mirror of
https://github.com/impact-eintr/netstack.git
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94 lines
2.9 KiB
Go
94 lines
2.9 KiB
Go
package header
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import (
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"encoding/binary"
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"netstack/tcpip"
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)
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/*
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Source Port | Destination Port |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Sequence Number |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Acknowledgment Number |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Data | |U|A|P|R|S|F| |
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| Offset| Reserved |R|C|S|S|Y|I| Window |
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| | |G|K|H|T|N|N| |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Checksum | Urgent Pointer |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Options | Padding |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| data |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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// TCPFields contains the fields of a TCP packet. It is used to describe the
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// fields of a packet that needs to be encoded.
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// tcp首部字段
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type TCPFields struct {
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// SrcPort is the "source port" field of a TCP packet.
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SrcPort uint16
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// DstPort is the "destination port" field of a TCP packet.
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DstPort uint16
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// SeqNum is the "sequence number" field of a TCP packet.
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SeqNum uint32
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// AckNum is the "acknowledgement number" field of a TCP packet.
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AckNum uint32
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// DataOffset is the "data offset" field of a TCP packet.
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DataOffset uint8
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// Flags is the "flags" field of a TCP packet.
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Flags uint8
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// WindowSize is the "window size" field of a TCP packet.
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WindowSize uint16
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// Checksum is the "checksum" field of a TCP packet.
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Checksum uint16
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// UrgentPointer is the "urgent pointer" field of a TCP packet.
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UrgentPointer uint16
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}
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const (
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srcPort = 0
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dstPort = 2
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seqNum = 4
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ackNum = 8
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dataOffset = 12
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tcpFlags = 13
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winSize = 14
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tcpChecksum = 16
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urgentPtr = 18
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)
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// TCP represents a TCP header stored in a byte array.
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type TCP []byte
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const (
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// TCPMinimumSize is the minimum size of a valid TCP packet.
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TCPMinimumSize = 20
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// TCPProtocolNumber is TCP's transport protocol number.
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TCPProtocolNumber tcpip.TransportProtocolNumber = 6
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)
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// SourcePort returns the "source port" field of the tcp header.
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func (b TCP) SourcePort() uint16 {
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return binary.BigEndian.Uint16(b[srcPort:])
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}
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// DestinationPort returns the "destination port" field of the tcp header.
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func (b TCP) DestinationPort() uint16 {
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return binary.BigEndian.Uint16(b[dstPort:])
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}
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