diff --git a/channeldb/db.go b/channeldb/db.go index 00b29f65f..6064975a3 100644 --- a/channeldb/db.go +++ b/channeldb/db.go @@ -1363,11 +1363,7 @@ func (c *ChannelStateDB) FetchClosedChannelForID(cid lnwire.ChannelID) ( // the pending funds in a channel that has been forcibly closed have been // swept. func (c *ChannelStateDB) MarkChanFullyClosed(chanPoint *wire.OutPoint) error { - var ( - openChannels []*OpenChannel - pruneLinkNode *btcec.PublicKey - ) - err := kvdb.Update(c.backend, func(tx kvdb.RwTx) error { + return kvdb.Update(c.backend, func(tx kvdb.RwTx) error { var b bytes.Buffer if err := graphdb.WriteOutpoint(&b, chanPoint); err != nil { return err @@ -1413,44 +1409,72 @@ func (c *ChannelStateDB) MarkChanFullyClosed(chanPoint *wire.OutPoint) error { // other open channels with this peer. If we don't we'll // garbage collect it to ensure we don't establish persistent // connections to peers without open channels. - pruneLinkNode = chanSummary.RemotePub - openChannels, err = c.fetchOpenChannels( - tx, pruneLinkNode, - ) + remotePub := chanSummary.RemotePub + openChannels, err := c.fetchOpenChannels(tx, remotePub) if err != nil { return fmt.Errorf("unable to fetch open channels for "+ "peer %x: %v", - pruneLinkNode.SerializeCompressed(), err) + remotePub.SerializeCompressed(), err) + } + + if len(openChannels) > 0 { + return nil + } + + // If there are no open channels with this peer, prune the + // link node. We do this within the same transaction to avoid + // a race condition where a new channel could be opened + // between this check and the deletion. + log.Infof("Pruning link node %x with zero open "+ + "channels from database", + remotePub.SerializeCompressed()) + + err = deleteLinkNode(tx, remotePub) + if err != nil { + return fmt.Errorf("unable to delete link "+ + "node: %w", err) } return nil - }, func() { - openChannels = nil - pruneLinkNode = nil - }) - if err != nil { - return err - } - - // Decide whether we want to remove the link node, based upon the number - // of still open channels. - return c.pruneLinkNode(openChannels, pruneLinkNode) + }, func() {}) } // pruneLinkNode determines whether we should garbage collect a link node from -// the database due to no longer having any open channels with it. If there are -// any left, then this acts as a no-op. -func (c *ChannelStateDB) pruneLinkNode(openChannels []*OpenChannel, - remotePub *btcec.PublicKey) error { +// the database due to no longer having any open channels with it. +// +// NOTE: This function should be called after an initial check shows no open +// channels exist. It will double-check within a write transaction to avoid a +// race condition where a channel could be opened between the initial check +// and the deletion. +func (c *ChannelStateDB) pruneLinkNode(remotePub *btcec.PublicKey) error { + return kvdb.Update(c.backend, func(tx kvdb.RwTx) error { + // Double-check for open channels to avoid deleting a link node + // if a channel was opened since the caller's initial check. + // + // NOTE: This avoids a race condition where a channel could be + // opened between the initial check and the deletion. + openChannels, err := c.fetchOpenChannels(tx, remotePub) + if err != nil { + return err + } + + // If channels exist now, don't prune. + if len(openChannels) > 0 { + return nil + } + + // No open channels, safe to prune the link node. + log.Infof("Pruning link node %x with zero open channels "+ + "from database", + remotePub.SerializeCompressed()) + + err = deleteLinkNode(tx, remotePub) + if err != nil { + return fmt.Errorf("unable to prune link node: %w", err) + } - if len(openChannels) > 0 { return nil - } - - log.Infof("Pruning link node %x with zero open channels from database", - remotePub.SerializeCompressed()) - - return c.linkNodeDB.DeleteLinkNode(remotePub) + }, func() {}) } // PruneLinkNodes attempts to prune all link nodes found within the database @@ -1479,7 +1503,11 @@ func (c *ChannelStateDB) PruneLinkNodes() error { return err } - err = c.pruneLinkNode(openChannels, linkNode.IdentityPub) + if len(openChannels) > 0 { + continue + } + + err = c.pruneLinkNode(linkNode.IdentityPub) if err != nil { return err }