track double spending in the txpool

Transactions in the txpool are marked when another transaction
is seen double spending one or more of its inputs.
This is then exposed wherever appropriate.

Note that being marked with this "double spend seen" flag does
NOT mean this transaction IS a double spend and will never be
mined: it just means that the network has seen at least another
transaction spending at least one of the same inputs, so care
should be taken to wait for a few confirmations before acting
upon that transaction (ie, mostly of use for merchants wanting
to accept unconfirmed transactions).

1 files changed, 32 insertions, 5 deletions

diff --git a/src/rpc/core_rpc_server.cpp b/src/rpc/core_rpc_server.cpp
index b3ce30d0c..e653b9520 100755
--- a/src/rpc/core_rpc_server.cpp
+++ b/src/rpc/core_rpc_server.cpp
@@ -478,15 +478,17 @@ namespace cryptonote
     // try the pool for any missing txes
     size_t found_in_pool = 0;
     std::unordered_set<crypto::hash> pool_tx_hashes;
+    std::unordered_map<crypto::hash, bool> double_spend_seen;
     if (!missed_txs.empty())
     {
-      std::list<transaction> pool_txs;
-      bool r = m_core.get_pool_transactions(pool_txs);
+      std::vector<tx_info> pool_tx_info;
+      std::vector<spent_key_image_info> pool_key_image_info;
+      bool r = m_core.get_pool_transactions_and_spent_keys_info(pool_tx_info, pool_key_image_info);
       if(r)
       {
         // sort to match original request
         std::list<transaction> sorted_txs;
-        std::list<cryptonote::transaction>::const_iterator i;
+        std::vector<tx_info>::const_iterator i;
         for (const crypto::hash &h: vh)
         {
           if (std::find(missed_txs.begin(), missed_txs.end(), h) == missed_txs.end())
@@ -500,11 +502,26 @@ namespace cryptonote
             sorted_txs.push_back(std::move(txs.front()));
             txs.pop_front();
           }
-          else if ((i = std::find_if(pool_txs.begin(), pool_txs.end(), [h](cryptonote::transaction &tx) { return h == cryptonote::get_transaction_hash(tx); })) != pool_txs.end())
+          else if ((i = std::find_if(pool_tx_info.begin(), pool_tx_info.end(), [h](const tx_info &txi) { return epee::string_tools::pod_to_hex(h) == txi.id_hash; })) != pool_tx_info.end())
           {
-            sorted_txs.push_back(*i);
+            cryptonote::transaction tx;
+            if (!cryptonote::parse_and_validate_tx_from_blob(i->tx_blob, tx))
+            {
+              res.status = "Failed to parse and validate tx from blob";
+              return true;
+            }
+            sorted_txs.push_back(tx);
             missed_txs.remove(h);
             pool_tx_hashes.insert(h);
+            const std::string hash_string = epee::string_tools::pod_to_hex(h);
+            for (const auto &ti: pool_tx_info)
+            {
+              if (ti.id_hash == hash_string)
+              {
+                double_spend_seen.insert(std::make_pair(h, ti.double_spend_seen));
+                break;
+              }
+            }
             ++found_in_pool;
           }
         }
@@ -530,11 +547,21 @@ namespace cryptonote
       if (e.in_pool)
       {
         e.block_height = e.block_timestamp = std::numeric_limits<uint64_t>::max();
+        if (double_spend_seen.find(tx_hash) != double_spend_seen.end())
+        {
+          e.double_spend_seen = double_spend_seen[tx_hash];
+        }
+        else
+        {
+          MERROR("Failed to determine double spend status for " << tx_hash);
+          e.double_spend_seen = false;
+        }
       }
       else
       {
         e.block_height = m_core.get_blockchain_storage().get_db().get_tx_block_height(tx_hash);
         e.block_timestamp = m_core.get_blockchain_storage().get_db().get_block_timestamp(e.block_height);
+        e.double_spend_seen = false;
       }
 
       // fill up old style responses too, in case an old wallet asks