remove legacy remnants and move ip,udp,ethernet logic into subpackages

udp/definitions.go

@@ -0,0 +1,5 @@
+package udp
+
+const (
+	sizeHeader = 8
+)

udp/frame.go

@@ -0,0 +1,129 @@
+package udp
+
+import (
+	"encoding/binary"
+	"errors"
+
+	"github.com/soypat/lneto/lneto2"
+)
+
+// NewUDPFrame returns a new UDPFrame with data set to buf.
+// An error is returned if the buffer size is smaller than 8.
+// Users should still call [Frame.ValidateSize] before working
+// with payload/options of frames to avoid panics.
+func NewFrame(buf []byte) (Frame, error) {
+	if len(buf) < sizeHeader {
+		return Frame{buf: buf}, errors.New("UDP packet too short")
+	}
+	return Frame{buf: buf}, nil
+}
+
+// Frame encapsulates the raw data of a UDP datagram
+// and provides methods for manipulating, validating and
+// retrieving fields and payload data. See [RFC768].
+//
+// [RFC768]: https://tools.ietf.org/html/rfc768
+type Frame struct {
+	buf []byte
+}
+
+// RawData returns the underlying slice with which the frame was created.
+func (ufrm Frame) RawData() []byte { return ufrm.buf }
+
+// SourcePort identifies the sending port for the UDP packet. Must be non-zero.
+func (ufrm Frame) SourcePort() uint16 {
+	return binary.BigEndian.Uint16(ufrm.buf[0:2])
+}
+
+// SetSourcePort sets UDP source port. See [Frame.SourcePort]
+func (ufrm Frame) SetSourcePort(src uint16) {
+	binary.BigEndian.PutUint16(ufrm.buf[0:2], src)
+}
+
+// DestinationPort identifies the receiving port for the UDP packet. Must be non-zero.
+func (ufrm Frame) DestinationPort() uint16 {
+	return binary.BigEndian.Uint16(ufrm.buf[2:4])
+}
+
+// SetDestinationPort sets UDP destination port. See [Frame.DestinationPort]
+func (ufrm Frame) SetDestinationPort(dst uint16) {
+	binary.BigEndian.PutUint16(ufrm.buf[2:4], dst)
+}
+
+// Length specifies length in bytes of UDP header and UDP payload. The minimum length
+// is 8 bytes (UDP header length). This field should match the result of the IP header
+// TotalLength field minus the IP header size: udp.Length == ip.TotalLength - 4*ip.IHL
+func (ufrm Frame) Length() uint16 {
+	return binary.BigEndian.Uint16(ufrm.buf[4:6])
+}
+
+// SetLength sets the UDP header's length field. See [Frame.Length].
+func (ufrm Frame) SetLength(length uint16) {
+	binary.BigEndian.PutUint16(ufrm.buf[4:6], length)
+}
+
+// CRC returns the checksum field in the UDP header.
+func (ufrm Frame) CRC() uint16 {
+	return binary.BigEndian.Uint16(ufrm.buf[6:8])
+}
+
+// SetCRC sets the UDP header's CRC field. See [Frame.CRC].
+func (ufrm Frame) SetCRC(checksum uint16) {
+	binary.BigEndian.PutUint16(ufrm.buf[6:8], checksum)
+}
+
+// Payload returns the payload content section of the UDP packet.
+// Be sure to call [Frame.ValidateSize] beforehand to avoid panic.
+func (ufrm Frame) Payload() []byte {
+	l := ufrm.Length()
+	return ufrm.buf[sizeHeader:l]
+}
+
+// func (ufrm Frame) CalculateIPv4Checksum(ifrm IPv4Frame) uint16 {
+// 	var crc lneto2.CRC791
+// 	ifrm.crcWriteUDPPseudo(&crc)
+// 	crc.AddUint16(ufrm.Length())
+// 	crc.AddUint16(ufrm.SourcePort())
+// 	crc.AddUint16(ufrm.DestinationPort())
+// 	crc.AddUint16(ufrm.Length()) // Length double tap.
+// 	crc.Write(ufrm.Payload())
+// 	return crc.Sum16()
+// }
+
+// func (ufrm Frame) CalculateIPv6Checksum(ifrm IPv6Frame) uint16 {
+// 	var crc lneto2.CRC791
+// 	ifrm.crcWritePseudo(&crc)
+// 	crc.AddUint16(ufrm.SourcePort())
+// 	crc.AddUint16(ufrm.DestinationPort())
+// 	crc.AddUint16(ufrm.Length()) // Length double tap.
+// 	crc.Write(ufrm.Payload())
+// 	return crc.Sum16()
+// }
+
+// ClearHeader zeros out the header contents.
+func (frm Frame) ClearHeader() {
+	for i := range frm.buf[:sizeHeader] {
+		frm.buf[i] = 0
+	}
+}
+
+//
+// Validation API.
+//
+
+var (
+	errBadLen = errors.New("udp: bad UDP length")
+	errShort  = errors.New("udp: short buffer")
+)
+
+// ValidateSize checks the frame's size fields and compares with the actual buffer
+// the frame. It returns a non-nil error on finding an inconsistency.
+func (ufrm Frame) ValidateSize(v *lneto2.Validator) {
+	ul := ufrm.Length()
+	if ul < sizeHeader {
+		v.AddError(errBadLen)
+	}
+	if int(ul) > len(ufrm.RawData()) {
+		v.AddError(errShort)
+	}
+}