Implement ICE restarts

When network conditions change or the current route is congested, it’s possible to restart ICE and gather/select a new candidate pair. Apparently this happens very frequently with cellular networks or with certain types of NATs.

Restart is done by calling createOffer with the iceRestart option when iceConnectionState == 'failed'.

As an optimization, ICE restart can be done preemptively when iceConnectionState == 'disconnected' (before 'failed') and it won’t immediately bounce back to connected.

[t-mullen]

• We currently avoid glare by sending a { renegotiate: true } message from the non-initiator to the initiator. We could expand this message to be { renegotiate: { iceRestart: true/false }. Offers from the non-initiator were not well-supported when I implemented renegotiation.

• I don’t think we need to listen for negotiationeeded. This wasn’t required for changing media, but it’s worth a test.

• That makes sense to me. Developers disabling trickle usually have very simple signalling setups (ie copy-paste) and we don’t want to break that.

[t-mullen]

simple-peer should detect the ice connection state 'failed' and do this transparently (no public API, except maybe a max number of restart attempts).

Restart is just renegotiation with iceRestart: true in createOffer (or by callingrestartIce() if that’s implemented in the browser).

https://developer.mozilla.org/en-US/docs/Web/API/RTCOfferOptions/iceRestart https://medium.com/the-making-of-whereby/ice-restarts-5d759caceda6