Re: [Xen-users] Usage of ifconfig in /etc/xen/scripts/vif-route

[Hans van Kranenburg <hans@xxxxxxxxxxx>]

Hoi,

On 3/29/19 9:43 PM, Gerdriaan Mulder wrote:
> 
> On a fresh install of xen-hypervisor (4.8) on a Debian stretch machine,
> the vif-route script still uses ifconfig. This gives a non-descriptive
> error when creating a domU, as you can see at the end of this email.

Yes, ugly non-user-friendly error is ugly.

> I've used xen-create-image for preparing the VM and can provide the
> exact command if needed, although I'm quite sure this doesn't help for
> solving the problem at hand.
> 
> The Debian stretch installation did not have net-tools installed. The
> package net-tools installs ifconfig et al. Although this may be a
> distribution packaging problem,

It is a packaging problem yes, you're right. That net-tools dependency
should be added.

> I've checked the current HEAD
> (cb70a26f78) of https://xenbits.xen.org/git-http/xen.git and the last
> commit for tools/hotplug/Linux/vif-route was in 2014. git blame reveals
> that the line containing ifconfig dates from 2011, commit cd98e007143.

A git log --follow, or tig --follow or any other way to follow renames,
reveils the code is from 2005.

> Since ifconfig has been deprecated in a couple of major
> distributions[0][1] some 8-10 years ago, I was wondering whether there
> is an equivalent iproute2 command for creating the vif in
> /etc/xen/scripts/vif-route. Currently it is: ifconfig ${dev} ${main_ip}
> netmask 255.255.255.255 up
> 
> I've searched the mailing lists for an iproute2 equivalent, but did not
> find it. I've tried to replace the ifconfig command (just below the
> "online)" case) into `ip link add name ${dev} type dummy`, but that
> errors with "RTNETLINK answers: File exists."
> (/var/log/xen/xen-hotplug.log).

I did not test this, but I think it would be:

ip link set up dev ${dev}
ip addr add ${main_ip}/32 dev ${dev}

However, I'm wondering why it would use /32. I never used vif-route,
only vif-bridge in the past and vif-openvswitch for a long time now.

What do relevant lines in output of ip a and ip r look like after doing
it with the current script (with net-tools installed)?

> Anyone got a good idea for not using the deprecated ifconfig here?

I think it makes the most sense to convert the upstream linux scripts to
use iproute2 based commands...

tools/hotplug/Linux/vif-bridge
tools/hotplug/Linux/vif-nat
tools/hotplug/Linux/vif-route

...and then it will also end up in Debian, but that will be in Buster+1.
In the meantime we might be able to bring back the dependency on
net-tools piggy-backing on a stable/security update. It's important
functionality (I mean, who starts a domU without networking?) and is
broken by default if the user has no other packages that accidentally
drag in net-tools. (In my case that's munin-plugins-core everywhere I
think).

The vif-openvswitch script in there was added in 2013 and already uses
ip link.

I had a deja vu feeling about this, and it seems I fixed a similar thing
a while ago:

https://salsa.debian.org/xen-team/debian-xen/commit/354019fccc76d66f308cad9c41602bd5db9d767d

However, for some reason I wasn't clever enough to also start grepping
outside debian/ for other occurences...

So, summarizing:
1) Can you test the above suggested alternative?
2) We should create a Debian bug about this (add missing dependency)
against src:xen.
3) If you can test vif-route, then I know someone on IRC who uses
vif-bridge, which I can ask, and if someone else wants to test vif-nat,
then I don't mind formatting and sending a proper patch with the
changes. I only currently don't have spare time to set up different
networking scenarios in a test environment to trigger all usage scenarios.

Hans

> Best regards,
> Gerdriaan Mulder
> 
> [0] https://lists.debian.org/debian-devel/2009/03/msg00780.html
> [1] https://www.archlinux.org/news/deprecation-of-net-tools/
> 
> +++ error messages from `xl create -c <configfile>`
> libxl: error: libxl_exec.c:118:libxl_report_child_exitstatus:
> /etc/xen/scripts/vif-route online [25514] exited with error status 1
> libxl: error: libxl_device.c:1237:device_hotplug_child_death_cb: script:
> /etc/xen/scripts/vif-route failed; error detected.
> libxl: error: libxl_create.c:1461:domcreate_attach_devices: unable to
> add nic devices
> libxl: error: libxl.c:1575:libxl__destroy_domid: non-existant domain 14
> libxl: error: libxl.c:1534:domain_destroy_callback: unable to destroy
> guest with domid 14
> libxl: error: libxl.c:1463:domain_destroy_cb: destruction of domain 14
> failed


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