xinetd configuration guide

The IPv6 support in xinetd started at release 2.1.8.8.pre*.

How can I configure a service to run over IPv6?

You can enable IPv6 support by adding a new service instance with the flags=IPv6 option, e.g:

service imap
{
        id            = imap-IPv4
        flags         = IPv4
        socket_type   = stream
        protocol      = tcp
        wait          = no
        user          = root
        server        = /usr/sbin/imapd
}
service imap
{
        id            = imap-IPv6
        flags         = IPv6
        socket_type   = stream
        protocol      = tcp
        wait          = no
        user          = root
        server        = /usr/sbin/imapd
}

Help! I did as you wrote above and get 'bind failed (Address already in use' messages from xinetd

It means that your system bind also to IPv4-mapped IPv6 addresses (i.e. IPv4 addresses) in case of binding IPv6 addresses. Simply get rid of the imap-IPv4 instance above (or add the disable = yes option to the instance) and reload xinetd.

In Linux 2.6.* the IPv4-mapped IPv6 addresses bind is the default. You can disable (but you shouldn't) IPv4-mapped IPv6 addresses binding by the command

# echo 1 > /proc/sys/net/ipv6/bindv6ony