10 files changed, 31 insertions, 8 deletions
diff --git a/src/policy/feerate.cpp b/src/policy/feerate.cpp
index ce149067b7..0ea56d8db7 100644
--- a/src/policy/feerate.cpp
+++ b/src/policy/feerate.cpp
@@ -1,5 +1,5 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
-// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2009-2021 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
diff --git a/src/policy/feerate.h b/src/policy/feerate.h
index 13c7ec2002..188a44b73d 100644
--- a/src/policy/feerate.h
+++ b/src/policy/feerate.h
@@ -1,5 +1,5 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
-// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2009-2021 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
diff --git a/src/policy/fees.cpp b/src/policy/fees.cpp
index 36cf786bd5..6499dbd97f 100644
--- a/src/policy/fees.cpp
+++ b/src/policy/fees.cpp
@@ -1,5 +1,5 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
-// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2009-2021 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
diff --git a/src/policy/fees.h b/src/policy/fees.h
index 37a7051045..6e25bb42b8 100644
--- a/src/policy/fees.h
+++ b/src/policy/fees.h
@@ -1,5 +1,5 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
-// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2009-2021 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 #ifndef BITCOIN_POLICY_FEES_H
diff --git a/src/policy/packages.cpp b/src/policy/packages.cpp
index cfd0539965..21f5488816 100644
--- a/src/policy/packages.cpp
+++ b/src/policy/packages.cpp
@@ -60,3 +60,20 @@ bool CheckPackage(const Package& txns, PackageValidationState& state)
     }
     return true;
 }
+
+bool IsChildWithParents(const Package& package)
+{
+    assert(std::all_of(package.cbegin(), package.cend(), [](const auto& tx){return tx != nullptr;}));
+    if (package.size() < 2) return false;
+
+    // The package is expected to be sorted, so the last transaction is the child.
+    const auto& child = package.back();
+    std::unordered_set<uint256, SaltedTxidHasher> input_txids;
+    std::transform(child->vin.cbegin(), child->vin.cend(),
+                   std::inserter(input_txids, input_txids.end()),
+                   [](const auto& input) { return input.prevout.hash; });
+
+    // Every transaction must be a parent of the last transaction in the package.
+    return std::all_of(package.cbegin(), package.cend() - 1,
+                       [&input_txids](const auto& ptx) { return input_txids.count(ptx->GetHash()) > 0; });
+}
diff --git a/src/policy/packages.h b/src/policy/packages.h
index 6b7ac3e450..d2744f1265 100644
--- a/src/policy/packages.h
+++ b/src/policy/packages.h
@@ -41,4 +41,10 @@ class PackageValidationState : public ValidationState<PackageValidationResult> {
  */
 bool CheckPackage(const Package& txns, PackageValidationState& state);
 
+/** Context-free check that a package is exactly one child and its parents; not all parents need to
+ * be present, but the package must not contain any transactions that are not the child's parents.
+ * It is expected to be sorted, which means the last transaction must be the child.
+ */
+bool IsChildWithParents(const Package& package);
+
 #endif // BITCOIN_POLICY_PACKAGES_H
diff --git a/src/policy/policy.cpp b/src/policy/policy.cpp
index 5d0bb68ec6..6aba6a4a5b 100644
--- a/src/policy/policy.cpp
+++ b/src/policy/policy.cpp
@@ -1,5 +1,5 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
-// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2009-2021 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
diff --git a/src/policy/policy.h b/src/policy/policy.h
index f6ac6500f6..89f6e72618 100644
--- a/src/policy/policy.h
+++ b/src/policy/policy.h
@@ -1,5 +1,5 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
-// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2009-2021 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
diff --git a/src/policy/rbf.cpp b/src/policy/rbf.cpp
index 7e6b0cf245..8fe4dc35b8 100644
--- a/src/policy/rbf.cpp
+++ b/src/policy/rbf.cpp
@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2020 The Bitcoin Core developers
+// Copyright (c) 2016-2021 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
diff --git a/src/policy/rbf.h b/src/policy/rbf.h
index be8c2e5b8b..fcec7052ed 100644
--- a/src/policy/rbf.h
+++ b/src/policy/rbf.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2016-2020 The Bitcoin Core developers
+// Copyright (c) 2016-2021 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.