1 files changed, 15 insertions, 5 deletions

diff --git a/src/node/transaction.cpp b/src/node/transaction.cpp
index 926dd0e31d..0c1295c0b5 100644
--- a/src/node/transaction.cpp
+++ b/src/node/transaction.cpp
@@ -34,7 +34,8 @@ TransactionError BroadcastTransaction(NodeContext& node, const CTransactionRef t
     assert(node.peerman);
     assert(node.mempool);
     std::promise<void> promise;
-    uint256 hashTx = tx->GetHash();
+    uint256 txid = tx->GetHash();
+    uint256 wtxid = tx->GetWitnessHash();
     bool callback_set = false;
 
     { // cs_main scope
@@ -44,12 +45,21 @@ TransactionError BroadcastTransaction(NodeContext& node, const CTransactionRef t
     // and return early.
     CCoinsViewCache &view = node.chainman->ActiveChainstate().CoinsTip();
     for (size_t o = 0; o < tx->vout.size(); o++) {
-        const Coin& existingCoin = view.AccessCoin(COutPoint(hashTx, o));
+        const Coin& existingCoin = view.AccessCoin(COutPoint(txid, o));
         // IsSpent doesn't mean the coin is spent, it means the output doesn't exist.
         // So if the output does exist, then this transaction exists in the chain.
         if (!existingCoin.IsSpent()) return TransactionError::ALREADY_IN_CHAIN;
     }
-    if (!node.mempool->exists(hashTx)) {
+    if (auto mempool_tx = node.mempool->get(txid); mempool_tx) {
+        // There's already a transaction in the mempool with this txid. Don't
+        // try to submit this transaction to the mempool (since it'll be
+        // rejected as a TX_CONFLICT), but do attempt to reannounce the mempool
+        // transaction if relay=true.
+        //
+        // The mempool transaction may have the same or different witness (and
+        // wtxid) as this transaction. Use the mempool's wtxid for reannouncement.
+        wtxid = mempool_tx->GetWitnessHash();
+    } else {
         // Transaction is not already in the mempool.
         if (max_tx_fee > 0) {
             // First, call ATMP with test_accept and check the fee. If ATMP
@@ -74,7 +84,7 @@ TransactionError BroadcastTransaction(NodeContext& node, const CTransactionRef t
         if (relay) {
             // the mempool tracks locally submitted transactions to make a
             // best-effort of initial broadcast
-            node.mempool->AddUnbroadcastTx(hashTx);
+            node.mempool->AddUnbroadcastTx(txid);
         }
 
         if (wait_callback) {
@@ -102,7 +112,7 @@ TransactionError BroadcastTransaction(NodeContext& node, const CTransactionRef t
     }
 
     if (relay) {
-        node.peerman->RelayTransaction(hashTx, tx->GetWitnessHash());
+        node.peerman->RelayTransaction(txid, wtxid);
     }
 
     return TransactionError::OK;