routing: add new error for invalid funding tx rejection

routing/errors.go

@@ -20,6 +20,10 @@ const (
 	// the purported funding output has actually already been spent on
 	// chain.
 	ErrChannelSpent
+
+	// ErrNoFundingTransaction is returned when we are unable to find the
+	// funding transaction described by the short channel ID on chain.
+	ErrNoFundingTransaction
 )
 
 // routerError is a structure that represent the error inside the routing package,

routing/router.go

@@ -1309,8 +1309,9 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 		channelID := lnwire.NewShortChanIDFromInt(msg.ChannelID)
 		fundingTx, err := r.fetchFundingTx(&channelID)
 		if err != nil {
-			return errors.Errorf("unable to fetch funding tx for "+
-				"chan_id=%v: %v", msg.ChannelID, err)
+			return newErrf(ErrNoFundingTransaction, "unable to "+
+				"fetch funding tx for chan_id=%v: %v",
+				msg.ChannelID, err)
 		}
 
 		// Recreate witness output to be sure that declared in channel