[Debian-eeepc-devel] Disabling wifi when wired (to save power)

[Trent W. Buck]

I never need BOTH wifi and wired networking (at the same time).  AFAIK,
with my current configuration[0], wpa_supplicant will CONSTANTLY poll
for APs when there are none around -- and I imagine this requires
significant power.

My idea is to say "on successfully negotiating a wired connection, turn
off wifi".  A simple post-up rule for eth0 doesn't work, because it
seems to be considered "up" before dhclient gets a DHCPRESPONSE or
DHCPACK.  So I guess I need to add a hook like

    # cat >/etc/dhcp3/dhclient-exit-hooks.d/twb-mutex-ifaces
    case $reason$interface in
        (BOUNDeth*) rfkill block wifi;;
    esac
    # chmod +x /etc/dhcp3/dhclient-exit-hooks.d/twb-mutex-ifaces

I'd be obliged if someone would confirm that wpa_supplicant's scanning
will chew up power and critique my approach (or suggest a better one).

PS: due to an unrelated issue (#573607), I can't actually use rfkill, so
for now subsitute "ifdown --force wlan0".

[0] My current /etc/network/interfaces looks like this:

    auto lo
    iface lo inet loopback
    allow-hotplug eth0
    iface eth0 inet dhcp
    allow-hotplug wlan0
    iface wlan0 inet manual
    wpa-roam /etc/wpa_supplicant.conf
    wpa-roam-default-iface wlan0-default
    iface wlan0-default inet dhcp