Implement BIP0066 changeover logic for v3 blocks.

This commit implements the changeover logic for version 3 blocks as
described by BIP0066.

blockchain/accept.go

@@ -107,6 +107,16 @@ func (b *BlockChain) maybeAcceptBlock(block *btcutil.Block, flags BehaviorFlags)
 	}
 
 	if !fastAdd {
+		// Reject version 2 blocks once a majority of the network has
+		// upgraded.  This is part of BIP0066.
+		if blockHeader.Version < 3 && b.isMajorityVersion(3, prevNode,
+			b.chainParams.BlockRejectNumRequired) {
+
+			str := "new blocks with version %d are no longer valid"
+			str = fmt.Sprintf(str, blockHeader.Version)
+			return ruleError(ErrBlockVersionTooOld, str)
+		}
+
 		// Reject version 1 blocks once a majority of the network has
 		// upgraded.  This is part of BIP0034.
 		if blockHeader.Version < 2 && b.isMajorityVersion(2, prevNode,

blockchain/validate.go

@@ -915,6 +915,16 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block) er
 		runScripts = false
 	}
 
+	// Get the previous block node.  This function is used over simply
+	// accessing node.parent directly as it will dynamically create previous
+	// block nodes as needed.  This helps allow only the pieces of the chain
+	// that are needed to remain in memory.
+	prevNode, err := b.getPrevNodeFromNode(node)
+	if err != nil {
+		log.Errorf("getPrevNodeFromNode: %v", err)
+		return err
+	}
+
 	// Blocks created after the BIP0016 activation time need to have the
 	// pay-to-script-hash checks enabled.
 	var scriptFlags txscript.ScriptFlags
@@ -922,6 +932,16 @@ func (b *BlockChain) checkConnectBlock(node *blockNode, block *btcutil.Block) er
 		scriptFlags |= txscript.ScriptBip16
 	}
 
+	// Enforce DER signatures for block versions 3+ once the majority of the
+	// network has upgraded to the enforcement threshold.  This is part of
+	// BIP0066.
+	blockHeader := &block.MsgBlock().Header
+	if blockHeader.Version >= 3 && b.isMajorityVersion(3, prevNode,
+		b.chainParams.BlockEnforceNumRequired) {
+
+		scriptFlags |= txscript.ScriptVerifyDERSignatures
+	}
+
 	// Now that the inexpensive checks are done and have passed, verify the
 	// transactions are actually allowed to spend the coins by running the
 	// expensive ECDSA signature check scripts.  Doing this last helps

mining.go

@@ -24,7 +24,7 @@ const (
 	// will require changes to the generated block.  Using the wire constant
 	// for generated block version could allow creation of invalid blocks
 	// for the updated version.
-	generatedBlockVersion = 2
+	generatedBlockVersion = 3
 
 	// minHighPriority is the minimum priority value that allows a
 	// transaction to be considered high priority.

wire/blockheader.go

@@ -11,7 +11,7 @@ import (
 )
 
 // BlockVersion is the current latest supported block version.
-const BlockVersion = 2
+const BlockVersion = 3
 
 // Version 4 bytes + Timestamp 4 bytes + Bits 4 bytes + Nonce 4 bytes +
 // PrevBlock and MerkleRoot hashes.