I did this
On Linux one can define IPv6 or IPv4 preference by editing /etc/gai.conf and CURL will apply the defined policy.
label ::1/128 0
label ::/0 1
label 2002::/16 2
label ::/96 3
label ::ffff:0:0/96 4
label fec0::/10 5
label fc00::/7 6
label 2001:0::/32 7
precedence ::1/128 50
precedence ::/0 40
precedence 2002::/16 30
precedence ::/96 20
precedence ::ffff:0:0/96 100
Result:
root@debian:~# curl my.ip.fi
87.138.*.*
On FreeBSD we can likewise set the policy:
root@freebsd:~ # service ip6addrctl status
Prefix Prec Label Use
::1/128 50 0 0
::/0 40 1 7
::ffff:0.0.0.0/96 100 4 0
2002::/16 30 2 0
2001::/32 5 5 0
fc00::/7 3 13 0
::/96 1 3 0
fec0::/10 1 11 0
3ffe::/16 1 12 0
Result:
root@freebsd:~ # curl my.ip.fi
*:*:*:*:be24:11ff:fe60:a3df
So on FreeBSD CURL seems to prefer IPv6 unconditionally.
I expected the following
CURL should prefer IPv4 if the address sorting policy is configured that way.
curl/libcurl version
root@debian:~# curl --version
curl 7.88.1 (x86_64-pc-linux-gnu) libcurl/7.88.1 OpenSSL/3.0.15 zlib/1.2.13 brotli/1.0.9 zstd/1.5.4 libidn2/2.3.3 libpsl/0.21.2 (+libidn2/2.3.3) libssh2/1.10.0 nghttp2/1.52.0 librtmp/2.3 OpenLDAP/2.5.13
Release-Date: 2023-02-20, security patched: 7.88.1-10+deb12u8
Protocols: dict file ftp ftps gopher gophers http https imap imaps ldap ldaps mqtt pop3 pop3s rtmp rtsp scp sftp smb smbs smtp smtps telnet tftp
Features: alt-svc AsynchDNS brotli GSS-API HSTS HTTP2 HTTPS-proxy IDN IPv6 Kerberos Largefile libz NTLM NTLM_WB PSL SPNEGO SSL threadsafe TLS-SRP UnixSockets zstd
root@freebsd:~ # curl --version
curl 8.11.1 (amd64-portbld-freebsd14.1) libcurl/8.11.1 OpenSSL/3.0.15 zlib/1.3.1 brotli/1.1.0 zstd/1.5.6 libidn2/2.3.7 libpsl/0.21.5 libssh2/1.11.1 nghttp2/1.64.0
Release-Date: 2024-12-11
Protocols: dict file ftp ftps gopher gophers http https imap imaps ipfs ipns pop3 pop3s rtsp scp sftp smtp smtps telnet tftp ws wss
Features: alt-svc AsynchDNS brotli GSS-API HSTS HTTP2 HTTPS-proxy IDN IPv6 Kerberos Largefile libz NTLM PSL SPNEGO SSL threadsafe TLS-SRP UnixSockets zstd
operating system
Linux debian 6.1.0-30-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.124-1 (2025-01-12) x86_64 GNU/Linux
FreeBSD freebsd.ettlingen.hausen.com 14.2-RELEASE FreeBSD 14.2-RELEASE releng/14.2-n269506-c8918d6c7412 GENERIC amd64
I did this
On Linux one can define IPv6 or IPv4 preference by editing
/etc/gai.confand CURL will apply the defined policy.Result:
On FreeBSD we can likewise set the policy:
Result:
So on FreeBSD CURL seems to prefer IPv6 unconditionally.
I expected the following
CURL should prefer IPv4 if the address sorting policy is configured that way.
curl/libcurl version
operating system