From c6a63ceeb4956933588995bcf01dc3095aaeb1fc Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Thu, 19 Mar 2015 09:51:59 -0700
Subject: Always use a 50% chance to choose between tried and new entries
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This change was suggested as Countermeasure 2 in
Eclipse Attacks on Bitcoin’s Peer-to-Peer Network, Ethan Heilman,
Alison Kendler, Aviv Zohar, Sharon Goldberg. ePrint Archive Report
2015/263. March 2015.
---
 src/addrman.cpp | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

(limited to 'src/addrman.cpp')

diff --git a/src/addrman.cpp b/src/addrman.cpp
index eb431ec59..5d9527f0e 100644
--- a/src/addrman.cpp
+++ b/src/addrman.cpp
@@ -332,14 +332,13 @@ void CAddrMan::Attempt_(const CService& addr, int64_t nTime)
     info.nAttempts++;
 }
 
-CAddress CAddrMan::Select_(int nUnkBias)
+CAddress CAddrMan::Select_()
 {
     if (size() == 0)
         return CAddress();
 
-    double nCorTried = sqrt(nTried) * (100.0 - nUnkBias);
-    double nCorNew = sqrt(nNew) * nUnkBias;
-    if ((nCorTried + nCorNew) * GetRandInt(1 << 30) / (1 << 30) < nCorTried) {
+    // Use a 50% chance for choosing between tried and new table entries.
+    if (nTried > 0 && (nNew == 0 || GetRandInt(2) == 0)) {
         // use a tried node
         double fChanceFactor = 1.0;
         while (1) {
-- 
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