Merge #20536: wallet: Error with "Transaction too large" if the funded tx will end up being too large after signing

48a0319babb409cf486a9eb7c776810f70b06cb2 Add a test that selects too large if BnB is used (Andrew Chow)
3e69939b78d0143d514c5d9b6c6a9844c9bb901c Fail if maximum weight is too large (Andrew Chow)
51e2cd322cfc7271af309e3a2243448a2ec0cad4 Have CalculateMaximumSignedTxSize also compute tx weight (Andrew Chow)

Pull request description:

  Currently the `Transaction too large` is calculated on the transaction that is returned from `CreateTransaction`. This does not make sense for when `CreateTransaction` is being used for `fundrawtransaction` as no signing occurs so the final returned transaction is missing signatures. Thus users may successfully fund a transaction but fail to broadcast it after it has been fully signed.

  So instead we should figure out whether the transaction we are funding will be too large after it is signed. We can do this by having `CalculateMaximumSignedTxSize` also return the transaction weight and then comparing that weight against the maximum weight.

ACKs for top commit:
  instagibbs:
    ACK https://github.com/bitcoin/bitcoin/pull/20536/commits/48a0319babb409cf486a9eb7c776810f70b06cb2
  meshcollider:
    utACK 48a0319babb409cf486a9eb7c776810f70b06cb2
  Xekyo:
    utACK with nits 48a0319babb409cf486a9eb7c776810f70b06cb2

Tree-SHA512: 1700c60b07f67e2d5c591c5ccd131ac9f1861fab3def961c3c9c4b3281ec1063fe8e4f0f7f1038cac72692340856406bcee8fb45c8104d2ad34357a0ec878ac7

1 files changed, 14 insertions, 7 deletions

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 08e480225d..9e0befac43 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1611,14 +1611,15 @@ bool CWallet::ImportScriptPubKeys(const std::string& label, const std::set<CScri
     return true;
 }
 
-int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, bool use_max_sig)
+// Returns pair of vsize and weight
+std::pair<int64_t, int64_t> CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, bool use_max_sig)
 {
     std::vector<CTxOut> txouts;
     for (const CTxIn& input : tx.vin) {
         const auto mi = wallet->mapWallet.find(input.prevout.hash);
         // Can not estimate size without knowing the input details
         if (mi == wallet->mapWallet.end()) {
-            return -1;
+            return std::make_pair(-1, -1);
         }
         assert(input.prevout.n < mi->second.tx->vout.size());
         txouts.emplace_back(mi->second.tx->vout[input.prevout.n]);
@@ -1627,13 +1628,16 @@ int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wall
 }
 
 // txouts needs to be in the order of tx.vin
-int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, bool use_max_sig)
+std::pair<int64_t, int64_t> CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, bool use_max_sig)
 {
     CMutableTransaction txNew(tx);
     if (!wallet->DummySignTx(txNew, txouts, use_max_sig)) {
-        return -1;
+        return std::make_pair(-1, -1);
     }
-    return GetVirtualTransactionSize(CTransaction(txNew));
+    CTransaction ctx(txNew);
+    int64_t vsize = GetVirtualTransactionSize(ctx);
+    int64_t weight = GetTransactionWeight(ctx);
+    return std::make_pair(vsize, weight);
 }
 
 int CalculateMaximumSignedInputSize(const CTxOut& txout, const CWallet* wallet, bool use_max_sig)
@@ -2779,6 +2783,7 @@ bool CWallet::CreateTransactionInternal(
     CMutableTransaction txNew;
     FeeCalculation feeCalc;
     CAmount nFeeNeeded;
+    std::pair<int64_t, int64_t> tx_sizes;
     int nBytes;
     {
         std::set<CInputCoin> setCoins;
@@ -2962,7 +2967,8 @@ bool CWallet::CreateTransactionInternal(
                     txNew.vin.push_back(CTxIn(coin.outpoint,CScript()));
                 }
 
-                nBytes = CalculateMaximumSignedTxSize(CTransaction(txNew), this, coin_control.fAllowWatchOnly);
+                tx_sizes = CalculateMaximumSignedTxSize(CTransaction(txNew), this, coin_control.fAllowWatchOnly);
+                nBytes = tx_sizes.first;
                 if (nBytes < 0) {
                     error = _("Signing transaction failed");
                     return false;
@@ -3072,7 +3078,8 @@ bool CWallet::CreateTransactionInternal(
         tx = MakeTransactionRef(std::move(txNew));
 
         // Limit size
-        if (GetTransactionWeight(*tx) > MAX_STANDARD_TX_WEIGHT)
+        if ((sign && GetTransactionWeight(*tx) > MAX_STANDARD_TX_WEIGHT) ||
+            (!sign && tx_sizes.second > MAX_STANDARD_TX_WEIGHT))
         {
             error = _("Transaction too large");
             return false;