diff options
Diffstat (limited to 'vendor/github.com/google/gopacket/layers/ip4.go')
-rw-r--r-- | vendor/github.com/google/gopacket/layers/ip4.go | 311 |
1 files changed, 311 insertions, 0 deletions
diff --git a/vendor/github.com/google/gopacket/layers/ip4.go b/vendor/github.com/google/gopacket/layers/ip4.go new file mode 100644 index 0000000..3f31b27 --- /dev/null +++ b/vendor/github.com/google/gopacket/layers/ip4.go @@ -0,0 +1,311 @@ +// Copyright 2012 Google, Inc. All rights reserved. +// Copyright 2009-2011 Andreas Krennmair. All rights reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the LICENSE file in the root of the source +// tree. + +package layers + +import ( + "encoding/binary" + "errors" + "fmt" + "net" + "strings" + + "github.com/google/gopacket" +) + +type IPv4Flag uint8 + +const ( + IPv4EvilBit IPv4Flag = 1 << 2 // http://tools.ietf.org/html/rfc3514 ;) + IPv4DontFragment IPv4Flag = 1 << 1 + IPv4MoreFragments IPv4Flag = 1 << 0 +) + +func (f IPv4Flag) String() string { + var s []string + if f&IPv4EvilBit != 0 { + s = append(s, "Evil") + } + if f&IPv4DontFragment != 0 { + s = append(s, "DF") + } + if f&IPv4MoreFragments != 0 { + s = append(s, "MF") + } + return strings.Join(s, "|") +} + +// IPv4 is the header of an IP packet. +type IPv4 struct { + BaseLayer + Version uint8 + IHL uint8 + TOS uint8 + Length uint16 + Id uint16 + Flags IPv4Flag + FragOffset uint16 + TTL uint8 + Protocol IPProtocol + Checksum uint16 + SrcIP net.IP + DstIP net.IP + Options []IPv4Option + Padding []byte +} + +// LayerType returns LayerTypeIPv4 +func (i *IPv4) LayerType() gopacket.LayerType { return LayerTypeIPv4 } +func (i *IPv4) NetworkFlow() gopacket.Flow { + return gopacket.NewFlow(EndpointIPv4, i.SrcIP, i.DstIP) +} + +type IPv4Option struct { + OptionType uint8 + OptionLength uint8 + OptionData []byte +} + +func (i IPv4Option) String() string { + return fmt.Sprintf("IPv4Option(%v:%v)", i.OptionType, i.OptionData) +} + +// for the current ipv4 options, return the number of bytes (including +// padding that the options used) +func (ip *IPv4) getIPv4OptionSize() uint8 { + optionSize := uint8(0) + for _, opt := range ip.Options { + switch opt.OptionType { + case 0: + // this is the end of option lists + optionSize++ + case 1: + // this is the padding + optionSize++ + default: + optionSize += opt.OptionLength + + } + } + // make sure the options are aligned to 32 bit boundary + if (optionSize % 4) != 0 { + optionSize += 4 - (optionSize % 4) + } + return optionSize +} + +// SerializeTo writes the serialized form of this layer into the +// SerializationBuffer, implementing gopacket.SerializableLayer. +func (ip *IPv4) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error { + optionLength := ip.getIPv4OptionSize() + bytes, err := b.PrependBytes(20 + int(optionLength)) + if err != nil { + return err + } + if opts.FixLengths { + ip.IHL = 5 + (optionLength / 4) + ip.Length = uint16(len(b.Bytes())) + } + bytes[0] = (ip.Version << 4) | ip.IHL + bytes[1] = ip.TOS + binary.BigEndian.PutUint16(bytes[2:], ip.Length) + binary.BigEndian.PutUint16(bytes[4:], ip.Id) + binary.BigEndian.PutUint16(bytes[6:], ip.flagsfrags()) + bytes[8] = ip.TTL + bytes[9] = byte(ip.Protocol) + if err := ip.AddressTo4(); err != nil { + return err + } + copy(bytes[12:16], ip.SrcIP) + copy(bytes[16:20], ip.DstIP) + + curLocation := 20 + // Now, we will encode the options + for _, opt := range ip.Options { + switch opt.OptionType { + case 0: + // this is the end of option lists + bytes[curLocation] = 0 + curLocation++ + case 1: + // this is the padding + bytes[curLocation] = 1 + curLocation++ + default: + bytes[curLocation] = opt.OptionType + bytes[curLocation+1] = opt.OptionLength + + // sanity checking to protect us from buffer overrun + if len(opt.OptionData) > int(opt.OptionLength-2) { + return errors.New("option length is smaller than length of option data") + } + copy(bytes[curLocation+2:curLocation+int(opt.OptionLength)], opt.OptionData) + curLocation += int(opt.OptionLength) + } + } + + if opts.ComputeChecksums { + ip.Checksum = checksum(bytes) + } + binary.BigEndian.PutUint16(bytes[10:], ip.Checksum) + return nil +} + +func checksum(bytes []byte) uint16 { + // Clear checksum bytes + bytes[10] = 0 + bytes[11] = 0 + + // Compute checksum + var csum uint32 + for i := 0; i < len(bytes); i += 2 { + csum += uint32(bytes[i]) << 8 + csum += uint32(bytes[i+1]) + } + for { + // Break when sum is less or equals to 0xFFFF + if csum <= 65535 { + break + } + // Add carry to the sum + csum = (csum >> 16) + uint32(uint16(csum)) + } + // Flip all the bits + return ^uint16(csum) +} + +func (ip *IPv4) flagsfrags() (ff uint16) { + ff |= uint16(ip.Flags) << 13 + ff |= ip.FragOffset + return +} + +// DecodeFromBytes decodes the given bytes into this layer. +func (ip *IPv4) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error { + flagsfrags := binary.BigEndian.Uint16(data[6:8]) + + ip.Version = uint8(data[0]) >> 4 + ip.IHL = uint8(data[0]) & 0x0F + ip.TOS = data[1] + ip.Length = binary.BigEndian.Uint16(data[2:4]) + ip.Id = binary.BigEndian.Uint16(data[4:6]) + ip.Flags = IPv4Flag(flagsfrags >> 13) + ip.FragOffset = flagsfrags & 0x1FFF + ip.TTL = data[8] + ip.Protocol = IPProtocol(data[9]) + ip.Checksum = binary.BigEndian.Uint16(data[10:12]) + ip.SrcIP = data[12:16] + ip.DstIP = data[16:20] + ip.Options = ip.Options[:0] + // Set up an initial guess for contents/payload... we'll reset these soon. + ip.BaseLayer = BaseLayer{Contents: data} + + // This code is added for the following enviroment: + // * Windows 10 with TSO option activated. ( tested on Hyper-V, RealTek ethernet driver ) + if ip.Length == 0 { + // If using TSO(TCP Segmentation Offload), length is zero. + // The actual packet length is the length of data. + ip.Length = uint16(len(data)) + } + + if ip.Length < 20 { + return fmt.Errorf("Invalid (too small) IP length (%d < 20)", ip.Length) + } else if ip.IHL < 5 { + return fmt.Errorf("Invalid (too small) IP header length (%d < 5)", ip.IHL) + } else if int(ip.IHL*4) > int(ip.Length) { + return fmt.Errorf("Invalid IP header length > IP length (%d > %d)", ip.IHL, ip.Length) + } + if cmp := len(data) - int(ip.Length); cmp > 0 { + data = data[:ip.Length] + } else if cmp < 0 { + df.SetTruncated() + if int(ip.IHL)*4 > len(data) { + return errors.New("Not all IP header bytes available") + } + } + ip.Contents = data[:ip.IHL*4] + ip.Payload = data[ip.IHL*4:] + // From here on, data contains the header options. + data = data[20 : ip.IHL*4] + // Pull out IP options + for len(data) > 0 { + if ip.Options == nil { + // Pre-allocate to avoid growing the slice too much. + ip.Options = make([]IPv4Option, 0, 4) + } + opt := IPv4Option{OptionType: data[0]} + switch opt.OptionType { + case 0: // End of options + opt.OptionLength = 1 + ip.Options = append(ip.Options, opt) + ip.Padding = data[1:] + break + case 1: // 1 byte padding + opt.OptionLength = 1 + default: + opt.OptionLength = data[1] + opt.OptionData = data[2:opt.OptionLength] + } + if len(data) >= int(opt.OptionLength) { + data = data[opt.OptionLength:] + } else { + return fmt.Errorf("IP option length exceeds remaining IP header size, option type %v length %v", opt.OptionType, opt.OptionLength) + } + ip.Options = append(ip.Options, opt) + } + return nil +} + +func (i *IPv4) CanDecode() gopacket.LayerClass { + return LayerTypeIPv4 +} + +func (i *IPv4) NextLayerType() gopacket.LayerType { + if i.Flags&IPv4MoreFragments != 0 || i.FragOffset != 0 { + return gopacket.LayerTypeFragment + } + return i.Protocol.LayerType() +} + +func decodeIPv4(data []byte, p gopacket.PacketBuilder) error { + ip := &IPv4{} + err := ip.DecodeFromBytes(data, p) + p.AddLayer(ip) + p.SetNetworkLayer(ip) + if err != nil { + return err + } + return p.NextDecoder(ip.NextLayerType()) +} + +func checkIPv4Address(addr net.IP) (net.IP, error) { + if c := addr.To4(); c != nil { + return c, nil + } + if len(addr) == net.IPv6len { + return nil, errors.New("address is IPv6") + } + return nil, fmt.Errorf("wrong length of %d bytes instead of %d", len(addr), net.IPv4len) +} + +func (ip *IPv4) AddressTo4() error { + var src, dst net.IP + + if addr, err := checkIPv4Address(ip.SrcIP); err != nil { + return fmt.Errorf("Invalid source IPv4 address (%s)", err) + } else { + src = addr + } + if addr, err := checkIPv4Address(ip.DstIP); err != nil { + return fmt.Errorf("Invalid destination IPv4 address (%s)", err) + } else { + dst = addr + } + ip.SrcIP = src + ip.DstIP = dst + return nil +} |