.1 () port 8888
* using HTTP/1.x
* ALPN: curl offers h2,http/1.1
* ALPN: server accepted h2
* Server certificate:
...
* Connected to 127.0.0.1 (127.0.0.1) port 8888
* using HTTP/2
* [HTTP/2] [1] OPENED stream for https://ftp.mozilla.org/
...
> POST / HTTP/2
...
< HTTP/2 405

* Host ftp.mozilla.org:443 was resolved.
* ALPN: curl offers h2,http/1.1
* ALPN: server accepted h2
* Server certificate:
...
* Connected to ftp.mozilla.org () port 443
* using HTTP/2
* [HTTP/2] [1] OPENED stream for https://ftp.mozilla.org/
...
> POST / HTTP/2
...
< HTTP/2 405

But I expected:

• No * using HTTP/1.x in SOCKSified request; it should use HTTP2 from the beginning, just like without-proxy result

PHP Version

PHP 8.4.16 (cli)

Operating System

No response

[arnaud-lb]

According to libcurl documentation ¹, CURLOPT_HTTP_VERSION causes libcurl to prefer the specified protocol, but it will still perform protocol negotiation with the server. It seems to me that in both cases in your script, libcurl prefers http2 (ALPN: curl offers h2,http/1.1) and ends up using http2 as well (ALPN: server accepted h2; ...; using HTTP/2). Negotiation happens as part of the TLS handshake, so this is not adding any extra latency.

Footnotes

1. https://curl.se/libcurl/c/CURLOPT_HTTP_VERSION.html ↩

this is not adding any extra latency.

I thought "* using HTTP/1.x" creates another latency but thanks for explaining this.