3 files changed, 57 insertions, 12 deletions
diff --git a/src/cryptonote_protocol/cryptonote_protocol_defs.h b/src/cryptonote_protocol/cryptonote_protocol_defs.h
index db159f0f4..d5bb50930 100644
--- a/src/cryptonote_protocol/cryptonote_protocol_defs.h
+++ b/src/cryptonote_protocol/cryptonote_protocol_defs.h
@@ -146,9 +146,11 @@ namespace cryptonote
     struct request
     {
       std::vector<blobdata>   txs;
+      std::string _; // padding
 
       BEGIN_KV_SERIALIZE_MAP()
         KV_SERIALIZE(txs)
+        KV_SERIALIZE(_)
       END_KV_SERIALIZE_MAP()
     };
   };
diff --git a/src/cryptonote_protocol/cryptonote_protocol_handler.h b/src/cryptonote_protocol/cryptonote_protocol_handler.h
index d7b74c06d..618b635cc 100644
--- a/src/cryptonote_protocol/cryptonote_protocol_handler.h
+++ b/src/cryptonote_protocol/cryptonote_protocol_handler.h
@@ -131,6 +131,7 @@ namespace cryptonote
     bool should_download_next_span(cryptonote_connection_context& context) const;
     void drop_connection(cryptonote_connection_context &context, bool add_fail, bool flush_all_spans);
     bool kick_idle_peers();
+    bool check_standby_peers();
     int try_add_next_blocks(cryptonote_connection_context &context);
 
     t_core& m_core;
@@ -143,6 +144,7 @@ namespace cryptonote
     boost::mutex m_sync_lock;
     block_queue m_block_queue;
     epee::math_helper::once_a_time_seconds<30> m_idle_peer_kicker;
+    epee::math_helper::once_a_time_milliseconds<100> m_standby_checker;
 
     boost::mutex m_buffer_mutex;
     double get_avg_block_size();
diff --git a/src/cryptonote_protocol/cryptonote_protocol_handler.inl b/src/cryptonote_protocol/cryptonote_protocol_handler.inl
index 5ba637c2f..999ec5650 100644
--- a/src/cryptonote_protocol/cryptonote_protocol_handler.inl
+++ b/src/cryptonote_protocol/cryptonote_protocol_handler.inl
@@ -1210,6 +1210,7 @@ skip:
   bool t_cryptonote_protocol_handler<t_core>::on_idle()
   {
     m_idle_peer_kicker.do_call(boost::bind(&t_cryptonote_protocol_handler<t_core>::kick_idle_peers, this));
+    m_standby_checker.do_call(boost::bind(&t_cryptonote_protocol_handler<t_core>::check_standby_peers, this));
     return m_core.on_idle();
   }
   //------------------------------------------------------------------------------------------------------------------------
@@ -1245,6 +1246,22 @@ skip:
   }
   //------------------------------------------------------------------------------------------------------------------------
   template<class t_core>
+  bool t_cryptonote_protocol_handler<t_core>::check_standby_peers()
+  {
+    m_p2p->for_each_connection([&](cryptonote_connection_context& context, nodetool::peerid_type peer_id, uint32_t support_flags)->bool
+    {
+      if (context.m_state == cryptonote_connection_context::state_standby)
+      {
+        LOG_PRINT_CCONTEXT_L2("requesting callback");
+        ++context.m_callback_request_count;
+        m_p2p->request_callback(context);
+      }
+      return true;
+    });
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------
+  template<class t_core>
   int t_cryptonote_protocol_handler<t_core>::handle_request_chain(int command, NOTIFY_REQUEST_CHAIN::request& arg, cryptonote_connection_context& context)
   {
     MLOG_P2P_MESSAGE("Received NOTIFY_REQUEST_CHAIN (" << arg.block_ids.size() << " blocks");
@@ -1338,14 +1355,13 @@ skip:
     bool start_from_current_chain = false;
     if (!force_next_span)
     {
-      bool first = true;
-      while (1)
+      do
       {
         size_t nblocks = m_block_queue.get_num_filled_spans();
         size_t size = m_block_queue.get_data_size();
         if (nblocks < BLOCK_QUEUE_NBLOCKS_THRESHOLD || size < BLOCK_QUEUE_SIZE_THRESHOLD)
         {
-          if (!first)
+          if (context.m_state != cryptonote_connection_context::state_standby)
           {
             LOG_DEBUG_CC(context, "Block queue is " << nblocks << " and " << size << ", resuming");
           }
@@ -1368,10 +1384,9 @@ skip:
           break;
         }
 
-        if (first)
+        if (context.m_state != cryptonote_connection_context::state_standby)
         {
           LOG_DEBUG_CC(context, "Block queue is " << nblocks << " and " << size << ", pausing");
-          first = false;
           context.m_state = cryptonote_connection_context::state_standby;
         }
 
@@ -1385,13 +1400,8 @@ skip:
           return true;
         }
 
-        for (size_t n = 0; n < 50; ++n)
-        {
-          if (m_stopping)
-            return true;
-          boost::this_thread::sleep_for(boost::chrono::milliseconds(100));
-        }
-      }
+        return true;
+      } while(0);
       context.m_state = cryptonote_connection_context::state_synchronizing;
     }
 
@@ -1726,8 +1736,39 @@ skip:
   bool t_cryptonote_protocol_handler<t_core>::relay_transactions(NOTIFY_NEW_TRANSACTIONS::request& arg, cryptonote_connection_context& exclude_context)
   {
     // no check for success, so tell core they're relayed unconditionally
+    const bool pad_transactions = m_core.pad_transactions();
+    size_t bytes = pad_transactions ? 9 /* header */ + 4 /* 1 + 'txs' */ + tools::get_varint_data(arg.txs.size()).size() : 0;
     for(auto tx_blob_it = arg.txs.begin(); tx_blob_it!=arg.txs.end(); ++tx_blob_it)
+    {
       m_core.on_transaction_relayed(*tx_blob_it);
+      if (pad_transactions)
+        bytes += tools::get_varint_data(tx_blob_it->size()).size() + tx_blob_it->size();
+    }
+
+    if (pad_transactions)
+    {
+      // stuff some dummy bytes in to stay safe from traffic volume analysis
+      static constexpr size_t granularity = 1024;
+      size_t padding = granularity - bytes % granularity;
+      const size_t overhead = 2 /* 1 + '_' */ + tools::get_varint_data(padding).size();
+      if (overhead > padding)
+        padding = 0;
+      else
+        padding -= overhead;
+      arg._ = std::string(padding, ' ');
+
+      std::string arg_buff;
+      epee::serialization::store_t_to_binary(arg, arg_buff);
+
+      // we probably lowballed the payload size a bit, so added a but too much. Fix this now.
+      size_t remove = arg_buff.size() % granularity;
+      if (remove > arg._.size())
+        arg._.clear();
+      else
+        arg._.resize(arg._.size() - remove);
+      // if the size of _ moved enough, we might lose byte in size encoding, we don't care
+    }
+
     return relay_post_notify<NOTIFY_NEW_TRANSACTIONS>(arg, exclude_context);
   }
   //------------------------------------------------------------------------------------------------------------------------