package beacon import ( "context" "time" "github.com/filecoin-project/lotus/chain/types" "github.com/filecoin-project/specs-actors/actors/abi" logging "github.com/ipfs/go-log" "golang.org/x/xerrors" ) var log = logging.Logger("beacon") type Response struct { Entry types.BeaconEntry Err error } type RandomBeacon interface { Entry(context.Context, uint64) <-chan Response VerifyEntry(types.BeaconEntry, types.BeaconEntry) error MaxBeaconRoundForEpoch(abi.ChainEpoch, types.BeaconEntry) uint64 } func ValidateBlockValues(b RandomBeacon, h *types.BlockHeader, prevEntry types.BeaconEntry) error { maxRound := b.MaxBeaconRoundForEpoch(h.Height, prevEntry) if maxRound == prevEntry.Round { if len(h.BeaconEntries) != 0 { return xerrors.Errorf("expected not to have any beacon entries in this block, got %d", len(h.BeaconEntries)) } return nil } last := h.BeaconEntries[len(h.BeaconEntries)-1] if last.Round != maxRound { return xerrors.Errorf("expected final beacon entry in block to be at round %d, got %d", maxRound, last.Round) } for i, e := range h.BeaconEntries { if err := b.VerifyEntry(e, prevEntry); err != nil { return xerrors.Errorf("beacon entry %d (%d - %x (%d)) was invalid: %w", i, e.Round, e.Data, len(e.Data), err) } prevEntry = e } return nil } func BeaconEntriesForBlock(ctx context.Context, beacon RandomBeacon, round abi.ChainEpoch, prev types.BeaconEntry) ([]types.BeaconEntry, error) { start := time.Now() maxRound := beacon.MaxBeaconRoundForEpoch(round, prev) if maxRound == prev.Round { return nil, nil } // TODO: this is a sketchy way to handle the genesis block not having a beacon entry if prev.Round == 0 { prev.Round = maxRound - 1 } cur := maxRound var out []types.BeaconEntry for cur > prev.Round { rch := beacon.Entry(ctx, cur) select { case resp := <-rch: if resp.Err != nil { return nil, xerrors.Errorf("beacon entry request returned error: %w", resp.Err) } out = append(out, resp.Entry) cur = resp.Entry.Round - 1 case <-ctx.Done(): return nil, xerrors.Errorf("context timed out waiting on beacon entry to come back for round %d: %w", round, ctx.Err()) } } log.Debugw("fetching beacon entries", "took", time.Since(start), "numEntries", len(out)) reverse(out) return out, nil } func reverse(arr []types.BeaconEntry) { for i := 0; i < len(arr)/2; i++ { arr[i], arr[len(arr)-(1+i)] = arr[len(arr)-(1+i)], arr[i] } }