don't burn part of the rewards that would go to treasury

src/main/scala/io/iohk/ethereum/consensus/ConsensusConfig.scala

@@ -31,7 +31,6 @@ object ConsensusConfig extends Logger {
     final val HeaderExtraData = "header-extra-data"
     final val BlockCacheSize = "block-cashe-size"
     final val MiningEnabled = "mining-enabled"
-    final val TreasuryOptOut = "treasury-opt-out"
   }
 
   final val AllowedProtocols = Set(
@@ -69,15 +68,16 @@ object ConsensusConfig extends Logger {
       .take(BlockHeaderValidator.MaxExtraDataSize)
     val blockCacheSize = config.getInt(Keys.BlockCacheSize)
     val miningEnabled = config.getBoolean(Keys.MiningEnabled)
-    val optOut = config.getBoolean(Keys.TreasuryOptOut)
+    // treasuryOptOut should always be false(no funds burned), keep for backwards compatibility
+    val treasuryOptOut = false
 
     new ConsensusConfig(
       protocol = protocol,
       coinbase = coinbase,
       headerExtraData = headerExtraData,
       blockCacheSize = blockCacheSize,
       miningEnabled = miningEnabled,
-      treasuryOptOut = optOut
+      treasuryOptOut = treasuryOptOut
     )
   }
 }

src/main/scala/io/iohk/ethereum/consensus/validators/BlockHeaderValidator.scala

@@ -49,6 +49,7 @@ object BlockHeaderError {
   case class HeaderFieldNotEmptyError(msg: String) extends BlockHeaderError
   case class HeaderNotMatchParentError(msg: String) extends BlockHeaderError
   case object CheckpointHeaderTreasuryOptOutError extends BlockHeaderError
+  case object BlockHeaderTreasuryOptOutError extends BlockHeaderError
 
   case class HeaderUnexpectedError(msg: String) extends BlockHeaderError
 }

src/main/scala/io/iohk/ethereum/consensus/validators/BlockHeaderValidatorSkeleton.scala

@@ -85,6 +85,7 @@ abstract class BlockHeaderValidatorSkeleton(blockchainConfig: BlockchainConfig)
       _ <- validateNumber(blockHeader, parentHeader)
       _ <- validateExtraFields(blockHeader)
       _ <- validateEvenMore(blockHeader)
+      _ <- validateExtraFieldsTreasuryOptOut(blockHeader)
     } yield BlockHeaderValid
   }
 
@@ -239,6 +240,24 @@ abstract class BlockHeaderValidatorSkeleton(blockchainConfig: BlockchainConfig)
     }
   }
 
+  /**
+    * Validates [[io.iohk.ethereum.domain.BlockHeader.extraFields]] match extrafields - treasuryOptOut when enabled always to false(not burning rewards)
+    *
+    * @param blockHeader BlockHeader to validate.
+    * @return BlockHeader if valid, an [[BlockHeaderTreasuryOptOutError]] otherwise
+    */
+  private def validateExtraFieldsTreasuryOptOut(
+      blockHeader: BlockHeader
+  ): Either[BlockHeaderError, BlockHeaderValid] = {
+
+    blockHeader.extraFields match {
+      case HefPostEcip1097(treasuryOptOut, _) if !treasuryOptOut => Right(BlockHeaderValid)
+      case HefPostEcip1098(treasuryOptOut) if !treasuryOptOut => Right(BlockHeaderValid)
+      case HefEmpty => Right(BlockHeaderValid)
+      case _ => Left(BlockHeaderTreasuryOptOutError)
+    }
+  }
+
   override def validateHeaderOnly(blockHeader: BlockHeader): Either[BlockHeaderError, BlockHeaderValid] = {
     for {
       _ <- validateExtraData(blockHeader)

src/main/scala/io/iohk/ethereum/ledger/BlockPreparator.scala

@@ -44,10 +44,7 @@ class BlockPreparator(
     *  1. Reward for block is distributed as:
     *      a. If treasury is disabled or it's has been selfdestructed:
     *            Pay 100% of it to the miner
-    *      b. If a. isn't true and the miner opted out:
-    *            Pay 80% of it to the miner
-    *            Never generate the 20% else
-    *      c. If a. isn't true and the miner opted in:
+    *      b. If a. isn't true:
     *            Pay 80% of it to the miner
     *            Pay 20% of it to the treasury contract
     *  2. Miner is payed a reward for the inclusion of ommers
@@ -76,13 +73,6 @@ class BlockPreparator(
           val worldAfterMinerReward = increaseAccountBalance(minerAddress, UInt256(minerReward))(worldStateProxy)
           log.debug(s"Paying block $blockNumber reward of $minerReward to miner with address $minerAddress")
           worldAfterMinerReward
-        } else if (block.header.treasuryOptOut.get) {
-          val minerReward = minerRewardForOmmers + minerRewardForBlock * MinerRewardPercentageAfterECIP1098 / 100
-          val worldAfterMinerReward = increaseAccountBalance(minerAddress, UInt256(minerReward))(worldStateProxy)
-          log.debug(
-            s"Paying block $blockNumber reward of $minerReward to miner with address $minerAddress, miner opted-out of treasury"
-          )
-          worldAfterMinerReward
         } else {
           val minerReward = minerRewardForOmmers + minerRewardForBlock * MinerRewardPercentageAfterECIP1098 / 100
           val worldAfterMinerReward = increaseAccountBalance(minerAddress, UInt256(minerReward))(worldStateProxy)

src/test/scala/io/iohk/ethereum/consensus/pow/validators/EthashBlockHeaderValidatorSpec.scala

@@ -188,14 +188,26 @@ class EthashBlockHeaderValidatorSpec
     res shouldBe Right(BlockHeaderValid)
   }
 
-  it should "mark as valid a post ecip1098 block opt-out with opt out defined" in new EphemBlockchainTestSetup {
+  it should "mark as invalid a post ecip1098 block opt-out with opt out defined" in new EphemBlockchainTestSetup {
     val ecip1098BlockNumber = validBlockHeader.number / 2
     val blockchainConfigWithECIP1098Enabled: BlockchainConfig =
       blockchainConfig.copy(ecip1098BlockNumber = ecip1098BlockNumber)
     val blockHeaderValidator = new BlockValidatorWithPowMocked(blockchainConfigWithECIP1098Enabled)
 
     val validHeader = validBlockHeader.copy(extraFields = HefPostEcip1098(treasuryOptOut = true))
 
+    val validationResult = blockHeaderValidator.validate(validHeader, validParentBlockHeader)
+    validationResult shouldBe Left(BlockHeaderTreasuryOptOutError)
+  }
+
+  it should "mark as valid a post ecip1098 block opt-out with opt out undefined" in new EphemBlockchainTestSetup {
+    val ecip1098BlockNumber = validBlockHeader.number / 2
+    val blockchainConfigWithECIP1098Enabled: BlockchainConfig =
+      blockchainConfig.copy(ecip1098BlockNumber = ecip1098BlockNumber)
+    val blockHeaderValidator = new BlockValidatorWithPowMocked(blockchainConfigWithECIP1098Enabled)
+
+    val validHeader = validBlockHeader.copy(extraFields = HefPostEcip1098(treasuryOptOut = false))
+
     val validationResult = blockHeaderValidator.validate(validHeader, validParentBlockHeader)
     validationResult shouldBe Right(BlockHeaderValid)
   }

src/test/scala/io/iohk/ethereum/ledger/BlockRewardSpec.scala

@@ -130,13 +130,17 @@ class BlockRewardSpec extends AnyFlatSpec with Matchers with ScalaCheckPropertyC
         MinerRewardPercentageAfterECIP1098 * blockReward / 100,
         TreasuryRewardPercentageAfterECIP1098 * blockReward / 100
       ),
-      (Some(true), true, MinerRewardPercentageAfterECIP1098 * blockReward / 100, 0)
+      (
+        Some(true),
+        true,
+        MinerRewardPercentageAfterECIP1098 * blockReward / 100,
+        TreasuryRewardPercentageAfterECIP1098 * blockReward / 100
+      )
     )
 
     forAll(table) { case (minerOptsOut, contractDeployed, minerReward, treasuryReward) =>
       val minerAddress = validAccountAddress
       val block = sampleBlock(minerAddress, Nil, minerOptsOut)
-
       val worldBeforeExecution =
         if (contractDeployed) worldState
         else {