92 lines
2.2 KiB
Go
92 lines
2.2 KiB
Go
package engine
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import "net"
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type L3Info struct {
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Version uint8
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Protocol uint8
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IHL uint8
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SrcIP [4]byte
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DstIP [4]byte
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Length uint16
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}
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func (i L3Info) SrcIPAddr() net.IP { return net.IP(i.SrcIP[:]) }
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func (i L3Info) DstIPAddr() net.IP { return net.IP(i.DstIP[:]) }
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type TCPInfo struct {
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SrcPort uint16
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DstPort uint16
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Seq uint32
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Ack uint32
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HdrLen uint8
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SYN bool
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FIN bool
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RST bool
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ACK bool
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}
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type UDPInfo struct {
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SrcPort uint16
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DstPort uint16
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}
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func ParseL3(data []byte) (l3 L3Info, transport []byte, ok bool) {
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if len(data) < 20 {
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return
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}
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version := data[0] >> 4
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if version != 4 {
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return
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}
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ihl := data[0] & 0x0F
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if ihl < 5 || len(data) < int(ihl)*4 {
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return
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}
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totalLen := int(uint16(data[2])<<8 | uint16(data[3]))
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if totalLen < int(ihl)*4 || totalLen > len(data) {
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totalLen = len(data)
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}
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return L3Info{
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Version: 4,
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Protocol: data[9],
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IHL: ihl,
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Length: uint16(totalLen),
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SrcIP: [4]byte{data[12], data[13], data[14], data[15]},
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DstIP: [4]byte{data[16], data[17], data[18], data[19]},
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}, data[ihl*4:totalLen], true
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}
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func ParseTCP(transport []byte) (TCPInfo, []byte, bool) {
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if len(transport) < 20 {
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return TCPInfo{}, nil, false
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}
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dataOff := uint8(transport[12]>>4) * 4
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if dataOff < 20 || len(transport) < int(dataOff) {
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return TCPInfo{}, nil, false
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}
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flags := transport[13]
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payloadLen := len(transport) - int(dataOff)
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return TCPInfo{
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SrcPort: uint16(transport[0])<<8 | uint16(transport[1]),
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DstPort: uint16(transport[2])<<8 | uint16(transport[3]),
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Seq: uint32(transport[4])<<24 | uint32(transport[5])<<16 | uint32(transport[6])<<8 | uint32(transport[7]),
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Ack: uint32(transport[8])<<24 | uint32(transport[9])<<16 | uint32(transport[10])<<8 | uint32(transport[11]),
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HdrLen: dataOff,
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SYN: flags&0x02 != 0,
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FIN: flags&0x01 != 0,
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RST: flags&0x04 != 0,
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ACK: flags&0x10 != 0,
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}, transport[dataOff : dataOff+uint8(payloadLen)], true
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}
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func ParseUDP(transport []byte) (UDPInfo, []byte, bool) {
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if len(transport) < 8 {
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return UDPInfo{}, nil, false
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}
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return UDPInfo{
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SrcPort: uint16(transport[0])<<8 | uint16(transport[1]),
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DstPort: uint16(transport[2])<<8 | uint16(transport[3]),
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}, transport[8:], true
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}
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