[Babel-users] Detecting link-layer disconnection (Was: babels bug with uninitialized data somewhere?)

[Juliusz Chroboczek]

> Doesn't babeld notice when an interface goes down, and immediately tries
> to find another route?

Yes, it does.

> (well, unplugging a cable is not the same as going down, but I guess the
> kernel could tell us anyway)

We already monitor the Ethernet carrier, but the functionality is disabled
by default -- see the "-l" flag in the babeld manual page.  It's pretty
useless in practice, since most Ethernet interfaces are behind a switch.

> If I recall correctly, Quagga already watches interfaces for link-layer
> events, so quagga-babel probably benefits from it.

If memory serves, it's also disabled by default in Quagga (see the
interface command "link-detect").

> On a related note, I once tried to use nl80211 [1] for detecting 802.11
> association/deassociation events: basically, an elaborate version of
> running « iw dev wlan0 station dump » at regular interval.

We can do much better than that.  Search the Linux kernel for recent
commits by Antonio Quartulli.

-- Juliusz