ip=dhcp woes

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

Hello,

I have a machine with four network interfaces and I'm using ip=dhcp
during development on it.

in ic_dynamic the procedure is the following (assuming no successful
reply is received in time):

  timeout = 2s + random([0, 1]) s
loop:
  send bootp on 1st dev
  wait 1s
  send bootp on 2nd dev
  wait 1s
  send bootp on 3rd dev
  wait 1s
  send bootp on 4th dev
  wait timeout
  timeout = timeout * 4 / 7
  goto loop;

My problem now is: The dhcp server is reachable via the first device and
takes little more than 1s to respond. A reply must match the last sent
request to be accepted.

So the obvious questions are:

Why is only the last timeout increased for each loop? Why is there a
difference at all between the waits which results in a special casing of
the last device?

Alternatively, why not accept a reply on eth0 when eth1 has already sent
a request? Then the procedure could be:

  timeout = 2s + random([0, 1]) s
loop:
  send bootp on 1st dev
  send bootp on 2nd dev
  send bootp on 3rd dev
  send bootp on 4th dev
  wait timeout
  timeout = timeout * 4 / 7
  goto loop;

which looks more effective.

Is there anything I missed?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |