apply some of @ddirect suggestions

arp/handler.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/ethernet"
+	"github.com/soypat/lneto/internal"
 )
 
 type Handler struct {
@@ -143,7 +144,7 @@ func (h *Handler) StartQuery(dstHWAddr, proto []byte) error {
 		return errors.New("bad protocol address length")
 	} else if dstHWAddr != nil && len(dstHWAddr) != len(h.ourHWAddr) {
 		return errors.New("mismatch hardware size")
-	} else if dstHWAddr != nil && !allZeros(dstHWAddr) {
+	} else if dstHWAddr != nil && !internal.IsZeroed(dstHWAddr...) {
 		return errors.New("write-to buffer must be zeroed out")
 	}
 	h.queries = h.queries[:len(h.queries)+1]
@@ -238,7 +239,7 @@ func (h *Handler) Demux(ethFrame []byte, frameOffset int) error {
 			if mac == nil && bytes.Equal(q.protoaddr, protoaddr) {
 				q.hwaddr = append(q.hwaddr, hwaddr...)
 				if q.dstHw != nil {
-					if !allZeros(q.dstHw) {
+					if !internal.IsZeroed(q.dstHw...) {
 						slog.Error("race-condition:ARP-reused-buffer")
 					}
 					copy(q.dstHw, hwaddr) // External write to user buffer.
@@ -258,12 +259,3 @@ func trySetEthernetDst(ethFrame []byte, dst []byte) {
 		copy(ethFrame[:6], dst)
 	}
 }
-
-func allZeros(b []byte) bool {
-	for i := range b {
-		if b[i] != 0 {
-			return false
-		}
-	}
-	return true
-}

examples/bridge/main.go

@@ -359,7 +359,7 @@ func (s *Stack) StartLookupIP(host string) error {
 	var u internet.StackUDPPort
 	dns4 := dnsSrvs.As4()
 	u.SetStackNode(&s.dns, dns4[:], dns.ServerPort)
-	err = s.udps.Register(&u, nil)
+	err = s.udps.Register(&u)
 	if err != nil {
 		return err
 	}
@@ -405,7 +405,7 @@ func (s *Stack) BeginDHCPRequest(request [4]byte) error {
 	}
 	var u internet.StackUDPPort
 	u.SetStackNode(&s.dhcp, nil, dhcpv4.DefaultServerPort)
-	err = s.udps.Register(&u, nil)
+	err = s.udps.Register(&u)
 	if err != nil {
 		return err
 	}
@@ -417,7 +417,7 @@ func (s *Stack) StartNTP(addr netip.Addr) error {
 	var u internet.StackUDPPort
 	addr4 := addr.As4()
 	u.SetStackNode(&s.ntp, addr4[:], ntp.ServerPort)
-	err := s.udps.Register(&u, nil)
+	err := s.udps.Register(&u)
 	return err
 }
 

examples/stack/main.go

@@ -239,7 +239,7 @@ func (stack *Stack) OpenTCPListener(port uint16) (*internet.NodeTCPListener, err
 	if err != nil {
 		return nil, err
 	}
-	err = stack.tcpports.Register(&listener, nil) // Passive TCP requires no MAC setting.
+	err = stack.tcpports.Register(&listener) // Passive TCP requires no MAC setting.
 	if err != nil {
 		return nil, err
 	}
@@ -261,7 +261,7 @@ func (stack *Stack) OpenPassiveTCP(port uint16, iss tcp.Value) (*tcp.Conn, error
 	if err != nil {
 		return nil, err
 	}
-	err = stack.tcpports.Register(conn, nil) // Passive MAC with no listening.
+	err = stack.tcpports.Register(conn) // Passive MAC with no listening.
 	if err != nil {
 		return nil, err
 	}

internal/ip.go

@@ -56,3 +56,14 @@ func SetIPAddrs(buf []byte, id uint16, src, dst []byte) (err error) {
 	copy(dstaddr, dst)
 	return nil
 }
+
+// IsZeroed returns true if all arguments are set to their zero value.
+func IsZeroed[T comparable](a ...T) bool {
+	var z T
+	for i := range a {
+		if a[i] != z {
+			return false
+		}
+	}
+	return true
+}

internet/definitions.go

@@ -165,6 +165,7 @@ func (h *handlers) demuxByPort(buf []byte, offset int, port uint16) (*node, erro
 	err := node.demux(buf, offset)
 	if h.tryHandleError(node, err) {
 		err = nil
+		node = nil // Node is destroyed in tryHandleError and invalidated.
 	}
 	return node, err
 }
@@ -174,12 +175,13 @@ func (h *handlers) demuxByPort(buf []byte, offset int, port uint16) (*node, erro
 func (h *handlers) encapsulateAny(buf []byte, offsetIP, offsetThisFrame int) (_ *node, n int, err error) {
 	for i := range h.nodes {
 		node := &h.nodes[i]
-		if node.IsInvalid() || (len(node.remoteAddr) > 0 && isAllZeros(node.remoteAddr)) {
+		if node.IsInvalid() {
 			continue
 		}
 		n, err = node.encapsulate(buf, offsetIP, offsetThisFrame)
 		if h.tryHandleError(node, err) {
-			err = nil // CLOSE error handled gracefully by deleting node.
+			err = nil  // CLOSE error handled gracefully by deleting node.
+			node = nil // Node is destroyed in tryHandleError and invalidated.
 		}
 		if n > 0 {
 			return node, n, err
@@ -191,15 +193,6 @@ func (h *handlers) encapsulateAny(buf []byte, offsetIP, offsetThisFrame int) (_
 	return nil, 0, err // Return last written error.
 }
 
-func isAllZeros(b []byte) bool {
-	for i := range b {
-		if b[i] != 0 {
-			return false
-		}
-	}
-	return true
-}
-
 var (
 	errZeroMaxNodesArg = errors.New("zero max nodes arg")
 	errZeroPort        = errors.New("port must be greater than zero")

internet/stack-ports.go

@@ -4,11 +4,13 @@ import (
 	"encoding/binary"
 	"errors"
 	"io"
+	"log/slog"
 	"math"
 	"strconv"
 
 	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/ethernet"
+	"github.com/soypat/lneto/internal"
 )
 
 type StackPorts struct {
@@ -16,6 +18,7 @@ type StackPorts struct {
 	handlers   handlers
 	dstPortOff uint16
 	protocol   uint16
+	// stores last node to demux/encapsulate.
 }
 
 func (ps *StackPorts) ResetUDP(maxNodes int) error {
@@ -52,12 +55,7 @@ func (ps *StackPorts) Encapsulate(carrierData []byte, offsetToIP, offsetToFrame
 	if int(ps.dstPortOff)+offsetToFrame+2 > len(carrierData) {
 		return 0, io.ErrShortBuffer
 	}
-	var node *node
+	_, n, err = ps.handlers.encapsulateAny(carrierData, offsetToIP, offsetToFrame)
-	node, n, err = ps.handlers.encapsulateAny(carrierData, offsetToIP, offsetToFrame)
-	if n > 0 && len(node.remoteAddr) == 6 && offsetToIP >= 14 {
-		efrm, _ := ethernet.NewFrame(carrierData[offsetToIP-14:])
-		*efrm.DestinationHardwareAddr() = [6]byte(node.remoteAddr)
-	}
 	return n, err
 }
 
@@ -72,15 +70,84 @@ func (ps *StackPorts) Demux(b []byte, offset int) (err error) {
 
 // Register registers a port StackNode on StackPorts.
 // If dstMAC is set to non-nil, length six buffer then
-func (ps *StackPorts) Register(h StackNode, dstMAC []byte) error {
+func (ps *StackPorts) Register(h StackNode) error {
 	port := h.LocalPort()
 	proto := h.Protocol()
 	if port <= 0 {
 		return errZeroPort
 	} else if proto != uint64(ps.protocol) {
 		return errInvalidProto
-	} else if dstMAC != nil && len(dstMAC) != 6 {
+	}
+	return ps.handlers.registerByPortProto(nodeFromStackNode(h, port, proto, nil))
+}
+
+// StackPortsMACFiltered is a StackPorts implementation but that avoids calling encapsulate on nodes
+// with a non-nil MAC address registered via Register method that is set to all zero values.
+// If the address is set to nil no filtering occurs. MAC Address is set automatically on the ethernet frame by StackPortsMACFiltered when non-nil.
+type StackPortsMACFiltered struct {
+	sp StackPorts
+}
+
+func (mfsp *StackPortsMACFiltered) Register(h StackNode, addr []byte) error {
+	port := h.LocalPort()
+	proto := h.Protocol()
+	if port <= 0 {
+		return errZeroPort
+	} else if proto != uint64(mfsp.sp.protocol) {
+		return errInvalidProto
+	} else if addr != nil && len(addr) != 6 {
 		return errors.New("invalid MAC")
 	}
-	return ps.handlers.registerByPortProto(nodeFromStackNode(h, port, proto, dstMAC))
+	return mfsp.sp.handlers.registerByPortProto(nodeFromStackNode(h, port, proto, addr))
+}
+
+func (ps *StackPortsMACFiltered) ResetUDP(maxNodes int) error {
+	return ps.sp.ResetUDP(maxNodes)
+}
+
+func (ps *StackPortsMACFiltered) ResetTCP(maxNodes int) error {
+	return ps.sp.ResetTCP(maxNodes)
+}
+
+func (ps *StackPortsMACFiltered) Reset(protocol uint64, dstPortOffset uint16, maxNodes int) error {
+	return ps.sp.Reset(protocol, dstPortOffset, maxNodes)
+}
+
+func (ps *StackPortsMACFiltered) LocalPort() uint16 { return 0 }
+
+func (ps *StackPortsMACFiltered) Protocol() uint64 { return uint64(ps.sp.protocol) }
+
+func (ps *StackPortsMACFiltered) ConnectionID() *uint64 { return &ps.sp.connID }
+
+func (ps *StackPortsMACFiltered) Demux(b []byte, offset int) (err error) {
+	// No MAC Filtering on ingress. TODO?
+	return ps.sp.Demux(b, offset)
+}
+
+func (ps *StackPortsMACFiltered) Encapsulate(carrierData []byte, offsetToIP, offsetToFrame int) (n int, err error) {
+	if int(ps.sp.dstPortOff)+offsetToFrame+2 > len(carrierData) {
+		return 0, io.ErrShortBuffer
+	}
+	h := &ps.sp.handlers
+	for i := range h.nodes {
+		node := &h.nodes[i]
+		if node.IsInvalid() || (len(node.remoteAddr) > 0 && internal.IsZeroed(node.remoteAddr...)) {
+			continue
+		}
+		n, err = node.encapsulate(carrierData, offsetToIP, offsetToFrame)
+		if h.tryHandleError(node, err) {
+			err = nil // CLOSE error handled gracefully by deleting node.
+		}
+		if n > 0 {
+			if len(node.remoteAddr) == 6 && offsetToIP >= 14 {
+				efrm, _ := ethernet.NewFrame(carrierData[offsetToIP-14:])
+				*efrm.DestinationHardwareAddr() = [6]byte(node.remoteAddr)
+			}
+			return n, err
+		} else if err != nil {
+			// Make sure not to hang on one handler that keeps returning an error.
+			h.error("handlers:encapsulate", slog.String("func", "encapsulateAny"), slog.String("ctx", h.context), slog.String("err", err.Error()))
+		}
+	}
+	return 0, err // Return last written error.
 }

x/xnet/stack-async.go

@@ -250,7 +250,7 @@ func (s *StackAsync) DialTCP(conn *tcp.Conn, localPort uint16, addrp netip.AddrP
 	if err != nil {
 		return err
 	}
-	err = s.tcps.Register(conn, mac) // MAC is set later on by ARP response arriving to our network.
+	err = s.tcps.Register(conn) // MAC is set later on by ARP response arriving to our network.
 	if err != nil {
 		conn.Abort()
 		return err
@@ -265,7 +265,7 @@ func (s *StackAsync) ListenTCP(conn *tcp.Conn, localPort uint16) (err error) {
 	if err != nil {
 		return err
 	}
-	err = s.tcps.Register(conn, nil)
+	err = s.tcps.Register(conn)
 	if err != nil {
 		conn.Abort()
 		return err
@@ -306,7 +306,7 @@ func (s *StackAsync) StartLookupIP(host string) error {
 	}
 	dns4 := s.dnssv.As4()
 	s.dnsUDP.SetStackNode(&s.dns, dns4[:], dns.ServerPort)
-	err = s.udps.Register(&s.dnsUDP, nil)
+	err = s.udps.Register(&s.dnsUDP)
 	return err
 }
 
@@ -353,7 +353,7 @@ func (s *StackAsync) StartDHCPv4Request(request [4]byte) error {
 	}
 
 	s.dhcpUDP.SetStackNode(&s.dhcp, nil, dhcpv4.DefaultServerPort)
-	err = s.udps.Register(&s.dhcpUDP, nil)
+	err = s.udps.Register(&s.dhcpUDP)
 	if err != nil {
 		return err
 	}
@@ -367,7 +367,7 @@ func (s *StackAsync) StartNTP(addr netip.Addr) error {
 
 	addr4 := addr.As4()
 	s.ntpUDP.SetStackNode(&s.ntp, addr4[:], ntp.ServerPort)
-	err := s.udps.Register(&s.ntpUDP, nil)
+	err := s.udps.Register(&s.ntpUDP)
 	return err
 }