github.com/borderzero/water@v0.0.1/waterutil/tun_ipv4.go (about)

     1  package waterutil
     2  
     3  import (
     4  	"net"
     5  )
     6  
     7  func IPv4DSCP(packet []byte) byte {
     8  	return packet[1] >> 2
     9  }
    10  
    11  func IPv4ECN(packet []byte) byte {
    12  	return packet[1] & 0x03
    13  }
    14  
    15  func IPv4Identification(packet []byte) [2]byte {
    16  	return [2]byte{packet[4], packet[5]}
    17  }
    18  
    19  func IPv4TTL(packet []byte) byte {
    20  	return packet[8]
    21  }
    22  
    23  func IPv4Protocol(packet []byte) IPProtocol {
    24  	return IPProtocol(packet[9])
    25  }
    26  
    27  func IPv4Source(packet []byte) net.IP {
    28  	return net.IPv4(packet[12], packet[13], packet[14], packet[15])
    29  }
    30  
    31  func SetIPv4Source(packet []byte, source net.IP) {
    32  	copy(packet[12:16], source.To4())
    33  }
    34  
    35  func IPv4Destination(packet []byte) net.IP {
    36  	return net.IPv4(packet[16], packet[17], packet[18], packet[19])
    37  }
    38  
    39  func SetIPv4Destination(packet []byte, dest net.IP) {
    40  	copy(packet[16:20], dest.To4())
    41  }
    42  
    43  func IPv4Payload(packet []byte) []byte {
    44  	ihl := packet[0] & 0x0F
    45  	return packet[ihl*4:]
    46  }
    47  
    48  // For TCP/UDP
    49  func IPv4SourcePort(packet []byte) uint16 {
    50  	payload := IPv4Payload(packet)
    51  	return (uint16(payload[0]) << 8) | uint16(payload[1])
    52  }
    53  
    54  func IPv4DestinationPort(packet []byte) uint16 {
    55  	payload := IPv4Payload(packet)
    56  	return (uint16(payload[2]) << 8) | uint16(payload[3])
    57  }
    58  
    59  func SetIPv4SourcePort(packet []byte, port uint16) {
    60  	payload := IPv4Payload(packet)
    61  	payload[0] = byte(port >> 8)
    62  	payload[1] = byte(port & 0xFF)
    63  }
    64  
    65  func SetIPv4DestinationPort(packet []byte, port uint16) {
    66  	payload := IPv4Payload(packet)
    67  	payload[2] = byte(port >> 8)
    68  	payload[3] = byte(port & 0xFF)
    69  }