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eth/downloader: only roll back light sync if not fully validating #21537

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Merged
merged 1 commit into from
Sep 9, 2020
Merged

eth/downloader: only roll back light sync if not fully validating #21537

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16 changes: 9 additions & 7 deletions eth/downloader/downloader.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1501,18 +1501,20 @@ func (d *Downloader) processHeaders(origin uint64, pivot uint64, td *big.Int) er
rollbackErr = err

// If some headers were inserted, track them as uncertain
if n > 0 && rollback == 0 {
if (mode == FastSync || frequency > 1) && n > 0 && rollback == 0 {
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Shouldn't it be frequency==1 ? Why do we add rollbacks only when the header check is every N:th block, but not when it's every block?

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Well, if it checked every block, there's nothing to roll back. We should only roll back if we checked every 24th block for PoW, since we don't know if the previous ones were valid or not

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If we pass the pivot point, the frequency is 1. In this case, we don't need to rollback?

what about this:

if frequency > 1 && n > 0 && rollback == 0 {

rollback = chunk[0].Number.Uint64()
}
log.Debug("Invalid header encountered", "number", chunk[n].Number, "hash", chunk[n].Hash(), "parent", chunk[n].ParentHash, "err", err)
log.Warn("Invalid header encountered", "number", chunk[n].Number, "hash", chunk[n].Hash(), "parent", chunk[n].ParentHash, "err", err)
return fmt.Errorf("%w: %v", errInvalidChain, err)
}
// All verifications passed, track all headers within the alloted limits
head := chunk[len(chunk)-1].Number.Uint64()
if head-rollback > uint64(fsHeaderSafetyNet) {
rollback = head - uint64(fsHeaderSafetyNet)
} else {
rollback = 1
if mode == FastSync {
head := chunk[len(chunk)-1].Number.Uint64()
if head-rollback > uint64(fsHeaderSafetyNet) {
rollback = head - uint64(fsHeaderSafetyNet)
} else {
rollback = 1
}
}
}
// Unless we're doing light chains, schedule the headers for associated content retrieval
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7 changes: 3 additions & 4 deletions eth/downloader/downloader_test.go
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Expand Up @@ -1020,10 +1020,9 @@ func testShiftedHeaderAttack(t *testing.T, protocol int, mode SyncMode) {
// Tests that upon detecting an invalid header, the recent ones are rolled back
// for various failure scenarios. Afterwards a full sync is attempted to make
// sure no state was corrupted.
func TestInvalidHeaderRollback63Fast(t *testing.T) { testInvalidHeaderRollback(t, 63, FastSync) }
func TestInvalidHeaderRollback64Fast(t *testing.T) { testInvalidHeaderRollback(t, 64, FastSync) }
func TestInvalidHeaderRollback65Fast(t *testing.T) { testInvalidHeaderRollback(t, 65, FastSync) }
func TestInvalidHeaderRollback65Light(t *testing.T) { testInvalidHeaderRollback(t, 65, LightSync) }
func TestInvalidHeaderRollback63Fast(t *testing.T) { testInvalidHeaderRollback(t, 63, FastSync) }
func TestInvalidHeaderRollback64Fast(t *testing.T) { testInvalidHeaderRollback(t, 64, FastSync) }
func TestInvalidHeaderRollback65Fast(t *testing.T) { testInvalidHeaderRollback(t, 65, FastSync) }

func testInvalidHeaderRollback(t *testing.T, protocol int, mode SyncMode) {
t.Parallel()
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