Libvirt Go: Network Update Function and Example

Libvirt Go Network Update: Modifying Network Configurations

This code snippet showcases the Update function within the libvirt-go package, allowing you to modify an existing network in libvirt. The function takes various parameters, including the update command, section, parent index, XML configuration, and flags, providing flexibility in network manipulation.

Core Function:

// See also https://libvirt.org/html/libvirt-libvirt-network.html#virNetworkUpdate
func (n *Network) Update(cmd NetworkUpdateCommand, section NetworkUpdateSection, parentIndex int, xml string, flags NetworkUpdateFlags) error {
	cxml := C.CString(xml)
	defer C.free(unsafe.Pointer(cxml))
	var err C.virError
	result := C.virNetworkUpdateWrapper(n.ptr, C.uint(cmd), C.uint(section), C.int(parentIndex), cxml, C.uint(flags), &err)
	if result == -1 {
		return makeError(&err)
	}
	return nil
}

Example Usage:

This example demonstrates updating a network's bridge name. You'll need the libvirt-go package installed to run this code.

package main

import (
	"fmt"
	"github.com/libvirt/libvirt-go"
)

func main() {
	// Connect to the hypervisor
	conn, err := libvirt.NewConnect("qemu:///system")
	if err != nil {
		fmt.Println("Failed to connect to the hypervisor:", err)
		return
	}
	defer conn.Close()

	// Lookup the network by name
	network, err := conn.LookupNetworkByName("my_network")
	if err != nil {
		fmt.Println("Failed to lookup network:", err)
		return
	}

	// Update the network
	xml := `
		<network>
			<name>my_network</name>
			<bridge name='br0'/>
		</network>
	`
	err = network.Update(libvirt.NETWORK_UPDATE_COMMAND_MODIFY, libvirt.NETWORK_UPDATE_SECTION_BRIDGE, -1, xml, libvirt.NETWORK_UPDATE_AFFECT_CURRENT)
	if err != nil {
		fmt.Println("Failed to update network:", err)
		return
	}

	fmt.Println("Network updated successfully")
}

Explanation:

1. Connect to libvirt: Establish a connection to the hypervisor.
2. Lookup the Network: Retrieve the network object using its name.
3. Prepare XML Configuration: Define the updated XML configuration, in this case, changing the bridge name to 'br0'.
4. Update Network: Use the Update function to apply the XML modifications. The parameters specify the command (NETWORK_UPDATE_COMMAND_MODIFY), section (NETWORK_UPDATE_SECTION_BRIDGE), and flags (NETWORK_UPDATE_AFFECT_CURRENT) for the update.
5. Handle Errors: Check for errors after each step. If successful, print a confirmation message.

Note: This example is a basic demonstration. You can modify the XML configuration and utilize other update options to achieve more complex network updates.