Merge pull request #1074 from rickshaw5724/avoidReadingTimeStampCounter

Avoid reading time stamp counter

src/NetMQ/Core/Utils/OpCode.cs

@@ -11,6 +11,15 @@ internal static class Opcode
 
         public static bool Open()
         {
+            // Look for an environment variable: "NETQM_SUPPRESS_RDTSC" with any value.
+            // The application can set this environment variable when this code is running in a system where
+            // it is not desirable to read the processor's time stamp counter.
+            // While this is supported in modern CPUs, the technique used for allocating executable memory, copying OP Code
+            // for the read of the time stamp and invoking the OP Code can be detected as Malware by some anti-virus vendors.
+            // https://github.com/zeromq/netmq/issues/1071
+            string val = Environment.GetEnvironmentVariable("NETQM_SUPPRESS_RDTSC");
+            if (!string.IsNullOrEmpty(val))
+                return false;
 #if NETSTANDARD1_1_OR_GREATER || NET471_OR_GREATER
             if (RuntimeInformation.ProcessArchitecture != Architecture.X86 &&
                 RuntimeInformation.ProcessArchitecture != Architecture.X64)