initial commit

pkg/vip/arp_linux.go.bak

@@ -0,0 +1,173 @@
+// +build linux
+
+// These syscalls are only supported on Linux, so this uses a build directive during compilation. Other OS's will use the arp_unsupported.go and receive an error
+
+package vip
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"net"
+	"syscall"
+	"unsafe"
+)
+
+const (
+	opARPRequest = 1
+	opARPReply   = 2
+	hwLen        = 6
+)
+
+var (
+	ethernetBroadcast = net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}
+	// arpRequest is used to flip between garp request or garp reply
+	arpRequest = true
+)
+
+func htons(p uint16) uint16 {
+	var b [2]byte
+	binary.BigEndian.PutUint16(b[:], p)
+	return *(*uint16)(unsafe.Pointer(&b))
+}
+
+// arpHeader specifies the header for an ARP message.
+type arpHeader struct {
+	hardwareType          uint16
+	protocolType          uint16
+	hardwareAddressLength uint8
+	protocolAddressLength uint8
+	opcode                uint16
+}
+
+// arpMessage represents an ARP message.
+type arpMessage struct {
+	arpHeader
+	senderHardwareAddress []byte
+	senderProtocolAddress []byte
+	targetHardwareAddress []byte
+	targetProtocolAddress []byte
+}
+
+// bytes returns the wire representation of the ARP message.
+func (m *arpMessage) bytes() ([]byte, error) {
+	buf := new(bytes.Buffer)
+
+	if err := binary.Write(buf, binary.BigEndian, m.arpHeader); err != nil {
+		return nil, fmt.Errorf("binary write failed: %v", err)
+	}
+	buf.Write(m.senderHardwareAddress)
+	buf.Write(m.senderProtocolAddress)
+	buf.Write(m.targetHardwareAddress)
+	buf.Write(m.targetProtocolAddress)
+
+	return buf.Bytes(), nil
+}
+
+// gratuitousARP return a gARP request or gARP reply alternatively
+// because different devices may support either one of them
+func gratuitousARP(ip net.IP, mac net.HardwareAddr) (*arpMessage, error) {
+	if ip.To4() == nil {
+		return nil, fmt.Errorf("%q is not an IPv4 address", ip)
+	}
+	if len(mac) != hwLen {
+		return nil, fmt.Errorf("%q is not an Ethernet MAC address", mac)
+	}
+
+	m := &arpMessage{
+		arpHeader: arpHeader{
+			1,           // Ethernet
+			0x0800,      // IPv4
+			hwLen,       // 48-bit MAC Address
+			net.IPv4len, // 32-bit IPv4 Address
+			opARPReply,  // ARP Reply
+		},
+	}
+
+	// https://tools.ietf.org/html/rfc5944#section-4.6
+	// In either case, the ARP Sender Hardware Address is
+	// set to the link-layer address to which this cache entry should be
+	// updated.
+	m.senderHardwareAddress = mac
+
+	// When using an ARP Reply packet, the Target Hardware
+	// Address is also set to the link-layer address to which this cache
+	// entry should be updated (this field is not used in an ARP Request
+	// packet).
+	m.targetHardwareAddress = mac
+
+	// In either case, the ARP Sender Protocol Address and
+	// ARP Target Protocol Address are both set to the IP address of the
+	// cache entry to be updated,
+	m.senderProtocolAddress = ip.To4()
+	m.targetProtocolAddress = ip.To4()
+
+	// send arpRequest and arpReply alternatively
+	arpRequest = !arpRequest
+	if arpRequest {
+		m.arpHeader.opcode = opARPRequest
+
+		// this field is not used in an ARP Request packet
+		m.targetHardwareAddress = ethernetBroadcast
+	}
+
+	return m, nil
+}
+
+// sendARP sends the given ARP message via the specified interface.
+func sendARP(iface *net.Interface, m *arpMessage) error {
+	fd, err := syscall.Socket(syscall.AF_PACKET, syscall.SOCK_DGRAM, int(htons(syscall.ETH_P_ARP)))
+	if err != nil {
+		return fmt.Errorf("failed to get raw socket: %v", err)
+	}
+	defer syscall.Close(fd)
+
+	if err := syscall.BindToDevice(fd, iface.Name); err != nil {
+		return fmt.Errorf("failed to bind to device: %v", err)
+	}
+
+	ll := syscall.SockaddrLinklayer{
+		Protocol: htons(syscall.ETH_P_ARP),
+		Ifindex:  iface.Index,
+		Pkttype:  0, // syscall.PACKET_HOST
+		Hatype:   m.hardwareType,
+		Halen:    m.hardwareAddressLength,
+	}
+	target := ethernetBroadcast
+	for i := 0; i < len(target); i++ {
+		ll.Addr[i] = target[i]
+	}
+
+	b, err := m.bytes()
+	if err != nil {
+		return fmt.Errorf("failed to convert ARP message: %v", err)
+	}
+
+	if err := syscall.Bind(fd, &ll); err != nil {
+		return fmt.Errorf("failed to bind: %v", err)
+	}
+	if err := syscall.Sendto(fd, b, 0, &ll); err != nil {
+		return fmt.Errorf("failed to send: %v", err)
+	}
+
+	return nil
+}
+
+// ARPSendGratuitous sends a gratuitous ARP message via the specified interface.
+func ARPSendGratuitous(cidr, iface string) error {
+	i, err := net.InterfaceByName(iface)
+	if err != nil {
+		return fmt.Errorf("failed to get interface %q: %v", iface, err)
+	}
+	ip, _, err := net.ParseCIDR(cidr)
+	if err != nil {
+		return fmt.Errorf("failed to parse cidr: %s", cidr)
+	}
+
+	//log.Infof("Broadcasting ARP update for %s (%s) via %s", address, iface.HardwareAddr, iface.Name)
+	m, err := gratuitousARP(ip, i.HardwareAddr)
+	if err != nil {
+		return err
+	}
+	return sendARP(i, m)
+}