Ban forked peers who are stuck in a getblocks loop.

Merged from almightyruler/cloudcoin@fdecc06
nochowderforyou · Jul 11, 2015 · c351f77 · c351f77
1 parent 196e127
commit c351f77
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Showing 2 changed files with 36 additions and 0 deletions.
diff --git a/src/main.cpp b/src/main.cpp
@@ -3306,6 +3306,11 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         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 */
+
         pfrom->nTimeOffset = nTime - GetTime();
 
         if (GetBoolArg("-synctime", true))
@@ -3482,6 +3487,31 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             pindex = pindex->pnext;
         int nLimit = 1000;
         LogPrint("net", "getblocks %d to %s limit %d\n", (pindex ? pindex->nHeight : -1), hashStop.ToString(), nLimit);
+
+        // 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++;
+                    LogPrintf("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
@@ -198,6 +198,9 @@ class CNode
     int64_t nLastSend;
     int64_t nLastRecv;
     int64_t nTimeConnected;
+    int nHighestHeightRequested;  /* CDC v1.3.3 */
+    int nHeightBackwards;  /* CDC v1.3.3 */
+    int64 nHeightBackwardsLast;  /* CDC v1.3.3 */
     CAddress addr;
     std::string addrName;
     CService addrLocal;
@@ -260,6 +263,9 @@ class CNode
         nLastRecv = 0;
         nSendBytes = 0;
         nRecvBytes = 0;
+        nHighestHeightRequested = 0;  /* CDC v1.3.3 */
+        nHeightBackwards = 0;  /* CDC v1.3.3 */
+        nHeightBackwardsLast = GetTime();  /* CDC v1.3.3 */
         nTimeConnected = GetTime();
         addr = addrIn;
         addrName = addrNameIn == "" ? addr.ToStringIPPort() : addrNameIn;