Implement "feefilter" P2P message.

The "feefilter" p2p message is used to inform other nodes of your mempool min fee which is the feerate that any new transaction must meet to be accepted to your mempool.  This will allow them to filter invs to you according to this feerate.

2 files changed, 32 insertions, 0 deletions

diff --git a/src/policy/fees.cpp b/src/policy/fees.cpp
index de3c060d6a..7b0e8b7d08 100644
--- a/src/policy/fees.cpp
+++ b/src/policy/fees.cpp
@@ -8,6 +8,7 @@
 
 #include "amount.h"
 #include "primitives/transaction.h"
+#include "random.h"
 #include "streams.h"
 #include "txmempool.h"
 #include "util.h"
@@ -580,3 +581,21 @@ void CBlockPolicyEstimator::Read(CAutoFile& filein)
     priStats.Read(filein);
     nBestSeenHeight = nFileBestSeenHeight;
 }
+
+FeeFilterRounder::FeeFilterRounder(const CFeeRate& minIncrementalFee)
+{
+    CAmount minFeeLimit = minIncrementalFee.GetFeePerK() / 2;
+    feeset.insert(0);
+    for (double bucketBoundary = minFeeLimit; bucketBoundary <= MAX_FEERATE; bucketBoundary *= FEE_SPACING) {
+        feeset.insert(bucketBoundary);
+    }
+}
+
+CAmount FeeFilterRounder::round(CAmount currentMinFee)
+{
+    std::set<double>::iterator it = feeset.lower_bound(currentMinFee);
+    if ((it != feeset.begin() && insecure_rand() % 3 != 0) || it == feeset.end()) {
+        it--;
+    }
+    return *it;
+}
diff --git a/src/policy/fees.h b/src/policy/fees.h
index 3fa31c39e7..cdd984de7d 100644
--- a/src/policy/fees.h
+++ b/src/policy/fees.h
@@ -286,4 +286,17 @@ private:
     CFeeRate feeLikely, feeUnlikely;
     double priLikely, priUnlikely;
 };
+
+class FeeFilterRounder
+{
+public:
+    /** Create new FeeFilterRounder */
+    FeeFilterRounder(const CFeeRate& minIncrementalFee);
+
+    /** Quantize a minimum fee for privacy purpose before broadcast **/
+    CAmount round(CAmount currentMinFee);
+
+private:
+    std::set<double> feeset;
+};
 #endif /*BITCOIN_POLICYESTIMATOR_H */