Merge #7187: Keep reorgs fast for SequenceLocks checks

982670c Add LockPoints (Alex Morcos)

1 files changed, 70 insertions, 19 deletions

diff --git a/src/main.cpp b/src/main.cpp
index 027a36394c..76dc01ea79 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -794,7 +794,25 @@ bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeig
     return EvaluateSequenceLocks(block, CalculateSequenceLocks(tx, flags, prevHeights, block));
 }
 
-bool CheckSequenceLocks(const CTransaction &tx, int flags)
+bool TestLockPointValidity(const LockPoints* lp)
+{
+    AssertLockHeld(cs_main);
+    assert(lp);
+    // If there are relative lock times then the maxInputBlock will be set
+    // If there are no relative lock times, the LockPoints don't depend on the chain
+    if (lp->maxInputBlock) {
+        // Check whether chainActive is an extension of the block at which the LockPoints
+        // calculation was valid.  If not LockPoints are no longer valid
+        if (!chainActive.Contains(lp->maxInputBlock)) {
+            return false;
+        }
+    }
+
+    // LockPoints still valid
+    return true;
+}
+
+bool CheckSequenceLocks(const CTransaction &tx, int flags, LockPoints* lp, bool useExistingLockPoints)
 {
     AssertLockHeld(cs_main);
     AssertLockHeld(mempool.cs);
@@ -810,25 +828,57 @@ bool CheckSequenceLocks(const CTransaction &tx, int flags)
     // *next* block, we need to use one more than chainActive.Height()
     index.nHeight = tip->nHeight + 1;
 
-    // pcoinsTip contains the UTXO set for chainActive.Tip()
-    CCoinsViewMemPool viewMemPool(pcoinsTip, mempool);
-    std::vector<int> prevheights;
-    prevheights.resize(tx.vin.size());
-    for (size_t txinIndex = 0; txinIndex < tx.vin.size(); txinIndex++) {
-        const CTxIn& txin = tx.vin[txinIndex];
-        CCoins coins;
-        if (!viewMemPool.GetCoins(txin.prevout.hash, coins)) {
-            return error("%s: Missing input", __func__);
+    std::pair<int, int64_t> lockPair;
+    if (useExistingLockPoints) {
+        assert(lp);
+        lockPair.first = lp->height;
+        lockPair.second = lp->time;
+    }
+    else {
+        // pcoinsTip contains the UTXO set for chainActive.Tip()
+        CCoinsViewMemPool viewMemPool(pcoinsTip, mempool);
+        std::vector<int> prevheights;
+        prevheights.resize(tx.vin.size());
+        for (size_t txinIndex = 0; txinIndex < tx.vin.size(); txinIndex++) {
+            const CTxIn& txin = tx.vin[txinIndex];
+            CCoins coins;
+            if (!viewMemPool.GetCoins(txin.prevout.hash, coins)) {
+                return error("%s: Missing input", __func__);
+            }
+            if (coins.nHeight == MEMPOOL_HEIGHT) {
+                // Assume all mempool transaction confirm in the next block
+                prevheights[txinIndex] = tip->nHeight + 1;
+            } else {
+                prevheights[txinIndex] = coins.nHeight;
+            }
         }
-        if (coins.nHeight == MEMPOOL_HEIGHT) {
-            // Assume all mempool transaction confirm in the next block
-            prevheights[txinIndex] = tip->nHeight + 1;
-        } else {
-            prevheights[txinIndex] = coins.nHeight;
+        lockPair = CalculateSequenceLocks(tx, flags, &prevheights, index);
+        if (lp) {
+            lp->height = lockPair.first;
+            lp->time = lockPair.second;
+            // Also store the hash of the block with the highest height of
+            // all the blocks which have sequence locked prevouts.
+            // This hash needs to still be on the chain
+            // for these LockPoint calculations to be valid
+            // Note: It is impossible to correctly calculate a maxInputBlock
+            // if any of the sequence locked inputs depend on unconfirmed txs,
+            // except in the special case where the relative lock time/height
+            // is 0, which is equivalent to no sequence lock. Since we assume
+            // input height of tip+1 for mempool txs and test the resulting
+            // lockPair from CalculateSequenceLocks against tip+1.  We know
+            // EvaluateSequenceLocks will fail if there was a non-zero sequence
+            // lock on a mempool input, so we can use the return value of
+            // CheckSequenceLocks to indicate the LockPoints validity
+            int maxInputHeight = 0;
+            BOOST_FOREACH(int height, prevheights) {
+                // Can ignore mempool inputs since we'll fail if they had non-zero locks
+                if (height != tip->nHeight+1) {
+                    maxInputHeight = std::max(maxInputHeight, height);
+                }
+            }
+            lp->maxInputBlock = tip->GetAncestor(maxInputHeight);
         }
     }
-
-    std::pair<int, int64_t> lockPair = CalculateSequenceLocks(tx, flags, &prevheights, index);
     return EvaluateSequenceLocks(index, lockPair);
 }
 
@@ -1017,6 +1067,7 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
         CCoinsViewCache view(&dummy);
 
         CAmount nValueIn = 0;
+        LockPoints lp;
         {
         LOCK(pool.cs);
         CCoinsViewMemPool viewMemPool(pcoinsTip, pool);
@@ -1060,7 +1111,7 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
         // be mined yet.
         // Must keep pool.cs for this unless we change CheckSequenceLocks to take a
         // CoinsViewCache instead of create its own
-        if (!CheckSequenceLocks(tx, STANDARD_LOCKTIME_VERIFY_FLAGS))
+        if (!CheckSequenceLocks(tx, STANDARD_LOCKTIME_VERIFY_FLAGS, &lp))
             return state.DoS(0, false, REJECT_NONSTANDARD, "non-BIP68-final");
         }
 
@@ -1092,7 +1143,7 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
             }
         }
 
-        CTxMemPoolEntry entry(tx, nFees, GetTime(), dPriority, chainActive.Height(), pool.HasNoInputsOf(tx), inChainInputValue, fSpendsCoinbase, nSigOps);
+        CTxMemPoolEntry entry(tx, nFees, GetTime(), dPriority, chainActive.Height(), pool.HasNoInputsOf(tx), inChainInputValue, fSpendsCoinbase, nSigOps, lp);
         unsigned int nSize = entry.GetTxSize();
 
         // Check that the transaction doesn't have an excessive number of