Function _system_resolvers

network_diagnostics.py:1042–1050

This host's real upstream DNS servers (resolv.conf, or nmcli when only the systemd-resolved stub is present).

()

    m = _mac_norm(mac)
    if not m:
        return {'klass': 'invalid', 'vendor': None, 'note': 'not a MAC'}
    b0 = _mac_first_octet(m)
    prefix6 = m.replace(':', '')[:6]
    if b0 & 0x01:  # multicast/broadcast — never a valid source address
        return {'klass': 'invalid', 'vendor': None, 'note': 'multicast/broadcast'}
    if not (b0 & 0x02):  # universal — legitimately-registered OUI
        vendor = _vendor_for_prefix(prefix6)
        return {'klass': 'universal', 'vendor': vendor, 'note': None}
    # Locally-administered: virtual, disguised-vendor, or privacy randomization.
    for pfx, name in _MAC_VIRTUAL_PREFIXES.items():
        if m.startswith(pfx):
            return {'klass': 'virtual_laa', 'vendor': name, 'note': 'VM/container NIC'}