Use direct UDP traffic if allowed

[yarrick]

On startup, iodine should get the ip of the iodined server (via NS dns lookup or similar) and try sending direct UDP to it. If a response arrives, skip the DNS protocol entirely and just send data directly. This will give very good performance and eliminates the need for OpenVPN running on udp/53 on another public ip.

[yarrick]

Added way for client to ask for external IP of server in [879]

[yarrick]

Updated client to get remote IP in [880].

[yarrick]

Commited [882], send raw udp login message directly to server

[yarrick]

In [883], server responds to raw login

[yarrick]

Client does basic handling of raw reply after [884]

[guest]

Issue 66 prevents direct UDP from working on win32:  http://dev.kryo.se/iodine/ticket/66

[yarrick]

Replying to guest:

Issue 66 prevents direct UDP from working on win32:  http://dev.kryo.se/iodine/ticket/66

Use the -n option on the server to work around this. And this feature does not yet work anywhere.. :)

[yarrick]

One-way raw traffic now working, after [903].

[yarrick]

Basic tunnel works, [904].

Left to do:

• Keepalive message, every 30 seconds or so (like old P packet)
• Cmdline option to turn off raw mode
• Test raw and dns mode simultaneously on one server

[yarrick]

[906], added -r cmd line option to skip raw mode.

[yarrick]

[908], now sends keepalive message so server and any NAT firewalls know connection still is up