multi: add base lookup option to AddLocalAlias

diff --git a/aliasmgr/aliasmgr.go b/aliasmgr/aliasmgr.go
index 258d205..a8cd248 100644
--- a/aliasmgr/aliasmgr.go
+++ b/aliasmgr/aliasmgr.go
@@ -239,14 +239,43 @@ func (m *Manager) populateMaps() error {
 	return nil
 }
 
+// addAliasCfg is a struct that hosts various options related to adding a local
+// alias to the alias manager.
+type addAliasCfg struct {
+	// baseLookup signals that the alias should also store a reverse look-up
+	// to the base scid.
+	baseLookup bool
+}
+
+// AddLocalAliasOption is a functional option that modifies the configuration
+// for adding a local alias.
+type AddLocalAliasOption func(cfg *addAliasCfg)
+
+// WithBaseLookup is a functional option that controls whether a reverse lookup
+// will be stored from the alias to the base scid.
+func WithBaseLookup() AddLocalAliasOption {
+	return func(cfg *addAliasCfg) {
+		cfg.baseLookup = true
+	}
+}
+
 // AddLocalAlias adds a database mapping from the passed alias to the passed
 // base SCID. The gossip boolean marks whether or not to create a mapping
 // that the gossiper will use. It is set to false for the upgrade path where
 // the feature-bit is toggled on and there are existing channels. The linkUpdate
-// flag is used to signal whether this function should also trigger an update
-// on the htlcswitch scid alias maps.
+// flag is used to signal whether this function should also trigger an update on
+// the htlcswitch scid alias maps.
+//
+// NOTE: The following aliases will not be persisted (will be lost on restart):
+//   - Aliases that were created without gossip flag.
+//   - Aliases that correspond to confirmed channels.
 func (m *Manager) AddLocalAlias(alias, baseScid lnwire.ShortChannelID,
-	gossip, linkUpdate bool) error {
+	gossip, linkUpdate bool, opts ...AddLocalAliasOption) error {
+
+	cfg := addAliasCfg{}
+	for _, opt := range opts {
+		opt(&cfg)
+	}
 
 	// We need to lock the manager for the whole duration of this method,
 	// except for the very last part where we call the link updater. In
@@ -302,8 +331,9 @@ func (m *Manager) AddLocalAlias(alias, baseScid lnwire.ShortChannelID,
 	// Update the aliasToBase and baseToSet maps.
 	m.baseToSet[baseScid] = append(m.baseToSet[baseScid], alias)
 
-	// Only store the gossiper map if gossip is true.
-	if gossip {
+	// Only store the gossiper map if gossip is true, or if the caller
+	// explicitly asked to store this reverse mapping.
+	if gossip || cfg.baseLookup {
 		m.aliasToBase[alias] = baseScid
 	}
 
@@ -342,7 +372,9 @@ func (m *Manager) GetAliases(
 }
 
 // FindBaseSCID finds the base SCID for a given alias. This is used in the
-// gossiper to find the correct SCID to lookup in the graph database.
+// gossiper to find the correct SCID to lookup in the graph database. It can
+// also be used to look up the base for manual aliases that were added over the
+// RPC.
 func (m *Manager) FindBaseSCID(
 	alias lnwire.ShortChannelID) (lnwire.ShortChannelID, error) {
 
@@ -446,7 +478,7 @@ func (m *Manager) DeleteLocalAlias(alias,
 	}
 
 	// Finally, we'll delete the aliasToBase mapping from the Manager's
-	// cache (but this is only set if we gossip the alias).
+	// cache.
 	delete(m.aliasToBase, alias)
 
 	// We definitely need to unlock the Manager before calling the link
diff --git a/aliasmgr/aliasmgr_test.go b/aliasmgr/aliasmgr_test.go
index b288ade..3237e5b 100644
--- a/aliasmgr/aliasmgr_test.go
+++ b/aliasmgr/aliasmgr_test.go
@@ -179,10 +179,19 @@ func TestAliasLifecycle(t *testing.T) {
 	require.Equal(t, StartingAlias, firstRequested)
 
 	// We now manually add the next alias from the range as a custom alias.
+	// This time we also use the base lookup option, in order to be able to
+	// go from alias back to the base scid.
 	secondAlias := getNextScid(firstRequested)
-	err = aliasStore.AddLocalAlias(secondAlias, baseScid, false, true)
+	err = aliasStore.AddLocalAlias(
+		secondAlias, baseScid, false, true, WithBaseLookup(),
+	)
+	require.NoError(t, err)
+
+	baseLookup, err := aliasStore.FindBaseSCID(secondAlias)
 	require.NoError(t, err)
 
+	require.Equal(t, baseScid, baseLookup)
+
 	// When we now request another alias from the allocation list, we expect
 	// the third one (tx position 2) to be returned.
 	thirdRequested, err := aliasStore.RequestAlias()
diff --git a/funding/interfaces.go b/funding/interfaces.go
index 30cae08..669f01a 100644
--- a/funding/interfaces.go
+++ b/funding/interfaces.go
@@ -1,6 +1,7 @@
 package funding
 
 import (
+	"github.com/lightningnetwork/lnd/aliasmgr"
 	"github.com/lightningnetwork/lnd/lnpeer"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
@@ -36,8 +37,8 @@ type aliasHandler interface {
 	GetPeerAlias(lnwire.ChannelID) (lnwire.ShortChannelID, error)
 
 	// AddLocalAlias persists an alias to an underlying alias store.
-	AddLocalAlias(lnwire.ShortChannelID, lnwire.ShortChannelID, bool,
-		bool) error
+	AddLocalAlias(lnwire.ShortChannelID, lnwire.ShortChannelID, bool, bool,
+		...aliasmgr.AddLocalAliasOption) error
 
 	// GetAliases returns the set of aliases given the main SCID of a
 	// channel. This SCID will be an alias for zero-conf channels and will
diff --git a/funding/manager_test.go b/funding/manager_test.go
index 5f217d4..57d9299 100644
--- a/funding/manager_test.go
+++ b/funding/manager_test.go
@@ -21,6 +21,7 @@ import (
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcwallet/wallet"
+	"github.com/lightningnetwork/lnd/aliasmgr"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/chainreg"
 	acpt "github.com/lightningnetwork/lnd/chanacceptor"
@@ -162,7 +163,8 @@ func (m *mockAliasMgr) GetPeerAlias(lnwire.ChannelID) (lnwire.ShortChannelID,
 }
 
 func (m *mockAliasMgr) AddLocalAlias(lnwire.ShortChannelID,
-	lnwire.ShortChannelID, bool, bool) error {
+	lnwire.ShortChannelID, bool, bool,
+	...aliasmgr.AddLocalAliasOption) error {
 
 	return nil
 }
diff --git a/lnrpc/routerrpc/router_server.go b/lnrpc/routerrpc/router_server.go
index 894edf2..a1b0eba 100644
--- a/lnrpc/routerrpc/router_server.go
+++ b/lnrpc/routerrpc/router_server.go
@@ -1713,8 +1713,13 @@ func (s *Server) XAddLocalChanAliases(_ context.Context,
 					rpcAlias)
 			}
 
+			// We set the baseLookup flag as we want the alias
+			// manager to keep a mapping from the alias back to its
+			// base scid, in order to be able to provide it via the
+			// FindBaseLocalChanAlias RPC.
 			err = s.cfg.AliasMgr.AddLocalAlias(
 				aliasScid, baseScid, false, true,
+				aliasmgr.WithBaseLookup(),
 			)
 			if err != nil {
 				return nil, fmt.Errorf("error adding scid "+
diff --git a/peer/brontide.go b/peer/brontide.go
index ad3ffdc..d1f9ef1 100644
--- a/peer/brontide.go
+++ b/peer/brontide.go
@@ -19,6 +19,7 @@ import (
 	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btclog/v2"
+	"github.com/lightningnetwork/lnd/aliasmgr"
 	"github.com/lightningnetwork/lnd/brontide"
 	"github.com/lightningnetwork/lnd/buffer"
 	"github.com/lightningnetwork/lnd/chainntnfs"
@@ -404,8 +405,8 @@ type Config struct {
 	RequestAlias func() (lnwire.ShortChannelID, error)
 
 	// AddLocalAlias persists an alias to an underlying alias store.
-	AddLocalAlias func(alias, base lnwire.ShortChannelID,
-		gossip, liveUpdate bool) error
+	AddLocalAlias func(alias, base lnwire.ShortChannelID, gossip,
+		liveUpdate bool, opts ...aliasmgr.AddLocalAliasOption) error
 
 	// AuxLeafStore is an optional store that can be used to store auxiliary
 	// leaves for certain custom channel types.