add basic stack skelly

internet/basicstack.go

@@ -1,4 +1,115 @@
 package internet
 
+import (
+	"errors"
+	"io"
+	"log/slog"
+
+	"github.com/soypat/lneto"
+	"github.com/soypat/lneto/internal"
+	"github.com/soypat/lneto/ipv4"
+	"github.com/soypat/lneto/tcp"
+)
+
 type StackBasic struct {
+	ip        [4]byte
+	validator lneto.Validator
+	handlers  []handler
+	logger
+}
+
+type handler struct {
+	proto  lneto.IPProto
+	port   uint16
+	recv   func([]byte, int) error
+	handle func([]byte, int) (int, error)
+}
+
+func (is *StackBasic) Recv(frame []byte) error {
+	ifrm, err := ipv4.NewFrame(frame)
+	if err != nil {
+		return err
+	}
+	if *ifrm.DestinationAddr() != is.ip {
+		return errors.New("packet not for us")
+	}
+	is.validator.ResetErr()
+	ifrm.ValidateExceptCRC(&is.validator)
+	if err = is.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)))
+		return errors.New("IPv4 CRC mismatch")
+	}
+	off := ifrm.HeaderLength()
+	totalLen := ifrm.TotalLength()
+	for i := range is.handlers {
+		h := &is.handlers[i]
+		if h.proto == ifrm.Protocol() {
+			return h.recv(frame[:totalLen], off)
+		}
+	}
+	return nil
+}
+
+func (is *StackBasic) Handle(frame []byte) (int, error) {
+	if len(frame) < 256 {
+		return 0, io.ErrShortBuffer
+	}
+	ifrm, _ := ipv4.NewFrame(frame)
+	const ihl = 5
+	const headerlen = ihl * 4
+	ifrm.SetVersionAndIHL(4, 5)
+	*ifrm.SourceAddr() = is.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")
+		}
+
+		n, err := h.handle(frame[:], headerlen)
+		if err != nil {
+			is.error("IPv4Stack:handle", slog.String("proto", 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()))
+			}
+			return totalLen, 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...)
 }