From 59503acde9eef6520fc177c1cde71fe486d72533 Mon Sep 17 00:00:00 2001
From: theoreticalbts <theoreticalbts@users.noreply.github.com>
Date: Tue, 2 Feb 2016 13:58:58 -0500
Subject: [PATCH] Cap auto-cancel fees at deferred_fee #549

---
 libraries/chain/db_update.cpp                        | 11 +++++++++++
 libraries/chain/include/graphene/chain/evaluator.hpp | 12 ++++++++----
 .../graphene/chain/transaction_evaluation_state.hpp  |  1 +
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/libraries/chain/db_update.cpp b/libraries/chain/db_update.cpp
index 76dc1df9..3855c50b 100644
--- a/libraries/chain/db_update.cpp
+++ b/libraries/chain/db_update.cpp
@@ -264,6 +264,17 @@ void database::clear_expired_orders()
             canceler.fee_paying_account = order.seller;
             canceler.order = order.id;
             canceler.fee = current_fee_schedule().calculate_fee( canceler );
+            if( canceler.fee.amount > order.deferred_fee )
+            {
+               // Cap auto-cancel fees at deferred_fee; see #549
+               wlog( "At block ${b}, fee for clearing expired order ${oid} was capped at deferred_fee ${fee}", ("b", head_block_num())("oid", order.id)("fee", order.deferred_fee) );
+               canceler.fee = asset( order.deferred_fee, asset_id_type() );
+            }
+            // we know the fee for this op is set correctly since it is set by the chain.
+            // this allows us to avoid a hung chain:
+            // - if #549 case above triggers
+            // - if the fee is incorrect, which may happen due to #435 (although since cancel is a fixed-fee op, it shouldn't)
+            cancel_context.skip_fee_schedule_check = true;
             apply_operation(cancel_context, canceler);
          }
      });
diff --git a/libraries/chain/include/graphene/chain/evaluator.hpp b/libraries/chain/include/graphene/chain/evaluator.hpp
index cfbbaea2..a80a2df8 100644
--- a/libraries/chain/include/graphene/chain/evaluator.hpp
+++ b/libraries/chain/include/graphene/chain/evaluator.hpp
@@ -20,6 +20,7 @@
  */
 #pragma once
 #include <graphene/chain/exceptions.hpp>
+#include <graphene/chain/transaction_evaluation_state.hpp>
 #include <graphene/chain/protocol/operations.hpp>
 
 namespace graphene { namespace chain {
@@ -224,10 +225,13 @@ namespace graphene { namespace chain {
          const auto& op = o.get<typename DerivedEvaluator::operation_type>();
 
          prepare_fee(op.fee_payer(), op.fee);
-         GRAPHENE_ASSERT( core_fee_paid >= db().current_fee_schedule().calculate_fee( op ).amount,
-                    insufficient_fee,
-                    "Insufficient Fee Paid",
-                    ("core_fee_paid",core_fee_paid)("required",db().current_fee_schedule().calculate_fee( op ).amount) );
+         if( !trx_state->skip_fee_schedule_check )
+         {
+            GRAPHENE_ASSERT( core_fee_paid >= db().current_fee_schedule().calculate_fee( op ).amount,
+                       insufficient_fee,
+                       "Insufficient Fee Paid",
+                       ("core_fee_paid",core_fee_paid)("required",db().current_fee_schedule().calculate_fee( op ).amount) );
+         }
 
          return eval->do_evaluate(op);
       }
diff --git a/libraries/chain/include/graphene/chain/transaction_evaluation_state.hpp b/libraries/chain/include/graphene/chain/transaction_evaluation_state.hpp
index 4c28e122..4a5b5183 100644
--- a/libraries/chain/include/graphene/chain/transaction_evaluation_state.hpp
+++ b/libraries/chain/include/graphene/chain/transaction_evaluation_state.hpp
@@ -43,5 +43,6 @@ namespace graphene { namespace chain {
          database*                        _db = nullptr;
          bool                             _is_proposed_trx = false;
          bool                             skip_fee = false;
+         bool                             skip_fee_schedule_check = false;
    };
 } } // namespace graphene::chain