github.com/apernet/sing-tun@v0.2.6-0.20240323130332-b9f6511036ad/internal/clashtcpip/udp.go (about)

     1  package clashtcpip
     2  
     3  import (
     4  	"encoding/binary"
     5  )
     6  
     7  const UDPHeaderSize = 8
     8  
     9  type UDPPacket []byte
    10  
    11  func (p UDPPacket) Length() uint16 {
    12  	return binary.BigEndian.Uint16(p[4:])
    13  }
    14  
    15  func (p UDPPacket) SetLength(length uint16) {
    16  	binary.BigEndian.PutUint16(p[4:], length)
    17  }
    18  
    19  func (p UDPPacket) SourcePort() uint16 {
    20  	return binary.BigEndian.Uint16(p)
    21  }
    22  
    23  func (p UDPPacket) SetSourcePort(port uint16) {
    24  	binary.BigEndian.PutUint16(p, port)
    25  }
    26  
    27  func (p UDPPacket) DestinationPort() uint16 {
    28  	return binary.BigEndian.Uint16(p[2:])
    29  }
    30  
    31  func (p UDPPacket) SetDestinationPort(port uint16) {
    32  	binary.BigEndian.PutUint16(p[2:], port)
    33  }
    34  
    35  func (p UDPPacket) Payload() []byte {
    36  	return p[UDPHeaderSize:p.Length()]
    37  }
    38  
    39  func (p UDPPacket) Checksum() uint16 {
    40  	return binary.BigEndian.Uint16(p[6:])
    41  }
    42  
    43  func (p UDPPacket) SetChecksum(sum [2]byte) {
    44  	p[6] = sum[0]
    45  	p[7] = sum[1]
    46  }
    47  
    48  func (p UDPPacket) OffloadChecksum() {
    49  	p.SetChecksum(zeroChecksum)
    50  }
    51  
    52  func (p UDPPacket) ResetChecksum(psum uint32) {
    53  	p.SetChecksum(zeroChecksum)
    54  	p.SetChecksum(Checksum(psum, p))
    55  }
    56  
    57  func (p UDPPacket) Valid() bool {
    58  	return len(p) >= UDPHeaderSize && uint16(len(p)) >= p.Length()
    59  }