Factor BroadcastTransaction out of sendrawtransaction

Factor out a new BroadcastTransaction function, performing the core work of the
sendrawtransaction rpc, so that it can be used from the GUI code. Move it from
src/rpc/ to src/node/.

src/node/transaction.cpp

@@ -0,0 +1,79 @@
+// Copyright (c) 2010 Satoshi Nakamoto
+// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <consensus/validation.h>
+#include <net.h>
+#include <rpc/server.h>
+#include <txmempool.h>
+#include <validation.h>
+#include <validationinterface.h>
+#include <node/transaction.h>
+
+#include <future>
+
+uint256 BroadcastTransaction(const CTransactionRef tx, const bool allowhighfees) {
+    std::promise<void> promise;
+    const uint256& hashTx = tx->GetHash();
+
+    CAmount nMaxRawTxFee = maxTxFee;
+    if (allowhighfees)
+        nMaxRawTxFee = 0;
+
+    { // cs_main scope
+    LOCK(cs_main);
+    CCoinsViewCache &view = *pcoinsTip;
+    bool fHaveChain = false;
+    for (size_t o = 0; !fHaveChain && o < tx->vout.size(); o++) {
+        const Coin& existingCoin = view.AccessCoin(COutPoint(hashTx, o));
+        fHaveChain = !existingCoin.IsSpent();
+    }
+    bool fHaveMempool = mempool.exists(hashTx);
+    if (!fHaveMempool && !fHaveChain) {
+        // push to local node and sync with wallets
+        CValidationState state;
+        bool fMissingInputs;
+        if (!AcceptToMemoryPool(mempool, state, std::move(tx), &fMissingInputs,
+                                nullptr /* plTxnReplaced */, false /* bypass_limits */, nMaxRawTxFee)) {
+            if (state.IsInvalid()) {
+                throw JSONRPCError(RPC_TRANSACTION_REJECTED, FormatStateMessage(state));
+            } else {
+                if (fMissingInputs) {
+                    throw JSONRPCError(RPC_TRANSACTION_ERROR, "Missing inputs");
+                }
+                throw JSONRPCError(RPC_TRANSACTION_ERROR, FormatStateMessage(state));
+            }
+        } 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.
+            CallFunctionInValidationInterfaceQueue([&promise] {
+                promise.set_value();
+            });
+        }
+    } else if (fHaveChain) {
+        throw JSONRPCError(RPC_TRANSACTION_ALREADY_IN_CHAIN, "transaction already in block 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)
+        throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
+
+    CInv inv(MSG_TX, hashTx);
+    g_connman->ForEachNode([&inv](CNode* pnode)
+    {
+        pnode->PushInventory(inv);
+    });
+
+    return hashTx;
+}