From 6b91d8e5100d09d7ebfcca408ca7daecb8cc56ce Mon Sep 17 00:00:00 2001
From: soypat <graded.sp@gmail.com>
Date: Thu, 13 Feb 2025 23:19:19 -0300
Subject: [PATCH] handle clientsynseg

---
 examples/stack/main.go |  2 +-
 tcp/control.go         |  2 +-
 tcp/handler.go         | 23 +++++++++++------------
 3 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/examples/stack/main.go b/examples/stack/main.go
index 6a18b03..c6ce01d 100644
--- a/examples/stack/main.go
+++ b/examples/stack/main.go
@@ -41,7 +41,7 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
-	err = pStack.handler.Open(tcp.StateListen, gen.DstTCP, gen.SrcTCP, iss)
+	err = pStack.handler.Open(gen.DstTCP, iss)
 	if err != nil {
 		log.Fatal(err)
 	}
diff --git a/tcp/control.go b/tcp/control.go
index a4bf173..b86074f 100644
--- a/tcp/control.go
+++ b/tcp/control.go
@@ -138,7 +138,7 @@ type recvSpace struct {
 	WND Size  // receive window defined by local. Permitted number of remote unacked octets in flight.
 }
 
-// Open implements a passive opening of a connection (wait for incoming packets).
+// Open implements a passive opening of a connection (wait for incoming packets from an unknown remote port).
 // Upon success [ControlBlock] enters LISTEN state, such as that of a server.
 // To open an active connection use [ControlBlock.Send] with a segment generated with [ClientSynSegment].
 func (tcb *ControlBlock) Open(iss Value, wnd Size) (err error) {
diff --git a/tcp/handler.go b/tcp/handler.go
index 33b8dcc..6444bbf 100644
--- a/tcp/handler.go
+++ b/tcp/handler.go
@@ -51,7 +51,8 @@ func (h *Handler) LocalPort() uint16 {
 	return h.localPort
 }
 
-func (h *Handler) Open(state State, localPort, remotePort uint16, iss Value) error {
+// Open prepares a passive connection. Set remote port to non-zero to
+func (h *Handler) Open(localPort uint16, iss Value) error {
 	// Open will fail unless SCB in closed state.
 	err := h.scb.Open(iss, Size(h.bufRx.Size()))
 	if err != nil {
@@ -63,7 +64,7 @@ func (h *Handler) Open(state State, localPort, remotePort uint16, iss Value) err
 		bufRx:      h.bufRx,
 		connid:     h.connid + 1,
 		localPort:  localPort,
-		remotePort: remotePort,
+		remotePort: 0,
 		validator:  h.validator,
 		logger:     h.logger,
 		closing:    false,
@@ -139,15 +140,9 @@ func (h *Handler) Send(b []byte) (int, error) {
 		return 0, err
 	}
 	var segment Segment
-	if h.AwaitingSyn() {
+	if h.AwaitingSynSend() {
 		// Handling init syn segment.
-		segment = Segment{
-			SEQ:     h.scb.ISS(),
-			ACK:     0,
-			Flags:   FlagSYN,
-			WND:     h.scb.RecvWindow(),
-			DATALEN: 0,
-		}
+		segment = ClientSynSegment(h.scb.ISS(), h.scb.RecvWindow())
 	} else {
 		var ok bool
 		available := min(h.bufTx.Buffered(), len(b)-sizeHeaderTCP)
@@ -181,11 +176,15 @@ func (h *Handler) Send(b []byte) (int, error) {
 	return sizeHeaderTCP + int(segment.DATALEN), nil
 }
 
-// AwaitingSyn checks if the Handler is waiting for a Syn to arrive.
-func (h *Handler) AwaitingSyn() bool {
+// AwaitingSynResponse checks if the Handler is waiting for a Syn to arrive.
+func (h *Handler) AwaitingSynResponse() bool {
 	return h.remotePort != 0 && h.scb.State() == StateSynSent
 }
 
+func (h *Handler) AwaitingSynSend() bool {
+	return h.remotePort != 0 && h.scb.State() == StateClosed
+}
+
 func (h *Handler) isClosed() bool {
 	return h.closing || h.scb.State().IsClosed()
 }