Subject: Re: HW-assisted VLAN handling
To: Jason Thorpe <>
From: Jonathan Stone <>
List: tech-kern
Date: 01/30/2005 13:14:05
In message <>,
Jason Thorpe writes:

>I would also suggest that you eliminate the whole "nvlans" thing, and 
>simply always add/remove the filtering list, and always thwack the 
>interface when a VLAN is added/removed.  I.e. handle it exactly the 
>same way that multicast addresses are handled.  For interfaces that 
>support HWTAGGING but not HWFILTERING, then the fact that the list is 
>not empty is the same as checking nvlans != 0.
>Make sense?

How many VLANs can the hardware handle in hardware?  4k (common limit
on Cisco switches)?  16k?  What's the maximum the IEEE packet format allows?

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.

Do we need an analagous mode here?