Returns a list of IPv6 addresses configured on the interface ifname.

def _in6_getifaddr(ifname):
    """
    Returns a list of IPv6 addresses configured on the interface ifname.
    """

    # Get the output of ifconfig
    try:
        f = os.popen("%s %s" % (conf.prog.ifconfig, ifname))
    except OSError:
        log_interactive.warning("Failed to execute ifconfig.")
        return []

    # Iterate over lines and extract IPv6 addresses
    ret = []
    for line in f:
        if "inet6" in line:
            addr = line.rstrip().split(None, 2)[1]  # The second element is the IPv6 address  # noqa: E501
        else:
            continue
        if '%' in line:  # Remove the interface identifier if present
            addr = addr.split("%", 1)[0]

        # Check if it is a valid IPv6 address
        try:
            inet_pton(socket.AF_INET6, addr)
        except (socket.error, ValueError):
            continue

        # Get the scope and keep the address
        scope = in6_getscope(addr)
        ret.append((addr, scope, ifname))

    return ret