[Click] What makes userlevel ToDevice(eth0) fail when FromDevice(eth0) is activated?

[Markku Savela]

I've bridge configuration (OpenWrt)

br-lan (IP 192.168.3.1)
    eth0 (no ip address)
    wlan0 (no ip addresss)
and
    mon.wlan0

I'm trying configuration roughly like

... -> Queue(200) -> ToDevice(eth0);
FromDevice(mon.wlan0) -> ... some click ...
FromDevice(eth0) -> ...some click

In the above configuration packets ToDevice(eth0)
just disappear (verified by adding Print between
Queue).

However, if I comment out the FromDevice(eth0)
block, ToDevice(eth0) starts working.

Looks like something in Linux kernel stops
accepting the packets? What could it be?