rpc: use private broadcast from sendrawtransaction RPC if -privatebroadcast is ON

Author: vasild

src/rpc/mempool.cpp

@@ -8,10 +8,12 @@
 #include <node/mempool_persist.h>
 
 #include <chainparams.h>
+#include <common/args.h>
 #include <consensus/validation.h>
 #include <core_io.h>
 #include <kernel/mempool_entry.h>
 #include <net_processing.h>
+#include <netbase.h> // for g_reachable_nets
 #include <node/mempool_persist_args.h>
 #include <node/types.h>
 #include <policy/rbf.h>
@@ -44,11 +46,21 @@ static RPCHelpMan sendrawtransaction()
 {
     return RPCHelpMan{
         "sendrawtransaction",
-        "Submit a raw transaction (serialized, hex-encoded) to local node and network.\n"
-        "\nThe transaction will be sent unconditionally to all peers, so using sendrawtransaction\n"
-        "for manual rebroadcast may degrade privacy by leaking the transaction's origin, as\n"
-        "nodes will normally not rebroadcast non-wallet transactions already in their mempool.\n"
+        "Submit a raw transaction (serialized, hex-encoded) to the network.\n"
+
+        "\nIf -privatebroadcast is disabled, then the transaction will be put into the\n"
+        "local mempool of the node and will be sent unconditionally to all currently\n"
+        "connected peers, so using sendrawtransaction for manual rebroadcast will degrade\n"
+        "privacy by leaking the transaction's origin, as nodes will normally not\n"
+        "rebroadcast non-wallet transactions already in their mempool.\n"
+
+        "\nIf -privatebroadcast is enabled, then the transaction will be sent only via\n"
+        "dedicated, short-lived connections to Tor or I2P peers or IPv4/IPv6 peers\n"
+        "through the Tor network. This conceals the transaction origin. The transaction\n"
+        "will only enter the local mempool when it is received back from the network.\n"
+
         "\nA specific exception, RPC_TRANSACTION_ALREADY_IN_UTXO_SET, may throw if the transaction cannot be added to the mempool.\n"
+
         "\nRelated RPCs: createrawtransaction, signrawtransactionwithkey\n",
         {
             {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The hex string of the raw transaction"},
@@ -98,11 +110,23 @@ static RPCHelpMan sendrawtransaction()
             std::string err_string;
             AssertLockNotHeld(cs_main);
             NodeContext& node = EnsureAnyNodeContext(request.context);
+            const bool private_broadcast_enabled{gArgs.GetBoolArg("-privatebroadcast", DEFAULT_PRIVATE_BROADCAST)};
+            if (private_broadcast_enabled &&
+                !g_reachable_nets.Contains(NET_ONION) &&
+                !g_reachable_nets.Contains(NET_I2P)) {
+                throw JSONRPCError(RPC_MISC_ERROR,
+                                   "-privatebroadcast is enabled, but none of the Tor or I2P networks is "
+                                   "reachable. Maybe the location of the Tor proxy couldn't be retrieved "
+                                   "from the Tor daemon at startup. Check whether the Tor daemon is running "
+                                   "and that -torcontrol, -torpassword and -i2psam are configured properly.");
+            }
+            const auto method = private_broadcast_enabled ? node::TxBroadcast::NO_MEMPOOL_PRIVATE_BROADCAST
+                                                          : node::TxBroadcast::MEMPOOL_AND_BROADCAST_TO_ALL;
             const TransactionError err = BroadcastTransaction(node,
                                                               tx,
                                                               err_string,
                                                               max_raw_tx_fee,
-                                                              node::TxBroadcast::MEMPOOL_AND_BROADCAST_TO_ALL,
+                                                              method,
                                                               /*wait_callback=*/true);
             if (TransactionError::OK != err) {
                 throw JSONRPCTransactionError(err, err_string);