add stringer methods

tcp/definitions.go

@@ -73,6 +73,13 @@ func (seg Segment) isFirstSYN() bool {
 	return seg.Flags == FlagSYN && seg.ACK == 0 && seg.DATALEN == 0 && seg.WND > 0
 }
 
+func (seg Segment) String() string {
+	if seg.DATALEN == 0 {
+		return fmt.Sprintf("SEG %s ACK=%d SEQ=%d WND=%d", seg.Flags, seg.ACK, seg.SEQ, seg.WND)
+	}
+	return fmt.Sprintf("SEG %s ACK=%d SEQ=%d WND=%d DATALEN=%d", seg.Flags, seg.ACK, seg.SEQ, seg.WND, seg.DATALEN)
+}
+
 // ClientSynSegment is a the first packet sent over a TCP connection to a server. Typically the client
 // will call ClientSynSegment to generate a new SYN packet to send over to the server to initiate communications:
 //

tcp/frame.go

@@ -174,8 +174,10 @@ func (frm Frame) ClearHeader() {
 }
 
 func (tfrm Frame) String() string {
+	src := tfrm.SourcePort()
+	dst := tfrm.DestinationPort()
 	seg := tfrm.Segment(len(tfrm.Payload()))
-	return fmt.Sprintf("%+v", seg)
+	return fmt.Sprintf("TCP :%d -> :%d %s", src, dst, seg.String())
 }
 
 //

tcp/handler.go

@@ -11,7 +11,8 @@ import (
 )
 
 var (
-	errMismatchedPort = errors.New("mismatched port")
+	errMismatchedSrcPort = errors.New("source port mismatch")
+	errMismatchedDstPort = errors.New("destination port mismatch")
 )
 
 // Handler is a low level TCP handling data structure. It implements logic
@@ -120,13 +121,14 @@ func (h *Handler) Recv(b []byte) error {
 	if err != nil {
 		return err
 	}
+
 	remotePort := tfrm.SourcePort()
 	if h.remotePort != 0 && remotePort != h.remotePort {
-		return errMismatchedPort
+		return errMismatchedSrcPort
 	}
 	dstPort := tfrm.DestinationPort()
 	if h.localPort != dstPort {
-		return errMismatchedPort
+		return errMismatchedDstPort
 	}
 	payload := tfrm.Payload()
 	if len(payload) > h.bufRx.Free() {
@@ -160,6 +162,9 @@ func (h *Handler) Recv(b []byte) error {
 		h.debug("tcp.Handler:rx-remoteport-set", slog.Uint64("port", uint64(h.localPort)), slog.Uint64("remoteport", uint64(remotePort)))
 		h.remotePort = remotePort
 	}
+	if h.logenabled(internal.LevelTrace) {
+		h.trace("tcp.Handler:rx-done", slog.Uint64("port", uint64(h.localPort)), slog.Uint64("remoteport", uint64(remotePort)), slog.String("seg", segIncoming.String()))
+	}
 	return nil
 }