mirror of
https://github.com/SagerNet/sing-tun.git
synced 2025-04-02 19:37:40 +03:00
90 lines
1.6 KiB
Go
90 lines
1.6 KiB
Go
package clashtcpip
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import (
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"encoding/binary"
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"net"
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)
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const (
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TCPFin uint16 = 1 << 0
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TCPSyn uint16 = 1 << 1
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TCPRst uint16 = 1 << 2
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TCPPuh uint16 = 1 << 3
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TCPAck uint16 = 1 << 4
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TCPUrg uint16 = 1 << 5
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TCPEce uint16 = 1 << 6
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TCPEwr uint16 = 1 << 7
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TCPNs uint16 = 1 << 8
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)
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const TCPHeaderSize = 20
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type TCPPacket []byte
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func (p TCPPacket) SourcePort() uint16 {
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return binary.BigEndian.Uint16(p)
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}
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func (p TCPPacket) SetSourcePort(port uint16) {
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binary.BigEndian.PutUint16(p, port)
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}
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func (p TCPPacket) DestinationPort() uint16 {
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return binary.BigEndian.Uint16(p[2:])
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}
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func (p TCPPacket) SetDestinationPort(port uint16) {
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binary.BigEndian.PutUint16(p[2:], port)
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}
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func (p TCPPacket) Flags() uint16 {
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return uint16(p[13] | (p[12] & 0x1))
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}
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func (p TCPPacket) Checksum() uint16 {
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return binary.BigEndian.Uint16(p[16:])
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}
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func (p TCPPacket) SetChecksum(sum [2]byte) {
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p[16] = sum[0]
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p[17] = sum[1]
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}
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func (p TCPPacket) ResetChecksum(psum uint32) {
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p.SetChecksum(zeroChecksum)
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p.SetChecksum(Checksum(psum, p))
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}
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func (p TCPPacket) Valid() bool {
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return len(p) >= TCPHeaderSize
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}
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func (p TCPPacket) Verify(sourceAddress net.IP, targetAddress net.IP) error {
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var checksum [2]byte
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checksum[0] = p[16]
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checksum[1] = p[17]
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// reset checksum
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p[16] = 0
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p[17] = 0
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// restore checksum
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defer func() {
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p[16] = checksum[0]
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p[17] = checksum[1]
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}()
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// check checksum
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s := uint32(0)
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s += Sum(sourceAddress)
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s += Sum(targetAddress)
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s += uint32(TCP)
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s += uint32(len(p))
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check := Checksum(s, p)
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if checksum[0] != check[0] || checksum[1] != check[1] {
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return ErrInvalidChecksum
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}
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return nil
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}
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