First DNS Query Fails on Windows Server

[moloch--]

Describe the bug

The first DNS-C2 query on Windows Server operating system consistently fails, however subsequent attempts to establish a session are successful. This only seems to affect Windows Server-based operating systems

To Reproduce
Steps to reproduce the behavior:

1. Deploy DNS C2 implant on Windows Server

Expected behavior
Establishes session on first attempt.

Desktop (please complete the following information):

• OS: Windows Server 2k8, and Server 2016
• Version: v0.0.7 (master)

[digital-shokunin]

Not sure if this is related, but after fixing the last issue in #135 I was able to build an implant and test out C2 communications. It seems the implant is reaching the C2 but communication seems to be broken:

[moloch--]

Yea, I've been trying to find sometime to look into more details as to why this is so unreliable. It somewhat related to Windows' Go ( golang/go#33097 (comment) ). The current DNS implementation also lacks redundancy in send/recv/ack, which isn't helping the situation. In my experience if you let the implant sit for a little bit the handshake will eventually go thru.

I've also found v0.0.6 to be slightly more reliable, though there's no significant changes between this and master.