Re: AW: Re: AW: Re: VLAN and Network Drivers 2.4.x

Jeff Garzik
2002-04-24T18:11:00Z

On Wed, Apr 24, 2002 at 11:04:47AM -0700, Ben Greear wrote:
> Jeff Garzik wrote:
>
> > On Wed, Apr 24, 2002 at 10:31:29AM -0700, Ben Greear wrote:
> >
> >>Also, is there any good reason that we can't get at least a compile
> >>time change into some of the drivers like tulip where we know we can
> >>get at least MOST of the cards supported with a small change?
> >>
> >
> > The tulip patch is butt-ugly - the oversized allocation isn't needed,
> > and it just flat-out turns off large packet protection. That's really
> > not what you want to do, even for the best tulip cards. If an oversized
> > gram (non-VLAN) makes it into a network which such a patched tulip
> > driver, you can DoS. So, I view the current tulip patch as unacceptable
> > too -- for security reasons, we should not even take it as a compile
> > time patch. (and I recommend against using that patch on production
> > machines, for the same security reasons)
>
>
> I can DOS a tulip card with very small packets too ;)

A tulip card? Or the stack?

Can you DoS it when CONFIG_NET_HW_FLOWCONTROL is enabled?
That's basically NAPI without the fancy acronym...

> > The proper tulip patch does not need to change packet allocation size
> > at all (it's already plenty big enough), and it needs to copy the RX
> > fragment handling code from 8139cp (which is admittedly ugly, slow path)
> > or write fresh fragment handling code. Along with that fragment
> > handling code comes a safe way to do VLAN, and non-standard large MTUs
> > in general.
>
> In the general case, where the packets are only 1518 (ie no DoS or mis-configured
> hardware is in effect), is there a need for the "ugly, slow path" code to run?

It depends on the chip, but most generally: no

Jeff