core: bugfix state change race condition in txpool (#3412)

The transaction pool keeps track of the current nonce in its local pendingState. When a
new block comes in the pendingState is reset. During the reset it fetches multiple times
the current state through the use of the currentState callback. When a second block comes
in during the reset its possible that the state changes during the reset. If that block
holds transactions that are currently in the pool the local pendingState that is used to
determine nonces can get out of sync.

1 files changed, 2 insertions, 2 deletions

diff --git a/light/txpool.go b/light/txpool.go
index 309bc3a32..4a06d317d 100644
--- a/light/txpool.go
+++ b/light/txpool.go
@@ -500,7 +500,7 @@ func (tp *TxPool) GetTransaction(hash common.Hash) *types.Transaction {
 
 // GetTransactions returns all currently processable transactions.
 // The returned slice may be modified by the caller.
-func (self *TxPool) GetTransactions() (txs types.Transactions) {
+func (self *TxPool) GetTransactions() (txs types.Transactions, err error) {
 	self.mu.RLock()
 	defer self.mu.RUnlock()
 
@@ -510,7 +510,7 @@ func (self *TxPool) GetTransactions() (txs types.Transactions) {
 		txs[i] = tx
 		i++
 	}
-	return txs
+	return txs, nil
 }
 
 // Content retrieves the data content of the transaction pool, returning all the