Enforce v4 block switchover

This enforces the switch over to block v4 once a supermajority is met, as
per BIP65.

core/src/main/java/org/bitcoinj/core/AbstractBlockChain.java

@@ -544,12 +544,13 @@ private void connectBlock(final Block block, StoredBlock storedPrev, boolean exp
             if (expensiveChecks && block.getTimeSeconds() <= getMedianTimestampOfRecentBlocks(head, blockStore))
                 throw new VerificationException("Block's timestamp is too early");
 
-            // BIP 66: Enforce block version 3 once it's a supermajority of blocks
+            // BIP 66 & 65: Enforce block version 3/4 once they are a supermajority of blocks
             // NOTE: This requires 1,000 blocks since the last checkpoint (on main
             // net, less on test) in order to be applied. It is also limited to
-            // stopping addition of new v2 blocks to the tip of the chain.
-            if (block.getVersion() == Block.BLOCK_VERSION_BIP34) {
-                final Integer count = versionTally.getCountAtOrAbove(Block.BLOCK_VERSION_BIP66);
+            // stopping addition of new v2/3 blocks to the tip of the chain.
+            if (block.getVersion() == Block.BLOCK_VERSION_BIP34
+                || block.getVersion() == Block.BLOCK_VERSION_BIP66) {
+                final Integer count = versionTally.getCountAtOrAbove(block.getVersion() + 1);
                 if (count != null
                     && count >= params.getMajorityRejectBlockOutdated()) {
                     throw new VerificationException.BlockVersionOutOfDate(block.getVersion());

core/src/main/java/org/bitcoinj/core/Block.java

@@ -84,6 +84,8 @@ public enum VerifyFlag {
     public static final long BLOCK_VERSION_BIP34 = 2;
     /** Block version introduced in BIP 66: Strict DER signatures */
     public static final long BLOCK_VERSION_BIP66 = 3;
+    /** Block version introduced in BIP 65: OP_CHECKLOCKTIMEVERIFY */
+    public static final long BLOCK_VERSION_BIP65 = 4;
 
     // Fields defined as part of the protocol format.
     private long version;

core/src/test/java/org/bitcoinj/core/BlockChainTest.java

@@ -38,6 +38,7 @@
 import java.util.Locale;
 
 import static org.bitcoinj.core.Coin.*;
+import org.bitcoinj.store.BlockStoreException;
 import static org.bitcoinj.testing.FakeTxBuilder.createFakeBlock;
 import static org.bitcoinj.testing.FakeTxBuilder.createFakeTx;
 import static org.junit.Assert.*;
@@ -230,6 +231,20 @@ public void badDifficulty() throws Exception {
      */
     @Test
     public void badBip66Version() throws Exception {
+        testDeprecatedBlockVersion(Block.BLOCK_VERSION_BIP34, Block.BLOCK_VERSION_BIP66);
+    }
+
+    /**
+     * Test that version 3 blocks are rejected once version 4 blocks are a super
+     * majority.
+     */
+    @Test
+    public void badBip65Version() throws Exception {
+        testDeprecatedBlockVersion(Block.BLOCK_VERSION_BIP66, Block.BLOCK_VERSION_BIP65);
+    }
+
+    private void testDeprecatedBlockVersion(final long deprecatedVersion, final long newVersion)
+            throws Exception {
         final BlockStore versionBlockStore = new MemoryBlockStore(unitTestParams);
         final BlockChain versionChain = new BlockChain(unitTestParams, versionBlockStore);
 
@@ -240,18 +255,18 @@ public void badBip66Version() throws Exception {
 
         // Put in just enough v2 blocks to be a minority
         for (height = 0; height < (unitTestParams.getMajorityWindow() - unitTestParams.getMajorityRejectBlockOutdated()); height++) {
-            chainHead = FakeTxBuilder.createFakeBlock(versionBlockStore, Block.BLOCK_VERSION_BIP34, timeSeconds, height);
+            chainHead = FakeTxBuilder.createFakeBlock(versionBlockStore, deprecatedVersion, timeSeconds, height);
             versionChain.add(chainHead.block);
             timeSeconds += 60;
         }
         // Fill the rest of the window with v3 blocks
         for (; height < unitTestParams.getMajorityWindow(); height++) {
-            chainHead = FakeTxBuilder.createFakeBlock(versionBlockStore, Block.BLOCK_VERSION_BIP66, timeSeconds, height);
+            chainHead = FakeTxBuilder.createFakeBlock(versionBlockStore, newVersion, timeSeconds, height);
             versionChain.add(chainHead.block);
             timeSeconds += 60;
         }
 
-        chainHead = FakeTxBuilder.createFakeBlock(versionBlockStore, Block.BLOCK_VERSION_BIP34, timeSeconds, height);
+        chainHead = FakeTxBuilder.createFakeBlock(versionBlockStore, deprecatedVersion, timeSeconds, height);
         // Trying to add a new v2 block should result in rejection
         thrown.expect(VerificationException.BlockVersionOutOfDate.class);
         try {