ipv6: StackIP and StackAsync.Addr refactor (#105)

* apply StackIP changes and internet package test passing

* fix tests and examples

* remove old Reset method on StackIP

* use encapsulate for ipv6

* add TCP over IPv6 tests

examples/berkeley-listener/berkeley_server.go

@@ -27,6 +27,7 @@ import (
 	"github.com/soypat/lneto/internal"
 	"github.com/soypat/lneto/internal/ltesto"
 	"github.com/soypat/lneto/internet/pcap"
+	"github.com/soypat/lneto/ipv4"
 	"github.com/soypat/lneto/tcp"
 	"github.com/soypat/lneto/x/xnet"
 )
@@ -134,7 +135,8 @@ func run() error {
 			pfbuf = fmt.Appendf(pfbuf[:0], "%-3s %3d", context, len(pkt))
 			pfbuf = append(pfbuf, ' ', '[')
 			pfbuf, err = pf.FormatFrames(pfbuf, frames, pkt)
-			pfbuf = bytes.ReplaceAll(pfbuf, stack.Addr().AppendTo(nil), []byte("us"))
+			addr := stack.Addr4()
+			pfbuf = bytes.ReplaceAll(pfbuf, ipv4.AppendFormatAddr(nil, addr), []byte("us"))
 			pfbuf = bytes.ReplaceAll(pfbuf, ethernet.AppendAddr(nil, stack.HardwareAddress()), []byte("us"))
 			pfbuf = append(pfbuf, ']', '\n')
 			if err != nil {
@@ -158,11 +160,11 @@ func run() error {
 				} else if n != nwrite {
 					log.Fatalf("mismatch written bytes %d!=%d", nwrite, n)
 				}
-				if flagMockClient && mockStack.Addr().IsValid() {
+				if flagMockClient && mockStack.Addr4() != ([4]byte{}) {
 					mockStack.IngressEthernet(buf[:nwrite])
 				}
 			}
-			if flagMockClient && mockStack.Addr().IsValid() {
+			if flagMockClient && mockStack.Addr4() != ([4]byte{}) {
 				n, _ := mockStack.EgressEthernet(buf[:])
 				if n > 0 {
 					stack.IngressEthernet(buf[:n])
@@ -222,7 +224,7 @@ func run() error {
 	if err = stack.AssimilateDHCPResults(results); err != nil {
 		return fmt.Errorf("assimilating DHCP results: %w", err)
 	}
-	slog.Info("dhcp-complete", slog.String("assignedIP", results.AssignedAddr.String()), slog.String("routerIP", results.Router.String()))
+	slog.Info("dhcp-complete", slog.String("assignedIP", string(ipv4.AppendFormatAddr(nil, results.AssignedAddr4))), slog.String("routerIP", results.Router.String()))
 
 	// Resolve router HW and set gateway
 	routerHw, err := rstack.DoResolveHardwareAddress6(results.Router, 2*time.Second, 2)
@@ -246,7 +248,7 @@ func run() error {
 	}
 	defer ln.Close()
 
-	fmt.Printf("Listening (Berkeley) on %s:%d\n", stack.Addr().String(), flagPort)
+	fmt.Printf("Listening (Berkeley) on %s:%d\n", string(ipv4.AppendFormatAddr(nil, stack.Addr4())), flagPort)
 
 	// Optionally run an in-memory mock client that dials the berkeley listener
 	if flagMockClient {
@@ -326,9 +328,9 @@ func tryPoll(iface ltesto.Interface, poll time.Duration) (dataMayBeReady bool, _
 }
 
 func mockClient(stack *xnet.StackAsync, port uint16, subnet netip.Prefix) {
-	target := netip.AddrPortFrom(stack.Addr(), port)
+	target := netip.AddrPortFrom(netip.AddrFrom4(stack.Addr4()), port)
 	err := mockStack.Reset(xnet.StackConfig{
-		StaticAddress:     subnet.Addr().Next(),
+		StaticAddress4:    subnet.Addr().Next().As4(),
 		MaxActiveTCPPorts: 1,
 		HardwareAddress:   stack.Gateway6(),
 		Hostname:          "the-other",
@@ -368,7 +370,7 @@ func mockClient(stack *xnet.StackAsync, port uint16, subnet netip.Prefix) {
 	hdr.SetMethod("GET")
 	hdr.SetRequestURI("/")
 	hdr.SetProtocol("HTTP/1.1")
-	hdr.Set("Host", stack.Addr().String())
+	hdr.Set("Host", string(ipv4.AppendFormatAddr(nil, stack.Addr4())))
 	hdr.Set("User-Agent", "lneto-mock")
 	hdr.Set("Connection", "close")
 	req, err := hdr.AppendRequest(nil)

examples/httpserver/main.go

@@ -26,6 +26,7 @@ import (
 	"github.com/soypat/lneto/internal"
 	"github.com/soypat/lneto/internal/ltesto"
 	"github.com/soypat/lneto/internet/pcap"
+	"github.com/soypat/lneto/ipv4"
 	"github.com/soypat/lneto/tcp"
 	"github.com/soypat/lneto/x/xnet"
 )
@@ -134,7 +135,8 @@ func run() (err error) {
 			pfbuf = fmt.Appendf(pfbuf[:0], "%-3s %3d", context, len(pkt))
 			pfbuf = append(pfbuf, ' ', '[')
 			pfbuf, err = pf.FormatFrames(pfbuf, frames, pkt)
-			pfbuf = bytes.ReplaceAll(pfbuf, stack.Addr().AppendTo(nil), []byte("us"))
+
+			pfbuf = bytes.ReplaceAll(pfbuf, ipv4.AppendFormatAddr(nil, stack.Addr4()), []byte("us"))
 			pfbuf = bytes.ReplaceAll(pfbuf, ethernet.AppendAddr(nil, stack.HardwareAddress()), []byte("us"))
 			pfbuf = append(pfbuf, ']', '\n')
 			if err != nil {
@@ -206,7 +208,7 @@ func run() (err error) {
 	if err != nil {
 		return fmt.Errorf("assimilating DHCP results: %w", err)
 	}
-	slog.Info("dhcp-complete", slog.String("assignedIP", results.AssignedAddr.String()), slog.String("routerIP", results.Router.String()))
+	slog.Info("dhcp-complete", slog.String("assignedIP", string(ipv4.AppendFormatAddr(nil, results.AssignedAddr4))), slog.String("routerIP", results.Router.String()))
 
 	const (
 		arpTimeout = 2 * time.Second
@@ -221,7 +223,7 @@ func run() (err error) {
 	stack.SetGateway6(routerHw)
 
 	svPort := uint16(flagPort)
-	fmt.Printf("Listening on %s:%d\n", stack.Addr().String(), svPort)
+	fmt.Printf("Listening on %s:%d\n", ipv4.AppendFormatAddr(nil, stack.Addr4()), svPort)
 
 	// Serve connections in a loop.
 	for {

examples/min-working-example/main-mwe.go

@@ -105,7 +105,7 @@ func run(ctx context.Context, stack *xnet.StackAsync) error {
 		},
 	})
 
-	laddr := net.TCPAddrFromAddrPort(netip.AddrPortFrom(results.AssignedAddr, 80))
+	laddr := net.TCPAddrFromAddrPort(netip.AddrPortFrom(netip.AddrFrom4(results.AssignedAddr4), 80))
 	// raddr := net.TCPAddr{} // If active (client) connection then set raddr in which case a net.Conn type is returned.
 	const sockstream = 0x1
 	c, err := berkstack.Socket(ctx, "tcp", syscall.AF_INET, sockstream, laddr, nil)

examples/xcurl/main.go

@@ -26,6 +26,7 @@ import (
 	"github.com/soypat/lneto/internal"
 	"github.com/soypat/lneto/internal/ltesto"
 	"github.com/soypat/lneto/internet/pcap"
+	"github.com/soypat/lneto/ipv4"
 	"github.com/soypat/lneto/tcp"
 	"github.com/soypat/lneto/x/xnet"
 )
@@ -156,7 +157,8 @@ func run() (err error) {
 			pfbuf = fmt.Appendf(pfbuf[:0], "%-3s %3d", context, len(pkt))
 			pfbuf = append(pfbuf, ' ', '[')
 			pfbuf, err = pf.FormatFrames(pfbuf, frames, pkt)
-			pfbuf = bytes.ReplaceAll(pfbuf, stack.Addr().AppendTo(nil), []byte("us"))
+			addr := stack.Addr4()
+			pfbuf = bytes.ReplaceAll(pfbuf, addr[:], []byte("us"))
 			pfbuf = bytes.ReplaceAll(pfbuf, ethernet.AppendAddr(nil, stack.HardwareAddress()), []byte("us"))
 			pfbuf = append(pfbuf, ']', '\n')
 			if err != nil {
@@ -231,7 +233,7 @@ func run() (err error) {
 	if err != nil {
 		return fmt.Errorf("assimilating DHCP results: %w", err)
 	}
-	slog.Info("dhcp-complete", slog.String("assignedIP", results.AssignedAddr.String()), slog.String("routerIP", results.Router.String()), slog.Any("DNS", results.DNSServers), slog.Any("subnet", results.Subnet.String()))
+	slog.Info("dhcp-complete", slog.String("assignedIP", string(ipv4.AppendFormatAddr(nil, results.AssignedAddr4))), slog.String("routerIP", results.Router.String()), slog.Any("DNS", results.DNSServers), slog.Any("subnet", results.Subnet.String()))
 	const (
 		arpTimeout = 2 * time.Second
 		arpRetries = 2

internet/definitions.go

@@ -7,6 +7,7 @@ import (
 	"slices"
 
 	"github.com/soypat/lneto"
+	"github.com/soypat/lneto/internal"
 )
 
 // node is a concrete StackNode as stored in Stacks. Methods are devirtualized for performance benefits, especially on TinyGo.
@@ -231,3 +232,31 @@ func incLim(v, max int) int {
 	}
 	return v
 }
+
+type logger struct {
+	log *slog.Logger
+}
+
+func (l logger) error(msg string, attrs ...slog.Attr) {
+	internal.LogAttrs(l.log, slog.LevelError, msg, attrs...)
+}
+func (l logger) info(msg string, attrs ...slog.Attr) {
+	internal.LogAttrs(l.log, slog.LevelInfo, msg, attrs...)
+}
+func (l logger) warn(msg string, attrs ...slog.Attr) {
+	internal.LogAttrs(l.log, slog.LevelWarn, msg, attrs...)
+}
+func (l logger) debug(msg string, attrs ...slog.Attr) {
+	internal.LogAttrs(l.log, slog.LevelDebug, msg, attrs...)
+}
+func (l logger) trace(msg string, attrs ...slog.Attr) {
+	internal.LogAttrs(l.log, internal.LevelTrace, msg, attrs...)
+}
+
+const enableAllocLog = internal.HeapAllocDebugging
+
+func debugLog(msg string) {
+	if enableAllocLog {
+		internal.LogAllocs(msg)
+	}
+}

internet/stack-ip.go

@@ -1,251 +1,68 @@
 package internet
 
 import (
-	"io"
 	"log/slog"
-	"net/netip"
 
 	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/ethernet"
-	"github.com/soypat/lneto/internal"
-	"github.com/soypat/lneto/ipv4"
-	"github.com/soypat/lneto/tcp"
-	"github.com/soypat/lneto/udp"
 )
 
 var _ lneto.StackNode = (*StackIP)(nil)
 
 type StackIP struct {
-	connID          uint64
+	connID uint64
-	ipID            uint16
+	stackip4
-	ip              [4]byte
+	stackip6
-	acceptMulticast bool
-	validator       lneto.Validator
-	handlers        handlers
 }
 
-func (sb *StackIP) Reset(addr netip.Addr, maxNodes int) error {
+func (stackip *StackIP) Reset(vld *lneto.Validator, maxNodes4, maxNodes6 int) error {
-	if maxNodes <= 0 {
+	if maxNodes4 <= 0 && maxNodes6 <= 0 || vld == nil {
 		return lneto.ErrInvalidConfig
 	}
-	err := sb.SetAddr(addr)
+	stackip.connID++
-	if err != nil {
+	stackip.reset4(vld, maxNodes4)
-		return err
+	stackip.reset6(vld, maxNodes6)
-	}
-	sb.handlers.reset("StackIP", maxNodes)
-	*sb = StackIP{
-		connID:          sb.connID + 1,
-		validator:       sb.validator,
-		handlers:        sb.handlers,
-		ip:              sb.ip,
-		acceptMulticast: sb.acceptMulticast,
-	}
 	return nil
 }
 
-func (sb *StackIP) SetAddr(addr netip.Addr) error {
+func (stackip *StackIP) ConnectionID() *uint64 {
-	if !addr.IsValid() {
+	return &stackip.connID
-		return lneto.ErrInvalidAddr
-	} else if !addr.Is4() {
-		return lneto.ErrUnsupported
-	}
-	sb.ip = addr.As4()
-	return nil
 }
 
-func (sb *StackIP) ConnectionID() *uint64 {
+func (stackip *StackIP) Protocol() uint64 {
-	return &sb.connID
-}
-
-func (sb *StackIP) Protocol() uint64 {
 	return uint64(ethernet.TypeIPv4) // Only support ipv4 for now.
 }
 
-func (sb *StackIP) LocalPort() uint16 { return 0 }
+func (stackip *StackIP) LocalPort() uint16 { return 0 }
 
-func (sb *StackIP) Addr() netip.Addr {
+func (stackip *StackIP) SetLogger(logger *slog.Logger) {
-	return netip.AddrFrom4(sb.ip)
+	stackip.stackip4.handlers.log = logger
+	stackip.stackip6.handlers.log = logger
 }
 
-func (sb *StackIP) SetAcceptMulticast(accept bool) {
+func (stackip *StackIP) Demux(carrierData []byte, offset int) error {
-	sb.acceptMulticast = accept
-}
-
-func (sb *StackIP) SetLogger(logger *slog.Logger) {
-	sb.handlers.log = logger
-}
-
-func (sb *StackIP) Demux(carrierData []byte, offset int) error {
 	debugLog("ip:demux")
-	sb.handlers.info("StackIP.Demux:start")
+	if len(carrierData) < 1 {
-	frame := carrierData[offset:] // we don't care about carrier data in IP.
+		return lneto.ErrTruncatedFrame
-	ifrm, err := ipv4.NewFrame(frame)
-	if err != nil {
-		return err
 	}
-	dst := ifrm.DestinationAddr()
+	version := carrierData[offset] >> 4
-	if sb.ip != ([4]byte{}) && *dst != sb.ip {
+	switch version {
-		if !sb.acceptMulticast || dst[0]&0xF0 != 0xE0 {
+	case 4:
-			sb.handlers.debug("ip:not-for-us")
+		return stackip.stackip4.demux4(carrierData, offset)
-			return lneto.ErrPacketDrop // Not meant for us.
+	case 6:
-		}
+		return stackip.stackip6.demux6(carrierData, offset)
+	default:
+		return lneto.ErrUnsupported
 	}
-
-	sb.validator.ResetErr()
-	ifrm.ValidateExceptCRC(&sb.validator)
-	if err = sb.validator.ErrPop(); err != nil {
-		sb.handlers.error("ip:Demux.validate")
-		return err
-	}
-
-	if ifrm.CalculateHeaderCRC() != 0 {
-		sb.handlers.error("ip:demux.crc")
-		return lneto.ErrBadCRC
-	}
-	off := ifrm.HeaderLength()
-	totalLen := ifrm.TotalLength()
-	proto := ifrm.Protocol()
-	node := sb.handlers.nodeByProto(uint16(proto))
-	// nodeIdx := getNodeByProto(sb.handlers, uint16(proto))
-	if node == nil {
-		// Drop packet.
-		sb.handlers.info("ip:demux.drop", internal.SlogAddr4("dstaddr", ifrm.DestinationAddr()), slog.String("proto", ifrm.Protocol().String()))
-		return lneto.ErrPacketDrop
-	}
-	// Incoming CRC Validation of common IP Protocols.
-	var crc lneto.CRC791
-	switch proto {
-	case lneto.IPProtoTCP:
-		ifrm.CRCWriteTCPPseudo(&crc)
-		if crc.PayloadSum16(ifrm.Payload()) != 0 {
-			sb.handlers.error("ip:demux.tcpcrc")
-			return lneto.ErrBadCRC
-		}
-	case lneto.IPProtoUDP:
-		ufrm, err := udp.NewFrame(ifrm.Payload())
-		if err != nil {
-			return err
-		}
-		ufrm.ValidateSize(&sb.validator)
-		if err = sb.validator.ErrPop(); err != nil {
-			sb.handlers.error("ip:demux.udpvalidatesize")
-			return err
-		}
-		frameLen := ufrm.Length()
-		ifrm.CRCWriteUDPPseudo(&crc, frameLen)
-		if crc.PayloadSum16(ufrm.RawData()[:frameLen]) != 0 {
-			sb.handlers.error("ip:demux.udpcrc")
-			return lneto.ErrBadCRC
-		}
-	}
-	sb.handlers.info("ipDemux", slog.String("ipproto", proto.String()), slog.Int("plen", int(totalLen)))
-	err = node.callbacks.Demux(frame[:totalLen], off)
-	if sb.handlers.tryHandleError(node, err) {
-		sb.handlers.info("ipclose", slog.String("proto", proto.String()))
-		err = nil
-	}
-	return err
 }
 
-func (sb *StackIP) Encapsulate(carrierData []byte, offsetToIP, offsetToFrame int) (int, error) {
+func (stackip *StackIP) Encapsulate(carrierData []byte, offsetToIP, offsetToFrame int) (n int, err error) {
-	frame := carrierData[offsetToFrame:]
+	if offsetToFrame != offsetToIP {
-	if len(frame) < ipv4.MinimumMTU {
+		return 0, lneto.ErrBug
-		return 0, io.ErrShortBuffer
 	}
-	ifrm, _ := ipv4.NewFrame(frame)
+	n, err = stackip.stackip4.encapsulate4(carrierData, offsetToIP)
-	const ihl = 5
+	if len(stackip.stackip6.handlers.nodes) > 0 && n == 0 {
-	const headerlen = ihl * 4
+		n, err = stackip.stackip6.encapsulate6(carrierData, offsetToIP)
-	const dontFrag = 0x4000
-	ifrm.SetVersionAndIHL(4, ihl)
-	ifrm.SetToS(0)
-	seed := sb.ipID + uint16(sb.connID)
-	id := internal.Prand16(seed)
-	ifrm.SetID(id)
-	ifrm.SetFlags(dontFrag)
-	ifrm.SetTTL(64)
-	*ifrm.SourceAddr() = sb.ip
-	sb.ipID = id
-	// Children (TCP/UDP) start at offset headerlen (20 bytes after IP header start).
-	// offsetToIP is 0 relative to this slice (frame), children's frame starts at headerlen.
-	node, n, err := sb.handlers.encapsulateAny(carrierData, offsetToFrame, offsetToFrame+headerlen)
-	if n == 0 {
-		return n, err
-	}
-	proto := lneto.IPProto(node.proto)
-	totalLen := n + headerlen
-	ifrm.SetTotalLength(uint16(totalLen))
-	ifrm.SetProtocol(proto)
-	// Zero the CRC field so its value does not add to the final result.
-	ifrm.SetCRC(0)
-	crcValue := ifrm.CalculateHeaderCRC()
-	ifrm.SetCRC(crcValue)
-	// Calculate CRC for our newly generated packet.
-	var crc lneto.CRC791
-	payload := ifrm.Payload()
-	switch proto {
-	case lneto.IPProtoTCP:
-		ifrm.CRCWriteTCPPseudo(&crc)
-		tfrm, _ := tcp.NewFrame(payload)
-		// Zero the CRC field so its value does not add to the final result.
-		tfrm.SetCRC(0)
-		crcValue = crc.PayloadSum16(payload)
-		tfrm.SetCRC(crcValue)
-	case lneto.IPProtoUDP:
-		ufrm, _ := udp.NewFrame(payload)
-		ifrm.CRCWriteUDPPseudo(&crc, uint16(n))
-		ufrm.SetLength(uint16(n))
-		// Zero the CRC field so its value does not add to the final result.
-		ufrm.SetCRC(0)
-		crcValue = lneto.NeverZeroSum(crc.PayloadSum16(payload))
-		ufrm.SetCRC(crcValue)
-	}
-	return totalLen, err
-}
-
-func (sb *StackIP) Register(h lneto.StackNode) error {
-	proto := h.Protocol()
-	if proto > 255 {
-		return lneto.ErrInvalidConfig
-	}
-	return sb.handlers.registerByPortProto(nodeFromStackNode(h, h.LocalPort(), proto, nil))
-}
-
-func (sb *StackIP) IsRegistered(proto lneto.IPProto) bool {
-	return sb.handlers.nodeByProto(uint16(proto)) != nil
-}
-
-func (sb *StackIP) recvicmp(icmpData []byte) error {
-	var crc lneto.CRC791
-	if crc.PayloadSum16(icmpData) != 0 {
-		return lneto.ErrBadCRC
-	}
-	return nil
-}
-
-type logger struct {
-	log *slog.Logger
-}
-
-func (l logger) error(msg string, attrs ...slog.Attr) {
-	internal.LogAttrs(l.log, slog.LevelError, msg, attrs...)
-}
-func (l logger) info(msg string, attrs ...slog.Attr) {
-	internal.LogAttrs(l.log, slog.LevelInfo, msg, attrs...)
-}
-func (l logger) warn(msg string, attrs ...slog.Attr) {
-	internal.LogAttrs(l.log, slog.LevelWarn, msg, attrs...)
-}
-func (l logger) debug(msg string, attrs ...slog.Attr) {
-	internal.LogAttrs(l.log, slog.LevelDebug, msg, attrs...)
-}
-func (l logger) trace(msg string, attrs ...slog.Attr) {
-	internal.LogAttrs(l.log, internal.LevelTrace, msg, attrs...)
-}
-
-const enableAllocLog = internal.HeapAllocDebugging
-
-func debugLog(msg string) {
-	if enableAllocLog {
-		internal.LogAllocs(msg)
 	}
+	return n, err
 }

internet/stack-ip4.go

@@ -0,0 +1,183 @@
+package internet
+
+import (
+	"io"
+	"log/slog"
+
+	"github.com/soypat/lneto"
+	"github.com/soypat/lneto/internal"
+	"github.com/soypat/lneto/ipv4"
+	"github.com/soypat/lneto/tcp"
+	"github.com/soypat/lneto/udp"
+)
+
+// stackip4 is NOT a StackNode implementation.
+// It is meant to be embedded within StackNodes.
+// var _ lneto.StackNode = (*stackip4)(nil)
+
+type stackip4 struct {
+	handlers        handlers
+	vld             *lneto.Validator
+	ipID            uint16
+	ip4             [4]byte
+	acceptMulticast bool
+}
+
+func (si4 *stackip4) reset4(vld *lneto.Validator, maxNodes int) {
+	*si4 = stackip4{
+		ip4:             [4]byte{},
+		ipID:            1,
+		acceptMulticast: false,
+		handlers:        si4.handlers,
+		vld:             vld,
+	}
+	si4.handlers.reset("stackip4", maxNodes)
+}
+
+func (si4 *stackip4) Register4(h lneto.StackNode) error {
+	proto := h.Protocol()
+	if proto > 255 {
+		return lneto.ErrInvalidConfig
+	}
+	return si4.handlers.registerByPortProto(nodeFromStackNode(h, h.LocalPort(), proto, nil))
+}
+
+func (si4 *stackip4) IsRegistered4(proto lneto.IPProto) bool {
+	return si4.handlers.nodeByProto(uint16(proto)) != nil
+}
+
+func (si4 *stackip4) SetAcceptMulticast4(accept bool) {
+	si4.acceptMulticast = accept
+}
+func (si4 *stackip4) Addr4() [4]byte { return si4.ip4 }
+func (si4 *stackip4) SetAddr4(ip4 [4]byte) {
+	si4.ip4 = ip4
+}
+
+func (si4 *stackip4) demux4(carrierData []byte, offset int) error {
+	debugLog("ip4:demux")
+	si4.handlers.info("demux:start")
+	frame := carrierData[offset:] // we don't care about carrier data in IP.
+	ifrm, err := ipv4.NewFrame(frame)
+	if err != nil {
+		return err
+	}
+	dst := ifrm.DestinationAddr()
+	if si4.ip4 != ([4]byte{}) && *dst != si4.ip4 {
+		if !si4.acceptMulticast || dst[0]&0xF0 != 0xE0 {
+			si4.handlers.debug("ip:not-for-us")
+			return lneto.ErrPacketDrop // Not meant for us.
+		}
+	}
+
+	si4.vld.ResetErr()
+	ifrm.ValidateExceptCRC(si4.vld)
+	if err = si4.vld.ErrPop(); err != nil {
+		si4.handlers.error("ip:Demux.validate")
+		return err
+	}
+
+	if ifrm.CalculateHeaderCRC() != 0 {
+		si4.handlers.error("ip:demux.crc")
+		return lneto.ErrBadCRC
+	}
+	off := ifrm.HeaderLength()
+
+	proto := ifrm.Protocol()
+	node := si4.handlers.nodeByProto(uint16(proto))
+	// nodeIdx := getNodeByProto(sb.handlers, uint16(proto))
+	if node == nil {
+		// Drop packet.
+		si4.handlers.info("ip:demux.drop", internal.SlogAddr4("dstaddr", ifrm.DestinationAddr()), slog.String("proto", ifrm.Protocol().String()))
+		return lneto.ErrPacketDrop
+	}
+	// Incoming CRC Validation of common IP Protocols.
+	var crc lneto.CRC791
+	switch proto {
+	case lneto.IPProtoTCP:
+		ifrm.CRCWriteTCPPseudo(&crc)
+		if crc.PayloadSum16(ifrm.Payload()) != 0 {
+			si4.handlers.error("ip:demux.tcpcrc")
+			return lneto.ErrBadCRC
+		}
+	case lneto.IPProtoUDP:
+		ufrm, err := udp.NewFrame(ifrm.Payload())
+		if err != nil {
+			return err
+		}
+		ufrm.ValidateSize(si4.vld)
+		if err = si4.vld.ErrPop(); err != nil {
+			si4.handlers.error("ip:demux.udpvalidatesize")
+			return err
+		}
+		frameLen := ufrm.Length()
+		ifrm.CRCWriteUDPPseudo(&crc, frameLen)
+		if crc.PayloadSum16(ufrm.RawData()[:frameLen]) != 0 {
+			si4.handlers.error("ip:demux.udpcrc")
+			return lneto.ErrBadCRC
+		}
+	}
+	totalLen := ifrm.TotalLength()
+	si4.handlers.info("ipDemux", slog.String("ipproto", proto.String()), slog.Int("tlen", int(totalLen)))
+	err = node.callbacks.Demux(frame[:totalLen], off)
+	if si4.handlers.tryHandleError(node, err) {
+		si4.handlers.info("ipclose", slog.String("proto", proto.String()))
+		err = nil
+	}
+	return err
+}
+
+func (si4 *stackip4) encapsulate4(carrierData []byte, offsetToIP int) (int, error) {
+	frame := carrierData[offsetToIP:]
+	if len(frame) < ipv4.MinimumMTU {
+		return 0, io.ErrShortBuffer
+	}
+	ifrm, _ := ipv4.NewFrame(frame)
+	const ihl = 5
+	const headerlen = ihl * 4
+	const dontFrag = 0x4000
+	ifrm.SetVersionAndIHL(4, ihl)
+	ifrm.SetToS(0)
+	seed := (si4.ipID + 1) ^ uint16(si4.ip4[0])
+	id := internal.Prand16(seed)
+	ifrm.SetID(id)
+	ifrm.SetFlags(dontFrag)
+	ifrm.SetTTL(64)
+	*ifrm.SourceAddr() = si4.ip4
+	si4.ipID = id
+	// Children (TCP/UDP) start at offset headerlen (20 bytes after IP header start).
+	// offsetToIP is 0 relative to this slice (frame), children's frame starts at headerlen.
+	node, n, err := si4.handlers.encapsulateAny(carrierData, offsetToIP, offsetToIP+headerlen)
+	if n == 0 {
+		return n, err
+	}
+	proto := lneto.IPProto(node.proto)
+	totalLen := n + headerlen
+	ifrm.SetTotalLength(uint16(totalLen))
+	ifrm.SetProtocol(proto)
+	// Zero the CRC field so its value does not add to the final result.
+	ifrm.SetCRC(0)
+	crcValue := ifrm.CalculateHeaderCRC()
+	ifrm.SetCRC(crcValue)
+	// Calculate CRC for our newly generated packet.
+	var crc lneto.CRC791
+	payload := ifrm.Payload()
+	switch proto {
+	case lneto.IPProtoTCP:
+		ifrm.CRCWriteTCPPseudo(&crc)
+		tfrm, _ := tcp.NewFrame(payload)
+		// Zero the CRC field so its value does not add to the final result.
+		tfrm.SetCRC(0)
+		crcValue = crc.PayloadSum16(payload)
+		tfrm.SetCRC(crcValue)
+	case lneto.IPProtoUDP:
+		ufrm, _ := udp.NewFrame(payload)
+		ifrm.CRCWriteUDPPseudo(&crc, uint16(n))
+		ufrm.SetLength(uint16(n))
+		// Zero the CRC field so its value does not add to the final result.
+		ufrm.SetCRC(0)
+		crcValue = lneto.NeverZeroSum(crc.PayloadSum16(payload))
+		ufrm.SetCRC(crcValue)
+	}
+	return totalLen, err
+}

internet/stack-ip6.go

@@ -0,0 +1,144 @@
+package internet
+
+import (
+	"log/slog"
+
+	"github.com/soypat/lneto"
+	"github.com/soypat/lneto/ipv6"
+	"github.com/soypat/lneto/tcp"
+	"github.com/soypat/lneto/udp"
+)
+
+// stackip6 is NOT a StackNode implementation.
+// It is meant to be embedded within StackNodes.
+// var _ lneto.StackNode = (*stackip6)(nil)
+
+type stackip6 struct {
+	handlers        handlers
+	vld             *lneto.Validator
+	ip6             [16]byte
+	acceptMulticast bool
+}
+
+func (si6 *stackip6) Register6(h lneto.StackNode) error {
+	proto := h.Protocol()
+	if proto > 255 {
+		return lneto.ErrInvalidConfig
+	}
+	return si6.handlers.registerByPortProto(nodeFromStackNode(h, h.LocalPort(), proto, nil))
+}
+
+func (si6 *stackip6) IsRegistered6(proto lneto.IPProto) bool {
+	return si6.handlers.nodeByProto(uint16(proto)) != nil
+}
+
+func (si6 *stackip6) SetAcceptMulticast6(accept bool) { si6.acceptMulticast = accept }
+func (si6 *stackip6) Addr6() [16]byte                 { return si6.ip6 }
+func (si6 *stackip6) SetAddr6(ip6 [16]byte)           { si6.ip6 = ip6 }
+
+func (si6 *stackip6) reset6(vld *lneto.Validator, maxNodes int) {
+	*si6 = stackip6{
+		handlers: si6.handlers,
+		vld:      vld,
+	}
+	si6.handlers.reset("stackip6", maxNodes)
+}
+
+func (si6 *stackip6) demux6(carrierData []byte, offset int) error {
+	debugLog("ip6:demux")
+	si6.handlers.info("StackIP6.Demux:start")
+	ifrm, err := ipv6.NewFrame(carrierData[offset:])
+	if err != nil {
+		return err
+	}
+	dst := ifrm.DestinationAddr()
+	if si6.ip6 != ([16]byte{}) && *dst != si6.ip6 {
+		if !si6.acceptMulticast || dst[0] != 0xFF {
+			si6.handlers.debug("ip6:not-for-us")
+			return lneto.ErrPacketDrop
+		}
+	}
+
+	si6.vld.ResetErr()
+	ifrm.ValidateSize(si6.vld)
+	if err = si6.vld.ErrPop(); err != nil {
+		si6.handlers.error("ip6:Demux.validate")
+		return err
+	}
+
+	proto := ifrm.NextHeader()
+	node := si6.handlers.nodeByProto(uint16(proto))
+	if node == nil {
+		si6.handlers.info("ip6:demux.drop", slog.String("proto", proto.String()))
+		return lneto.ErrPacketDrop
+	}
+	payload := ifrm.Payload()
+	var crc lneto.CRC791
+	switch proto {
+	case lneto.IPProtoTCP:
+		ifrm.CRCWritePseudo(&crc)
+		if crc.PayloadSum16(payload) != 0 {
+			si6.handlers.error("ip6:demux.tcpcrc")
+			return lneto.ErrBadCRC
+		}
+	case lneto.IPProtoUDP:
+		ufrm, err := udp.NewFrame(payload)
+		if err != nil {
+			return err
+		}
+		ufrm.ValidateSize(si6.vld)
+		if err = si6.vld.ErrPop(); err != nil {
+			si6.handlers.error("ip6:demux.udpvalidatesize")
+			return err
+		}
+		ifrm.CRCWritePseudo(&crc)
+		if crc.PayloadSum16(payload) != 0 {
+			si6.handlers.error("ip6:demux.udpcrc")
+			return lneto.ErrBadCRC
+		}
+	}
+	const headerlen = 40
+	plen := ifrm.PayloadLength()
+	si6.handlers.info("ip6Demux", slog.String("ipproto", proto.String()), slog.Int("plen", int(plen)))
+	err = node.callbacks.Demux(carrierData[offset:offset+headerlen+int(plen)], headerlen)
+	if si6.handlers.tryHandleError(node, err) {
+		si6.handlers.info("ip6close", slog.String("proto", proto.String()))
+		err = nil
+	}
+	return err
+}
+
+func (si6 *stackip6) encapsulate6(carrierData []byte, offsetToIP int) (int, error) {
+	ifrm, err := ipv6.NewFrame(carrierData[offsetToIP:])
+	if err != nil {
+		return 0, err
+	}
+	// Set default parameters which node is free to change.
+	ifrm.SetVersionTrafficAndFlow(6, 0, 0)
+	ifrm.SetHopLimit(64)
+	*ifrm.SourceAddr() = si6.ip6
+	const headerlen = 40
+	node, n, err := si6.handlers.encapsulateAny(carrierData, offsetToIP, offsetToIP+headerlen)
+	if n == 0 {
+		return n, err
+	}
+	proto := lneto.IPProto(node.proto)
+	ifrm.SetNextHeader(proto)
+	ifrm.SetPayloadLength(uint16(n))
+	var crc lneto.CRC791
+	payload := ifrm.Payload()
+	switch proto {
+	case lneto.IPProtoTCP:
+		ifrm.CRCWritePseudo(&crc)
+		tfrm, _ := tcp.NewFrame(payload)
+		tfrm.SetCRC(0)
+		tfrm.SetCRC(crc.PayloadSum16(payload))
+	case lneto.IPProtoUDP:
+		ufrm, _ := udp.NewFrame(payload)
+		ufrm.SetLength(uint16(n))
+		ifrm.CRCWritePseudo(&crc)
+		ufrm.SetCRC(0)
+		ufrm.SetCRC(lneto.NeverZeroSum(crc.PayloadSum16(payload)))
+	}
+	return headerlen + n, err
+}

internet/stackbasic_test.go

@@ -5,6 +5,7 @@ import (
 	"net/netip"
 	"testing"
 
+	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/tcp"
 )
 
@@ -44,7 +45,7 @@ func TestBasicStack2(t *testing.T) {
 
 func expectExchange(t *testing.T, from, to *StackIP, buf []byte) {
 	t.Helper()
-	n, err := from.Encapsulate(buf, -1, 0)
+	n, err := from.Encapsulate(buf, 0, 0)
 	if err != nil {
 		t.Error("expectExchange:encapsulate:", err)
 	} else if n == 0 {
@@ -90,15 +91,97 @@ func testClientServerEstablish(t *testing.T, client, server *StackIP, connClient
 	}
 }
 
+func TestBasicStack6(t *testing.T) {
+	rng := rand.New(rand.NewSource(1))
+	var sbCl, sbSv StackIP
+	var connCl, connSv tcp.Conn
+	setupClientServer6(t, rng, &sbCl, &sbSv, &connCl, &connSv)
+	var buf [2048]byte
+	nextToSend := &sbCl
+	nextToRecv := &sbSv
+	exchangeAndExpectStates := func(clState, svState tcp.State) {
+		t.Helper()
+		expectExchange(t, nextToSend, nextToRecv, buf[:])
+		gotCl := connCl.State()
+		gotSv := connSv.State()
+		if gotCl != clState {
+			t.Errorf("want client state %s, got %s", clState, gotCl)
+		}
+		if gotSv != svState {
+			t.Errorf("want server state %s, got %s", svState, gotSv)
+		}
+		nextToSend, nextToRecv = nextToRecv, nextToSend
+	}
+	exchangeAndExpectStates(tcp.StateSynSent, tcp.StateSynRcvd)
+	exchangeAndExpectStates(tcp.StateEstablished, tcp.StateSynRcvd)
+	exchangeAndExpectStates(tcp.StateEstablished, tcp.StateEstablished)
+}
+
+func TestBasicStack6Established(t *testing.T) {
+	rng := rand.New(rand.NewSource(1))
+	var sbCl, sbSv StackIP
+	var connCl, connSv tcp.Conn
+	setupClientServer6(t, rng, &sbCl, &sbSv, &connCl, &connSv)
+	testClientServerEstablish(t, &sbCl, &sbSv, &connCl, &connSv)
+}
+
+func setupClientServer6(t *testing.T, rng *rand.Rand, client, server *StackIP, connClient, connServer *tcp.Conn) {
+	t.Helper()
+	_ = rng
+	const maxNodes = 1
+	bufsize := 2048
+	svip6 := netip.AddrFrom16([16]byte{0x20, 0x01, 0x0d, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}) // 2001:db8::1
+	clip6 := netip.AddrFrom16([16]byte{0x20, 0x01, 0x0d, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2}) // 2001:db8::2
+	svip := netip.AddrPortFrom(svip6, 80)
+	clip := netip.AddrPortFrom(clip6, 1337)
+	if err := server.Reset(new(lneto.Validator), 0, maxNodes); err != nil {
+		t.Fatal(err)
+	}
+	if err := client.Reset(new(lneto.Validator), 0, maxNodes); err != nil {
+		t.Fatal(err)
+	}
+	server.SetAddr6(svip6.As16())
+	client.SetAddr6(clip6.As16())
+	err := connServer.Configure(tcp.ConnConfig{
+		RxBuf:             make([]byte, bufsize),
+		TxBuf:             make([]byte, bufsize),
+		TxPacketQueueSize: 3,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = connClient.Configure(tcp.ConnConfig{
+		RxBuf:             make([]byte, bufsize),
+		TxBuf:             make([]byte, bufsize),
+		TxPacketQueueSize: 3,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = connServer.OpenListen(svip.Port(), 200); err != nil {
+		t.Fatal(err)
+	}
+	if err = connClient.OpenActive(clip.Port(), svip, 100); err != nil {
+		t.Fatal(err)
+	}
+	if err = server.Register6(connServer); err != nil {
+		t.Fatal(err)
+	}
+	if err = client.Register6(connClient); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func setupClientServer(t *testing.T, rng *rand.Rand, client, server *StackIP, connClient, connServer *tcp.Conn) {
 	const maxNodes = 1
 	bufsize := 2048
 	// Ensure buffer sizes are OK with reused buffers.
 	svip := netip.AddrPortFrom(netip.AddrFrom4([4]byte{192, 168, 1, 0}), 80)
 	clip := netip.AddrPortFrom(netip.AddrFrom4([4]byte{192, 168, 1, 1}), 1337)
-	server.Reset(svip.Addr(), maxNodes)
+	server.Reset(new(lneto.Validator), maxNodes, 0)
-	client.Reset(clip.Addr(), maxNodes)
+	client.Reset(new(lneto.Validator), maxNodes, 0)
-
+	server.SetAddr4(svip.Addr().As4())
+	client.SetAddr4(clip.Addr().As4())
 	err := connServer.Configure(tcp.ConnConfig{
 		RxBuf:             make([]byte, bufsize),
 		TxBuf:             make([]byte, bufsize),
@@ -127,11 +210,11 @@ func setupClientServer(t *testing.T, rng *rand.Rand, client, server *StackIP, co
 		t.Fatal(err)
 	}
 
-	err = server.Register(connServer)
+	err = server.Register4(connServer)
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = client.Register(connClient)
+	err = client.Register4(connClient)
 	if err != nil {
 		t.Fatal(err)
 	}

internet/tcplistener_test.go

@@ -6,6 +6,7 @@ import (
 	"net/netip"
 	"testing"
 
+	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/tcp"
 )
 
@@ -24,7 +25,7 @@ func TestListener_SingleConnection(t *testing.T) {
 	if err := listener.Reset(serverPort, pool); err != nil {
 		t.Fatal(err)
 	}
-	if err := serverStack.Register(&listener); err != nil {
+	if err := serverStack.Register4(&listener); err != nil {
 		t.Fatal(err)
 	}
 
@@ -77,7 +78,7 @@ func TestListener_AcceptAfterEstablished(t *testing.T) {
 	if err := listener.Reset(serverPort, pool); err != nil {
 		t.Fatal(err)
 	}
-	if err := serverStack.Register(&listener); err != nil {
+	if err := serverStack.Register4(&listener); err != nil {
 		t.Fatal(err)
 	}
 
@@ -105,7 +106,7 @@ func TestListener_AcceptAfterEstablished(t *testing.T) {
 	// Setup second client and verify we can still accept.
 	var client2Stack StackIP
 	var client2Conn tcp.Conn
-	setupClient(t, &client2Stack, &client2Conn, serverStack.Addr(), serverPort, 1338)
+	setupClient(t, &client2Stack, &client2Conn, netip.AddrFrom4(serverStack.Addr4()), serverPort, 1338)
 
 	// Complete full handshake for client2.
 	expectExchange(t, &client2Stack, &serverStack, buf[:]) // SYN
@@ -147,14 +148,14 @@ func TestListener_MultiConn(t *testing.T) {
 	if err := listener.Reset(serverPort, pool); err != nil {
 		t.Fatal(err)
 	}
-	if err := serverStack.Register(&listener); err != nil {
+	if err := serverStack.Register4(&listener); err != nil {
 		t.Fatal(err)
 	}
 
 	// Setup remaining clients.
 	for i := 1; i < numClients; i++ {
 		clientPort := uint16(1337 + i)
-		setupClient(t, &clientStacks[i], &clientConns[i], serverStack.Addr(), serverPort, clientPort)
+		setupClient(t, &clientStacks[i], &clientConns[i], netip.AddrFrom4(serverStack.Addr4()), serverPort, clientPort)
 	}
 
 	var buf [2048]byte
@@ -324,7 +325,7 @@ func TestListener_RSTOnPoolExhaustion(t *testing.T) {
 	if err := listener.Reset(serverPort, pool); err != nil {
 		t.Fatal(err)
 	}
-	if err := serverStack.Register(&listener); err != nil {
+	if err := serverStack.Register4(&listener); err != nil {
 		t.Fatal(err)
 	}
 
@@ -340,10 +341,10 @@ func TestListener_RSTOnPoolExhaustion(t *testing.T) {
 
 	// Setup client2 and send its SYN — pool is full, server should queue RST.
 	const client2Port = uint16(1338)
-	setupClient(t, &client2Stack, &client2Conn, serverStack.Addr(), serverPort, client2Port)
+	setupClient(t, &client2Stack, &client2Conn, netip.AddrFrom4(serverStack.Addr4()), serverPort, client2Port)
 
 	// Client2 sends SYN.
-	n, err := client2Stack.Encapsulate(buf[:], -1, 0)
+	n, err := client2Stack.Encapsulate(buf[:], 0, 0)
 	if err != nil {
 		t.Fatal("client2 encapsulate:", err)
 	} else if n == 0 {
@@ -356,7 +357,7 @@ func TestListener_RSTOnPoolExhaustion(t *testing.T) {
 	}
 
 	// Server encapsulates — should produce RST (no connection data pending).
-	n, err = serverStack.Encapsulate(buf[:], -1, 0)
+	n, err = serverStack.Encapsulate(buf[:], 0, 0)
 	if err != nil {
 		t.Fatal("server encapsulate RST:", err)
 	} else if n == 0 {
@@ -619,7 +620,8 @@ func setupClient(t *testing.T, client *StackIP, conn *tcp.Conn, serverAddr netip
 	t.Helper()
 	bufsize := 2048
 	clientIP := netip.AddrFrom4([4]byte{192, 168, 1, byte(clientPort % 256)})
-	client.Reset(clientIP, 1)
+	client.Reset(new(lneto.Validator), 1, 0)
+	client.SetAddr4(clientIP.As4())
 	err := conn.Configure(tcp.ConnConfig{
 		RxBuf:             make([]byte, bufsize),
 		TxBuf:             make([]byte, bufsize),
@@ -633,7 +635,7 @@ func setupClient(t *testing.T, client *StackIP, conn *tcp.Conn, serverAddr netip
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = client.Register(conn)
+	err = client.Register4(conn)
 	if err != nil {
 		t.Fatal(err)
 	}

x/xnet/stack-async.go

@@ -36,6 +36,8 @@ type StackAsync struct {
 	udps     internet.StackPortsMACFiltered
 	tcps     internet.StackPortsMACFiltered
 
+	defaultValidator lneto.Validator
+
 	dhcpUDP     internet.StackUDPPort
 	dhcp        dhcpv4.Client
 	dhcpResults DHCPResults
@@ -63,11 +65,13 @@ type StackAsync struct {
 }
 
 type StackConfig struct {
-	StaticAddress netip.Addr
+	// StaticAddress6 [16]byte
-	DNSServer     netip.Addr
+	StaticAddress4 [4]byte
-	NTPServer     netip.Addr
+
-	RandSeed      int64
+	DNSServer netip.Addr
-	Hostname      string
+	NTPServer netip.Addr
+	RandSeed  int64
+	Hostname  string
 
 	// MaxActiveTCPPorts and MaxActiveUDPPorts are a memory guardrail to limit
 	// number of simultaneous open TCP/UDP ports. The memory impact at the stack level
@@ -148,16 +152,11 @@ func (s *StackAsync) Reset(cfg StackConfig) error {
 		return lneto.ErrInvalidConfig
 	}
 	mac := cfg.HardwareAddress
-	addr := cfg.StaticAddress
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	s.prng = uint32(cfg.RandSeed)
 	s.hostname = cfg.Hostname
-	if !addr.IsValid() {
+
-		addr = netip.AddrFrom4([4]byte{}) // If static not set DHCP will be performed and address will be zero.
-	} else if addr.Is6() {
-		return lneto.ErrUnsupported
-	}
 	const linkNodes = 2 // ARP and IP nodes
 	ecfg := internet.StackEthernetConfig{
 		MTU:         int(cfg.MTU),
@@ -178,11 +177,12 @@ func (s *StackAsync) Reset(cfg StackConfig) error {
 		s.link.OnEncapsulate(s.arpt.patchEgressMAC)
 	}
 	const ipNodes = 3 // 3 IP protocols possible: UDP, TCP, ICMP.
-	err = s.ip.Reset(addr, ipNodes)
+	err = s.ip.Reset(&s.defaultValidator, ipNodes, 0)
 	if err != nil {
 		return err
 	}
-	s.ip.SetAcceptMulticast(cfg.AcceptMulticast)
+	s.ip.SetAddr4(cfg.StaticAddress4)
+	s.ip.SetAcceptMulticast4(cfg.AcceptMulticast)
 	s.arpt.passivePeers = uint8(cfg.PassivePeers)
 	err = s.resetARP()
 	if err != nil {
@@ -201,7 +201,7 @@ func (s *StackAsync) Reset(cfg StackConfig) error {
 		if err != nil {
 			return err
 		}
-		err = s.ip.Register(&s.tcps)
+		err = s.ip.Register4(&s.tcps)
 		if err != nil {
 			return err
 		}
@@ -213,7 +213,7 @@ func (s *StackAsync) Reset(cfg StackConfig) error {
 	if err != nil {
 		return err
 	}
-	err = s.ip.Register(&s.udps)
+	err = s.ip.Register4(&s.udps)
 	if err != nil {
 		return err
 	}
@@ -243,17 +243,11 @@ func (s *StackAsync) Reset(cfg StackConfig) error {
 
 func (s *StackAsync) resetARP() error {
 	mac := s.link.HardwareAddr6()
-	addr := s.ip.Addr()
+	addr := s.ip.Addr4()
-	if !addr.IsValid() {
-		return lneto.ErrInvalidAddr
-	}
 	proto := ethernet.TypeIPv4
-	if addr.Is6() {
-		proto = ethernet.TypeIPv6
-	}
 	err := s.arp.Reset(arp.HandlerConfig{
 		HardwareAddr: mac[:],
-		ProtocolAddr: addr.AsSlice(),
+		ProtocolAddr: addr[:],
 		MaxQueries:   5,
 		MaxPending:   5,
 		HardwareType: 1,
@@ -298,26 +292,21 @@ func (s *StackAsync) prand32() uint32 {
 	return seed
 }
 
-func (s *StackAsync) SetIPAddr(addr netip.Addr) error {
+func (s *StackAsync) SetAddr4(addr [4]byte) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	return s.setIPAddr(addr)
+	return s.setIPAddr4(addr)
 }
 
-func (s *StackAsync) setIPAddr(addr netip.Addr) error {
+func (s *StackAsync) setIPAddr4(addr [4]byte) error {
-	err := s.ip.SetAddr(addr)
+	s.ip.SetAddr4(addr)
-	if err != nil {
+	return s.arp.UpdateProtoAddr(addr[:])
-		return err
-	}
-	ip := addr.As4()
-	err = s.arp.UpdateProtoAddr(ip[:])
-	return err
 }
 
-func (s *StackAsync) Addr() netip.Addr {
+func (s *StackAsync) Addr4() [4]byte {
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	return s.ip.Addr()
+	return s.ip.Addr4()
 }
 
 func (s *StackAsync) SetSubnet(subnetMask netip.Prefix) {
@@ -359,10 +348,10 @@ func (s *StackAsync) EnableICMP(enabled bool) (err error) {
 		enabled = false // ensure aborted.
 	}
 	if enabled {
-		if s.ip.IsRegistered(lneto.IPProtoICMP) {
+		if s.ip.IsRegistered4(lneto.IPProtoICMP) {
 			return nil
 		}
-		err = s.ip.Register(&s.icmp)
+		err = s.ip.Register4(&s.icmp)
 	} else {
 		s.icmp.Abort()
 	}
@@ -625,7 +614,7 @@ func (s *StackAsync) DiscardResolveHardwareAddress6(ip netip.Addr) error {
 type DHCPResults struct {
 	DNSServers    []netip.Addr
 	Router        netip.Addr
-	AssignedAddr  netip.Addr
+	AssignedAddr4 [4]byte
 	ServerAddr    netip.Addr
 	BroadcastAddr netip.Addr
 	Gateway       netip.Addr
@@ -665,8 +654,8 @@ func (stack *StackAsync) AssimilateDHCPResults(results *DHCPResults) error {
 	if results.Subnet.IsValid() {
 		stack.arpt.subnet = results.Subnet
 	}
-	if results.AssignedAddr.IsValid() {
+	if !internal.IsZeroed(results.AssignedAddr4) {
-		err := stack.setIPAddr(results.AssignedAddr)
+		err := stack.setIPAddr4(results.AssignedAddr4)
 		if err != nil {
 			return err
 		}
@@ -696,7 +685,7 @@ func (s *StackAsync) populateDHCPResults() error {
 	s.dhcpResults = DHCPResults{
 		Router:        router,
 		Subnet:        s.dhcp.SubnetPrefix(),
-		AssignedAddr:  netip.AddrFrom4(assigned4),
+		AssignedAddr4: assigned4,
 		ServerAddr:    addr4(s.dhcp.ServerAddr()),
 		BroadcastAddr: addr4(s.dhcp.BroadcastAddr()),
 		Gateway:       addr4(s.dhcp.GatewayAddr()),

x/xnet/stack-go.go

@@ -76,7 +76,7 @@ func (s StackGo) SocketNetip(ctx context.Context, network string, family, sotype
 	}
 	if laddr.Addr() == netip.IPv4Unspecified() {
 		// Specify address.
-		laddr = netip.AddrPortFrom(s.blk.async.ip.Addr(), laddr.Port())
+		laddr = netip.AddrPortFrom(netip.AddrFrom4(s.blk.async.ip.Addr4()), laddr.Port())
 	} else if laddr.Addr().Is6() {
 		return nil, lneto.ErrUnsupported
 	}

x/xnet/xnet_arp_test.go

@@ -16,13 +16,13 @@ func TestARPLocal(t *testing.T) {
 	// Most common case: we have a router in between computers.
 	s1.SetGateway6(routerHw)
 	s2.SetGateway6(routerHw)
-	addr1 := netip.AddrPortFrom(s1.Addr(), 1024) // dialer, client.
+	addr1 := netip.AddrPortFrom(netip.AddrFrom4(s1.Addr4()), 1024) // dialer, client.
-	addr2 := netip.AddrPortFrom(s2.Addr(), 80)   // listener, server.
+	addr2 := netip.AddrPortFrom(netip.AddrFrom4(s2.Addr4()), 80)   // listener, server.
 	err := s1.AssimilateDHCPResults(&DHCPResults{
 		Router:        netip.AddrFrom4([4]byte{10, 0, 0, 255}),
 		BroadcastAddr: netip.AddrFrom4([4]byte{255, 255, 255, 255}),
-		AssignedAddr:  s1.Addr(),
+		AssignedAddr4: s1.Addr4(),
-		Subnet:        netip.PrefixFrom(s2.Addr(), 24), // Subnet containing s2 will force an ARP on s1.
+		Subnet:        netip.PrefixFrom(netip.AddrFrom4(s2.Addr4()), 24), // Subnet containing s2 will force an ARP on s1.
 		TRenewal:      1000,
 		TRebind:       1000,
 		TLease:        1000,

x/xnet/xnet_bench_test.go

@@ -17,7 +17,7 @@ func BenchmarkARPExchange(b *testing.B) {
 	err := c1.Reset(StackConfig{
 		Hostname:        "C1",
 		RandSeed:        1,
-		StaticAddress:   netip.AddrFrom4([4]byte{192, 168, 1, 1}),
+		StaticAddress4:  [4]byte{192, 168, 1, 1},
 		HardwareAddress: [6]byte{0xde, 0xad, 0xbe, 0xef, 0x00, 0x00},
 		MTU:             MTU,
 	})
@@ -27,7 +27,7 @@ func BenchmarkARPExchange(b *testing.B) {
 	err = c2.Reset(StackConfig{
 		Hostname:        "C2",
 		RandSeed:        2,
-		StaticAddress:   queryAddr,
+		StaticAddress4:  queryAddr.As4(),
 		HardwareAddress: [6]byte{0xc0, 0xff, 0xee, 0xc0, 0xff, 0xee},
 		MTU:             MTU,
 	})
@@ -85,7 +85,7 @@ func BenchmarkTCPHandshake(b *testing.B) {
 	err := sv.Reset(StackConfig{
 		Hostname:          "Server",
 		RandSeed:          1,
-		StaticAddress:     netip.AddrFrom4([4]byte{10, 0, 0, 1}),
+		StaticAddress4:    [4]byte{10, 0, 0, 1},
 		MaxActiveTCPPorts: 1,
 		HardwareAddress:   [6]byte{0xbe, 0xef, 0, 0, 0, 1},
 		MTU:               MTU,
@@ -96,7 +96,7 @@ func BenchmarkTCPHandshake(b *testing.B) {
 	err = client.Reset(StackConfig{
 		Hostname:          "Client",
 		RandSeed:          2,
-		StaticAddress:     netip.AddrFrom4([4]byte{10, 0, 0, 2}),
+		StaticAddress4:    [4]byte{10, 0, 0, 2},
 		MaxActiveTCPPorts: 1,
 		HardwareAddress:   [6]byte{0xbe, 0xef, 0, 0, 0, 2},
 		MTU:               MTU,
@@ -134,7 +134,7 @@ func BenchmarkTCPHandshake(b *testing.B) {
 		if err != nil {
 			b.Fatal(err)
 		}
-		err = client.DialTCP(clconn, 1337, netip.AddrPortFrom(sv.Addr(), svPort))
+		err = client.DialTCP(clconn, 1337, netip.AddrPortFrom(netip.AddrFrom4(sv.Addr4()), svPort))
 		if err != nil {
 			b.Fatal(err)
 		}

x/xnet/xnet_concurrent_test.go

@@ -37,7 +37,7 @@ func TestTCPListener_ConcurrentEcho(t *testing.T) {
 	err := serverStack.Reset(StackConfig{
 		Hostname:          "Server",
 		RandSeed:          seed,
-		StaticAddress:     serverIP,
+		StaticAddress4:    serverIP.As4(),
 		MaxActiveTCPPorts: numClients,
 		HardwareAddress:   serverMAC,
 		MTU:               MTU,
@@ -75,11 +75,11 @@ func TestTCPListener_ConcurrentEcho(t *testing.T) {
 
 	for i := range clientStacks {
 		clientMAC := [6]byte{0xaa, 0xbb, 0xcc, 0x00, 0x01, byte(i + 1)}
-		clientIP := netip.AddrFrom4([4]byte{10, 0, 0, byte(i + 10)})
+		clientIP := [4]byte{10, 0, 0, byte(i + 10)}
 		err := clientStacks[i].Reset(StackConfig{
 			Hostname:          fmt.Sprintf("Client%d", i),
 			RandSeed:          int64(seed + i + 1),
-			StaticAddress:     clientIP,
+			StaticAddress4:    clientIP,
 			MaxActiveTCPPorts: 1,
 			HardwareAddress:   clientMAC,
 			MTU:               MTU,
@@ -185,10 +185,10 @@ func routePacketToClient(pkt []byte, clients []StackAsync) {
 	if len(pkt) < 20+ethernet.MaxOverheadSize { //  20 min IP header
 		return
 	}
-	dstIP := netip.AddrFrom4([4]byte{pkt[30], pkt[31], pkt[32], pkt[33]})
+	dstIP := [4]byte{pkt[30], pkt[31], pkt[32], pkt[33]}
 
 	for i := range clients {
-		if clients[i].Addr() == dstIP {
+		if clients[i].Addr4() == dstIP {
 			clients[i].IngressEthernet(pkt)
 			return
 		}

x/xnet/xnet_dns_test.go

@@ -27,7 +27,7 @@ func TestDNS_QueryReceivesAnswer(t *testing.T) {
 	err := client.Reset(StackConfig{
 		Hostname:        "DNSClient",
 		RandSeed:        seed,
-		StaticAddress:   clientAddr,
+		StaticAddress4:  clientAddr.As4(),
 		DNSServer:       dnsServerAddr,
 		HardwareAddress: clientMAC,
 		MTU:             uint16(MTU),

x/xnet/xnet_fuzz_test.go

@@ -26,7 +26,7 @@ func FuzzStackPacketHTTP(f *testing.F) {
 	if err != nil {
 		f.Fatal(err)
 	}
-	err = s2.DialTCP(c2, 1337, netip.AddrPortFrom(s1.Addr(), c1.LocalPort()))
+	err = s2.DialTCP(c2, 1337, netip.AddrPortFrom(netip.AddrFrom4(s1.Addr4()), c1.LocalPort()))
 	if err != nil {
 		f.Fatal(err)
 	}
@@ -92,7 +92,7 @@ func FuzzStackPacketHTTP(f *testing.F) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		err = s2.DialTCP(c2, 1337, netip.AddrPortFrom(s1.Addr(), c1.LocalPort()))
+		err = s2.DialTCP(c2, 1337, netip.AddrPortFrom(netip.AddrFrom4(s1.Addr4()), c1.LocalPort()))
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -275,7 +275,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 	v1, v2 := byte(seed1), byte(seed2)
 	cfg1 := StackConfig{
 		Hostname:          "s1",
-		StaticAddress:     netip.AddrFrom4([4]byte{1, 0, 0, v1}),
+		StaticAddress4:    [4]byte{1, 0, 0, v1},
 		RandSeed:          seed1,
 		MaxActiveTCPPorts: 1,
 		MaxActiveUDPPorts: 1,
@@ -291,7 +291,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 	}
 	cfg2 := StackConfig{
 		Hostname:          "s2",
-		StaticAddress:     netip.AddrFrom4([4]byte{1, 0, 0, v2}),
+		StaticAddress4:    [4]byte{1, 0, 0, v2},
 		RandSeed:          seed2,
 		MaxActiveTCPPorts: 1,
 		MaxActiveUDPPorts: 1,
@@ -360,7 +360,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 				if verbose {
 					fmt.Fprintln(fzoutput, "TCP dial")
 				}
-				err = s1.DialTCP(&tcp1, port1, netip.AddrPortFrom(s2.Addr(), port2))
+				err = s1.DialTCP(&tcp1, port1, netip.AddrPortFrom(netip.AddrFrom4(s2.Addr4()), port2))
 				if err != nil {
 					t.Fatal(i, err)
 				}
@@ -387,7 +387,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 				if verbose {
 					fmt.Fprintln(fzoutput, "UDP dial 1")
 				}
-				err = s1.DialUDP(&udp1, port1, netip.AddrPortFrom(s2.Addr(), port2))
+				err = s1.DialUDP(&udp1, port1, netip.AddrPortFrom(netip.AddrFrom4(s2.Addr4()), port2))
 				if err != nil {
 					t.Fatal(i, err)
 				}
@@ -396,7 +396,7 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 				if verbose {
 					fmt.Fprintln(fzoutput, "UDP dial 2")
 				}
-				err = s2.DialUDP(&udp2, port2, netip.AddrPortFrom(s1.Addr(), port1))
+				err = s2.DialUDP(&udp2, port2, netip.AddrPortFrom(netip.AddrFrom4(s1.Addr4()), port1))
 				if err != nil {
 					t.Fatal(i, err)
 				}
@@ -447,13 +447,13 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 			switch icmpaction {
 			case 0:
 				s1.icmp.Reset()
-				_, err = s1.icmp.PingStart(s2.Addr().As4(), buf[:pingMinPayload], pingMinPayload+uint16(action.Rand)%pingMinPayload)
+				_, err = s1.icmp.PingStart(s2.Addr4(), buf[:pingMinPayload], pingMinPayload+uint16(action.Rand)%pingMinPayload)
 				if err != nil {
 					t.Fatal(i, err)
 				}
 			case 1:
 				s2.icmp.Reset()
-				_, err = s2.icmp.PingStart(s1.Addr().As4(), buf[:pingMinPayload], pingMinPayload+uint16(action.Rand)%pingMinPayload)
+				_, err = s2.icmp.PingStart(s1.Addr4(), buf[:pingMinPayload], pingMinPayload+uint16(action.Rand)%pingMinPayload)
 				if err != nil {
 					t.Fatal(i, err)
 				}
@@ -466,17 +466,17 @@ func testStackSeeded(t *testing.T, seed1, seed2 int64) {
 			}
 			switch action {
 			case 0: // s1 queries s2 address.
-				s1.StartResolveHardwareAddress6(s2.Addr())
+				s1.StartResolveHardwareAddress6(netip.AddrFrom4(s2.Addr4()))
 			case 1: // s2 queries s1 address.
-				s2.StartResolveHardwareAddress6(s1.Addr())
+				s2.StartResolveHardwareAddress6(netip.AddrFrom4(s1.Addr4()))
 			case 2: // s1 checks query result for s2.
-				s1.ResultResolveHardwareAddress6(s2.Addr())
+				s1.ResultResolveHardwareAddress6(netip.AddrFrom4(s2.Addr4()))
 			case 3: // s2 checks query result for s1.
-				s2.ResultResolveHardwareAddress6(s1.Addr())
+				s2.ResultResolveHardwareAddress6(netip.AddrFrom4(s1.Addr4()))
 			case 4: // s1 discards pending query.
-				s1.DiscardResolveHardwareAddress6(s2.Addr())
+				s1.DiscardResolveHardwareAddress6(netip.AddrFrom4(s2.Addr4()))
 			case 5: // s2 discards pending query.
-				s2.DiscardResolveHardwareAddress6(s1.Addr())
+				s2.DiscardResolveHardwareAddress6(netip.AddrFrom4(s1.Addr4()))
 			}
 		}
 		// Exchange data while checking stack does not enter runaway infinite frame send loop.

x/xnet/xnet_icmp_test.go

@@ -1,7 +1,6 @@
 package xnet
 
 import (
-	"net/netip"
 	"testing"
 )
 
@@ -37,7 +36,7 @@ func TestStackAsync_ICMPEcho(t *testing.T) {
 			sender.SetGateway6(receiver.HardwareAddress())
 			receiver.SetGateway6(sender.HardwareAddress())
 
-			key, err := sender.icmp.PingStart(receiver.Addr().As4(), tt.pattern, tt.size)
+			key, err := sender.icmp.PingStart(receiver.Addr4(), tt.pattern, tt.size)
 			if err != nil {
 				t.Fatal(err)
 			}
@@ -92,15 +91,15 @@ func newICMPStacks(t testing.TB, randSeed int64, mtu int) (*StackAsync, *StackAs
 
 	// Use the seed to generate two adjacent IPs (10.0.0.x) and MACs.
 	base := byte(randSeed & 0x7F) // keep in safe range 0..127
-	addr1 := netip.AddrFrom4([4]byte{10, 0, 0, base})
+	addr1 := [4]byte{10, 0, 0, base}
-	addr2 := netip.AddrFrom4([4]byte{10, 0, 0, base + 1})
+	addr2 := [4]byte{10, 0, 0, base + 1}
 	mac1 := [6]byte{0xbe, 0xef, 0, 0, 0, base}
 	mac2 := [6]byte{0xbe, 0xef, 0, 0, 0, base + 1}
 
 	if err := s1.Reset(StackConfig{
 		Hostname:        "icmp-stack-1",
 		RandSeed:        randSeed,
-		StaticAddress:   addr1,
+		StaticAddress4:  addr1,
 		HardwareAddress: mac1,
 		MTU:             uint16(mtu),
 		ICMPQueueLimit:  icmpQueue,
@@ -111,7 +110,7 @@ func newICMPStacks(t testing.TB, randSeed int64, mtu int) (*StackAsync, *StackAs
 	if err := s2.Reset(StackConfig{
 		Hostname:        "icmp-stack-2",
 		RandSeed:        ^randSeed,
-		StaticAddress:   addr2,
+		StaticAddress4:  addr2,
 		HardwareAddress: mac2,
 		MTU:             uint16(mtu),
 		ICMPQueueLimit:  icmpQueue,

x/xnet/xnet_listener_test.go

@@ -21,7 +21,7 @@ func TestStackAsyncListener_SingleConnection(t *testing.T) {
 	err := client.Reset(StackConfig{
 		Hostname:          "Client",
 		RandSeed:          seed,
-		StaticAddress:     netip.AddrFrom4([4]byte{10, 0, 0, 1}),
+		StaticAddress4:    [4]byte{10, 0, 0, 1},
 		MaxActiveTCPPorts: 1,
 		HardwareAddress:   [6]byte{0xbe, 0xef, 0, 0, 0, 1},
 		MTU:               MTU,
@@ -32,7 +32,7 @@ func TestStackAsyncListener_SingleConnection(t *testing.T) {
 	err = sv.Reset(StackConfig{
 		Hostname:          "Server",
 		RandSeed:          ^seed,
-		StaticAddress:     netip.AddrFrom4([4]byte{10, 0, 0, 2}),
+		StaticAddress4:    [4]byte{10, 0, 0, 2},
 		MaxActiveTCPPorts: 1, // Note: We use listener, not direct TCP conn registration.
 		HardwareAddress:   [6]byte{0xbe, 0xef, 0, 0, 0, 2},
 		MTU:               MTU,
@@ -78,7 +78,7 @@ func TestStackAsyncListener_SingleConnection(t *testing.T) {
 	}
 
 	// Client dials server.
-	err = client.DialTCP(&clConn, clPort, netip.AddrPortFrom(sv.Addr(), svPort))
+	err = client.DialTCP(&clConn, clPort, netip.AddrPortFrom(netip.AddrFrom4(sv.Addr4()), svPort))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -133,7 +133,7 @@ func TestStackAsyncListener_MultiSequentialConn(t *testing.T) {
 	err := sv.Reset(StackConfig{
 		Hostname:          "Server",
 		RandSeed:          ^seed,
-		StaticAddress:     netip.AddrFrom4([4]byte{10, 0, 0, 2}),
+		StaticAddress4:    [4]byte{10, 0, 0, 2},
 		MaxActiveTCPPorts: 1, // Note: We use listener, not direct TCP conn registration.
 		HardwareAddress:   [6]byte{0xbe, 0xef, 0, 0, 0, 2},
 		MTU:               MTU,
@@ -173,7 +173,7 @@ func TestStackAsyncListener_MultiSequentialConn(t *testing.T) {
 		err := client.Reset(StackConfig{
 			Hostname:          "Client",
 			RandSeed:          seed,
-			StaticAddress:     caddrp.Addr(),
+			StaticAddress4:    caddrp.Addr().As4(),
 			MaxActiveTCPPorts: 1,
 			HardwareAddress:   chw,
 			MTU:               MTU,
@@ -193,7 +193,7 @@ func TestStackAsyncListener_MultiSequentialConn(t *testing.T) {
 			t.Fatal(err)
 		}
 		// Client dials server.
-		err = client.DialTCP(&clConn, caddrp.Port(), netip.AddrPortFrom(sv.Addr(), svPort))
+		err = client.DialTCP(&clConn, caddrp.Port(), netip.AddrPortFrom(netip.AddrFrom4(sv.Addr4()), svPort))
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -207,7 +207,7 @@ func TestStackAsyncListener_MultiSequentialConn(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		} else if svconn.RemotePort() != clConn.LocalPort() ||
-			[4]byte(svconn.RemoteAddr()) != client.Addr().As4() {
+			[4]byte(svconn.RemoteAddr()) != client.Addr4() {
 			t.Fatal("race condition to listener acquisition")
 		}
 		// Verify both connections are established.

x/xnet/xnet_mdns_test.go

@@ -34,9 +34,9 @@ func TestMDNS_QueryResponse(t *testing.T) {
 		Port: 80,
 	}
 
-	responderAddr := netip.AddrFrom4([4]byte{192, 168, 1, 50})
+	responderAddr := [4]byte{192, 168, 1, 50}
 	responderMAC := [6]byte{0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0x01}
-	querierAddr := netip.AddrFrom4([4]byte{192, 168, 1, 100})
+	querierAddr := [4]byte{192, 168, 1, 100}
 	querierMAC := [6]byte{0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0x02}
 	mcastAddr := []byte{224, 0, 0, 251}
 
@@ -45,7 +45,7 @@ func TestMDNS_QueryResponse(t *testing.T) {
 	err = responderStack.Reset(StackConfig{
 		Hostname:          "responder",
 		RandSeed:          1234,
-		StaticAddress:     responderAddr,
+		StaticAddress4:    responderAddr,
 		HardwareAddress:   responderMAC,
 		MTU:               MTU,
 		MaxActiveUDPPorts: 1,
@@ -75,7 +75,7 @@ func TestMDNS_QueryResponse(t *testing.T) {
 	err = querierStack.Reset(StackConfig{
 		Hostname:          "querier",
 		RandSeed:          5678,
-		StaticAddress:     querierAddr,
+		StaticAddress4:    querierAddr,
 		HardwareAddress:   querierMAC,
 		MTU:               MTU,
 		MaxActiveUDPPorts: 1,
@@ -280,7 +280,7 @@ func newMDNSStack(t *testing.T, hostname string, seed int64,
 	err := stack.Reset(StackConfig{
 		Hostname:          hostname,
 		RandSeed:          seed,
-		StaticAddress:     addr,
+		StaticAddress4:    addr.As4(),
 		HardwareAddress:   mac,
 		MTU:               MTU,
 		MaxActiveUDPPorts: 1,

x/xnet/xnet_subnettable_test.go

@@ -53,7 +53,7 @@ func TestStackAsync_ListenerSynAckAddressedToClient(t *testing.T) {
 	err := sv.Reset(StackConfig{
 		Hostname:          "Server1",
 		RandSeed:          1234,
-		StaticAddress:     netip.AddrFrom4([4]byte{10, 0, 0, 2}),
+		StaticAddress4:    [4]byte{10, 0, 0, 2},
 		MaxActiveTCPPorts: 1,
 		HardwareAddress:   serverMAC,
 		MTU:               mtu,
@@ -89,7 +89,7 @@ func TestStackAsync_ListenerSynAckAddressedToClient(t *testing.T) {
 	err = client.Reset(StackConfig{
 		Hostname:          "Client1",
 		RandSeed:          5678,
-		StaticAddress:     netip.AddrFrom4([4]byte{10, 0, 0, 1}),
+		StaticAddress4:    [4]byte{10, 0, 0, 1},
 		MaxActiveTCPPorts: 1,
 		HardwareAddress:   clientMAC,
 		MTU:               mtu,
@@ -106,7 +106,7 @@ func TestStackAsync_ListenerSynAckAddressedToClient(t *testing.T) {
 	}); err != nil {
 		t.Fatal(err)
 	}
-	if err = client.DialTCP(&clConn, 54321, netip.AddrPortFrom(sv.Addr(), svPort)); err != nil {
+	if err = client.DialTCP(&clConn, 54321, netip.AddrPortFrom(netip.AddrFrom4(sv.Addr4()), svPort)); err != nil {
 		t.Fatal(err)
 	}
 

x/xnet/xnet_test.go

@@ -178,7 +178,7 @@ func newTCPStacks(t testing.TB, randSeed int64, mtu int) (s1, s2 *StackAsync, c1
 	err := s1.Reset(StackConfig{
 		Hostname:          "Stack1",
 		RandSeed:          randSeed,
-		StaticAddress:     netip.AddrFrom4([4]byte{10, 0, 0, byte1}),
+		StaticAddress4:    [4]byte{10, 0, 0, byte1},
 		MaxActiveTCPPorts: 1,
 		HardwareAddress:   [6]byte{0xbe, 0xef, 0, 0, 0, byte1},
 		MTU:               uint16(mtu),
@@ -192,7 +192,7 @@ func newTCPStacks(t testing.TB, randSeed int64, mtu int) (s1, s2 *StackAsync, c1
 	err = s2.Reset(StackConfig{
 		Hostname:          "Stack2",
 		RandSeed:          ^randSeed,
-		StaticAddress:     netip.AddrFrom4([4]byte{10, 0, 0, byte2}),
+		StaticAddress4:    [4]byte{10, 0, 0, byte2},
 		MaxActiveTCPPorts: 1,
 		HardwareAddress:   [6]byte{0xbe, 0xef, 0, 0, 0, byte2},
 		MTU:               uint16(mtu),
@@ -257,7 +257,7 @@ func (tst *tester) TestTCPSetupAndEstablish(svStack, clStack *StackAsync, svConn
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = clStack.DialTCP(clConn, clPort, netip.AddrPortFrom(svStack.Addr(), svPort))
+	err = clStack.DialTCP(clConn, clPort, netip.AddrPortFrom(netip.AddrFrom4(svStack.Addr4()), svPort))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -464,12 +464,12 @@ func (tst *tester) TCPExchange(expect tcpExpectExchange, stack1, stack2 *StackAs
 	if tst.getInt(protoIPv4, pcap.FieldClassVersion) != 4 {
 		t.Errorf("did not get IP version=4, got=%d", tst.getInt(protoIPv4, pcap.FieldClassVersion))
 	}
-	srcAddr := src.Addr()
+	srcAddr := src.Addr4()
-	dstAddr := dst.Addr()
+	dstAddr := dst.Addr4()
-	if !bytes.Equal(srcAddr.AsSlice(), tst.getData(protoIPv4, pcap.FieldClassSrc)) {
+	if !bytes.Equal(srcAddr[:], tst.getData(protoIPv4, pcap.FieldClassSrc)) {
 		t.Errorf("mismatched ip src addr %d", tst.getData(protoIPv4, pcap.FieldClassSrc))
 	}
-	if !bytes.Equal(dstAddr.AsSlice(), tst.getData(protoIPv4, pcap.FieldClassDst)) {
+	if !bytes.Equal(dstAddr[:], tst.getData(protoIPv4, pcap.FieldClassDst)) {
 		t.Errorf("mismatched ip dst addr %d", tst.getData(protoIPv4, pcap.FieldClassDst))
 	}
 	tfrm := tst.getTCPFrame()
@@ -514,8 +514,8 @@ func (tst *tester) ARPExchangeOnly(querying, target *StackAsync) {
 	qHw := querying.HardwareAddress()
 	tgtHw := target.HardwareAddress()
 	broadcast := ethernet.BroadcastAddr()
-	qIP := querying.Addr()
+	qIP := querying.Addr4()
-	tgtIP := target.Addr()
+	tgtIP := target.Addr4()
 
 	// Validate Ethernet layer (request is broadcast)
 	if !bytes.Equal(qHw[:], tst.getData(protoEthernet, pcap.FieldClassSrc)) {
@@ -534,10 +534,10 @@ func (tst *tester) ARPExchangeOnly(querying, target *StackAsync) {
 	if !bytes.Equal(qHw[:], tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 6, 0)) {
 		t.Errorf("request: mismatched ARP sender HW")
 	}
-	if !bytes.Equal(qIP.AsSlice(), tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 4, 0)) {
+	if !bytes.Equal(qIP[:], tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 4, 0)) {
 		t.Errorf("request: mismatched ARP sender proto")
 	}
-	if !bytes.Equal(tgtIP.AsSlice(), tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 4, 1)) {
+	if !bytes.Equal(tgtIP[:], tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 4, 1)) {
 		t.Errorf("request: mismatched ARP target proto")
 	}
 
@@ -579,13 +579,13 @@ func (tst *tester) ARPExchangeOnly(querying, target *StackAsync) {
 	if !bytes.Equal(tgtHw[:], tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 6, 0)) {
 		t.Errorf("reply: mismatched ARP sender HW (should be target's MAC)")
 	}
-	if !bytes.Equal(tgtIP.AsSlice(), tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 4, 0)) {
+	if !bytes.Equal(tgtIP[:], tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 4, 0)) {
 		t.Errorf("reply: mismatched ARP sender proto (should be target's IP)")
 	}
 	if !bytes.Equal(qHw[:], tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 6, 1)) {
 		t.Errorf("reply: mismatched ARP target HW (should be querying's MAC)")
 	}
-	if !bytes.Equal(qIP.AsSlice(), tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 4, 1)) {
+	if !bytes.Equal(qIP[:], tst.getFieldByClassLen(protoARP, pcap.FieldClassSrc, 4, 1)) {
 		t.Errorf("reply: mismatched ARP target proto (should be querying's IP)")
 	}
 
@@ -597,7 +597,7 @@ func (tst *tester) ARPExchangeOnly(querying, target *StackAsync) {
 	setzero(buf[:n])
 
 	// === PHASE 3: Verify querying stack learned target's MAC ===
-	resolvedHw, err := querying.ResultResolveHardwareAddress6(tgtIP)
+	resolvedHw, err := querying.ResultResolveHardwareAddress6(netip.AddrFrom4(tgtIP))
 	if err != nil {
 		t.Errorf("ARP query result failed: %v", err)
 	} else if resolvedHw != tgtHw {
@@ -929,7 +929,7 @@ func TestTCPConn_BufferNotClearedOnPassiveClose(t *testing.T) {
 func TestStackAsync_ICMPEchoChecksum(t *testing.T) {
 	const MTU = ethernet.MaxMTU
 	const MaxFrameLength = MTU + ethernet.MaxOverheadSize // Ethernet header+FCS+VLAN.
-	stackAddr := netip.AddrFrom4([4]byte{192, 168, 1, 99})
+	stackAddr := [4]byte{192, 168, 1, 99}
 	stackMAC := [6]byte{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff}
 	routerAddr := [4]byte{192, 168, 1, 1}
 	routerMAC := [6]byte{0x00, 0x11, 0x22, 0x33, 0x44, 0x55}
@@ -938,7 +938,7 @@ func TestStackAsync_ICMPEchoChecksum(t *testing.T) {
 	err := stack.Reset(StackConfig{
 		Hostname:        "ICMPTest",
 		RandSeed:        42,
-		StaticAddress:   stackAddr,
+		StaticAddress4:  stackAddr,
 		HardwareAddress: stackMAC,
 		MTU:             MTU,
 		ICMPQueueLimit:  2,
@@ -954,7 +954,7 @@ func TestStackAsync_ICMPEchoChecksum(t *testing.T) {
 		SrcMAC:  routerMAC,
 		DstMAC:  stackMAC,
 		SrcIPv4: routerAddr,
-		DstIPv4: stackAddr.As4(),
+		DstIPv4: stackAddr,
 	}
 	icmpPayload := []byte("abcdefghijklmnopqrstuvwxyz012345") // 32 bytes, typical ping payload.
 	const (