add TCPConn type

examples/stack/main.go

@@ -1,17 +1,13 @@
 package main
 
 import (
-	"bytes"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"log"
 	"log/slog"
 	"net"
-	"net/http"
 	"net/netip"
-	"net/url"
 	"os"
 	"time"
 
@@ -19,6 +15,7 @@ import (
 	"github.com/soypat/lneto/arp"
 	"github.com/soypat/lneto/ethernet"
 	"github.com/soypat/lneto/internal"
+	"github.com/soypat/lneto/internal/ltesto"
 	"github.com/soypat/lneto/ipv4"
 	"github.com/soypat/lneto/ipv6"
 	"github.com/soypat/lneto/tcp"
@@ -57,7 +54,7 @@ func main() {
 		log.Fatal(err)
 	}
 
-	tap := NewHTTPTap("http://127.0.0.1:7070")
+	tap := ltesto.NewHTTPTapClient("http://127.0.0.1:7070")
 	defer tap.Close()
 
 	fmt.Println("hosting server at ", addrPort.String())
@@ -520,65 +517,6 @@ func addHandler(handlers []handler, h Handler, remoteAddr []byte, lport uint16)
 	return handlers
 }
 
-func NewHTTPTap(baseURL string) *HTTPTap {
-	var h HTTPTap
-	h.sendurl = baseURL + "/send"
-	h.recvurl = baseURL + "/recv"
-	_, err := url.Parse(h.sendurl)
-	if err != nil {
-		panic(err)
-	}
-	var data [2048]byte
-	var n int = -1
-	for n != 0 {
-		n, _ = h.Read(data[:]) // Empty remote data.
-	}
-	return &h
-}
-
-type TAPNop struct{}
-
-func (h *TAPNop) Read(b []byte) (int, error)  { return 0, nil }
-func (h *TAPNop) Write(b []byte) (int, error) { return 0, nil }
-func (h *TAPNop) Close() error                { return nil }
-
-type HTTPTap struct {
-	c       http.Client
-	recvurl string
-	sendurl string
-}
-
-func (h *HTTPTap) Read(b []byte) (int, error) {
-	resp, err := h.c.Get(h.recvurl)
-	if err != nil {
-		return 0, err
-	} else if resp.StatusCode != 200 {
-		return 0, errors.New(resp.Status + " for " + h.recvurl)
-	}
-	var data []byte
-	err = json.NewDecoder(resp.Body).Decode(&data)
-	if err != nil {
-		return 0, err
-	} else if len(b) < len(data) {
-		return 0, fmt.Errorf("got too large packet %d for buffer %d", len(data), len(b))
-	}
-	copy(b, data)
-	return len(data), nil
-}
-
-func (h *HTTPTap) Write(b []byte) (int, error) {
-	data, _ := json.Marshal(b)
-	resp, err := h.c.Post(h.sendurl, "application/json", bytes.NewReader(data))
-	if err != nil {
-		return 0, err
-	} else if resp.StatusCode != 200 {
-		return 0, errors.New(resp.Status + " for " + h.sendurl)
-	}
-	return len(b), nil
-}
-
-func (h *HTTPTap) Close() error { return nil }
-
 func tcpChecksum(ipFrame []byte, tcpPayload int) uint16 {
 	version := ipFrame[0] >> 4
 	var tfrm tcp.Frame

examples/stackbasic/main.go

@@ -0,0 +1,278 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"log/slog"
+	"net"
+	"net/netip"
+	"os"
+	"time"
+
+	"github.com/soypat/lneto"
+	"github.com/soypat/lneto/arp"
+	"github.com/soypat/lneto/ethernet"
+	"github.com/soypat/lneto/internal"
+	"github.com/soypat/lneto/internal/ltesto"
+	"github.com/soypat/lneto/internet"
+)
+
+const (
+	mtu       = 2048
+	iface     = "192.168.10.1/24"
+	stackIP   = "192.168.10.2"
+	stackPort = 80
+	iss       = 100
+)
+
+var stackHWAddr = [6]byte{0xc0, 0xff, 0xee, 0x00, 0xde, 0xad}
+
+func main() {
+	ip := netip.MustParseAddr(stackIP)
+	iface := netip.MustParsePrefix(iface)
+	if !iface.Contains(ip) {
+		log.Fatal("interface does not contain stack address")
+	}
+	addrPort := netip.AddrPortFrom(ip, stackPort)
+	slogger := logger{slog.Default()}
+	lStack, handler, err := NewEthernetTCPStack(stackHWAddr, addrPort, slogger)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	logger := slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+		Level: slog.LevelDebug,
+	}))
+	handler.SetLoggers(logger, logger)
+
+	err = handler.OpenListen(addrPort.Port(), iss)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	tap := ltesto.NewHTTPTapClient("http://127.0.0.1:7070")
+	defer tap.Close()
+
+	fmt.Println("hosting server at ", addrPort.String())
+	var buf [mtu]byte
+	for {
+		nread, err := tap.Read(buf[:])
+		if err != nil {
+			slogger.error("tap-err", slog.String("err", err.Error()))
+			log.Fatal(err)
+		} else if nread > 0 {
+			err = lStack.RecvEth(buf[:nread])
+			if err != nil {
+				slogger.error("recv", slog.String("err", err.Error()), slog.Int("plen", nread))
+			} else {
+				slogger.info("recv", slog.Int("plen", nread))
+			}
+		}
+		nw, err := lStack.HandleEth(buf[:])
+		if err != nil {
+			slogger.error("handle", slog.String("err", err.Error()))
+		} else if nw > 0 {
+			_, err = tap.Write(buf[:nw])
+			if err != nil {
+				log.Fatal(err)
+			} else {
+				slogger.info("write", slog.Int("plen", nw))
+			}
+		}
+		if nread == 0 && nw == 0 {
+			time.Sleep(5 * time.Millisecond)
+		}
+	}
+}
+
+func NewEthernetTCPStack(mac [6]byte, ip netip.AddrPort, slogger logger) (*LinkStack, *internet.TCPConn, error) {
+	var err error
+	lStack := LinkStack{
+		logger: slogger,
+		mac:    mac,
+		mtu:    mtu,
+	}
+
+	var ipStack internet.StackBasic
+	addr := ip.Addr()
+	addr4 := addr.As4()
+	_ = addr4
+	ipStack.SetAddr(addr)
+	lStack.Register(handler{
+		raddr: nil, //addr4[:],
+		recv: func(b []byte, i int) error {
+			return ipStack.Recv(b[i:])
+		},
+		handle: func(b []byte, i int) (int, error) {
+			return ipStack.Handle(b[i:])
+		},
+		proto: uint32(lneto.IPProtoIPv4),
+		lport: 0,
+	})
+	var conn internet.TCPConn
+	err = conn.Configure(&internet.TCPConnConfig{
+		RxBuf:             make([]byte, mtu),
+		TxBuf:             make([]byte, mtu),
+		TxPacketQueueSize: 3,
+		Logger:            slog.Default(),
+	})
+	if err != nil {
+		return nil, nil, err
+	}
+	err = conn.OpenListen(ip.Port(), 100)
+	if err != nil {
+		return nil, nil, err
+	}
+	err = ipStack.RegisterTCPConn(&conn)
+	if err != nil {
+		return nil, nil, err
+	}
+	proto := ethernet.TypeIPv4
+	if ip.Addr().Is6() {
+		proto = ethernet.TypeIPv6
+	}
+	arphandler, err := arp.NewHandler(arp.HandlerConfig{
+		HardwareAddr: mac[:],
+		ProtocolAddr: ip.Addr().AsSlice(),
+		MaxQueries:   1,
+		MaxPending:   1,
+		HardwareType: 1,
+		ProtocolType: proto,
+	})
+	if err != nil {
+		return nil, nil, err
+	}
+	arpStack := ARPStack{
+		handler: *arphandler,
+	}
+
+	err = lStack.Register(ipStack, mac)
+	if err != nil {
+		return nil, nil, err
+	}
+	return &lStack, &conn, nil
+}
+
+type handler struct {
+	raddr  []byte
+	recv   func([]byte, int) error
+	handle func([]byte, int) (int, error)
+	proto  uint32
+	lport  uint16
+}
+
+type LinkStack struct {
+	handlers []handler
+	logger
+	mac [6]byte
+	mtu uint16
+}
+
+func (ls *LinkStack) Register(h handler) error {
+	proto := h.proto
+	for i := range ls.handlers {
+		if proto == ls.handlers[i].proto {
+			return errors.New("protocol already registered")
+		}
+	}
+	ls.handlers = append(ls.handlers, h)
+	return nil
+}
+
+func (ls *LinkStack) RecvEth(ethFrame []byte) (err error) {
+
+	efrm, err := ethernet.NewFrame(ethFrame)
+	if err != nil {
+		return err
+	}
+	etype := efrm.EtherTypeOrSize()
+	dstaddr := efrm.DestinationHardwareAddr()
+	if !efrm.IsBroadcast() && ls.mac != *dstaddr {
+		return fmt.Errorf("incoming %s mismatch hwaddr %s", etype.String(), net.HardwareAddr(dstaddr[:]).String())
+	}
+	var vld lneto.Validator
+	efrm.ValidateSize(&vld)
+	if err := vld.Err(); err != nil {
+		return err
+	}
+
+	for i := range ls.handlers {
+		h := &ls.handlers[i]
+		if h.proto == uint32(etype) {
+			return h.recv(efrm.Payload(), 0)
+		}
+	}
+
+	return nil
+}
+
+func (ls *LinkStack) HandleEth(dst []byte) (n int, err error) {
+	if len(dst) < int(ls.mtu) {
+		return 0, io.ErrShortBuffer
+	}
+	for i := range ls.handlers {
+		h := &ls.handlers[i]
+		n, err = h.handle(dst[:ls.mtu], 14)
+		if err != nil {
+			ls.error("handling", slog.String("proto", ethernet.Type(h.proto).String()), slog.String("err", err.Error()))
+			continue
+		}
+		if n > 0 {
+			// Found packet
+			efrm, _ := ethernet.NewFrame(dst[:14])
+			copy(efrm.DestinationHardwareAddr()[:], h.raddr)
+			*efrm.SourceHardwareAddr() = ls.mac
+			efrm.SetEtherType(ethernet.Type(h.proto))
+
+			return n + 14, nil
+		}
+	}
+	return 0, err
+}
+
+type ARPStack struct {
+	handler arp.Handler
+}
+
+func (as *ARPStack) Protocol() uint32 { return uint32(ethernet.TypeARP) }
+
+func (as *ARPStack) Recv(EtherFrame []byte, arpOff int) error {
+	afrm, _ := arp.NewFrame(EtherFrame[arpOff:])
+	slog.Info("recv", slog.String("in", afrm.String()))
+	return as.handler.Recv(EtherFrame[arpOff:])
+}
+
+func (as *ARPStack) Handle(EtherFrame []byte, arpOff int) (int, error) {
+	n, err := as.handler.Send(EtherFrame[arpOff:])
+	if err != nil || n == 0 {
+		return 0, err
+	}
+	afrm, _ := arp.NewFrame(EtherFrame[arpOff:])
+	hwaddr, _ := afrm.Target()
+	efrm, _ := ethernet.NewFrame(EtherFrame)
+	copy(efrm.DestinationHardwareAddr()[:], hwaddr)
+	slog.Info("handle", slog.String("out", afrm.String()))
+	return n, err
+}
+
+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...)
+}

examples/tap/main.go

@@ -1,15 +1,15 @@
 package main
 
 import (
-	"encoding/json"
 	"errors"
 	"fmt"
 	"log"
 	"log/slog"
 	"net/http"
 	"net/netip"
+	"time"
 
-	"github.com/soypat/lneto/internal"
+	"github.com/soypat/lneto/internal/ltesto"
 )
 
 func main() {
@@ -23,102 +23,32 @@ func main() {
 
 func run() error {
 	var (
-		flagNet   = "192.168.10.1/24"
-		flagiface = "tap0"
-		flagMTU   = 1500
+		flagNet             = "192.168.10.1/24"
+		flagiface           = "tap0"
+		flagMTU             = 1500
+		flagPacketQueueSize = 2048
 	)
-	slogger := slog.Default()
 	ip, err := netip.ParsePrefix(flagNet)
 	if err != nil {
 		return err
 	}
-	tap, err := internal.NewTap(flagiface, ip)
+	sv, err := ltesto.NewHTTPTapServer(flagiface, ip, flagMTU, flagPacketQueueSize, flagPacketQueueSize)
 	if err != nil {
 		return err
 	}
-	defer tap.Close()
-	s := stack{
-		out: make(chan []byte, 256),
-		in:  make(chan []byte, 2048),
-	}
-	sv := http.NewServeMux()
-	sv.HandleFunc("/send", func(w http.ResponseWriter, r *http.Request) {
-		var data []byte
-		err := json.NewDecoder(r.Body).Decode(&data)
-		if err != nil {
-			http.Error(w, err.Error(), http.StatusBadRequest)
-		} else {
-			select {
-			case s.out <- data:
-				slog.Info("http-send", slog.Int("plen", len(data)))
-			default:
-				http.Error(w, "outgoing packet queue full", http.StatusInternalServerError)
-			}
-		}
-	})
-	sv.HandleFunc("/recv", func(w http.ResponseWriter, r *http.Request) {
-		select {
-		case data := <-s.in:
-			json.NewEncoder(w).Encode(data)
-			slog.Info("http-recv", slog.Int("plen", len(data)))
-		default:
-			json.NewEncoder(w).Encode("") // send empty string.
-		}
-	})
+	defer sv.Close()
 	fmt.Println("listening on http://127.0.0.1:7070/recv  and  http://127.0.0.1:7070/send")
 	go http.ListenAndServe(":7070", sv)
 
-	buf := make([]byte, flagMTU)
 	for {
-		n, err := tap.Read(buf[:])
+		result, err := sv.HandleTap()
 		if err != nil {
-			log.Fatal(err)
-		} else if n > 0 {
-			err = s.recv(buf[:n])
-			if err != nil {
-				slogger.Error("recv", slog.String("err", err.Error()), slog.Int("plen", n))
-			} else {
-				slogger.Info("recv", slog.Int("plen", n))
-			}
+			slog.Error("handletap:error", slog.String("err", err.Error()), slog.Any("result", result))
 		}
-		n, err = s.handle(buf[:])
-		if err != nil {
-			slogger.Error("handle", slog.String("err", err.Error()))
-		} else if n > 0 {
-			_, err = tap.Write(buf[:n])
-			if err != nil {
-				log.Fatal(err)
-			} else {
-				slogger.Info("write", slog.Int("plen", n))
-			}
+		if result.Failed {
+			return errors.New("tap failed, exit program")
+		} else if result.ReceivedSize == 0 && result.SentSize == 0 {
+			time.Sleep(200 * time.Millisecond) // No data exchanged, sleep a bit to not hog CPU.
 		}
 	}
 }
-
-type stack struct {
-	out chan []byte
-	in  chan []byte
-}
-
-func (s *stack) recv(b []byte) (err error) {
-	bcopy := append([]byte{}, b...)
-RETRY:
-	select {
-	case s.in <- bcopy:
-	default:
-		err = errors.New("receive queue packet full, dropping packet")
-		<-s.in
-		goto RETRY
-	}
-	return err
-}
-
-func (s *stack) handle(b []byte) (n int, _ error) {
-	select {
-	case incoming := <-s.out:
-		n = copy(b, incoming)
-	default:
-		// pass if no data available.
-	}
-	return n, nil
-}

internal/ltesto/httptap.go

@@ -0,0 +1,211 @@
+package ltesto
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"net/netip"
+	"net/url"
+
+	"github.com/soypat/lneto/internal"
+)
+
+// NewHTTPTapClient returns a HTTPTapClient ready for use.
+func NewHTTPTapClient(baseURL string) *HTTPTapClient {
+	var h HTTPTapClient
+	h.sendurl = baseURL + "/send"
+	h.recvurl = baseURL + "/recv"
+	_, err := url.Parse(h.sendurl)
+	if err != nil {
+		panic(err)
+	}
+	return &h
+}
+
+type HTTPTapClient struct {
+	c       http.Client
+	recvurl string
+	sendurl string
+}
+
+func (h *HTTPTapClient) ReadDiscard() {
+	var data [2048]byte
+	var n int = -1
+	for n != 0 {
+		n, _ = h.Read(data[:]) // Empty remote data.
+	}
+}
+
+func (h *HTTPTapClient) Read(b []byte) (int, error) {
+	resp, err := h.c.Get(h.recvurl)
+	if err != nil {
+		return 0, err
+	} else if resp.StatusCode != 200 {
+		return 0, errors.New(resp.Status + " for " + h.recvurl)
+	}
+	var data []byte
+	err = json.NewDecoder(resp.Body).Decode(&data)
+	if err != nil {
+		return 0, err
+	} else if len(b) < len(data) {
+		return 0, fmt.Errorf("got too large packet %d for buffer %d", len(data), len(b))
+	}
+	copy(b, data)
+	return len(data), nil
+}
+
+func (h *HTTPTapClient) Write(b []byte) (int, error) {
+	data, _ := json.Marshal(b)
+	resp, err := h.c.Post(h.sendurl, "application/json", bytes.NewReader(data))
+	if err != nil {
+		return 0, err
+	} else if resp.StatusCode != 200 {
+		return 0, errors.New(resp.Status + " for " + h.sendurl)
+	}
+	return len(b), nil
+}
+
+func (h *HTTPTapClient) Close() error { return nil }
+
+type HTTPTapServer struct {
+	router    *http.ServeMux
+	stack     stack
+	tap       *internal.Tap
+	buf       []byte
+	tapfailed bool
+}
+
+func NewHTTPTapServer(iface string, ip netip.Prefix, mtu, queueOut, queueIn int) (*HTTPTapServer, error) {
+	tap, err := internal.NewTap(iface, ip)
+	if err != nil {
+		return nil, err
+	}
+
+	s := stack{
+		out: make(chan []byte, queueOut),
+		in:  make(chan []byte, queueIn),
+	}
+	sv := http.NewServeMux()
+	sv.HandleFunc("/send", func(w http.ResponseWriter, r *http.Request) {
+		var data []byte
+		err := json.NewDecoder(r.Body).Decode(&data)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+		} else {
+			select {
+			case s.out <- data:
+				slog.Info("http-send", slog.Int("plen", len(data)))
+			default:
+				http.Error(w, "outgoing packet queue full", http.StatusInternalServerError)
+			}
+		}
+	})
+	sv.HandleFunc("/recv", func(w http.ResponseWriter, r *http.Request) {
+		select {
+		case data := <-s.in:
+			json.NewEncoder(w).Encode(data)
+			slog.Info("http-recv", slog.Int("plen", len(data)))
+		default:
+			json.NewEncoder(w).Encode("") // send empty string.
+		}
+	})
+	taps := HTTPTapServer{
+		router: sv,
+		stack:  s,
+		tap:    tap,
+		buf:    make([]byte, mtu),
+	}
+	return &taps, nil
+}
+
+func (sv *HTTPTapServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	sv.router.ServeHTTP(w, r)
+}
+
+func (sv *HTTPTapServer) Close() error {
+	return sv.tap.Close()
+}
+
+type HandleTapResult struct {
+	Failed       bool
+	SentSize     int
+	ReceivedSize int
+}
+
+func (sv *HTTPTapServer) HandleTap() (result HandleTapResult, err error) {
+	result.ReceivedSize, err = sv.readTap()
+	result.Failed = sv.tapfailed
+	if result.Failed && err != nil {
+		return result, err
+	}
+	var err2 error
+	result.ReceivedSize, err2 = sv.writeTap()
+	result.Failed = result.Failed || sv.tapfailed
+	if err2 != nil && err == nil {
+		err = err2
+	} else if err2 != nil {
+		err = errors.Join(err, err2)
+	}
+	return result, err
+}
+
+func (sv *HTTPTapServer) readTap() (int, error) {
+	buf := sv.buf
+	n, err := sv.tap.Read(buf[:])
+	if err != nil {
+		sv.tapfailed = true
+		return n, err
+	} else if n > 0 {
+		err = sv.stack.recv(buf[:n])
+		if err != nil {
+			return n, err
+		}
+	}
+	return n, nil
+}
+
+func (sv *HTTPTapServer) writeTap() (int, error) {
+	buf := sv.buf
+	n, err := sv.stack.handle(buf[:])
+	if err != nil {
+		return n, err
+	} else if n > 0 {
+		n, err = sv.tap.Write(buf[:n])
+		if err != nil {
+			sv.tapfailed = true
+			return n, err
+		}
+	}
+	return n, err
+}
+
+type stack struct {
+	out chan []byte
+	in  chan []byte
+}
+
+func (s *stack) recv(b []byte) (err error) {
+	bcopy := append([]byte{}, b...)
+RETRY:
+	select {
+	case s.in <- bcopy:
+	default:
+		err = errors.New("receive queue packet full, dropping packet")
+		<-s.in
+		goto RETRY
+	}
+	return err
+}
+
+func (s *stack) handle(b []byte) (n int, _ error) {
+	select {
+	case incoming := <-s.out:
+		n = copy(b, incoming)
+	default:
+		// pass if no data available.
+	}
+	return n, nil
+}

internet/basicstack.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"io"
 	"log/slog"
+	"net/netip"
 
 	"github.com/soypat/lneto"
 	"github.com/soypat/lneto/internal"
@@ -19,35 +20,42 @@ type StackBasic struct {
 }
 
 type handler struct {
-	proto  lneto.IPProto
-	port   uint16
 	recv   func([]byte, int) error
 	handle func([]byte, int) (int, error)
+	proto  lneto.IPProto
+	port   uint16
 }
 
-func (is *StackBasic) Recv(frame []byte) error {
+func (sb *StackBasic) SetAddr(addr netip.Addr) {
+	if !addr.Is4() {
+		panic("only support IPv4")
+	}
+	sb.ip = addr.As4()
+}
+
+func (sb *StackBasic) Recv(frame []byte) error {
 	ifrm, err := ipv4.NewFrame(frame)
 	if err != nil {
 		return err
 	}
-	if *ifrm.DestinationAddr() != is.ip {
+	if *ifrm.DestinationAddr() != sb.ip {
 		return errors.New("packet not for us")
 	}
-	is.validator.ResetErr()
-	ifrm.ValidateExceptCRC(&is.validator)
-	if err = is.validator.Err(); err != nil {
+	sb.validator.ResetErr()
+	ifrm.ValidateExceptCRC(&sb.validator)
+	if err = sb.validator.Err(); err != nil {
 		return err
 	}
 	gotCRC := ifrm.CRC()
 	wantCRC := ifrm.CalculateHeaderCRC()
 	if gotCRC != wantCRC {
-		is.error("IPv4Stack:Recv:crc-mismatch", slog.Uint64("want", uint64(wantCRC)), slog.Uint64("got", uint64(gotCRC)))
+		sb.error("IPv4Stack:Recv:crc-mismatch", slog.Uint64("want", uint64(wantCRC)), slog.Uint64("got", uint64(gotCRC)))
 		return errors.New("IPv4 CRC mismatch")
 	}
 	off := ifrm.HeaderLength()
 	totalLen := ifrm.TotalLength()
-	for i := range is.handlers {
-		h := &is.handlers[i]
+	for i := range sb.handlers {
+		h := &sb.handlers[i]
 		if h.proto == ifrm.Protocol() {
 			return h.recv(frame[:totalLen], off)
 		}
@@ -55,7 +63,7 @@ func (is *StackBasic) Recv(frame []byte) error {
 	return nil
 }
 
-func (is *StackBasic) Handle(frame []byte) (int, error) {
+func (sb *StackBasic) Handle(frame []byte) (int, error) {
 	if len(frame) < 256 {
 		return 0, io.ErrShortBuffer
 	}
@@ -63,38 +71,44 @@ func (is *StackBasic) Handle(frame []byte) (int, error) {
 	const ihl = 5
 	const headerlen = ihl * 4
 	ifrm.SetVersionAndIHL(4, 5)
-	*ifrm.SourceAddr() = is.ip
+	*ifrm.SourceAddr() = sb.ip
 	ifrm.SetToS(0)
-	for i := range is.handlers {
-		h := &is.handlers[i]
-		proto := lneto.IPProto(h.proto)
-		ifrm.SetProtocol(proto)
-		if len(h.raddr) == 4 {
-			copy(ifrm.DestinationAddr()[:], h.raddr)
-		} else {
-			copy(ifrm.DestinationAddr()[:], "\x00\x00\x00\x00")
-		}
-
+	ifrm.SetID(0)
+	for i := range sb.handlers {
+		h := &sb.handlers[i]
 		n, err := h.handle(frame[:], headerlen)
 		if err != nil {
-			is.error("IPv4Stack:handle", slog.String("proto", proto.String()), slog.String("err", err.Error()))
+			sb.error("IPv4Stack:handle", slog.String("proto", h.proto.String()), slog.String("err", err.Error()))
 			continue
 		}
 		if n > 0 {
 			const dontFrag = 0x4000
 			totalLen := n + headerlen
 			ifrm.SetTotalLength(uint16(totalLen))
-			ifrm.SetID(0)
 			ifrm.SetFlags(dontFrag)
 			ifrm.SetTTL(64)
 			ifrm.SetCRC(ifrm.CalculateHeaderCRC())
 			if ifrm.Protocol() == lneto.IPProtoTCP {
 				tfrm, _ := tcp.NewFrame(ifrm.Payload())
-				is.info("IPv4Stack:send", slog.String("ip", ifrm.String()), slog.String("tcp", tfrm.String()))
+				sb.info("IPv4Stack:send", slog.String("ip", ifrm.String()), slog.String("tcp", tfrm.String()))
 			}
 			return totalLen, nil
 		}
 	}
+	return 0, nil
+}
+
+func (sb *StackBasic) RegisterTCPConn(conn *TCPConn) error {
+	if conn.LocalPort() == 0 {
+		return errors.New("undefined local port")
+	}
+	sb.handlers = append(sb.handlers, handler{
+		recv:   conn.RecvIP,
+		handle: conn.HandleIP,
+		proto:  lneto.IPProtoIPv4,
+		port:   conn.LocalPort(),
+	})
+	return nil
 }
 
 type logger struct {
@@ -113,3 +127,6 @@ func (l logger) warn(msg string, attrs ...slog.Attr) {
 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...)
+}

internet/tcpconn.go

@@ -0,0 +1,158 @@
+package internet
+
+import (
+	"bytes"
+	"errors"
+	"log/slog"
+	"net/netip"
+	"time"
+
+	"github.com/soypat/lneto/ipv4"
+	"github.com/soypat/lneto/ipv6"
+	"github.com/soypat/lneto/tcp"
+)
+
+type TCPConn struct {
+	h          tcp.Handler
+	remoteAddr []byte
+	logger
+
+	rdead  time.Time
+	wdead  time.Time
+	lastTx time.Time
+	lastRx time.Time
+}
+type TCPConnConfig struct {
+	RxBuf             []byte
+	TxBuf             []byte
+	TxPacketQueueSize int
+	Logger            *slog.Logger
+}
+
+func (conn *TCPConn) Configure(config *TCPConnConfig) (err error) {
+	err = conn.h.SetBuffers(config.TxBuf, config.RxBuf, config.TxPacketQueueSize)
+	if err != nil {
+		return err
+	}
+	conn.logger.log = config.Logger
+	return nil
+}
+
+// LocalPort returns the local port on which the socket is listening or connected to.
+func (conn *TCPConn) LocalPort() uint16 { return conn.h.LocalPort() }
+
+// RemotePort returns the port of the incoming remote connection. Is non-zero if connection is established.
+func (conn *TCPConn) RemotePort() uint16 { return conn.h.RemotePort() }
+
+// State returns the TCP state of the socket.
+func (conn *TCPConn) State() tcp.State { return conn.h.State() }
+
+// BufferedInput returns the number of bytes in the socket's receive/input buffer.
+func (conn *TCPConn) BufferedInput() int { return conn.h.BufferedInput() }
+
+// OpenActive opens a connection to a remote peer with a known IP address and port combination.
+// iss is the initial send sequence number which is ideally a random number which is far away from the last sequence number used on a connection to the same host.
+func (conn *TCPConn) OpenActive(remote netip.AddrPort, localPort uint16, iss tcp.Value) error {
+	err := conn.h.OpenActive(localPort, remote.Port(), iss)
+	if err != nil {
+		return err
+	}
+	conn.reset(conn.h)
+	raddr := remote.Addr()
+	if raddr.Is4() {
+		addr4 := raddr.As4()
+		conn.remoteAddr = append(conn.remoteAddr[:0], addr4[:]...)
+	} else if raddr.Is6() {
+		addr6 := raddr.As16()
+		conn.remoteAddr = append(conn.remoteAddr[:0], addr6[:]...)
+	}
+	return nil
+}
+
+// OpenListen opens a passive connection which listens for the first SYN packet to be received on a local port.
+// iss is the initial send sequence number which is usually a randomly chosen number.
+func (conn *TCPConn) OpenListen(localPort uint16, iss tcp.Value) error {
+	err := conn.h.OpenListen(localPort, iss)
+	if err != nil {
+		return err
+	}
+	conn.reset(conn.h)
+	return nil
+}
+
+func (conn *TCPConn) RecvIP(buf []byte, off int) (err error) {
+	conn.trace("tcpconn.Recv:start")
+	if off >= len(buf) {
+		return errors.New("bad offset in TCPConn.Recv")
+	}
+	raddr, err := getIPAddr(buf[:off])
+	if err != nil {
+		return err
+	}
+	if conn.isRaddrSet() && !bytes.Equal(conn.remoteAddr, raddr) {
+		return errors.New("IP addr mismatch on TCPConn")
+	}
+	err = conn.h.Recv(buf[off:])
+	if err != nil {
+		return err
+	}
+	if !conn.isRaddrSet() && conn.h.RemotePort() != 0 {
+		conn.remoteAddr = append(conn.remoteAddr[:0], raddr...)
+	}
+	return nil
+}
+
+func (conn *TCPConn) HandleIP(buf []byte, off int) (n int, err error) {
+	if len(conn.remoteAddr) == 0 {
+		return 0, errors.New("unset IP address")
+	}
+	raddr, err := getIPAddr(buf[:off])
+	if err != nil {
+		return 0, err
+	} else if len(raddr) != len(conn.remoteAddr) {
+		return 0, errors.New("mismatched IP version")
+	}
+	n, err = conn.h.Send(buf[off:])
+	if err != nil {
+		return 0, err
+	}
+	copy(raddr, conn.remoteAddr)
+	return n, nil
+}
+
+func (conn *TCPConn) Send(response []byte) (n int, err error) {
+	conn.trace("tcpconn.Send:start")
+	return conn.h.Send(response)
+}
+
+func getIPAddr(buf []byte) (addr []byte, err error) {
+	switch buf[0] >> 4 {
+	case 4:
+		ifrm4, err := ipv4.NewFrame(buf)
+		if err != nil {
+			return addr, err
+		}
+		addr = ifrm4.SourceAddr()[:]
+	case 6:
+		ifrm6, err := ipv6.NewFrame(buf)
+		if err != nil {
+			return addr, err
+		}
+		addr = ifrm6.SourceAddr()[:]
+	default:
+		err = errors.New("unsupported IP version")
+	}
+	return addr, err
+}
+
+func (conn *TCPConn) isRaddrSet() bool {
+	return len(conn.remoteAddr) != 0
+}
+
+func (conn *TCPConn) reset(h tcp.Handler) {
+	*conn = TCPConn{
+		h:          h,
+		remoteAddr: conn.remoteAddr[:0],
+		logger:     conn.logger,
+	}
+}

tcp/definitions.go

@@ -16,7 +16,7 @@ var (
 	errDropSegment    = errors.New("drop segment")
 	errWindowTooLarge = errors.New("invalid window size > 2**16")
 
-	errBufferTooSmall        = errors.New("buffer too small")
+	errBufferTooSmall        = errors.New("tcp buffer too small")
 	errNeedClosedTCBToOpen   = errors.New("need closed TCB to call open")
 	errInvalidState          = errors.New("invalid state")
 	errConnNotExist          = errors.New("connection does not exist")

tcp/handler.go

@@ -73,12 +73,14 @@ func (h *Handler) OpenActive(localPort, remotePort uint16, iss Value) error {
 	}
 	if h.scb.State() != StateClosed {
 		return errNeedClosedTCBToOpen
+	} else if remotePort == 0 {
+		return errors.New("zero port on open call")
 	}
 	h.reset(localPort, remotePort, iss)
 	return nil
 }
 
-// OpenListen prepares a passive connection. Set remote port to non-zero to
+// OpenListen prepares a passive connection.
 func (h *Handler) OpenListen(localPort uint16, iss Value) error {
 	if h.bufRx.Size() < minBufferSize || h.bufTx.Size() < minBufferSize {
 		return errBufferTooSmall
@@ -230,7 +232,8 @@ func (h *Handler) Read(b []byte) (int, error) {
 	return h.bufRx.Read(b)
 }
 
-func (h *Handler) Buffered() int {
+// BufferedInput returns amount of bytes buffered in receive buffer.
+func (h *Handler) BufferedInput() int {
 	if h.State().IsClosed() {
 		return 0
 	}

tcp/handler_test.go

@@ -33,8 +33,8 @@ func sendDataFull(t *testing.T, client, server *Handler, data, packetBuf []byte)
 	err = server.Recv(packetBuf[:n])
 	if err != nil {
 		t.Fatal("server receiving:", err)
-	} else if server.Buffered() != len(data) {
-		t.Fatal("server did not receive full data packet", server.Buffered(), len(data))
+	} else if server.BufferedInput() != len(data) {
+		t.Fatal("server did not receive full data packet", server.BufferedInput(), len(data))
 	}
 	clear(packetBuf)
 	n, err = server.Read(packetBuf)