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Re: [libvirt] RFC: configuring host interfaces with libvirt



Adding Marius (SuSE sysconfig maintainer) in case I'm misspeaking :-)

David Lutterkort wrote:
On Tue, 2009-01-20 at 11:35 -0700, Jim Fehlig wrote:
David Lutterkort wrote:
For certain applications, we want libvirt to be able to configure host
network interfaces in a variety of ways; currently, we are most
interested in teaching libvirt how to set up ordinary ethernet
interfaces, bridges, bonding and vlan's.

Below is a high-level proposal of how that could be done. Please comment
copiously ;)

1. XML Format
=============

The first question is how the user would describe the host interfaces they
want. Below are some sketches of what an XML representation of the various
kinds of interfaces would look like. This covers the minimal amount of
settings for these to be useful, though I am sure we'll need to add more
over time.

<interface device="eth0" onboot="yes">
  <hwaddr>00:19:d2:9f:88:96</hwaddr>
  <dhcp peerdns="yes"/>
</interface>
For onboot="yes", something like startmode="onboot" would be better
IMO.  A startmode attribute would allow also using "manual", "hotplug",
"ifplug", "nfsroot", etc.

This makes only sense if these additional modes are completely
orthogonal; I am not sure what the start modes 'manual', 'ifplug', and
'nfsroot' should do.

manual
 Interface will be set up if ifup is called manually.
ifplugd
 Interface will be controlled from  ifplugd
nfsroot
 Nearly like auto, but interfaces with this startmode will never be
 shut down via rcnetwork stop

 For onboot, I assume you mean that they translate
into assignments in ifcfg in the following way

        no startmode attribute  -> ONBOOT=no
        startmode='onboot'      -> ONBOOT=yes
        startmode='hotplug'     -> ONBOOT=yes and HOTPLUG=yes

On SuSE, the related ifcfg syntax is

STARTMODE={manual|auto|hotplug|ifplugd|nfsroot|off}

WRT dhcp element, would it make sense to consider hostname (hostname to
send to server) and if to change the local hostname to the hostname
delivered via dhcp?  E.g.
    hostname="foo" (default `hostname`)
    sethostname

Also route:
    setrouting (default "yes")
    setdefaultroute (default "yes")

and NIS:
    nis (default "yes")
    setnisdomain (default "yes")

Yes, they all make sense, though I would probably not support them in
the very first cut.

What about dhcpv6?  A separate <dhcp6 /> element?

Yeah, we probably need a separate element for that since it pulls in a
slew of other config options.

<interface device="eth1" onboot="yes">
  <hwaddr>00:19:d2:9f:88:97</hwaddr>
  <static ipaddr="192.168.0.5" gateway="192.168.0.1" netmask="255.255.255.0"/>
</interface>
Similarly, support for IPv6 here.  Either 2 formats:

ipaddr="192.168.0.5" netmask="255.255.255.0"
ip6addr="2001:DB8:C::5/64"

or allow /len for both:

ipaddr="192.168.0.5/24"
ipaddr="2001:DB8:ABCD::1/64"

Looks a little strange, but it would simplify notation.

As for routing info, how about a separate route element:

<route gateway="192.168.0.1" /> # destination=default
<route destination="default" gateway="192.168.0.1" />
<route destination="10.0.0.0/8" gateway="192.168.0.2" />
<route destination="2001:DB8:C::/64" gateway="2001:DB8:C::1" />
<route destination="2001:DB8::/32"> # unrecheable route (loopback)

It would perhaps make sense to use iproute2 names, that is prefix
instead of destination and nexthop instead of gateway.

For now, I want to stay out of setting up static routes, but I think
that has to come sooner or later.

Don't recall if this was already brought up, but need a way to specify
MTU and perhaps ethtool settings as well.

Yeah, that is definitely needed.

<interface device="eth2" onboot="yes">
  <hwaddr>00:19:d2:9f:88:98</hwaddr>
</interface>

<bond name="bond00" onboot="yes" mode="active-backup">
  <slave device="eth0" primary="yes"/>
  <slave device="eth1"/>
</bond>
In addition to mode attribute for bonds, support for miimon,
arp_interval, and arp_ip_target?

Sure .. if the initscript suports it, it's easy enough to do ;)

<bridge name="br0" stp="off" onboot="yes">
  <member device="eth2"/>
  <dhcp peerdns="yes"/>
</bridge>
Attributes to support hellotime, forwarddelay, and maxage?  This would allow
    <bridge name="br0" stp="on" hellotime="1" maxage="4" fowarddelay="4"
..>

My main concern with these is that only forwarddelay, stp, and gcint are
controllable by Fedora/RHEL networking scripts. For hellotime and
maxage, we'd need to hook into the various ifup scripts atthe right
place. Are these directly supported by the SuSe infrastructure ?

This is probably best answered by Marius.

Jim


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