[ECOS] Re: Multi-cast support in Ethernet drivers

[Grant Edwards <grante at visi dot com>]

On 2007-07-20, Andrew Lunn <andrew@lunn.ch> wrote:
> On Thu, Jul 19, 2007 at 02:42:45PM +0400, Alexander Aganichev wrote:
>> On 7/17/07, Andrew Lunn <andrew@lunn.ch> wrote:
>>> > The stack sets up multi-cast MAC to 01:00:5e:00:00:01 and cannot talk
>>> > to my DHCP anymore.
>>>
>>> My first guess is that you are programming the filter incorrectly in
>>> your MAC chip. It could be you are blocking the broadcast address, or
>>> the unicast address for your device. Is the DHCP server broadcasting
>>> is response, or unicasting it?
>>
>> Shouldn't the upper layer provide broadcast address in the
>> list to ETH_DRV_SET_MC_LIST if it wants to receive broadcast
>> packets?

I've never seen that behavior.

>> My guess it is upper layer responsibility to do so, because of
>> otherwise I do not see any sense for that call...

I think it's there to allow multiple unicast addresses to be
used.  However, none of the drivers I've looked at implement
that.

> No, i would expect the default is that the upper layer expects
> the device to always receive broadcast.

Based on the Ethernet drivers I've worked on, that certainly
seems to be the case.

> However maybe your device does not?

If the Ethernet driver didn't pass on to the stack received
broadcast packetsARP wouldn't work, and you couldn't even ping
the device.

> It is at least something to test. Maybe take a look at the
> Linux driver and see what it does for its multicast call. You
> cannot directly use the code, since it is GPL, but you can
> look and see if it does anything interesting.

-- 
Grant Edwards                   grante             Yow!
                                  at               BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-BI-
                               visi.com            


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