udhcpc: dont use BPF filter, users report problems (bugs 4598, 6746), commit e4785ca653d0e219926692c229673b2c1b8d6ac4

Denys Vlasenko vda.linux at googlemail.com
Wed Feb 5 17:54:13 UTC 2014

On Wed, Feb 5, 2014 at 4:41 PM, Cristian Ionescu-Idbohrn
<cristian.ionescu-idbohrn at axis.com> wrote:
> On Wed, 5 Feb 2014, Denys Vlasenko wrote:
>> On Tue, Feb 4, 2014 at 8:48 PM, Cristian Ionescu-Idbohrn <cristian.ionescu-idbohrn at axis.com> wrote:
>> > The backside of this, IIRC, is that udhcpc will eat up huge chunks of
>> > CPU parsing "uninteresting" packets, on "heavy" loaded networks.
>> udhcpc does not listen to the network after it established a lease.
> As I said, it's not the wait to get a lease that is a problem but the
> high CPU load (parsing packets).
> Yes.  But imagine the usecase where you get a power outage and a farm
> of embedded systems fight to get a lease.  Also, every time a lease
> renew occurs CPU gets wasted parsing "uninteresting" packets.

While these machines could have done something useful
running their many other running processes...
Will they have many other active right after reboot (power outage)?
How many uninteresting bcast packets will be on the network
of a booting cluster? 1000/sec? Still insignificantly small.

> Yes.  I understand that.  Still, would you accept a patch that makes
> the BPF filter an option?

Do you have a theory why it doesn't work *for some people*?


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