Auto merge of #1588 - bitcartel:upstream_8427_dos_logging, r=daira

Upstream: Prevent possible DoS in logging

bitcoin/bitcoin#8427

src/main.cpp

@@ -5090,8 +5090,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         }
     }
 
-    else
-    {
+    else if (strCommand == "notfound") {
+        // We do not care about the NOTFOUND message, but logging an Unknown Command
+        // message would be undesirable as we transmit it ourselves.
+    }
+
+    else {
         // Ignore unknown commands for extensibility
         LogPrint("net", "Unknown command \"%s\" from peer=%d\n", SanitizeString(strCommand), pfrom->id);
     }