VIF network definition does not work with backend=domnet

[Shen Long <xen-mailinglist@xxxxxxxxxxxxxxxxxxxxxxx>]

Hello,

I use XEN on a gentoo home-lab/home-network server. I installed the Dom0 
with gentoo with a dedicated network card. I gave a spare network card 
on the machine to a dedicated network driver domain which also runs gentoo.
Now i discovered an issue with the VIF spec for new domUs.

Following problem. If i start a domu with a vif spec to connect to a 
backend domu it does fail with an error.
If i omit the vif spec, create the domu and immediately attach a network 
card with xl network-attach backend=netbackend it works.
Here's the netbackend.cfg, if i may forgot something:

> name = "netbackend"
> builder = "hvm"
> vcpus = 4
> memory = 4096
> pci = [ '03:00.0' ]
> disk = [ 'phy:/dev/mapper/xenhost-netbackend,xvda,w' ]
> netif="yes"
> usbdevice = [ "tablet" ]
> serial = "pty"
> on_poweroff = "destroy"
> on_reboot = "restart"
> on_crash = "restart"

My backend have several bridge-networks configured with associated 
network-vlans on my physical interface.
- home
- dmz
- foo
- infra

Here the test.cfg domu which "works":

name = "test"
builder = "hvm"
vcpus = 1
memory = 4096
#vif = [ 'backend=netbackend,bridge=dmz' ]
disk = [ 'file:/isos/systemrescue-11.03-amd64.iso,hda:cdrom,r' ]
usbdevice = [ "tablet" ]
serial = "pty"
on_poweroff = "destroy"
on_reboot = "restart"
on_crash = "restart"

It does not have a proper disk yet, because testing.
The Problem is, if i remove the hash from the vif spec, i get this error 
on `xl create test.cfg`:
# xl create /etc/xen/domuconfig/test.cnf
Parsing config from /etc/xen/domuconfig/test.cnf
libxl: error: libxl_dm.c:3157:device_model_spawn_outcome: Domain 
89:domain 89 device model: spawn failed (rc=-3)
libxl: error: libxl_dm.c:3377:device_model_postconfig_done: Domain 
89:Post DM startup configs failed, rc=-3
libxl: error: libxl_create.c:1937:domcreate_devmodel_started: Domain 
89:device model did not start: -3
libxl: error: libxl_aoutils.c:646:libxl__kill_xs_path: Device Model 
already exited
libxl: error: libxl_xshelp.c:206:libxl__xs_read_mandatory: xenstore read 
failed: `/libxl/89/type': No such file or directory
libxl: warning: libxl_dom.c:49:libxl__domain_type: unable to get domain 
type for domid=89, assuming HVM
libxl: error: libxl_domain.c:1616:domain_destroy_domid_cb: Domain 
89:xc_domain_destroy failed: No such process
libxl: error: libxl_domain.c:1133:domain_destroy_callback: Domain 
89:Unable to destroy guest
libxl: error: libxl_domain.c:1060:domain_destroy_cb: Domain 
89:Destruction of domain failed
As mentioned, i can comment out the vif spec and attach a network card 
with `xl network-attach test bridge=dmz backend=netbackend` which works 
perfectly fine. But i dont want to do it manually but instead use the 
auto feature to start my netbackend and have a little wait function in 
my xendomains init which does wait for netbackend to become available. 
To autostart all the systems when something failed.
Do i have an error in my setup or overlooked something?
Do you need more information to help here?
Do we have a proper bug in this scenario?
Or is it not implemented in that way, a missing feature or do i overlook 
something?
Best regards
Shen Long