restructure package, rename module/repo

2026-09-12 01:29:30 +00:00 · 2025-01-07 11:34:35 -03:00
parent 73f0b547b3
commit 9abf0c11b9
30 changed files with 20 additions and 18 deletions
@@ -0,0 +1,107 @@
+package tcp
+
+func (tcb *ControlBlock) rcvListen(seg Segment) (pending Flags, err error) {
+	switch {
+	case !seg.Flags.HasAll(FlagSYN):
+		err = errExpectedSYN
+	}
+	if err != nil {
+		return 0, err
+	}
+	// Initialize all connection state:
+	tcb.resetSnd(tcb.snd.ISS, seg.WND)
+	tcb.resetRcv(tcb.rcv.WND, seg.SEQ)
+
+	// We must respond with SYN|ACK frame after receiving SYN in listen state (three way handshake).
+	tcb.pending[0] = synack
+	tcb.state = StateSynRcvd
+	return synack, nil
+}
+
+func (tcb *ControlBlock) rcvSynSent(seg Segment) (pending Flags, err error) {
+	hasSyn := seg.Flags.HasAny(FlagSYN)
+	hasAck := seg.Flags.HasAny(FlagACK)
+	switch {
+	case !hasSyn:
+		err = errExpectedSYN
+
+	case hasAck && seg.ACK != tcb.snd.UNA+1:
+		err = errBadSegack
+	}
+	if err != nil {
+		return 0, err
+	}
+
+	if hasAck {
+		tcb.state = StateEstablished
+		pending = FlagACK
+		tcb.resetRcv(tcb.rcv.WND, seg.SEQ)
+	} else {
+		// Simultaneous connection sync edge case.
+		pending = synack
+		tcb.state = StateSynRcvd
+		tcb.resetSnd(tcb.snd.ISS, seg.WND)
+		tcb.resetRcv(tcb.rcv.WND, seg.SEQ)
+	}
+	return pending, nil
+}
+
+func (tcb *ControlBlock) rcvSynRcvd(seg Segment) (pending Flags, err error) {
+	switch {
+	// case !seg.Flags.HasAll(FlagACK):
+	// 	err = errors.New("rcvSynRcvd: expected ACK")
+	case seg.ACK != tcb.snd.UNA+1:
+		err = errBadSegack
+	}
+	if err != nil {
+		return 0, err
+	}
+	tcb.state = StateEstablished
+	return 0, nil
+}
+
+func (tcb *ControlBlock) rcvEstablished(seg Segment) (pending Flags, err error) {
+	flags := seg.Flags
+
+	dataToAck := seg.DATALEN > 0
+	hasFin := flags.HasAny(FlagFIN)
+	if dataToAck || hasFin {
+		pending = FlagACK
+		if hasFin {
+			// See Figure 5: TCP Connection State Diagram of RFC 9293.
+			tcb.state = StateCloseWait
+			tcb.pending[1] = FlagFIN // Queue FIN for after the CloseWait ACK.
+		}
+	}
+
+	return pending, nil
+}
+
+func (tcb *ControlBlock) rcvFinWait1(seg Segment) (pending Flags, err error) {
+	flags := seg.Flags
+	hasFin := flags&FlagFIN != 0
+	hasAck := flags&FlagACK != 0
+	switch {
+	case hasFin && hasAck && seg.ACK == tcb.snd.NXT:
+		// Special case: Server sent a FINACK response to our FIN so we enter TimeWait directly.
+		// We have to check ACK against send NXT to avoid simultaneous close sequence edge case.
+		tcb.state = StateTimeWait
+	case hasFin:
+		tcb.state = StateClosing
+	case hasAck:
+		// TODO(soypat): Check if this branch does NOT need ACK queued. Online flowcharts say not needed.
+		tcb.state = StateFinWait2
+	default:
+		return 0, errFinwaitExpectedACK
+	}
+	pending = FlagACK
+	return pending, nil
+}
+
+func (tcb *ControlBlock) rcvFinWait2(seg Segment) (pending Flags, err error) {
+	if !seg.Flags.HasAll(finack) {
+		return pending, errFinwaitExpectedFinack
+	}
+	tcb.state = StateTimeWait
+	return FlagACK, nil
+}