begin adding icmpv4

internet/stack-ip.go

@@ -11,6 +11,7 @@ import (
 	"github.com/soypat/lneto/ethernet"
 	"github.com/soypat/lneto/internal"
 	"github.com/soypat/lneto/ipv4"
+	"github.com/soypat/lneto/ipv4/icmpv4"
 	"github.com/soypat/lneto/tcp"
 	"github.com/soypat/lneto/udp"
 )
@@ -18,11 +19,12 @@ import (
 var _ StackNode = (*StackIP)(nil)
 
 type StackIP struct {
-	connID    uint64
-	ipID      uint16
-	ip        [4]byte
-	validator lneto.Validator
-	handlers  []node
+	connID      uint64
+	ipID        uint16
+	ip          [4]byte
+	validator   lneto.Validator
+	handlers    []node
+	pendingICMP [][]byte
 	logger
 }
 
@@ -36,11 +38,12 @@ func (sb *StackIP) Reset(addr netip.Addr, maxNodes int) error {
 	}
 	sb.handlers = slices.Grow(sb.handlers[:0], maxNodes)
 	*sb = StackIP{
-		connID:    sb.connID + 1,
-		validator: sb.validator,
-		handlers:  sb.handlers,
-		logger:    sb.logger,
-		ip:        sb.ip,
+		connID:      sb.connID + 1,
+		validator:   sb.validator,
+		handlers:    sb.handlers,
+		logger:      sb.logger,
+		ip:          sb.ip,
+		pendingICMP: make([][]byte, maxNodes*4),
 	}
 	return nil
 }
@@ -99,6 +102,9 @@ func (sb *StackIP) Demux(carrierData []byte, offset int) error {
 	off := ifrm.HeaderLength()
 	totalLen := ifrm.TotalLength()
 	proto := ifrm.Protocol()
+	if proto == lneto.IPProtoICMP {
+		return sb.recvicmp(ifrm.RawData(), ifrm.HeaderLength())
+	}
 	nodeIdx := getNodeByProto(sb.handlers, uint16(proto))
 	if nodeIdx < 0 {
 		// Drop packet.
@@ -218,6 +224,19 @@ func (sb *StackIP) Register(h StackNode) error {
 	})
 }
 
+func (sb *StackIP) recvicmp(carrierData []byte, offset int) error {
+	var crc lneto.CRC791
+	cfrm, err := icmpv4.NewFrame(carrierData[offset:])
+	if err != nil {
+		return err
+	}
+	cfrm.CRCWrite(&crc)
+	if crc.Sum16() != cfrm.CRC() {
+		return errors.New("ICMP CRC mismatch")
+	}
+	return nil
+}
+
 type logger struct {
 	log *slog.Logger
 }

ipv4/icmpv4/icmpv4.go

@@ -0,0 +1,138 @@
+package icmpv4
+
+import (
+	"encoding/binary"
+	"errors"
+
+	"github.com/soypat/lneto"
+)
+
+type Type uint8
+
+const (
+	TypeEchoReply Type = 0 // echo reply
+	TypeEcho      Type = 8 // echo
+
+	TypeDestinationUnreachable Type = 3 // destination unreachable
+	TypeSourceQuench           Type = 4 // source quench
+	TypeRedirect               Type = 5 // redirect
+
+	TypeTimeExceeded     Type = 11 // time exceeded
+	TypeParameterProblem Type = 12 // parameter problem
+
+	TypeTimestamp      Type = 13 // timestamp
+	TypeTimestampReply Type = 14 // timestamp reply
+
+	TypeInfoRequest      Type = 15 // information request
+	TypeInfoRequestReply Type = 16 // information request reply
+)
+
+type CodeTimeExceeded uint8
+
+const (
+	CodeExceededInTransit  CodeTimeExceeded = iota // TTL exceeded in transit
+	CodeFragmentReassembly                         // fragment reassembly time exceeded
+)
+
+type CodeDestinationUnreachable uint8
+
+const (
+	CodeNetUnreachable     CodeDestinationUnreachable = iota // net unreachable
+	CodeHostUnreachable                                      // host unreachable
+	CodeProtoUnreachable                                     // protocol unreachable
+	CodePortUnreachable                                      // port unreachable
+	CodeFragNeededAndDFSet                                   // fragmentation needed and DF set
+	CodeSourceRouteFailed                                    // source route failed
+)
+
+type CodeRedirect uint8
+
+const (
+	CodeRedirectForNetwork       CodeRedirect = iota // redirect for network
+	CodeRedirectForHost                              // redirect for host
+	CodeRedirectForToSAndNetwork                     // redirect for ToS+network
+	CodeRedirectToSAndHost                           // redirect for ToS+host
+)
+
+var (
+	errShortFrame = errors.New("icmpv4: short frame")
+)
+
+func NewFrame(buf []byte) (Frame, error) {
+	if len(buf) < 8 {
+		return Frame{}, errShortFrame
+	}
+	return Frame{buf: buf}, nil
+}
+
+type Frame struct {
+	buf []byte
+}
+
+func (frm Frame) Type() Type { return Type(frm.buf[0]) }
+
+func (frm Frame) SetType(t Type) { frm.buf[0] = uint8(t) }
+
+func (frm Frame) Code() uint8 { return frm.buf[1] }
+
+func (frm Frame) SetCode(code uint8) { frm.buf[1] = code }
+
+// CRC returns the checksum field of the frame.
+func (frm Frame) CRC() uint16 {
+	return binary.BigEndian.Uint16(frm.buf[2:4])
+}
+
+// SetCRC sets the checksum field of the frame.
+func (frm Frame) SetCRC(crc uint16) {
+	binary.BigEndian.PutUint16(frm.buf[2:4], crc)
+}
+
+// CRCWrite calculates the checksum of the ICMP packet. Treats the checksum field as zero as per RFC 792.
+func (frm Frame) CRCWrite(crc *lneto.CRC791) {
+	crc.AddUint16(binary.BigEndian.Uint16(frm.buf[0:2]))
+	crc.Write(frm.buf[4:])
+}
+
+func (frm Frame) payload() []byte {
+	return frm.buf[4:]
+}
+
+type FrameDestinationUnreachable struct {
+	Frame
+}
+
+func (frm FrameDestinationUnreachable) Code() CodeDestinationUnreachable {
+	return CodeDestinationUnreachable(frm.Frame.Code())
+}
+
+func (frm FrameDestinationUnreachable) SetCode(code CodeDestinationUnreachable) {
+	frm.Frame.SetCode(uint8(code))
+}
+
+type FrameEcho struct {
+	Frame
+}
+
+func (frm FrameEcho) Identifier() uint16 {
+	return binary.BigEndian.Uint16(frm.buf[4:6])
+}
+
+func (frm FrameEcho) SetIdentifier(id uint16) {
+	binary.BigEndian.PutUint16(frm.buf[4:6], id)
+}
+
+func (frm FrameEcho) SequenceNumber() uint16 {
+	return binary.BigEndian.Uint16(frm.buf[6:8])
+}
+
+func (frm FrameEcho) SetSequenceNumber(seq uint16) {
+	binary.BigEndian.PutUint16(frm.buf[6:8], seq)
+}
+
+func (frm FrameEcho) Data() []byte {
+	return frm.buf[8:]
+}
+
+func (frm FrameEcho) RawData() []byte {
+	return frm.buf
+}