2016-10-15 11:42 GMT+02:00 Harry Schmalzbauer <free...@omnilan.de>:

> Bezüglich Vincenzo Maffione's Nachricht vom 15.10.2016 09:32 (localtime):
> > 2016-10-14 15:38 GMT+02:00 Harry Schmalzbauer <free...@omnilan.de>:
> …
> >> I'm familar with epair(4), but not with tap(4).
> >> I don't understand the man page for tap, perhaps I should read pty(4)…
> >> But I guess I don't have to know the details of tap(4), since you
> >> confirmed that it can be connected to VALE.
> >>
> >
> > It's not necessary to understand the details. However, a TAP device is
> > conceptually similar to the two ends of an epair, with the difference
> that
> > in the TAP a network interface (e.g. tap0) is conecptually "connected"
> > back-to-back to a file descriptor. The file descriptor is written/read by
> > the hypervisor (to inject/intercept packets to/from the network stack),
> > while the tap0 interface can be attached to if_bridge.
> Hi Vincenzo, thanks for your explanation!
> >>
> >> So one could summarize:
> >> VALE (as part of netmap(4)) can act as a if_bridge(4) replacement in
> >> FreeBSD-10/11, keeping everything else involved untouched.
> >> Please correct me if I'm wrong.
> >>
> >
> > For simple cases yes. if_bridge may have features that are not supported
> by
> > netmap (i.e. configure ports as VLAN access ports). Moreover, if_bridge
> has
> > a interface (br0), whereas VALE bridges doesn't.
> Again, thank you for your time! (R)STP comes to my mind (which I don't
> need any more). And I'm not sure if VALE really lacks that, but I guess
> it wouldn't match VALEs philosophy/design at all…

Well, VALE is a programmable switch, meaning that you can plug in a custom
forwarding function (which is just a C function). The default forwarding
function implements an L2 learning bridge without STP, because it is
thought to be used as the preferred hypervisor virtual switch, so no L2
connectivity loops, and the STP comes with an overhead. If you really wish
to have VALE with STP, you could define your own custom forwarding function
that implements it.

> …
> >>> https://github.com/luigirizzo/netmap). Among the new features, there
> is
> >> a
> >>> new solution for bhyve networking, which will let you attach your bhyve
> >> VMs
> >>> directly to a VALE switch, without paying additional overheads related
> to
> >>> TAPs, epairs, and vtnet emulation. You can find additional information,
> >>> code and performance numbers here:
> >>> https://wiki.freebsd.org/SummerOfCode2016/PtnetDriverAndDeviceModel.
> >>
> >> Thanks for that hint!
> >> I guess it's about ptnetmap(4)? I read papers but haven't considered it
> >> could be production-ready for FreeBSD in the near future.
> >> It's extremely interesting and I'd love to be eraly adopter, but my
> >> (ESXi) setups are currently doing well and I don't have spare time or
> >> any business project to try out… :-(
> >>
> >
> > Yes, it's ptnetmap. However, bhyve is going to have support for VALE
> ports
> > anyway (even without ptnetmap), as QEMU already does, so at least you
> will
> > be able to replace TAPs with VALE ports (while still using vtnet devices
> > for the VM).
> Oic, I wasn't aware that there will be a VALE-vtnet direct path! That is
> really great news :-) And a big achievment for guests preferring
> "standard" drivers, ptnetmap could limit the guest OS choice I guess.

Yes ptnetmap is supported on QEMU and bhyve, and as a gues you can use only
FreeBSD and Linux, at the moment.

> For now, I'm happy having been in touch with netmap(4) – at least with a
> very little fraction of natmap – but I'll stay the legacy way utilizing
> if_bridge(4) and see if there are still oddities and try to find some
> time to track them down (involving LACP, VLANs, Jumbo-Frames and IPv6 –
> that was the problematic constellation)
> Since I have extra PHYs, I can do PCIe-passthrough like before (with
> ESXi) for some special guests. I'm looking forward to find out how this
> works with bhyve!
> No idea, but also ptnetmap is able to do that: not only you can
pass-through a VALE port, but also you can pass-through a physical


> Best,
> -Harry

Vincenzo Maffione
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