Merge #8601: Add option to opt into full-RBF when sending funds (rebase, original by petertodd)

86726d8 Rename `-optintofullrbf` option to `-walletrbf` (Wladimir J. van der Laan)
05fa823 wallet: Add BIP125 comment for MAXINT-1/-2 behavior (Wladimir J. van der Laan)
152f45b Add option to opt into full-RBF when sending funds (Peter Todd)

2 files changed, 15 insertions, 3 deletions

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index a8ef6d9511..4c10ea0edb 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -40,6 +40,7 @@ CFeeRate payTxFee(DEFAULT_TRANSACTION_FEE);
 unsigned int nTxConfirmTarget = DEFAULT_TX_CONFIRM_TARGET;
 bool bSpendZeroConfChange = DEFAULT_SPEND_ZEROCONF_CHANGE;
 bool fSendFreeTransactions = DEFAULT_SEND_FREE_TRANSACTIONS;
+bool fWalletRbf = DEFAULT_WALLET_RBF;
 
 const char * DEFAULT_WALLET_DAT = "wallet.dat";
 const uint32_t BIP32_HARDENED_KEY_LIMIT = 0x80000000;
@@ -2362,11 +2363,17 @@ bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend, CWalletTx& wt
 
                 // Fill vin
                 //
-                // Note how the sequence number is set to max()-1 so that the
-                // nLockTime set above actually works.
+                // Note how the sequence number is set to non-maxint so that
+                // the nLockTime set above actually works.
+                //
+                // BIP125 defines opt-in RBF as any nSequence < maxint-1, so
+                // we use the highest possible value in that range (maxint-2)
+                // to avoid conflicting with other possible uses of nSequence,
+                // and in the spirit of "smallest posible change from prior
+                // behavior."
                 BOOST_FOREACH(const PAIRTYPE(const CWalletTx*,unsigned int)& coin, setCoins)
                     txNew.vin.push_back(CTxIn(coin.first->GetHash(),coin.second,CScript(),
-                                              std::numeric_limits<unsigned int>::max()-1));
+                                              std::numeric_limits<unsigned int>::max() - (fWalletRbf ? 2 : 1)));
 
                 // Sign
                 int nIn = 0;
@@ -3246,6 +3253,7 @@ std::string CWallet::GetWalletHelpString(bool showDebug)
     strUsage += HelpMessageOpt("-spendzeroconfchange", strprintf(_("Spend unconfirmed change when sending transactions (default: %u)"), DEFAULT_SPEND_ZEROCONF_CHANGE));
     strUsage += HelpMessageOpt("-txconfirmtarget=<n>", strprintf(_("If paytxfee is not set, include enough fee so transactions begin confirmation on average within n blocks (default: %u)"), DEFAULT_TX_CONFIRM_TARGET));
     strUsage += HelpMessageOpt("-usehd", _("Use hierarchical deterministic key generation (HD) after BIP32. Only has effect during wallet creation/first start") + " " + strprintf(_("(default: %u)"), DEFAULT_USE_HD_WALLET));
+    strUsage += HelpMessageOpt("-walletrbf", strprintf(_("Send transactions with full-RBF opt-in enabled (default: %u)"), DEFAULT_WALLET_RBF));
     strUsage += HelpMessageOpt("-upgradewallet", _("Upgrade wallet to latest format on startup"));
     strUsage += HelpMessageOpt("-wallet=<file>", _("Specify wallet file (within data directory)") + " " + strprintf(_("(default: %s)"), DEFAULT_WALLET_DAT));
     strUsage += HelpMessageOpt("-walletbroadcast", _("Make the wallet broadcast transactions") + " " + strprintf(_("(default: %u)"), DEFAULT_WALLETBROADCAST));
@@ -3486,6 +3494,7 @@ bool CWallet::ParameterInteraction()
     nTxConfirmTarget = GetArg("-txconfirmtarget", DEFAULT_TX_CONFIRM_TARGET);
     bSpendZeroConfChange = GetBoolArg("-spendzeroconfchange", DEFAULT_SPEND_ZEROCONF_CHANGE);
     fSendFreeTransactions = GetBoolArg("-sendfreetransactions", DEFAULT_SEND_FREE_TRANSACTIONS);
+    fWalletRbf = GetBoolArg("-walletrbf", DEFAULT_WALLET_RBF);
 
     return true;
 }
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 7a771350cb..61aff6e45a 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -37,6 +37,7 @@ extern CFeeRate payTxFee;
 extern unsigned int nTxConfirmTarget;
 extern bool bSpendZeroConfChange;
 extern bool fSendFreeTransactions;
+extern bool fWalletRbf;
 
 static const unsigned int DEFAULT_KEYPOOL_SIZE = 100;
 //! -paytxfee default
@@ -53,6 +54,8 @@ static const bool DEFAULT_SPEND_ZEROCONF_CHANGE = true;
 static const bool DEFAULT_SEND_FREE_TRANSACTIONS = false;
 //! -txconfirmtarget default
 static const unsigned int DEFAULT_TX_CONFIRM_TARGET = 2;
+//! -walletrbf default
+static const bool DEFAULT_WALLET_RBF = false;
 //! Largest (in bytes) free transaction we're willing to create
 static const unsigned int MAX_FREE_TRANSACTION_CREATE_SIZE = 1000;
 static const bool DEFAULT_WALLETBROADCAST = true;