Merge #15713: refactor: Replace chain relayTransactions/submitMemoryPool by higher method

fb62f128bbfd8c6cd72ea8e23331a4bae23883ab Tidy up BroadcastTransaction() (John Newbery)
b8eecf8e79dad92ff07b851b1b29c2a66546bbc1 Remove unused submitToMemoryPool and relayTransactions Chain interfaces (Antoine Riard)
8753f5652b4710e66b50ce87788bf6f33619b75a Remove duplicate checks in SubmitMemoryPoolAndRelay (Antoine Riard)
611291c198eb2be9bf1aea1bf9b2187b18bdb3aa Introduce CWalletTx::SubmitMemoryPoolAndRelay (Antoine Riard)
8c8aa19b4b4fa56cd359092ef099bcfc7b26c334 Add BroadcastTransaction utility usage in Chain interface (Antoine Riard)

Pull request description:

  Remove CWalletTx::AcceptToMemoryPool

  Replace CWalletTx::RelayWalletTransaction by SubmitMemoryPoolAndRelay

  Add a relay flag to broadcastTransaction because wasn't sure of ReacceptWalletTransactions semantic.

  Obviously, working on implementing https://github.com/bitcoin/bitcoin/pull/14978#issuecomment-459373984 to add the new higher-method in Node interface, will add a commit, just need more thought to do it cleanly

ACKs for top commit:
  MarcoFalke:
    re-ACK fb62f128bbfd8c6cd72ea8e23331a4bae23883ab
  Sjors:
    re-ACK fb62f128bbfd8c6cd72ea8e23331a4bae23883ab

Tree-SHA512: a7ee48b0545f537fa65cac8ed4cb24e777ab90b877d4eefb87971fa93c6a59bd555b62ad8940c6ffb40592a0bd50787d27587af99f20b56af72b415b6394251f

1 files changed, 34 insertions, 26 deletions

diff --git a/src/node/transaction.cpp b/src/node/transaction.cpp
index 5cd567a5c..8e5649635 100644
--- a/src/node/transaction.cpp
+++ b/src/node/transaction.cpp
@@ -14,26 +14,30 @@
 
 #include <future>
 
-TransactionError BroadcastTransaction(const CTransactionRef tx, uint256& hashTx, std::string& err_string, const CAmount& highfee)
+TransactionError BroadcastTransaction(const CTransactionRef tx, std::string& err_string, const CAmount& max_tx_fee, bool relay, bool wait_callback)
 {
+    assert(g_connman);
     std::promise<void> promise;
-    hashTx = tx->GetHash();
+    uint256 hashTx = tx->GetHash();
+    bool callback_set = false;
 
     { // cs_main scope
     LOCK(cs_main);
+    // If the transaction is already confirmed in the chain, don't do anything
+    // and return early.
     CCoinsViewCache &view = *pcoinsTip;
-    bool fHaveChain = false;
-    for (size_t o = 0; !fHaveChain && o < tx->vout.size(); o++) {
+    for (size_t o = 0; o < tx->vout.size(); o++) {
         const Coin& existingCoin = view.AccessCoin(COutPoint(hashTx, o));
-        fHaveChain = !existingCoin.IsSpent();
+        // IsSpent doesnt mean the coin is spent, it means the output doesnt' exist.
+        // So if the output does exist, then this transaction exists in the chain.
+        if (!existingCoin.IsSpent()) return TransactionError::ALREADY_IN_CHAIN;
     }
-    bool fHaveMempool = mempool.exists(hashTx);
-    if (!fHaveMempool && !fHaveChain) {
-        // push to local node and sync with wallets
+    if (!mempool.exists(hashTx)) {
+        // Transaction is not already in the mempool. Submit it.
         CValidationState state;
         bool fMissingInputs;
         if (!AcceptToMemoryPool(mempool, state, std::move(tx), &fMissingInputs,
-                                nullptr /* plTxnReplaced */, false /* bypass_limits */, highfee)) {
+                nullptr /* plTxnReplaced */, false /* bypass_limits */, max_tx_fee)) {
             if (state.IsInvalid()) {
                 err_string = FormatStateMessage(state);
                 return TransactionError::MEMPOOL_REJECTED;
@@ -44,33 +48,37 @@ TransactionError BroadcastTransaction(const CTransactionRef tx, uint256& hashTx,
                 err_string = FormatStateMessage(state);
                 return TransactionError::MEMPOOL_ERROR;
             }
-        } else {
-            // If wallet is enabled, ensure that the wallet has been made aware
-            // of the new transaction prior to returning. This prevents a race
-            // where a user might call sendrawtransaction with a transaction
-            // to/from their wallet, immediately call some wallet RPC, and get
-            // a stale result because callbacks have not yet been processed.
+        }
+
+        // Transaction was accepted to the mempool.
+
+        if (wait_callback) {
+            // For transactions broadcast from outside the wallet, make sure
+            // that the wallet has been notified of the transaction before
+            // continuing.
+            //
+            // This prevents a race where a user might call sendrawtransaction
+            // with a transaction to/from their wallet, immediately call some
+            // wallet RPC, and get a stale result because callbacks have not
+            // yet been processed.
             CallFunctionInValidationInterfaceQueue([&promise] {
                 promise.set_value();
             });
+            callback_set = true;
         }
-    } else if (fHaveChain) {
-        return TransactionError::ALREADY_IN_CHAIN;
-    } else {
-        // Make sure we don't block forever if re-sending
-        // a transaction already in mempool.
-        promise.set_value();
     }
 
     } // cs_main
 
-    promise.get_future().wait();
-
-    if (!g_connman) {
-        return TransactionError::P2P_DISABLED;
+    if (callback_set) {
+        // Wait until Validation Interface clients have been notified of the
+        // transaction entering the mempool.
+        promise.get_future().wait();
     }
 
-    RelayTransaction(hashTx, *g_connman);
+    if (relay) {
+        RelayTransaction(hashTx, *g_connman);
+    }
 
     return TransactionError::OK;
 }