Ban forked peers who are stuck in a getblocks loop (algo #2)

almightyruler · Jul 6, 2015 · fdecc06 · fdecc06
1 parent da8cdb1
commit fdecc06
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Showing 4 changed files with 40 additions and 2 deletions.
diff --git a/src/clientversion.h b/src/clientversion.h
@@ -8,7 +8,7 @@
 // These need to be macros, as version.cpp's and cloudcoin-qt.rc's voodoo requires it
 #define CLIENT_VERSION_MAJOR       1
 #define CLIENT_VERSION_MINOR       3
-#define CLIENT_VERSION_REVISION    2
+#define CLIENT_VERSION_REVISION    3
 #define CLIENT_VERSION_BUILD       0
 
 // Converts the parameter X to a string after macro replacement on X has been performed.

diff --git a/src/main.cpp b/src/main.cpp
@@ -3021,6 +3021,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
         // ppcoin: ask for pending sync-checkpoint if any
         if (!IsInitialBlockDownload())
             Checkpoints::AskForPendingSyncCheckpoint(pfrom);
+
+        // CDC v1.3.3: reset counts to detect forked peers
+        pfrom->nHighestHeightRequested = 0;  /* CDC v1.3.3 */
+        pfrom->nHeightBackwards = 0;  /* CDC v1.3.3 */
+        pfrom->nHeightBackwardsLast = GetTime();  /* CDC v1.3.3 */
+
     }
 
 
@@ -3242,6 +3248,32 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
             pindex = pindex->pnext;
         int nLimit = 500;
         printf("getblocks %d to %s limit %d from %s\n", (pindex ? pindex->nHeight : -1), hashStop.ToString().substr(0,20).c_str(), nLimit, pfrom->addr.ToString().c_str());
+
+
+        // CDC v1.3.3: detect when peers go backwards in the height of blocks that they request, which is a sign of a forked client stuck in an endless loop. if this happens too many times, ban the peer.
+        if (pindex)    // only act when an explicit height is requested
+        {
+            if (pindex->nHeight > pfrom->nHighestHeightRequested)
+            {
+                pfrom->nHighestHeightRequested = pindex->nHeight;
+            } else {
+                if (pindex->nHeight < (pfrom->nHighestHeightRequested - 500))   // peer has gone backwards in height when requesting blocks
+                {
+                    if (pfrom->nHeightBackwardsLast < (GetTime() - 3600))  pfrom->nHeightBackwards = 0;  // reset penalty count if last backward leap was more than an hour ago
+                    pfrom->nHeightBackwards++;
+                    printf("peer %s: leap backwards in height request, from max %d to current %d. penalty=%d/100\n", pfrom->addr.ToString().c_str(), pfrom->nHighestHeightRequested, pindex->nHeight,
+                        pfrom->nHeightBackwards);
+                    pfrom->nHeightBackwardsLast = GetTime();
+                    pfrom->nHighestHeightRequested = pindex->nHeight;  // reset maximum to height of current request
+                }
+            }
+            if (pfrom->nHeightBackwards >= 100)
+            {
+                  pfrom->Misbehaving(100);
+                  return error("peer %s: sync repeatedly leaping backwards to lower height", pfrom->addr.ToString().c_str());
+            }
+        }
+
         for (; pindex; pindex = pindex->pnext)
         {
             if (pindex->GetBlockHash() == hashStop)

diff --git a/src/net.h b/src/net.h
@@ -165,6 +165,9 @@ class CNode
     int64 nLastRecv;
     int64 nLastSendEmpty;
     int64 nTimeConnected;
+    int nHighestHeightRequested;  /* CDC v1.3.3 */
+    int nHeightBackwards;  /* CDC v1.3.3 */
+    int64 nHeightBackwardsLast;  /* CDC v1.3.3 */
     int nHeaderStart;
     unsigned int nMessageStart;
     CAddress addr;
@@ -216,6 +219,9 @@ class CNode
         hSocket = hSocketIn;
         nLastSend = 0;
         nLastRecv = 0;
+        nHighestHeightRequested = 0;  /* CDC v1.3.3 */
+        nHeightBackwards = 0;  /* CDC v1.3.3 */
+        nHeightBackwardsLast = GetTime();  /* CDC v1.3.3 */
         nLastSendEmpty = GetTime();
         nTimeConnected = GetTime();
         nHeaderStart = -1;

diff --git a/src/version.h b/src/version.h
@@ -46,7 +46,7 @@ static const int MEMPOOL_GD_VERSION = 60002;
 
 #define DISPLAY_VERSION_MAJOR       1
 #define DISPLAY_VERSION_MINOR       3
-#define DISPLAY_VERSION_REVISION    2
+#define DISPLAY_VERSION_REVISION    3
 #define DISPLAY_VERSION_BUILD       0
 
 #endif