From 91eee1a42d1de4ed2b08d800003d15ece0cbbd7f Mon Sep 17 00:00:00 2001
From: Nik Bougalis <nikb@bougalis.net>
Date: Mon, 7 Sep 2015 08:59:16 -0700
Subject: [PATCH] Limit the number of offers that can be consumed during
 crossing

---
 src/ripple/app/tx/impl/CreateOffer.cpp | 24 ++++++++++++++++++++++++
 src/ripple/app/tx/impl/CreateOffer.h   |  5 +++++
 2 files changed, 29 insertions(+)

diff --git a/src/ripple/app/tx/impl/CreateOffer.cpp b/src/ripple/app/tx/impl/CreateOffer.cpp
index b13eb0fbe3..469a21bef1 100644
--- a/src/ripple/app/tx/impl/CreateOffer.cpp
+++ b/src/ripple/app/tx/impl/CreateOffer.cpp
@@ -224,6 +224,18 @@ CreateOffer::select_path (
     return std::make_pair (false, bridged_quality);
 }
 
+bool
+CreateOffer::reachedOfferCrossingLimit (Taker const& taker) const
+{
+    auto const crossings =
+        taker.get_direct_crossings () +
+        (2 * taker.get_bridge_crossings ());
+
+    // The crossing limit is part of the Ripple protocol and
+    // changing it is a transaction-processing change.
+    return crossings >= 850;
+}
+
 std::pair<TER, Amounts>
 CreateOffer::bridged_cross (
     Taker& taker,
@@ -358,6 +370,12 @@ CreateOffer::bridged_cross (
             break;
         }
 
+        if (reachedOfferCrossingLimit (taker))
+        {
+            j_.debug << "The offer crossing limit has been exceeded!";
+            break;
+        }
+
         // Postcondition: If we aren't done, then we *must* have consumed at
         //                least one offer fully.
         assert (direct_consumed || leg1_consumed || leg2_consumed);
@@ -432,6 +450,12 @@ CreateOffer::direct_cross (
             break;
         }
 
+        if (reachedOfferCrossingLimit (taker))
+        {
+            j_.debug << "The offer crossing limit has been exceeded!";
+            break;
+        }
+
         // Postcondition: If we aren't done, then we *must* have consumed the
         //                offer on the books fully!
         assert (direct_consumed);
diff --git a/src/ripple/app/tx/impl/CreateOffer.h b/src/ripple/app/tx/impl/CreateOffer.h
index 5e4a3a96e2..45b8c82492 100644
--- a/src/ripple/app/tx/impl/CreateOffer.h
+++ b/src/ripple/app/tx/impl/CreateOffer.h
@@ -97,6 +97,11 @@ private:
     bool
     step_account (OfferStream& stream, Taker const& taker);
 
+    // True if the number of offers that have been crossed
+    // exceeds the limit.
+    bool
+    reachedOfferCrossingLimit (Taker const& taker) const;
+
     // Fill offer as much as possible by consuming offers already on the books,
     // and adjusting account balances accordingly.
     //