Fix issue #1212 - Candidate with empty string

[DevRockstarZ]

Description

I made the first test code by myself, it can be not perfect 😢
I tested on my local terminal, it passes all the cases.
I created test PeerConnection to use AddICECandidate, and I tested 3 test cases.
Thanks for reviewing!

Reference issue

Fixes issue #1212

[Sean-Der]

Hey @DevRockstarZ this PR looks really good to me!

If you want to reopen I would love to merge this :) I will just squash your work into one commit. Really great work!

[DevRockstarZ]

@Sean-Der Thanks for your reply! I closed this PR because I thought you're working on this work in Pion-V3.
I thought this PR will unnecessary... 😢
If re-open this PR is fine, I will re-open it! Thanks!

[jsmouret]

Isn't it hiding the real issue?
pion/ice#271

[DevRockstarZ]

@jsmouret
I also think real issue is not cleared.
So I did temporary fix to do not print errors from empty candidate.
I think real issue will be cleared when pion releases version 3.
Thanks!

[Sean-Der]

You are right @jsmouret thanks for keeping me honest :)

So I think this is a two step process

• Update pion/ice to accept a nil candidate. AddRemoteCandidate when called with nil should then set a field on the agent.

in the contact loop it shouldn't go to failed unless this field has been set.

restart should update this field as well.

• then pion/webrtc should be updated to pass a nil candidate in.

This is a good amount of work, but I think there is a clear path forward! If anyone is interested in grabbing I can help :) the work done on the tests here is really great, I think we can use as is

[scorpionknifes]

Hey, @Sean-Der I'm reading into this and trying to clarify some stuff. (1st step ICE)

I'm reading into 5.6.3 RTCIceGathererState and

complete	The RTCIceTransport has completed gathering and the end-of-candidates indication for this transport has been sent. It will not gather candidates again until an ICE restart causes it to restart.

I'm assuming the field on the agent that should be set is GatheringState by agent.setGatheringState

Since GatheringState is already reset in agent.Restart i think we don't need to update this field.

I'm also not too sure where to check this in contact loop.

[Sean-Der]

ICEGatherState is good, I don't believe we need to update that! The implementation of Trickling out of Pion I think is complete.

What we need to do is

• Update the ICE Agent to not go to failed until it sees a end-of-candidates that check would go here
• Update pion/webrtc to accept nil candidates, and send a end-of-candidates notification into pion/ice
• Restart just needs to clear has-remote-sent-end-of-candidates flag

[scorpionknifes]

@Sean-Der, need some advice

how do I store end-of-candidate attribute in ICE Agent?

since we sending nil to AddICECandidate do we want to pass nil to ICE or should we create a new func?