[libvirt] RFC: configuring host interfaces with libvirt

[Jim Fehlig]

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.

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")

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

> <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"

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.

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

> <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?

> <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"
..>

Regards,
Jim