protocol: request txpool contents when synced

A newly synced Alice sends a (typically quite small) list of
txids in the local tpxool to a random peer Bob, who then uses
the existing tx relay system to send Alice any tx in his txpool
which is not in the list Alice sent

4 files changed, 53 insertions, 0 deletions

diff --git a/src/cryptonote_core/cryptonote_core.cpp b/src/cryptonote_core/cryptonote_core.cpp
index 8b1613b4b..de60367e6 100644
--- a/src/cryptonote_core/cryptonote_core.cpp
+++ b/src/cryptonote_core/cryptonote_core.cpp
@@ -1946,6 +1946,12 @@ namespace cryptonote
   {
     m_blockchain_storage.flush_invalid_blocks();
   }
+  //-----------------------------------------------------------------------------------------------
+  bool core::get_txpool_complement(const std::vector<crypto::hash> &hashes, std::vector<cryptonote::blobdata> &txes)
+  {
+    return m_mempool.get_complement(hashes, txes);
+  }
+  //-----------------------------------------------------------------------------------------------
   bool core::update_blockchain_pruning()
   {
     return m_blockchain_storage.update_blockchain_pruning();
diff --git a/src/cryptonote_core/cryptonote_core.h b/src/cryptonote_core/cryptonote_core.h
index 5dec890e8..6fb2f68ab 100644
--- a/src/cryptonote_core/cryptonote_core.h
+++ b/src/cryptonote_core/cryptonote_core.h
@@ -864,6 +864,15 @@ namespace cryptonote
       */
      void flush_invalid_blocks();
 
+     /**
+      * @brief returns the set of transactions in the txpool which are not in the argument
+      *
+      * @param hashes hashes of transactions to exclude from the result
+      *
+      * @return true iff success, false otherwise
+      */
+     bool get_txpool_complement(const std::vector<crypto::hash> &hashes, std::vector<cryptonote::blobdata> &txes);
+
    private:
 
      /**
diff --git a/src/cryptonote_core/tx_pool.cpp b/src/cryptonote_core/tx_pool.cpp
index 1bc475879..8c8e43c90 100644
--- a/src/cryptonote_core/tx_pool.cpp
+++ b/src/cryptonote_core/tx_pool.cpp
@@ -594,6 +594,39 @@ namespace cryptonote
     return true;
   }
   //---------------------------------------------------------------------------------
+  bool tx_memory_pool::get_complement(const std::vector<crypto::hash> &hashes, std::vector<cryptonote::blobdata> &txes) const
+  {
+    CRITICAL_REGION_LOCAL(m_transactions_lock);
+    CRITICAL_REGION_LOCAL1(m_blockchain);
+
+    m_blockchain.for_all_txpool_txes([this, &hashes, &txes](const crypto::hash &txid, const txpool_tx_meta_t &meta, const cryptonote::blobdata*) {
+      const auto relay_method = meta.get_relay_method();
+      if (relay_method != relay_method::block && relay_method != relay_method::fluff)
+        return true;
+      const auto i = std::find(hashes.begin(), hashes.end(), txid);
+      if (i == hashes.end())
+      {
+        cryptonote::blobdata bd;
+        try
+        {
+          if (!m_blockchain.get_txpool_tx_blob(txid, bd, cryptonote::relay_category::broadcasted))
+          {
+            MERROR("Failed to get blob for txpool transaction " << txid);
+            return true;
+          }
+          txes.emplace_back(std::move(bd));
+        }
+        catch (const std::exception &e)
+        {
+          MERROR("Failed to get blob for txpool transaction " << txid << ": " << e.what());
+          return true;
+        }
+      }
+      return true;
+    }, false);
+    return true;
+  }
+  //---------------------------------------------------------------------------------
   void tx_memory_pool::on_idle()
   {
     m_remove_stuck_tx_interval.do_call([this](){return remove_stuck_transactions();});
diff --git a/src/cryptonote_core/tx_pool.h b/src/cryptonote_core/tx_pool.h
index f716440ad..ca0e50415 100644
--- a/src/cryptonote_core/tx_pool.h
+++ b/src/cryptonote_core/tx_pool.h
@@ -441,6 +441,11 @@ namespace cryptonote
      */
     bool get_transaction_info(const crypto::hash &txid, tx_details &td) const;
 
+    /**
+     * @brief get transactions not in the passed set
+     */
+    bool get_complement(const std::vector<crypto::hash> &hashes, std::vector<cryptonote::blobdata> &txes) const;
+
   private:
 
     /**