IPv4 mapped addresses

If IPv6 is enabled (server.use-ipv6 in your config) and your operating system has not enabled "bindv6only" (sysctl net.ipv6.bindv6only or sysctl net.inet6.ip6.v6only), lighttpd binds to an ipv6 socket and accepts ipv4 connections on it. This results in IPv4 mapped addresses in the access.log like "::ffff:".

Debian enables ipv6 by default if it detects support for it; so if you don't need IPv6 you should disable that script in your lighttpd.conf; if you need IPv6 and don't like the mapped addresses you have to enable "bindv6only" and bind to the IPv4 address(es) and IPv6 address(es) yourself.

See also