lnwallet/chancloser: add state transitions for new protofsm rbf closer

In this commit, we add the state transitions for the new protofsm based
RBF chan closer. The underlying protocol is a new asymmetric co-op close
process, wherein either side can initiate a chan closer, and use their
settled funds to pay for fees within the channel.

lnwallet/chancloser/chancloser.go

@@ -539,8 +539,8 @@ func (c *ChanCloser) AuxOutputs() fn.Option[AuxCloseOutputs] {
 // upfront script is set, we check whether it matches the script provided by
 // our peer. If they do not match, we use the disconnect function provided to
 // disconnect from the peer.
-func validateShutdownScript(disconnect func() error, upfrontScript,
-	peerScript lnwire.DeliveryAddress, netParams *chaincfg.Params) error {
+func validateShutdownScript(upfrontScript, peerScript lnwire.DeliveryAddress,
+	netParams *chaincfg.Params) error {
 
 	// Either way, we'll make sure that the script passed meets our
 	// standards. The upfrontScript should have already been checked at an
@@ -568,12 +568,6 @@ func validateShutdownScript(disconnect func() error, upfrontScript,
 		chancloserLog.Warnf("peer's script: %x does not match upfront "+
 			"shutdown script: %x", peerScript, upfrontScript)
 
-		// Disconnect from the peer because they have violated option upfront
-		// shutdown.
-		if err := disconnect(); err != nil {
-			return err
-		}
-
 		return ErrUpfrontShutdownScriptMismatch
 	}
 
@@ -630,7 +624,6 @@ func (c *ChanCloser) ReceiveShutdown(msg lnwire.Shutdown) (
 		// If the remote node opened the channel with option upfront
 		// shutdown script, check that the script they provided matches.
 		if err := validateShutdownScript(
-			c.cfg.Disconnect,
 			c.cfg.Channel.RemoteUpfrontShutdownScript(),
 			msg.Address, c.cfg.ChainParams,
 		); err != nil {
@@ -681,7 +674,6 @@ func (c *ChanCloser) ReceiveShutdown(msg lnwire.Shutdown) (
 		// If the remote node opened the channel with option upfront
 		// shutdown script, check that the script they provided matches.
 		if err := validateShutdownScript(
-			c.cfg.Disconnect,
 			c.cfg.Channel.RemoteUpfrontShutdownScript(),
 			msg.Address, c.cfg.ChainParams,
 		); err != nil {

lnwallet/chancloser/chancloser_test.go

@@ -129,8 +129,8 @@ func TestMaybeMatchScript(t *testing.T) {
 			t.Parallel()
 
 			err := validateShutdownScript(
-				func() error { return nil }, test.upfrontScript,
-				test.shutdownScript, &chaincfg.SimNetParams,
+				test.upfrontScript, test.shutdownScript,
+				&chaincfg.SimNetParams,
 			)
 
 			if err != test.expectedErr {

lnwallet/chancloser/rbf_coop_states.go

@@ -250,6 +250,11 @@ type ChanStateObserver interface {
 	// new outgoing add messages.
 	DisableOutgoingAdds() error
 
+	// DisableChannel attempts to disable a channel (marking it ineligible
+	// to forward), and also sends out a network update to disable the
+	// channel.
+	DisableChannel() error
+
 	// MarkCoopBroadcasted persistently marks that the channel close
 	// transaction has been broadcast.
 	MarkCoopBroadcasted(*wire.MsgTx, bool) error