EVTM sender for MCP

[shubhagrawal30]

MCP can send UDP multicast packets through the LOS/biphase and TDRSS/highrate EVTM downlinks.

Scope:

• changes made to mcp and related files.
• no changes yet for receiving ground software (groundhog).
• some sporadic non-exhaustive formatting changes to old code.
• exhaustive (?) test code for the new evtm code
• no changes for possible integration with code for Iridium Pilot

Relevant Issue: #60

Testing Reception At Ground Station:

1. iperf: Run iperf -s -B 239.255.0.1 -u -i 1 -p 20001 and iperf -s -B 239.255.0.1 -u -i 1 -p 20001.
2. tcpdump: Run sudo tcpdump and see UDP packets sent to 239.255.0.1:20001 and 239.255.0.2:20002.
3. C code: Compile listener.c and run listener 239.255.0.1 20001 or listener 239.255.0.2 20002 (output will not be legible, but you should receive several packets).

TODOs for new GSs or FCs for testing:

1. Turn off ufw firewall on the ground station: sudo ufw disable. --> OR BETTER OPTION: run sudo ufw allow 20001/udp and sudo ufw allow 20001/udp to get incoming UDP traffice on the relevent ports!
2. On your flight computer, add a default gateway to the gondola network config in /etc/netplan/00-installer-config.yaml:     routes:         - to: default           via: 192.168.1.1

[shubhagrawal30]

Additionally, figured out how to not disable the entire ground station firewall, and instead add permissions for relevant ports.

[evanmayer]

Waiting for @ianlowe13 and @mxk62 approvals.