[Click] Input flush action for userspace FromDevice?

[Markku Savela]

I run into a problem while using userspace FromDevice for WLAN
monitor socket: when I reconfigure WIFI interface, I need to
ignore all before reconfiguration messages queued in the kernel
for the click FromDevice element.

Apparently there is no such "native flush" action for a socket,
and flushing input is just reading and discarding until socket
indicates "no data".

I cannot find such function in FromDevice or is there? First
that comes to mind is some kind of flush handler that
would read and discard input, until none... (there is, of
course, a small concern of reading forever and never seeing
"no data" if new data for socket is generated faster than
click can read).

Any thoughts? Should handler been written or is there another
way to trigger the "input flush" for FromDevice from another
click element? Would handler be "read" or "write" handler?