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rewrite ControlBlock.Open to only open passive connections; now use Send for active connections

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soypat
2025-02-13 22:56:27 -03:00
parent 0cb43c47a4
commit bbd74d04d8
6 changed files with 88 additions and 29 deletions
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tcp/control.go
+21 -13
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@@ -138,14 +138,13 @@ type recvSpace struct {
WND Size // receive window defined by local. Permitted number of remote unacked octets in flight.
}
// Open implements a passive/active opening of a connection.
// state must be StateListen or StateSynSent.
func (tcb *ControlBlock) Open(iss Value, wnd Size, state State) (err error) {
// Open implements a passive opening of a connection (wait for incoming packets).
// 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) {
switch {
case tcb._state != StateClosed && tcb._state != StateListen:
err = errTCBNotClosed
case state != StateListen && state != StateSynSent:
err = errInvalidState
case wnd > math.MaxUint16:
err = errWindowTooLarge
}
@@ -153,15 +152,17 @@ func (tcb *ControlBlock) Open(iss Value, wnd Size, state State) (err error) {
tcb.logerr("tcb:open", slog.String("err", err.Error()))
return err
}
tcb._state = state
tcb._state = StateListen
tcb.prepareToHandshake(iss, wnd)
tcb.trace("tcb:open-server")
return nil
}
// prepareToHandshake initializes the TCB send/receive spaces with initial send sequence number and local window.
func (tcb *ControlBlock) prepareToHandshake(iss Value, wnd Size) {
tcb.resetRcv(wnd, 0)
tcb.resetSnd(iss, 1)
tcb.pending = [2]Flags{}
if state == StateSynSent {
tcb.pending[0] = FlagSYN
}
tcb.trace("tcb:open", slog.String("state", tcb._state.String()))
return nil
}
// HasPending returns true if there is a pending control segment to send. Calls to Send will advance the pending queue.
@@ -305,6 +306,12 @@ func (tcb *ControlBlock) Send(seg Segment) error {
hasACK := seg.Flags.HasAny(FlagACK)
var newPending Flags
switch tcb._state {
case StateClosed:
if seg.Flags == FlagSYN {
tcb._state = StateSynSent
tcb.prepareToHandshake(seg.SEQ, seg.WND)
tcb.trace("tcb:open-client")
}
case StateSynRcvd:
if hasFIN {
tcb._state = StateFinWait1 // RFC 9293: 3.10.4 CLOSE call.
@@ -348,14 +355,15 @@ func (tcb *ControlBlock) Send(seg Segment) error {
func (tcb *ControlBlock) validateOutgoingSegment(seg Segment) (err error) {
hasAck := seg.Flags.HasAny(FlagACK)
checkSeq := !seg.Flags.HasAny(FlagRST)
isFirst := tcb._state == StateClosed && seg.isFirstSYN()
checkSeq := !isFirst && !seg.Flags.HasAny(FlagRST)
seglast := seg.Last()
// Extra check for when send Window is zero and no data is being sent.
zeroWindowOK := tcb.snd.WND == 0 && seg.DATALEN == 0 && seg.SEQ == tcb.snd.NXT
outOfWindow := checkSeq && !seg.SEQ.InWindow(tcb.snd.NXT, tcb.snd.WND) &&
!zeroWindowOK
switch {
case tcb._state == StateClosed:
case tcb._state == StateClosed && !isFirst:
err = io.ErrClosedPipe
case seg.WND > math.MaxUint16:
err = errWindowTooLarge