95 lines
2.7 KiB
Go
95 lines
2.7 KiB
Go
package weave
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import (
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"bytes"
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"code.google.com/p/gopacket"
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"code.google.com/p/gopacket/layers"
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"log"
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"net"
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)
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func NewEthernetDecoder() *EthernetDecoder {
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dec := &EthernetDecoder{}
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dec.parser = gopacket.NewDecodingLayerParser(layers.LayerTypeEthernet, &dec.eth, &dec.ip)
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return dec
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}
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func (dec *EthernetDecoder) DecodeLayers(data []byte) error {
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return dec.parser.DecodeLayers(data, &dec.decoded)
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}
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func (dec *EthernetDecoder) CheckFrameTooBigFunc(po PacketSink) func(error) error {
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return func(err error) error {
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if ftbe, ok := err.(FrameTooBigError); ok {
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// we know: 1. ip is valid, 2. it was ip and DF was set
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icmpFrame, err := dec.formICMPMTUPacket(ftbe.PMTU)
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if err != nil {
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return err
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}
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log.Printf("Injecting ICMP 3,4 (%v -> %v): PMTU= %v\n", dec.ip.DstIP, dec.ip.SrcIP, ftbe.PMTU)
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return po.WritePacket(icmpFrame)
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} else {
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return err
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}
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}
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}
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func (dec *EthernetDecoder) formICMPMTUPacket(mtu int) ([]byte, error) {
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buf := gopacket.NewSerializeBuffer()
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opts := gopacket.SerializeOptions{
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FixLengths: true,
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ComputeChecksums: true}
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ipHeaderSize := int(dec.ip.IHL) * 4 // IHL is the number of 32-byte words in the header
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payload := gopacket.Payload(dec.ip.BaseLayer.Contents[:ipHeaderSize+8])
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err := gopacket.SerializeLayers(buf, opts,
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&layers.Ethernet{
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SrcMAC: dec.eth.DstMAC,
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DstMAC: dec.eth.SrcMAC,
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EthernetType: dec.eth.EthernetType},
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&layers.IPv4{
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Version: 4,
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TOS: dec.ip.TOS,
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Id: 0,
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Flags: 0,
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FragOffset: 0,
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TTL: 64,
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Protocol: layers.IPProtocolICMPv4,
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DstIP: dec.ip.SrcIP,
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SrcIP: dec.ip.DstIP},
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&layers.ICMPv4{
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TypeCode: 0x304,
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Id: 0,
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Seq: uint16(mtu)},
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&payload)
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if err == nil {
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return buf.Bytes(), nil
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} else {
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return []byte{}, err
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}
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}
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var (
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// see http://en.wikipedia.org/wiki/Multicast_address#Ethernet
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broadcastMAC, _ = net.ParseMAC("ff:ff:ff:ff:ff:ff")
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zeroMAC, _ = net.ParseMAC("00:00:00:00:00:00")
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stpMACPrefix = []byte{0x01, 0x80, 0xC2, 0x00, 0x00}
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ipv4MulticastMACPrefix = []byte{0x01, 0x00, 0x5E}
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ipv6MulticastMACPrefix = []byte{0x33, 0x33}
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)
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func (dec *EthernetDecoder) DropFrame() bool {
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return bytes.Equal(stpMACPrefix, dec.eth.DstMAC[:len(stpMACPrefix)])
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}
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func (dec *EthernetDecoder) BroadcastFrame() bool {
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return bytes.Equal(broadcastMAC, dec.eth.DstMAC) ||
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// treat multicast frames as broadcast
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bytes.Equal(ipv4MulticastMACPrefix, dec.eth.DstMAC[:len(ipv4MulticastMACPrefix)]) ||
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bytes.Equal(ipv6MulticastMACPrefix, dec.eth.DstMAC[:len(ipv6MulticastMACPrefix)])
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}
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func (dec *EthernetDecoder) IsPMTUVerify() bool {
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return bytes.Equal(zeroMAC, dec.eth.SrcMAC) &&
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bytes.Equal(zeroMAC, dec.eth.DstMAC)
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}
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