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@ -74,10 +74,10 @@ func NewForkChoice(chainReader ChainReader, preserve func(header *types.Header) |
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// In the td mode, the new head is chosen if the corresponding
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// In the td mode, the new head is chosen if the corresponding
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// total difficulty is higher. In the extern mode, the trusted
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// total difficulty is higher. In the extern mode, the trusted
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// header is always selected as the head.
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// header is always selected as the head.
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func (f *ForkChoice) ReorgNeeded(current *types.Header, header *types.Header) (bool, error) { |
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func (f *ForkChoice) ReorgNeeded(current *types.Header, extern *types.Header) (bool, error) { |
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var ( |
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var ( |
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localTD = f.chain.GetTd(current.Hash(), current.Number.Uint64()) |
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localTD = f.chain.GetTd(current.Hash(), current.Number.Uint64()) |
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externTd = f.chain.GetTd(header.Hash(), header.Number.Uint64()) |
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externTd = f.chain.GetTd(extern.Hash(), extern.Number.Uint64()) |
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) |
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) |
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if localTD == nil || externTd == nil { |
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if localTD == nil || externTd == nil { |
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return false, errors.New("missing td") |
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return false, errors.New("missing td") |
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@ -88,21 +88,26 @@ func (f *ForkChoice) ReorgNeeded(current *types.Header, header *types.Header) (b |
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if ttd := f.chain.Config().TerminalTotalDifficulty; ttd != nil && ttd.Cmp(externTd) <= 0 { |
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if ttd := f.chain.Config().TerminalTotalDifficulty; ttd != nil && ttd.Cmp(externTd) <= 0 { |
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return true, nil |
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return true, nil |
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} |
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} |
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// If the total difficulty is higher than our known, add it to the canonical chain
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// If the total difficulty is higher than our known, add it to the canonical chain
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if diff := externTd.Cmp(localTD); diff > 0 { |
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return true, nil |
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} else if diff < 0 { |
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return false, nil |
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} |
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// Local and external difficulty is identical.
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// Second clause in the if statement reduces the vulnerability to selfish mining.
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// Second clause in the if statement reduces the vulnerability to selfish mining.
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// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
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// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
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reorg := externTd.Cmp(localTD) > 0 |
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reorg := false |
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if !reorg && externTd.Cmp(localTD) == 0 { |
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externNum, localNum := extern.Number.Uint64(), current.Number.Uint64() |
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number, headNumber := header.Number.Uint64(), current.Number.Uint64() |
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if externNum < localNum { |
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if number < headNumber { |
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reorg = true |
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reorg = true |
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} else if externNum == localNum { |
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} else if number == headNumber { |
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var currentPreserve, externPreserve bool |
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var currentPreserve, externPreserve bool |
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if f.preserve != nil { |
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if f.preserve != nil { |
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currentPreserve, externPreserve = f.preserve(current), f.preserve(extern) |
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currentPreserve, externPreserve = f.preserve(current), f.preserve(header) |
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} |
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reorg = !currentPreserve && (externPreserve || f.rand.Float64() < 0.5) |
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} |
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} |
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reorg = !currentPreserve && (externPreserve || f.rand.Float64() < 0.5) |
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} |
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} |
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return reorg, nil |
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return reorg, nil |
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} |
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} |
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