routing: add chans rejected due to failed chain validation to zombie index

In this commit, we start to add any channels that fail the normal chain
validation to the zombie index. With this change, we'll ensure that we
won't continue to re-process the same set of spent channels over and
over again.

Fixes #5191.

routing/router.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"runtime"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -23,6 +24,7 @@ import (
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwallet"
+	"github.com/lightningnetwork/lnd/lnwallet/btcwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chanvalidate"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/multimutex"
@@ -1309,6 +1311,37 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 		channelID := lnwire.NewShortChanIDFromInt(msg.ChannelID)
 		fundingTx, err := r.fetchFundingTx(&channelID)
 		if err != nil {
+			// In order to ensure we don't errnosuly mark a channel as
+			// a zmobie due to an RPC failure, we'll attempt to string
+			// match for the relevant errors.
+			//
+			// * btcd:
+			//    * https://github.com/btcsuite/btcd/blob/master/rpcserver.go#L1316
+			//    * https://github.com/btcsuite/btcd/blob/master/rpcserver.go#L1086
+			// * bitcoind:
+			//    * https://github.com/bitcoin/bitcoin/blob/7fcf53f7b4524572d1d0c9a5fdc388e87eb02416/src/rpc/blockchain.cpp#L770
+			//     * https://github.com/bitcoin/bitcoin/blob/7fcf53f7b4524572d1d0c9a5fdc388e87eb02416/src/rpc/blockchain.cpp#L954
+			switch {
+			case strings.Contains(err.Error(), "not found"):
+				fallthrough
+
+			case strings.Contains(err.Error(), "out of range"):
+				// If the funding transaction isn't found at all, then
+				// we'll mark the edge itself as a zombie so we don't
+				// continue to request it. We use the "zero key" for
+				// both node pubkeys so this edge can't be resurrected.
+				var zeroKey [33]byte
+				zErr := r.cfg.Graph.MarkEdgeZombie(
+					msg.ChannelID, zeroKey, zeroKey,
+				)
+				if zErr != nil {
+					return fmt.Errorf("unable to mark spent "+
+						"chan(id=%v) as a zombie: %w", msg.ChannelID,
+						zErr)
+				}
+			default:
+			}
+
 			return newErrf(ErrNoFundingTransaction, "unable to "+
 				"fetch funding tx for chan_id=%v: %v",
 				msg.ChannelID, err)
@@ -1355,6 +1388,22 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 			r.quit,
 		)
 		if err != nil {
+			// If we fail validation of the UTXO here, then we'll
+			// mark the channel as a zombie as otherwise, we may
+			// continue to continue to request it. We use the "zero
+			// key" for both node pubkeys so this edge can't be
+			// resurrected.
+			if errors.Is(err, btcwallet.ErrOutputSpent) {
+				var zeroKey [33]byte
+				zErr := r.cfg.Graph.MarkEdgeZombie(
+					msg.ChannelID, zeroKey, zeroKey,
+				)
+				if zErr != nil {
+					return fmt.Errorf("unable to mark spent "+
+						"chan(id=%v) as a zombie: %w", msg.ChannelID,
+						zErr)
+				}
+			}
 
 			return newErrf(ErrChannelSpent, "unable to fetch utxo "+
 				"for chan_id=%v, chan_point=%v: %v",