Tun and ALTQ

[Tom Rhodes]

On Tue, 8 Nov 2005 19:45:59 +0100
Max Laier <max at love2party.net> wrote:

> On Tuesday 08 November 2005 18:15, Brian Fundakowski Feldman wrote:
> > On Tue, Nov 08, 2005 at 02:39:02PM +0100, Marko Cuk wrote:
> > > It seems that it work. Thanks.
> > >
> > > Damn, for vlan's ( 802.1Q)  you should specify "em", for "tun", vice
> > > versa... what a mess, hehe.
> >
> > No prob; I don't see why using the em(4) backing the tun(4) wouldn't
> > work for ALTQ _IF_ you actually tagged the (PPPoE?) traffic on em(4).
> > I think that might be really hard, though, so for ALTQ you should
> > probably just specify the "logical" interface that you intend to
> > limit (that would be the IP tun(4) rather than the PPPoE em(4)).
> 
> The problem with tun(4) in contrast to vlan(4) is that in some cases the 
> packet has to go through userland (i.e. userland PPPoE).  During this detour 
> the packet loses the ALTQ mbuf_tag and thus can no longer be stuck into the 
> right queue.  That is why there is ALTQ support on tun(4) eventhough it 
> doesn't make that much sense to introduce "unnatural" queueing in the pseudo 
> interface.  For vlan(4) there is no such problem (VLANs are handled in the 
> kernel all the way) so it's easy to stick the ALTQ tags on the packet and 
> queue on the hardware interface underneath.
> 
> > Do you have suggestion on what would be good text to go into pf.conf(5)
> > so that this particular case is documented?
> 
> [-> doc@, maybe somebody is interested/creative? ]

I'll work with Max on this.

-- 
Tom Rhodes