commander: prevent potential disarms in-air

[julianoes]

This fixes the terrifying case where the drone disarms in-air just because it receives a MAVLink disarm command. We now check param2 for a magic number which enforces arming/disarming.

This is added to the mavlink protocol in:
mavlink/mavlink#1162

Testing done using MAVSDK mavlink/MAVSDK#817.

If you want to reproduce the test:

cmake -Bbuild -DCMAKE_BUILD_TYPE=Debug -H. && cmake --build build -j8 && build/src/integration_tests/integration_tests_runner --gtest_filter="SitlTest.ActionTakeoffAndKill"

[dagar]

Looks good, although I'm wondering about capturing more of these details in the state machine. I don't suppose the magic number (21196) is accessible through the mavlink spec?

[julianoes]

Looks good, although I'm wondering about capturing more of these details in the state machine.

I wonder too but that's one we know.

I don't suppose the magic number (21196) is accessible through the mavlink spec?

It's just in the description of that message.

I'm glad you're back @dagar! :)

[julianoes]

@ItsTimmy yay, the rover CI check prevented me from merging something that could break rover.

[MaEtUgR]

@julianoes Thanks for the hotfix! Just to be safe I tested the exact problem we had and it prevents disarming like expected.

What I still don't like and only makes this a hotfix for me is that RC and joystick are not handled by the same code path and checks and there arise other unexpected corner cases. One of them I found is that if you disarm in manual mode by RC it's allowed. By MAVLink command it's not.

[dagar]

What I still don't like and only makes this a hotfix for me is that RC and joystick are not handled by the same code path and checks and there arise other unexpected corner cases. One of them I found is that if you disarm in manual mode by RC it's allowed. By MAVLink command it's not.

That's the scenario I was thinking about above and why I'd like to pull most of this scattered logic together into a state machine.

[julianoes]

I don't disagree.