Pkg xen devel - Mar 2013 - Bug#702428: HVM networking tap/vif bug (Debian bug 702428)

Hi,

I've been testing the Debian packages ahead of the Debian 7 release
(which is very imminent)

I believe this is a serious bug[1] in the package, as it appears that
HVM networking is broken, or at the very least, requires some
undocumented configuration step

Specifically:

- I can start the HVM domU without any vif

- if I attach a vif, the domU will not start

Looking at /var/log/daemon.log, I notice:

xcp-fe: qemu-dm-10[9169]: can't add tap10.0 to bridge xapi1: Operation
not supported

while the output from dmesg suggests that the interface vif10.0 was
created.  It appears there is confusion between the vifX.Y and tapX.Y
naming schemes.

Can anybody comment on this?  Is this hardcoded into some config that I
should inspect?  Is it hard coded in the qemu-dm scripts?  It would be
very desirable to fix this before the wheezy release so that people
don't have a bad impression of XCP with HVM.

Regards,

Daniel


1. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=702428

I'm afraid I don't know about the issue you are seeing but I can comment
on one part:

On Sun, 2013-03-17 at 15:02 +0100, Daniel Pocock wrote:
> while the output from dmesg suggests that the interface vif10.0 was
> created.  It appears there is confusion between the vifX.Y and tapX.Y
> naming schemes.
An HVM guest with a network device should get *both* vifX.Y and tapX.Y,
they are kind of two faces of the same "device". The tapX.Y is the
emulated NIC (rtl8169 or e1000 or something) while the vifX.Y is the PV
NIC which the guest can choose to switch over too (for increased perf
etc) if it has a suitable driver (e.g. Linux PVHVM support, PV drivers
for Windows etc etc).

As to why tapX.Y cannot be added to a bridge, I've no idea, sorry. Are
you using bridge or vswitch? Can you manually enslave the tap device to
the bridge?

Ian.

-- 
Ian Campbell


Put your brain in gear before starting your mouth in motion.
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On Sun, 2013-03-17 at 15:02 +0100, Daniel Pocock wrote:
> xcp-fe: qemu-dm-10[9169]: can't add tap10.0 to bridge xapi1: Operation
> not supported
A google search for "linux add tap to bridge operation not supported"
shows lots of people having this sort issue (often in the absence of
Xen) although none of the links I followed contained a solution :-(.

Ian.
-- 
Ian Campbell


Expect a letter from a friend who will ask a favor of you.
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