ifconfig(8) - a tale of two states

[Roy Marples <roy%marples.name@localhost>]

Hi List!

Consider this ifconfig(8) output:
urtwn0: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        ssid ""
        powersave off
        chan 6
        address: 80:1f:02:82:35:c3
        media: IEEE802.11 OFDM54 monitor (OFDM54 mode 11g monitor)
        status: active
        inet 192.168.0.1/24 broadcast 192.168.0.255 flags 0x4<DETACHED>

Is this output too confusing?
We claim that the media is active but the address is detached and there is no SSID!

WTF BBQ!

Traditionally, ifconfig reports the status of the media.
If the interface has no media, no status was reported .... until recently.
Now, if the interface has no media, it prints the status of the link state.

ALL interfaces, even bridge(4), has a link state. According to CVS, this has 
always been the case. The link state can be UNKNOWN, DOWN or UP.
When an interface first registers it gains the state UNKNOWN - no claim is made 
if it's down or up. It's only when the interfaces realises it's state the change 
is made to UP or DOWN.

We've put a lot of work into changing our link state, it's there for a very good 
reason.

But, traditionally, NetBSD applications such as ifconfig, ifwatchd and even the 
portable dhcpcd have adhered to a common BSD facility - the media is the be all 
and end all of if the interface has a carrier or not. The problem here is that 
not all interfaces have media. A few years ago, I added media to PPP just to 
make it active, but didn't register any actual media values. This was totes the 
wrong thing to do! And has been recently reverted.

In a nutshell, the interface link state is the single source of truth regarding 
the link state. So to the make matter right, I added a small change to our 
net80211 stack to put the wireless interfce into a decent link state - HOSTAP, 
IBSS and AHDEMO remain unknown, but BSS and MONITOR are clearly down.
BSS will go up when we join a node, but MONITOR is just read only. It cannot send.
As such any addresses on the interface are useless.

Which brings us back to the beginning with more clarity. We have an active media 
state, but the interface link itself is down. Should we change the output of 
ifconfig somehow to include the link state or is this too much of a corner case 
to consider?

Comments welcome.

Roy