--haproxy-protocol doesn't work with --unix-socket

[jvgutierrez]

I did this

~# curl --haproxy-protocol --unix-socket /run/varnish-frontend.socket -k -v -H "X-Forwarded-Proto: https" http://127.0.0.1:80/
* Expire in 0 ms for 6 (transfer 0x55a23e318fb0)
*   Trying /run/varnish-frontend.socket...
* Expire in 200 ms for 4 (transfer 0x55a23e318fb0)
* Connected to 127.0.0.1 (/run/varnish-frontend.socket) port 80 (#0)
> PROXY TCP4  /run/varnish-frontend.socket 0 0
* Send failure: Broken pipe
* Failed sending HTTP request
* Connection #0 to host 127.0.0.1 left intact
curl: (55) Send failure: Broken pipe

I expected the following

From the curl verbose output pasted above, you can see a wrongly formated PROXYv1 protocol request:

PROXY TCP4  /run/varnish-frontend.socket 0 0

From the PROXY v1 protocol spec https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt it should look like PROXY TCP4 IP IP PORT PORT or PROXY UNKNOWN. I guess that to be able to provide anything else than PROXY UNKNOWN an additional parameter should be implemented in curl to allow specifying the source IP of the connection.

curl/libcurl version

curl 7.64.0 (x86_64-pc-linux-gnu) libcurl/7.64.0 OpenSSL/1.1.1d zlib/1.2.11 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.5) libssh2/1.8.0 nghttp2/1.36.0 librtmp/2.3
Release-Date: 2019-02-06
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtmp rtsp scp sftp smb smbs smtp smtps telnet tftp 
Features: AsynchDNS IDN IPv6 Largefile GSS-API Kerberos SPNEGO NTLM NTLM_WB SSL libz TLS-SRP HTTP2 UnixSockets HTTPS-proxy PSL 

operating system

Linux traffic-cache-atsupload-buster 4.19.0-16-amd64 #1 SMP Debian 4.19.181-1 (2021-03-19) x86_64 GNU/Linux