Merge pull request #4903

efad808 Avoid reject message feedback loops (Pieter Wuille)

src/main.cpp

@@ -4111,21 +4111,25 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
 
     else if (strCommand == "reject")
     {
-        if (fDebug)
-        {
-            string strMsg; unsigned char ccode; string strReason;
-            vRecv >> LIMITED_STRING(strMsg, CMessageHeader::COMMAND_SIZE) >> ccode >> LIMITED_STRING(strReason, 111);
+        if (fDebug) {
+            try {
+                string strMsg; unsigned char ccode; string strReason;
+                vRecv >> LIMITED_STRING(strMsg, CMessageHeader::COMMAND_SIZE) >> ccode >> LIMITED_STRING(strReason, 111);
 
-            ostringstream ss;
-            ss << strMsg << " code " << itostr(ccode) << ": " << strReason;
+                ostringstream ss;
+                ss << strMsg << " code " << itostr(ccode) << ": " << strReason;
 
-            if (strMsg == "block" || strMsg == "tx")
-            {
-                uint256 hash;
-                vRecv >> hash;
-                ss << ": hash " << hash.ToString();
+                if (strMsg == "block" || strMsg == "tx")
+                {
+                    uint256 hash;
+                    vRecv >> hash;
+                    ss << ": hash " << hash.ToString();
+                }
+                LogPrint("net", "Reject %s\n", SanitizeString(ss.str()));
+            } catch (std::ios_base::failure& e) {
+                // Avoid feedback loops by preventing reject messages from triggering a new reject message.
+                LogPrint("net", "Unparseable reject message received\n");
             }
-            LogPrint("net", "Reject %s\n", SanitizeString(ss.str()));
         }
     }