Merge branch 'port-D5370' into 'master'

[port] Don't park blocks when there is no actual reorg

See merge request bitcoin-cash-node/bitcoin-cash-node!56

src/validation.cpp

@@ -4218,13 +4218,15 @@ bool CChainState::AcceptBlock(const Config &config,
                      block.GetHash().ToString());
     }
 
-    // If this is a deep reorg (a regorg of more than one block), preemptively
-    // mark the chain as parked. If it has enough work, it'll unpark
-    // automatically. We mark the block as parked at the very last minute so we
-    // can make sure everything is ready to be reorged if needed.
+    // If connecting the new block would require rewinding more than one block
+    // from the active chain (i.e., a "deep reorg"), then mark the new block as
+    // parked. If it has enough work then it will be automatically unparked
+    // later, during FindMostWorkChain. We mark the block as parked at the very
+    // last minute so we can make sure everything is ready to be reorged if
+    // needed.
     if (gArgs.GetBoolArg("-parkdeepreorg", true)) {
         const CBlockIndex *pindexFork = chainActive.FindFork(pindex);
-        if (pindexFork && pindexFork->nHeight + 1 < pindex->nHeight) {
+        if (pindexFork && pindexFork->nHeight + 1 < chainActive.Height()) {
             LogPrintf("Park block %s as it would cause a deep reorg.\n",
                       pindex->GetBlockHash().ToString());
             pindex->nStatus = pindex->nStatus.withParked();

test/functional/abc-parkedchain.py

@@ -192,6 +192,26 @@ def check_reorg_protection(depth, extra_blocks):
         check_reorg_protection(6, 6)
         check_reorg_protection(100, 100)
 
+        # try deep reorg with a log check.
+        with parking_node.assert_debug_log(["Park block"]):
+            check_reorg_protection(3, 1)
+
+        self.log.info(
+            "Accepting many blocks at once (possibly out of order) should not park if there is no reorg.")
+        # rewind one block to make a reorg that is shallow.
+        node.invalidateblock(parking_node.getbestblockhash())
+        # generate a ton of blocks at once.
+        try:
+            with parking_node.assert_debug_log(["Park block"]):
+                node.generate(20)
+                wait_until(lambda: parking_node.getbestblockhash() ==
+                           node.getbestblockhash())
+        except AssertionError as exc:
+            # good, we want an absence of "Park block" messages
+            assert "does not partially match log" in exc.args[0]
+        else:
+            raise AssertionError("Parked block when there was no deep reorg")
+
         self.log.info("Test that unparking works when -parkdeepreorg=0")
         # Set up parking node height = fork + 4, node height = fork + 5
         node.invalidateblock(node.getbestblockhash())