add ARP; add tap internal calls; more lneto2 additions

arp/frame.go

@@ -0,0 +1,141 @@
+package arp
+
+import (
+	"encoding/binary"
+	"errors"
+
+	"github.com/soypat/lneto/lneto2"
+)
+
+// NewARPFrame returns a ARPFrame with data set to buf.
+// An error is returned if the buffer size is smaller than 28 (IPv4 min size).
+// Users should still call [ARPFrame.ValidateSize] before working
+// with payload/options of frames to avoid panics.
+func NewFrame(buf []byte) (Frame, error) {
+	if len(buf) < sizeHeaderv4 {
+		return Frame{buf: nil}, errors.New("ARP packet too short")
+	}
+	return Frame{buf: buf}, nil
+}
+
+// Frame encapsulates the raw data of an ARP packet
+// and provides methods for manipulating, validating and
+// retrieving fields and payload data. See [RFC826].
+//
+// [RFC826]: https://tools.ietf.org/html/rfc826
+type Frame struct {
+	buf []byte
+}
+
+// RawData returns the underlying slice with which the frame was created.
+func (afrm Frame) RawData() []byte { return afrm.buf }
+
+// HardwareType specifies the network link protocol type. Example: Ethernet is 1.
+func (afrm Frame) Hardware() (Type uint16, length uint8) {
+	Type = binary.BigEndian.Uint16(afrm.buf[0:2])
+	return Type, afrm.hwlen()
+}
+
+func (afrm Frame) hwlen() uint8 {
+	return afrm.buf[4]
+}
+
+// SetHardware sets the networl link protocol type. See [Frame.SetHardware].
+func (afrm Frame) SetHardware(Type uint16, length uint8) {
+	binary.BigEndian.PutUint16(afrm.buf[0:2], Type)
+	afrm.buf[4] = length
+}
+
+// Protocol returns the internet protocol type and length. See [lneto2.EtherType].
+func (afrm Frame) Protocol() (Type lneto2.EtherType, length uint8) {
+	Type = lneto2.EtherType(binary.BigEndian.Uint16(afrm.buf[2:4]))
+	return Type, afrm.protolen()
+}
+
+func (afrm Frame) protolen() uint8 { return afrm.buf[5] }
+
+// SetProtocol sets the protocol type and length fields of the ARP frame. See [Frame.Protocol] and [lneto2.EtherType].
+func (afrm Frame) SetProtocol(Type lneto2.EtherType, length uint8) {
+	binary.BigEndian.PutUint16(afrm.buf[2:4], uint16(Type))
+	afrm.buf[5] = length
+}
+
+// Operation returns the ARP header operation field. See [Operation].
+func (afrm Frame) Operation() Operation { return Operation(afrm.buf[6]) }
+
+// SetOperation sets the ARP header operation field. See [Operation].
+func (afrm Frame) SetOperation(b Operation) { afrm.buf[6] = uint8(b) }
+
+// Sender returns the hardware (MAC) and protocol addresses of sender of ARP packet.
+// In an ARP request MAC address is used to indicate
+// the address of the host sending the request. In an ARP reply MAC address is
+// used to indicate the address of the host that the request was looking for.
+func (afrm Frame) Sender() (hardwareAddr []byte, proto []byte) {
+	_, hlen := afrm.Hardware()
+	_, ilen := afrm.Protocol()
+	return afrm.buf[8 : 8+hlen], afrm.buf[8+hlen : 8+hlen+ilen]
+}
+
+// Target returns the hardware (MAC) and protocol addresses of target of ARP packet.
+// In an ARP request MAC target is ignored. In ARP reply MAC is used to indicate the address of host that originated request.
+func (afrm Frame) Target() (hardwareAddr []byte, proto []byte) {
+	_, hlen := afrm.Hardware()
+	_, ilen := afrm.Protocol()
+	toff := 8 + hlen + ilen
+	return afrm.buf[toff : toff+hlen], afrm.buf[toff+hlen : toff+hlen+ilen]
+}
+
+// Sender4 returns the IPv4 sender addresses. See [Frame.Sender].
+func (afrm Frame) Sender4() (hardwareAddr *[6]byte, proto *[4]byte) {
+	return (*[6]byte)(afrm.buf[8:14]), (*[4]byte)(afrm.buf[14:18])
+}
+
+// Target4 returns the IPv4 target addresses. See [Frame.Sender].
+func (afrm Frame) Target4() (hardwareAddr *[6]byte, proto *[4]byte) {
+	return (*[6]byte)(afrm.buf[18:24]), (*[4]byte)(afrm.buf[24:28])
+}
+
+// Sender6 returns the IPv6 sender addresses. See [Frame.Sender].
+func (afrm Frame) Sender16() (hardwareAddr *[6]byte, proto *[16]byte) {
+	return (*[6]byte)(afrm.buf[8:14]), (*[16]byte)(afrm.buf[14:30])
+}
+
+// Target6 returns the IPv6 target addresses. See [Frame.Sender].
+func (afrm Frame) Target16() (hardwareAddr *[6]byte, proto *[16]byte) {
+	return (*[6]byte)(afrm.buf[30:36]), (*[16]byte)(afrm.buf[36:52])
+}
+
+// ClearHeader zeros out the fixed(non-variable) header contents.
+func (afrm Frame) ClearHeader() {
+	for i := range afrm.buf[:8] {
+		afrm.buf[i] = 0
+	}
+}
+
+func (afrm Frame) Clip() Frame {
+	return Frame{buf: afrm.buf[:sizeHeader+2*int(afrm.hwlen())+2*int(afrm.protolen())]}
+}
+
+func (afrm Frame) SwapTargetSender() {
+	hwTarget, protoTarget := afrm.Target()
+	hwSender, protoSender := afrm.Sender()
+	for i := range hwTarget {
+		hwTarget[i], hwSender[i] = hwSender[i], hwTarget[i]
+	}
+	for i := range protoTarget {
+		protoTarget[i], protoSender[i] = protoSender[i], protoTarget[i]
+	}
+}
+
+// Validation API
+//
+// 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 (afrm Frame) ValidateSize(v *lneto2.Validator) {
+	_, hlen := afrm.Hardware()
+	_, ilen := afrm.Protocol()
+	minLen := 8 + 2*(hlen+ilen)
+	if len(afrm.buf) < int(minLen) {
+		v.AddError(errShortARP)
+	}
+}