Adding Dandelion++ support to public networks:

  - New flag in NOTIFY_NEW_TRANSACTION to indicate stem mode
  - Stem loops detected in tx_pool.cpp
  - Embargo timeout for a blackhole attack during stem phase

2 files changed, 29 insertions, 5 deletions

diff --git a/src/blockchain_db/blockchain_db.cpp b/src/blockchain_db/blockchain_db.cpp
index 1a6a19da5..01faf43c4 100644
--- a/src/blockchain_db/blockchain_db.cpp
+++ b/src/blockchain_db/blockchain_db.cpp
@@ -53,9 +53,7 @@ bool matches_category(relay_method method, relay_category category) noexcept
     case relay_category::all:
       return true;
     case relay_category::relayable:
-      if (method == relay_method::none)
-        return false;
-      return true;
+      return method != relay_method::none;
     case relay_category::broadcasted:
     case relay_category::legacy:
       break;
@@ -65,6 +63,7 @@ bool matches_category(relay_method method, relay_category category) noexcept
   {
     default:
     case relay_method::local:
+    case relay_method::stem:
       return false;
     case relay_method::block:
     case relay_method::fluff:
@@ -80,6 +79,7 @@ void txpool_tx_meta_t::set_relay_method(relay_method method) noexcept
   kept_by_block = 0;
   do_not_relay = 0;
   is_local = 0;
+  dandelionpp_stem = 0;
 
   switch (method)
   {
@@ -92,6 +92,9 @@ void txpool_tx_meta_t::set_relay_method(relay_method method) noexcept
     default:
     case relay_method::fluff:
       break;
+    case relay_method::stem:
+      dandelionpp_stem = 1;
+      break;
     case relay_method::block:
       kept_by_block = 1;
       break;
@@ -106,9 +109,26 @@ relay_method txpool_tx_meta_t::get_relay_method() const noexcept
     return relay_method::none;
   if (is_local)
     return relay_method::local;
+  if (dandelionpp_stem)
+    return relay_method::stem;
   return relay_method::fluff;
 }
 
+bool txpool_tx_meta_t::upgrade_relay_method(relay_method method) noexcept
+{
+  static_assert(relay_method::none < relay_method::local, "bad relay_method value");
+  static_assert(relay_method::local < relay_method::stem, "bad relay_method value");
+  static_assert(relay_method::stem < relay_method::fluff, "bad relay_method value");
+  static_assert(relay_method::fluff < relay_method::block, "bad relay_method value");
+
+  if (get_relay_method() < method)
+  {
+    set_relay_method(method);
+    return true;
+  }
+  return false;
+}
+
 const command_line::arg_descriptor<std::string> arg_db_sync_mode = {
   "db-sync-mode"
 , "Specify sync option, using format [safe|fast|fastest]:[sync|async]:[<nblocks_per_sync>[blocks]|<nbytes_per_sync>[bytes]]." 
diff --git a/src/blockchain_db/blockchain_db.h b/src/blockchain_db/blockchain_db.h
index d3a218365..3e2387da4 100644
--- a/src/blockchain_db/blockchain_db.h
+++ b/src/blockchain_db/blockchain_db.h
@@ -160,7 +160,7 @@ struct txpool_tx_meta_t
   uint64_t max_used_block_height;
   uint64_t last_failed_height;
   uint64_t receive_time;
-  uint64_t last_relayed_time;
+  uint64_t last_relayed_time; //!< If Dandelion++ stem, randomized embargo timestamp. Otherwise, last relayed timestmap.
   // 112 bytes
   uint8_t kept_by_block;
   uint8_t relayed;
@@ -168,13 +168,17 @@ struct txpool_tx_meta_t
   uint8_t double_spend_seen: 1;
   uint8_t pruned: 1;
   uint8_t is_local: 1;
-  uint8_t bf_padding: 5;
+  uint8_t dandelionpp_stem : 1;
+  uint8_t bf_padding: 4;
 
   uint8_t padding[76]; // till 192 bytes
 
   void set_relay_method(relay_method method) noexcept;
   relay_method get_relay_method() const noexcept;
 
+  //! \return True if `get_relay_method()` now returns `method`.
+  bool upgrade_relay_method(relay_method method) noexcept;
+
   //! See `relay_category` description
   bool matches(const relay_category category) const noexcept
   {