NetworkUpdate: Operation not supported: can't update 'ip' section of network 'default'

[a2geek]

I'm not entirely certain if this is a bug in my code or something is up with the NetworkUpdate call from this library.

I'm writing some code that will ultimately be installed into a VM in order to manage multiple VM's. The base OS layer does not have any libvirt dependencies, and this is the best solution for my needs. (So thanks for that!)

When I do a NetworkUpdate to add an IP>DHCP>Host entry, an error is generated: Operation not supported: can't update 'ip' section of network 'default'.

What I've done:

• verified the project is on the latest code.
• extracted the specific code, and it fails.
• used TLS connections (thinking there may be a different socket file to utilize)
• implemented with the libvirt/libvirt-go library, and it works.
• verified this also works from the virsh command-line.

Therefore, I think I've got a valid setup but haven't been able to identify what may be wrong (in either code base).

Running on Ubuntu 18.04.2.

$ virsh version
Compiled against library: libvirt 4.0.0
Using library: libvirt 4.0.0
Using API: QEMU 4.0.0
Running hypervisor: QEMU 2.11.1

Using this library (and it fails):

const networkDhcpXML = "<host name='vm-8029d8c8-ee6c-45b9-6476-3ba7381c3cb5' ip='192.168.123.7'/>"
const networkName = "default"
const socket = "/var/run/libvirt/libvirt-sock"

func main() {
	conn, err := net.DialTimeout("unix", socket, 2*time.Second)
	defer conn.Close()
	if err != nil {
		panic(err)
	}
	fmt.Printf("Connected to '%s'\n", socket)

	client := libvirt.New(conn)
	err = client.Connect()
	if err != nil {
		panic(err)
	}
	fmt.Printf("Connected to libvirt\n")

	net, err := client.NetworkLookupByName(networkName)
	if err != nil {
		panic(err)
	}
	fmt.Printf("net = %v\n", net)

	xmlDesc, err := client.NetworkGetXMLDesc(net, 0)
	if err != nil {
		panic(err)
	}
	fmt.Printf("networkXMLDesc=%s\n", xmlDesc)

	cmd := uint32(libvirt.NetworkUpdateCommandAddLast)
	section := uint32(libvirt.NetworkSectionIPDhcpHost)
	//netflags := libvirt.NetworkUpdateAffectLive | libvirt.NetworkUpdateAffectConfig
	fmt.Printf("NetworkUpdate(%v, %d, %d, -1, %s, %d)\n", net, cmd, section, networkDhcpXML, 0)
	err = client.NetworkUpdate(net, cmd, section, -1, networkDhcpXML, 0)
	if err != nil {
		panic(err)
	}
	fmt.Printf("Setup network DHCP\n")
}

Using the libvirt/libvirt-go library (and it works):

const networkDhcpXML = "<host name='vm-8029d8c8-ee6c-45b9-6476-3ba7381c3cb5' ip='192.168.123.7'/>"
const networkName = "default"

func main() {
	conn, err := libvirt.NewConnect("qemu:///system")
	if err != nil {
		panic(err)
	}
	defer conn.Close()

	net, err := conn.LookupNetworkByName(networkName)
	defer net.Free()
	if err != nil {
		panic(err)
	}
	fmt.Printf("net = %v\n", net)

	xmlDesc, err := net.GetXMLDesc(0)
	if err != nil {
		panic(err)
	}
	fmt.Printf("networkXMLDesc=%s\n", xmlDesc)

	cmd := libvirt.NETWORK_UPDATE_COMMAND_ADD_LAST
	section := libvirt.NETWORK_SECTION_IP_DHCP_HOST
	//netflags := libvirt.NetworkUpdateAffectLive | libvirt.NetworkUpdateAffectConfig
	fmt.Printf("NetworkUpdate(%v, %d, %d, -1, %s, %d)\n", net, cmd, section, networkDhcpXML, 0)
	err = net.Update(cmd, section, -1, networkDhcpXML, 0)
	if err != nil {
		panic(err)
	}
	fmt.Printf("Setup network DHCP\n")
}

Using virsh:

$ virsh net-update default add --section ip-dhcp-host --xml "<host name='vm-8029d8c8-ee6c-45b9-6476-3ba7381c3cb5' ip='192.168.123.7'/>"
Updated network default live state

If it's useful, the specific usage is in the libvirtManager here. It's been rejiggered into the samples to work out whatever issue is occurring.

Thanks for any information you may provide!

[trapgate]

The error you're getting seems to be coming from virNetworkDefUpdateIP in the libvirt sources. But that's not the right routine - you're trying to update the DHCP host settings, which is section "ip/dhcp/host", and is handled by virNetworkDefUpdateIPDHCPHost. You'd get this error if the section parameter passed into the NetworkUpdate call were wrong (3 instead of 4), but libvirt.NetworkSectionIpDhcpHost and NETWORK_SECTION_IP_DHCP_HOST are both 4, in the sources I'm looking at. (libvirt 4.0.0). It might be interesting to try some other values for the section parameter, and see if you get back sensible errors.

[a2geek]

I get the same response regardless of values (tried 1, 2, 3, 4, 5, and 500):

NetworkUpdate(3, 500, -1, <host name='vm-8029d8c8-ee6c-45b9-6476-3ba7381c3cb5' ip='192.168.123.7'/>, 0)
panic: Operation not supported: can't update 'ip' section of network 'default'

I am using Go 1.12 and modules. go.mod is:

$ cat go.mod
module ip-dhcp-host

go 1.12

require github.com/digitalocean/go-libvirt v0.0.0-20190715144809-7b622097a793

Just in case there's a specific version or something.

[a2geek]

Hmm. Going with your suggestion, I "widened" the net... I tried setting command, section, and flags to 4. Flags wouldn't allow it (actually gave me a flags related error).

But...

	cmd := uint32(4)
	section := uint32(4)
	fmt.Printf("NetworkUpdate(%d, %d, -1, %s, %d)\n", cmd, section, networkDhcpXML, 0)
	err = client.NetworkUpdate(net, cmd, section, -1, networkDhcpXML, 0)

Gave me:

NetworkUpdate(4, 4, -1, <host name='vm-8029d8c8-ee6c-45b9-6476-3ba7381c3cb5' ip='192.168.123.7'/>, 0)
Setup network DHCP

... and as proof:

$ virsh net-dumpxml default
<network>
  <name>default</name>
  <uuid>bcb85dc8-ad27-4861-9f85-692167fd79fa</uuid>
  <forward mode='nat'>
    <nat>
      <port start='1024' end='65535'/>
    </nat>
  </forward>
  <bridge name='virbr0' stp='on' delay='0'/>
  <mac address='52:54:00:82:d1:6e'/>
  <ip address='192.168.123.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.123.2' end='192.168.123.254'/>
      <host name='vm-8029d8c8-ee6c-45b9-6476-3ba7381c3cb5' ip='192.168.123.7'/>
      <host name='totally-fake-vm' ip='192.168.123.6'/>
    </dhcp>
  </ip>
</network>

... and running it again errors out (as expected):

NetworkUpdate(4, 4, -1, <host name='vm-8029d8c8-ee6c-45b9-6476-3ba7381c3cb5' ip='192.168.123.7'/>, 0)
panic: Requested operation is not valid: there is an existing dhcp host entry in network 'default' that matches "<host mac='unknown' name='vm-8029d8c8-ee6c-45b9-6476-3ba7381c3cb5' ip='192.168.123.7'/>"

Is something cross-wired somewhere? Even in my code? Sadly, I'm not spotting anything. (But also admitting I'm a Go rookie, haven't touched C in 30 years, and utter neophyte with Libvirt! LOL)

[karlskewes]

Thank you so much for posting this issue. We've just run into it with the terraform libvirt provider.

Seems there has been work going on upstream to improve a situation where command and section argument ordering is swapped around.

See:

• v1 fix (not merged) https://listman.redhat.com/archives/libvir-list/2021-March/msg00054.html
• v2 fix (merged) https://listman.redhat.com/archives/libvir-list/2021-March/msg00758.html

[cfergeau]

My take on this is cfergeau@8108763