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soypat
130 lines
3.8 KiB
Go
130 lines
3.8 KiB
Go
package udp
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import (
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"encoding/binary"
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"errors"
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"github.com/soypat/lneto/lneto2"
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)
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// NewUDPFrame returns a new UDPFrame with data set to buf.
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// An error is returned if the buffer size is smaller than 8.
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// Users should still call [Frame.ValidateSize] before working
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// with payload/options of frames to avoid panics.
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func NewFrame(buf []byte) (Frame, error) {
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if len(buf) < sizeHeader {
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return Frame{buf: buf}, errors.New("UDP packet too short")
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}
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return Frame{buf: buf}, nil
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}
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// Frame encapsulates the raw data of a UDP datagram
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// and provides methods for manipulating, validating and
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// retrieving fields and payload data. See [RFC768].
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//
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// [RFC768]: https://tools.ietf.org/html/rfc768
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type Frame struct {
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buf []byte
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}
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// RawData returns the underlying slice with which the frame was created.
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func (ufrm Frame) RawData() []byte { return ufrm.buf }
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// SourcePort identifies the sending port for the UDP packet. Must be non-zero.
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func (ufrm Frame) SourcePort() uint16 {
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return binary.BigEndian.Uint16(ufrm.buf[0:2])
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}
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// SetSourcePort sets UDP source port. See [Frame.SourcePort]
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func (ufrm Frame) SetSourcePort(src uint16) {
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binary.BigEndian.PutUint16(ufrm.buf[0:2], src)
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}
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// DestinationPort identifies the receiving port for the UDP packet. Must be non-zero.
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func (ufrm Frame) DestinationPort() uint16 {
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return binary.BigEndian.Uint16(ufrm.buf[2:4])
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}
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// SetDestinationPort sets UDP destination port. See [Frame.DestinationPort]
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func (ufrm Frame) SetDestinationPort(dst uint16) {
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binary.BigEndian.PutUint16(ufrm.buf[2:4], dst)
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}
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// Length specifies length in bytes of UDP header and UDP payload. The minimum length
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// is 8 bytes (UDP header length). This field should match the result of the IP header
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// TotalLength field minus the IP header size: udp.Length == ip.TotalLength - 4*ip.IHL
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func (ufrm Frame) Length() uint16 {
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return binary.BigEndian.Uint16(ufrm.buf[4:6])
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}
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// SetLength sets the UDP header's length field. See [Frame.Length].
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func (ufrm Frame) SetLength(length uint16) {
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binary.BigEndian.PutUint16(ufrm.buf[4:6], length)
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}
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// CRC returns the checksum field in the UDP header.
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func (ufrm Frame) CRC() uint16 {
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return binary.BigEndian.Uint16(ufrm.buf[6:8])
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}
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// SetCRC sets the UDP header's CRC field. See [Frame.CRC].
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func (ufrm Frame) SetCRC(checksum uint16) {
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binary.BigEndian.PutUint16(ufrm.buf[6:8], checksum)
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}
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// Payload returns the payload content section of the UDP packet.
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// Be sure to call [Frame.ValidateSize] beforehand to avoid panic.
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func (ufrm Frame) Payload() []byte {
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l := ufrm.Length()
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return ufrm.buf[sizeHeader:l]
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}
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// func (ufrm Frame) CalculateIPv4Checksum(ifrm IPv4Frame) uint16 {
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// var crc lneto2.CRC791
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// ifrm.crcWriteUDPPseudo(&crc)
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// crc.AddUint16(ufrm.Length())
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// crc.AddUint16(ufrm.SourcePort())
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// crc.AddUint16(ufrm.DestinationPort())
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// crc.AddUint16(ufrm.Length()) // Length double tap.
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// crc.Write(ufrm.Payload())
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// return crc.Sum16()
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// }
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// func (ufrm Frame) CalculateIPv6Checksum(ifrm IPv6Frame) uint16 {
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// var crc lneto2.CRC791
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// ifrm.crcWritePseudo(&crc)
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// crc.AddUint16(ufrm.SourcePort())
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// crc.AddUint16(ufrm.DestinationPort())
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// crc.AddUint16(ufrm.Length()) // Length double tap.
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// crc.Write(ufrm.Payload())
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// return crc.Sum16()
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// }
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// ClearHeader zeros out the header contents.
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func (frm Frame) ClearHeader() {
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for i := range frm.buf[:sizeHeader] {
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frm.buf[i] = 0
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}
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}
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//
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// Validation API.
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//
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var (
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errBadLen = errors.New("udp: bad UDP length")
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errShort = errors.New("udp: short buffer")
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)
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// ValidateSize checks the frame's size fields and compares with the actual buffer
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// the frame. It returns a non-nil error on finding an inconsistency.
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func (ufrm Frame) ValidateSize(v *lneto2.Validator) {
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ul := ufrm.Length()
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if ul < sizeHeader {
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v.AddError(errBadLen)
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}
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if int(ul) > len(ufrm.RawData()) {
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v.AddError(errShort)
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}
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}
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