Subject: Re: HW-assisted VLAN handling
To: Jonathan Stone <>
From: David Laight <>
List: tech-kern
Date: 01/30/2005 22:04:24
> The original multicast code had a mode where you could just give up on
> managing exact multicast hardware filters.  If you joined more groups
> than the hardware could filter, drivers would give up, accept all
> multicast, and revert to filtering in software.

Most chipsets don't have exact multicast filters.  They tend to work
by using a hash to one of 64 buckets (using the crc).

Some modern chips may support multiple local addresses - which could
be set to multicast addresses....

In any case, surely each user should have to enable the addresses they
want, and should only be passed addresss that match.

Of course you may not care - in practise you are likely to be running
all the protocols that catually put mcasts onto the lan, so wnat them
all anyway....


David Laight: