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package ipmanager
import (
"errors"
"net"
"strings"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
)
// BasicConfigurer can be used to enable vip-management on nodes
// that handle their own network connection, in setups where it is
// sufficient to add the virtual ip using `ip addr add ...` .
// After adding the virtual ip to the specified interface,
// a gratuitous ARP package is sent out to update the tables of
// nearby routers and other devices.
type BasicConfigurer struct {
*IPConfiguration
ntecontext uint32 //used by Windows to delete IP address
}
func newBasicConfigurer(config *IPConfiguration) (*BasicConfigurer, error) {
c := &BasicConfigurer{IPConfiguration: config, ntecontext: 0}
if c.Iface.HardwareAddr == nil || c.Iface.HardwareAddr.String() == "00:00:00:00:00:00" {
return nil, errors.New(`Cannot run vip-manager on the loopback device
as its hardware address is the local address (00:00:00:00:00:00),
which prohibits sending of gratuitous ARP messages`)
}
return c, nil
}
// queryAddress returns if the address is assigned
func (c *BasicConfigurer) queryAddress() bool {
iface, err := net.InterfaceByName(c.Iface.Name)
if err != nil {
return false
}
addresses, err := iface.Addrs()
if err != nil {
return false
}
for _, address := range addresses {
if strings.Contains(address.String(), c.getCIDR()) {
return true
}
}
return false
}
const (
MACAddressSize = 6
IPv4AddressSize = 4
)
// createGratuitousARP prepares a packet with a gratuitous ARP request
func (c *BasicConfigurer) createGratuitousARP() ([]byte, error) {
// Create the Ethernet layer
ethLayer := &layers.Ethernet{
SrcMAC: c.Iface.HardwareAddr,
DstMAC: net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, // Broadcast
EthernetType: layers.EthernetTypeARP,
}
// Create the ARP layer
arpLayer := &layers.ARP{
AddrType: layers.LinkTypeEthernet,
Protocol: layers.EthernetTypeIPv4,
HwAddressSize: MACAddressSize,
ProtAddressSize: IPv4AddressSize,
Operation: layers.ARPReply, // Gratuitous ARP is sent as a reply
SourceHwAddress: c.Iface.HardwareAddr,
SourceProtAddress: c.IPConfiguration.VIP.AsSlice(),
DstHwAddress: c.Iface.HardwareAddr, // Gratuitous ARP targets itself
DstProtAddress: c.IPConfiguration.VIP.AsSlice(),
}
// Create a packet with the layers
buffer := gopacket.NewSerializeBuffer()
opts := gopacket.SerializeOptions{
FixLengths: true,
ComputeChecksums: true,
}
if err := gopacket.SerializeLayers(buffer, opts, ethLayer, arpLayer); err != nil {
return nil, err
}
return buffer.Bytes(), nil
}
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