fix: allow BYE for early dialogs

Author: emiago

dialog_client.go

@@ -434,9 +434,10 @@ func (s *DialogClientSession) WriteBye(ctx context.Context, bye *sip.Request) er
 		return nil
 	}
 
-	// In case dialog was not updated
-	if sip.DialogState(state) != sip.DialogStateConfirmed {
-		return fmt.Errorf("Dialog not confirmed. ACK not send?")
+	// 	The caller's UA MAY send a BYE for either
+	//    confirmed or early dialog
+	if sip.DialogState(state) != sip.DialogStateConfirmed && !s.isEarlyDialog() {
+		return fmt.Errorf("Dialog not confirmed or did not receive yet any response")
 	}
 
 	tx, err := s.TransactionRequest(ctx, bye)
@@ -461,6 +462,10 @@ func (s *DialogClientSession) WriteBye(ctx context.Context, bye *sip.Request) er
 	}
 }
 
+func (s *DialogClientSession) isEarlyDialog() bool {
+	return s.InviteResponse != nil && s.InviteResponse.IsProvisional()
+}
+
 // newAckRequestUAC creates ACK request for 2xx INVITE
 // https://tools.ietf.org/html/rfc3261#section-13.2.2.4
 // NOTE: it does not copy Via header. This is left to transport or caller to enforce

dialog_server.go

@@ -374,6 +374,10 @@ func (s *DialogServerSession) WriteBye(ctx context.Context, bye *sip.Request) er
 		return nil
 	}
 
+	// https://datatracker.ietf.org/doc/html/rfc3261#section-15
+	// However, the callee's UA MUST NOT send a BYE on a confirmed dialog
+	// until it has received an ACK for its 2xx response or until the server
+	// transaction times out.
 	if sip.DialogState(state) != sip.DialogStateConfirmed {
 		return nil
 	}
@@ -386,11 +390,6 @@ func (s *DialogServerSession) WriteBye(ctx context.Context, bye *sip.Request) er
 
 	// This is tricky
 	defer s.inviteTx.Terminate() // Terminates INVITE in all cases
-
-	// https://datatracker.ietf.org/doc/html/rfc3261#section-15
-	// However, the callee's UA MUST NOT send a BYE on a confirmed dialog
-	// until it has received an ACK for its 2xx response or until the server
-	// transaction times out.
 	for {
 		state = s.state.Load()
 		if sip.DialogState(state) < sip.DialogStateConfirmed {