diff options
Diffstat (limited to 'dex/downloader/downloader.go')
| -rw-r--r-- | dex/downloader/downloader.go | 178 |
1 files changed, 135 insertions, 43 deletions
diff --git a/dex/downloader/downloader.go b/dex/downloader/downloader.go index e3960ea30..9d609584b 100644 --- a/dex/downloader/downloader.go +++ b/dex/downloader/downloader.go @@ -103,6 +103,7 @@ type Downloader struct { mode SyncMode // Synchronisation mode defining the strategy used (per sync cycle) mux *event.TypeMux // Event multiplexer to announce sync operation events + genesis uint64 // Genesis block number to limit sync to (e.g. light client CHT) queue *queue // Scheduler for selecting the hashes to download peers *peerSet // Set of active peers from which download can proceed stateDB ethdb.Database @@ -192,6 +193,9 @@ type BlockChain interface { // HasBlock verifies a block's presence in the local chain. HasBlock(common.Hash, uint64) bool + // HasFastBlock verifies a fast block's presence in the local chain. + HasFastBlock(common.Hash, uint64) bool + // GetBlockByHash retrieves a block from the local chain. GetBlockByHash(common.Hash) *types.Block @@ -442,7 +446,7 @@ func (d *Downloader) syncWithPeer(p *peerConnection, hash common.Hash, number ui } height := latest.Number.Uint64() - origin, err := d.findAncestor(p, height) + origin, err := d.findAncestor(p, latest) if err != nil { return err } @@ -691,41 +695,107 @@ func (d *Downloader) fetchGovState(p *peerConnection, } } -// findAncestor tries to locate the common ancestor link of the local chain and -// a remote peers blockchain. In the general case when our node was in sync and -// on the correct chain, checking the top N links should already get us a match. -// In the rare scenario when we ended up on a long reorganisation (i.e. none of -// the head links match), we do a binary search to find the common ancestor. -func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, error) { - // Figure out the valid ancestor range to prevent rewrite attacks - floor, ceil := int64(-1), d.lightchain.CurrentHeader().Number.Uint64() - - if d.mode == FullSync { - ceil = d.blockchain.CurrentBlock().NumberU64() - } else if d.mode == FastSync { - ceil = d.blockchain.CurrentFastBlock().NumberU64() +// calculateRequestSpan calculates what headers to request from a peer when trying to determine the +// common ancestor. +// It returns parameters to be used for peer.RequestHeadersByNumber: +// from - starting block number +// count - number of headers to request +// skip - number of headers to skip +// and also returns 'max', the last block which is expected to be returned by the remote peers, +// given the (from,count,skip) +func calculateRequestSpan(remoteHeight, localHeight uint64) (int64, int, int, uint64) { + var ( + from int + count int + MaxCount = MaxHeaderFetch / 16 + ) + // requestHead is the highest block that we will ask for. If requestHead is not offset, + // the highest block that we will get is 16 blocks back from head, which means we + // will fetch 14 or 15 blocks unnecessarily in the case the height difference + // between us and the peer is 1-2 blocks, which is most common + requestHead := int(remoteHeight) - 1 + if requestHead < 0 { + requestHead = 0 + } + // requestBottom is the lowest block we want included in the query + // Ideally, we want to include just below own head + requestBottom := int(localHeight - 1) + if requestBottom < 0 { + requestBottom = 0 } - if ceil >= MaxForkAncestry { - floor = int64(ceil - MaxForkAncestry) + totalSpan := requestHead - requestBottom + span := 1 + totalSpan/MaxCount + if span < 2 { + span = 2 + } + if span > 16 { + span = 16 } - p.log.Debug("Looking for common ancestor", "local", ceil, "remote", height) - // Request the topmost blocks to short circuit binary ancestor lookup - head := ceil - if head > height { - head = height + count = 1 + totalSpan/span + if count > MaxCount { + count = MaxCount + } + if count < 2 { + count = 2 } - from := int64(head) - int64(MaxHeaderFetch) + from = requestHead - (count-1)*span if from < 0 { from = 0 } - // Span out with 15 block gaps into the future to catch bad head reports - limit := 2 * MaxHeaderFetch / 16 - count := 1 + int((int64(ceil)-from)/16) - if count > limit { - count = limit + max := from + (count-1)*span + return int64(from), count, span - 1, uint64(max) +} + +// findAncestor tries to locate the common ancestor link of the local chain and +// a remote peers blockchain. In the general case when our node was in sync and +// on the correct chain, checking the top N links should already get us a match. +// In the rare scenario when we ended up on a long reorganisation (i.e. none of +// the head links match), we do a binary search to find the common ancestor. +func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header) (uint64, error) { + // Figure out the valid ancestor range to prevent rewrite attacks + var ( + floor = int64(-1) + localHeight uint64 + remoteHeight = remoteHeader.Number.Uint64() + ) + switch d.mode { + case FullSync: + localHeight = d.blockchain.CurrentBlock().NumberU64() + case FastSync: + localHeight = d.blockchain.CurrentFastBlock().NumberU64() + default: + localHeight = d.lightchain.CurrentHeader().Number.Uint64() + } + p.log.Debug("Looking for common ancestor", "local", localHeight, "remote", remoteHeight) + if localHeight >= MaxForkAncestry { + // We're above the max reorg threshold, find the earliest fork point + floor = int64(localHeight - MaxForkAncestry) + + // If we're doing a light sync, ensure the floor doesn't go below the CHT, as + // all headers before that point will be missing. + if d.mode == LightSync { + // If we dont know the current CHT position, find it + if d.genesis == 0 { + header := d.lightchain.CurrentHeader() + for header != nil { + d.genesis = header.Number.Uint64() + if floor >= int64(d.genesis)-1 { + break + } + header = d.lightchain.GetHeaderByHash(header.ParentHash) + } + } + // We already know the "genesis" block number, cap floor to that + if floor < int64(d.genesis)-1 { + floor = int64(d.genesis) - 1 + } + } } - go p.peer.RequestHeadersByNumber(uint64(from), count, 15, false, false) + from, count, skip, max := calculateRequestSpan(remoteHeight, localHeight) + + p.log.Trace("Span searching for common ancestor", "count", count, "from", from, "skip", skip) + go p.peer.RequestHeadersByNumber(uint64(from), count, skip, false, false) // Wait for the remote response to the head fetch number, hash := uint64(0), common.Hash{} @@ -751,9 +821,10 @@ func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, err return 0, errEmptyHeaderSet } // Make sure the peer's reply conforms to the request - for i := 0; i < len(headers); i++ { - if number := headers[i].Number.Int64(); number != from+int64(i)*16 { - p.log.Warn("Head headers broke chain ordering", "index", i, "requested", from+int64(i)*16, "received", number) + for i, header := range headers { + expectNumber := from + int64(i)*int64((skip+1)) + if number := header.Number.Int64(); number != expectNumber { + p.log.Warn("Head headers broke chain ordering", "index", i, "requested", expectNumber, "received", number) return 0, errInvalidChain } } @@ -761,20 +832,24 @@ func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, err finished = true for i := len(headers) - 1; i >= 0; i-- { // Skip any headers that underflow/overflow our requested set - if headers[i].Number.Int64() < from || headers[i].Number.Uint64() > ceil { + if headers[i].Number.Int64() < from || headers[i].Number.Uint64() > max { continue } // Otherwise check if we already know the header or not h := headers[i].Hash() n := headers[i].Number.Uint64() - if (d.mode == FullSync && d.blockchain.HasBlock(h, n)) || (d.mode != FullSync && d.lightchain.HasHeader(h, n)) { - number, hash = n, h - // If every header is known, even future ones, the peer straight out lied about its head - if number > height && i == limit-1 { - p.log.Warn("Lied about chain head", "reported", height, "found", number) - return 0, errStallingPeer - } + var known bool + switch d.mode { + case FullSync: + known = d.blockchain.HasBlock(h, n) + case FastSync: + known = d.blockchain.HasFastBlock(h, n) + default: + known = d.lightchain.HasHeader(h, n) + } + if known { + number, hash = n, h break } } @@ -798,10 +873,11 @@ func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, err return number, nil } // Ancestor not found, we need to binary search over our chain - start, end := uint64(0), head + start, end := uint64(0), remoteHeight if floor > 0 { start = uint64(floor) } + p.log.Trace("Binary searching for common ancestor", "start", start, "end", end) for start+1 < end { // Split our chain interval in two, and request the hash to cross check check := (start + end) / 2 @@ -834,7 +910,16 @@ func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, err // Modify the search interval based on the response h := headers[0].Hash() n := headers[0].Number.Uint64() - if (d.mode == FullSync && !d.blockchain.HasBlock(h, n)) || (d.mode != FullSync && !d.lightchain.HasHeader(h, n)) { + var known bool + switch d.mode { + case FullSync: + known = d.blockchain.HasBlock(h, n) + case FastSync: + known = d.blockchain.HasFastBlock(h, n) + default: + known = d.lightchain.HasHeader(h, n) + } + if !known { end = check break } @@ -1511,8 +1596,15 @@ func (d *Downloader) importBlockResults(results []*fetchResult) error { blocks[i] = types.NewBlockWithHeader(result.Header).WithBody(result.Transactions, result.Uncles) } if index, err := d.blockchain.InsertDexonChain(blocks); err != nil { - log.Debug("Downloaded item processing failed", "number", results[index].Header.Number, "hash", results[index].Header.Hash(), "err", err) - return errInvalidChain + if index < len(results) { + log.Debug("Downloaded item processing failed", "number", results[index].Header.Number, "hash", results[index].Header.Hash(), "err", err) + } else { + // The InsertChain method in blockchain.go will sometimes return an out-of-bounds index, + // when it needs to preprocess blocks to import a sidechain. + // The importer will put together a new list of blocks to import, which is a superset + // of the blocks delivered from the downloader, and the indexing will be off. + log.Debug("Downloaded item processing failed on sidechain import", "index", index, "err", err) + } } return nil } |