package vrrp
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import (
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"errors"
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"fmt"
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"net"
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"unsafe"
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)
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type VRRPPacket struct {
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Header [8]byte
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IPAddress [][4]byte
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Pshdr *PseudoHeader
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}
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type PseudoHeader struct {
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Saddr net.IP
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Daddr net.IP
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Zero uint8
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Protocol uint8
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Len uint16
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}
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func (psh *PseudoHeader) ToBytes() []byte {
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var octets = make([]byte, 36)
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copy(octets, psh.Saddr)
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copy(octets[16:], psh.Daddr)
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copy(octets[32:], []byte{psh.Zero, psh.Protocol, byte(psh.Len >> 8), byte(psh.Len)})
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return octets
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}
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func FromBytes(IPvXVersion byte, octets []byte) (*VRRPPacket, error) {
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if len(octets) < 8 {
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return nil, errors.New("faulty VRRP packet size")
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}
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var packet VRRPPacket
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for index := 0; index < 8; index++ {
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packet.Header[index] = octets[index]
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}
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//todo validate the number of IPvX addresses
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var countofaddrs = int(packet.GetIPvXAddrCount())
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switch IPvXVersion {
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case 4:
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case 6:
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countofaddrs = countofaddrs * 4
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default:
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return nil, fmt.Errorf("faulty IPvX version %d", IPvXVersion)
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}
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//to compatible with VRRP v2 packet, ignore the auth info
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if 8+countofaddrs*4 > len(octets) {
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return nil, fmt.Errorf("The value of filed IPvXAddrCount doesn't match the length of octets")
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}
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for index := 0; index < countofaddrs; index++ {
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var addr [4]byte
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addr[0] = octets[8+4*index]
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addr[1] = octets[8+4*index+1]
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addr[2] = octets[8+4*index+2]
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addr[3] = octets[8+4*index+3]
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packet.IPAddress = append(packet.IPAddress, addr)
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}
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return &packet, nil
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}
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func (packet *VRRPPacket) GetIPvXAddr(version byte) (addrs []net.IP) {
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switch version {
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case 4:
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for index := range packet.IPAddress {
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addrs = append(addrs, net.IPv4(
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packet.IPAddress[index][0],
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packet.IPAddress[index][1],
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packet.IPAddress[index][2],
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packet.IPAddress[index][3]))
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}
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return addrs
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case 6:
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for index := 0; index < int(packet.GetIPvXAddrCount()); index++ {
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var p = make(net.IP, net.IPv6len)
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for i := 0; i < 4; i++ {
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copy(p[4*i:], packet.IPAddress[index*4+i][:])
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}
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addrs = append(addrs, p)
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}
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return addrs
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default:
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return nil
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}
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}
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func (packet *VRRPPacket) AddIPvXAddr(version byte, ip net.IP) {
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switch version {
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case 4:
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packet.IPAddress = append(packet.IPAddress, [4]byte{ip[12], ip[13], ip[14], ip[15]})
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packet.setIPvXAddrCount(packet.GetIPvXAddrCount() + 1)
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//todo byte maybe overflow
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case 6:
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for index := 0; index < 4; index++ {
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packet.IPAddress = append(packet.IPAddress, [4]byte{ip[index*4+0], ip[index*4+1], ip[index*4+2], ip[index*4+3]})
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}
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packet.setIPvXAddrCount(packet.GetIPvXAddrCount() + 1)
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default:
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panic("VRRPPacket.AddIPvXAddr: only support IPv4 and IPv6 address")
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}
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}
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func (packet *VRRPPacket) GetVersion() byte {
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return (packet.Header[0] & 240) >> 4
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}
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func (packet *VRRPPacket) SetVersion(Version VRRPVersion) {
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packet.Header[0] = (packet.Header[0] & 15) | (byte(Version) << 4)
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}
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func (packet *VRRPPacket) GetType() byte {
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return packet.Header[0] & 15
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}
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func (packet *VRRPPacket) SetType() {
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packet.Header[0] = (packet.Header[0] & 240) | 1
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}
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func (packet *VRRPPacket) GetVirtualRouterID() byte {
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return packet.Header[1]
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}
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func (packet *VRRPPacket) SetVirtualRouterID(VirtualRouterID byte) {
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packet.Header[1] = VirtualRouterID
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}
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func (packet *VRRPPacket) GetPriority() byte {
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return packet.Header[2]
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}
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func (packet *VRRPPacket) SetPriority(Priority byte) {
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packet.Header[2] = Priority
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}
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func (packet *VRRPPacket) GetIPvXAddrCount() byte {
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return packet.Header[3]
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}
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func (packet *VRRPPacket) setIPvXAddrCount(count byte) {
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packet.Header[3] = count
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}
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func (packet *VRRPPacket) GetAdvertisementInterval() uint16 {
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return uint16(packet.Header[4]&15)<<8 | uint16(packet.Header[5])
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}
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func (packet *VRRPPacket) SetAdvertisementInterval(interval uint16) {
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packet.Header[4] = (packet.Header[4] & 240) | byte((interval>>8)&15)
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packet.Header[5] = byte(interval)
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}
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func (packet *VRRPPacket) GetCheckSum() uint16 {
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return uint16(packet.Header[6])<<8 | uint16(packet.Header[7])
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}
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func (packet *VRRPPacket) SetCheckSum(pshdr *PseudoHeader) {
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var PointerAdd = func(ptr unsafe.Pointer, bytes int) unsafe.Pointer {
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return unsafe.Pointer(uintptr(ptr) + uintptr(bytes))
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}
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var octets = pshdr.ToBytes()
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octets = append(octets, packet.ToBytes()...)
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var x = len(octets)
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var ptr = unsafe.Pointer(&octets[0])
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var sum uint32
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for x > 1 {
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sum = sum + uint32(*(*uint16)(ptr))
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ptr = PointerAdd(ptr, 2)
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x = x - 2
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}
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if x > 0 {
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sum = sum + uint32(*((*uint8)(ptr)))
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}
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for (sum >> 16) > 0 {
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sum = sum&65535 + sum>>16
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}
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sum = ^sum
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packet.Header[7] = byte(sum >> 8)
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packet.Header[6] = byte(sum)
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}
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func (packet *VRRPPacket) ValidateCheckSum(pshdr *PseudoHeader) bool {
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var PointerAdd = func(ptr unsafe.Pointer, bytes int) unsafe.Pointer {
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return unsafe.Pointer(uintptr(ptr) + uintptr(bytes))
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}
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var octets = pshdr.ToBytes()
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octets = append(octets, packet.ToBytes()...)
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var x = len(octets)
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var ptr = unsafe.Pointer(&octets[0])
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var sum uint32
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for x > 1 {
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sum = sum + uint32(*(*uint16)(ptr))
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ptr = PointerAdd(ptr, 2)
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x = x - 2
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}
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if x > 0 {
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sum = sum + uint32(*((*uint8)(ptr)))
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}
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for (sum >> 16) > 0 {
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sum = sum&65535 + sum>>16
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}
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if uint16(sum) == 65535 {
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return true
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} else {
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return false
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}
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}
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func (packet *VRRPPacket) ToBytes() []byte {
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var payload = make([]byte, 8+len(packet.IPAddress)*4)
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copy(payload, packet.Header[:])
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for index := range packet.IPAddress {
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copy(payload[8+index*4:], packet.IPAddress[index][:])
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}
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return payload
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}
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