svn commit: r205024 - head/sys/net

[Qing Li]

>
> We've got LINK_STATE_UNKNOWN, we can just initialize if_link_state to
> this value in ether_ifattach(). And Qing should treat this value as
> LINK_STATE_UP in routing decision until better times.
>

Thanks everyone for your input.

I generally try to avoid overloading a variable to have more than 1 meaning.
For example, the if_tun interface is in LINK_STATE_UNKNOWN until
it's opened, then the link can be one of the other two states.
Also, some of the pseudo drivers such as if_tun do not call ether_ifattach().

Right now I like to implement Robert's suggestion of using if_capabilities
field. I'd like to create a new flag, IFCAP_LINKSTATE_NOTIFY flag.
The routing decision will check against the if_link_state if this bit
is set.

Only a handful of drivers have this capability. So updating those drivers
is a small task.

Do we agree on this approach?

-- Qing