From 66e15e8f9759b827732865e5686c0203ce7dc1d4 Mon Sep 17 00:00:00 2001 From: Sjors Provoost Date: Tue, 4 Sep 2018 10:50:19 +0200 Subject: Explain GetAncestor check for m_failed_blocks in AcceptBlockHeader --- src/validation.cpp | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) (limited to 'src/validation.cpp') diff --git a/src/validation.cpp b/src/validation.cpp index fceb135854..af42f6d22b 100644 --- a/src/validation.cpp +++ b/src/validation.cpp @@ -3383,10 +3383,30 @@ bool CChainState::AcceptBlockHeader(const CBlockHeader& block, CValidationState& if (!ContextualCheckBlockHeader(block, state, chainparams, pindexPrev, GetAdjustedTime())) return error("%s: Consensus::ContextualCheckBlockHeader: %s, %s", __func__, hash.ToString(), FormatStateMessage(state)); - // If the previous block index isn't valid, determine if it descends from any block which - // has been found invalid (m_failed_blocks), then mark pindexPrev and any blocks - // between them as failed. + /* Determine if this block descends from any block which has been found + * invalid (m_failed_blocks), then mark pindexPrev and any blocks between + * them as failed. For example: + * + * D3 + * / + * B2 - C2 + * / \ + * A D2 - E2 - F2 + * \ + * B1 - C1 - D1 - E1 + * + * In the case that we attempted to reorg from E1 to F2, only to find + * C2 to be invalid, we would mark D2, E2, and F2 as BLOCK_FAILED_CHILD + * but NOT D3 (it was not in any of our candidate sets at the time). + * + * In any case D3 will also be marked as BLOCK_FAILED_CHILD at restart + * in LoadBlockIndex. + */ if (!pindexPrev->IsValid(BLOCK_VALID_SCRIPTS)) { + // The above does not mean "invalid": it checks if the previous block + // hasn't been validated up to BLOCK_VALID_SCRIPTS. This is a performance + // optimization, in the common case of adding a new block to the tip, + // we don't need to iterate over the failed blocks list. for (const CBlockIndex* failedit : m_failed_blocks) { if (pindexPrev->GetAncestor(failedit->nHeight) == failedit) { assert(failedit->nStatus & BLOCK_FAILED_VALID); -- cgit v1.2.3