[WIP] feat(webrtc): add experimental WebRTC transport to litep2p backend

[gab8i]

Description

Add webrtc-direct support to the litep2p backend

• webrtc-direct support gated behind a new --experimental-webrtc CLI flag.
• WebRTC listen_addr entries are skipped with a warning unless enabled.
• Persist the DTLS certificate to <net_config_path>/webrtc_certificate so the node keeps a stable identity across restarts. Fall back to an ephemeral cert otherwise.
• update network type to support WebRTCDirect

Integration

No behavioral change unless --experimental-webrtc is explicitly enabled.

Review Notes

This PR adds experimental webrtc-direct transport support to the litep2p network backend. It is fully opt-in: nothing changes for existing nodes unless the operator explicitly passes --experimental-webrtc and supplies a webrtc-direct listen address. Default backend (litep2p) behavior, the libp2p backend, and all existing transports are untouched.

Checklist

• My PR follows the labeling requirements of this project (at minimum one label for T required)
  • External contributors: Use /cmd label <label-name> to add labels
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• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	cargo/​thiserror@​2.0.12 ⏵ 2.0.18
	cargo/​sqlx@​0.8.2 ⏵ 0.8.6

View full report

[gab8i]

/cmd prdoc --audience node_dev --bump patch

[lexnv]

I think we shouldn't call with_webrtc if the provided listen addresses are empty.

One extra thing would be to warn if:

• experimental webrtc feature is enabled
• no webrtc addresses are provide

[gab8i]

Ok, that's easy to adjust. The idea was to keep the same approach for each transport layer, to support this litep2p does a no-op if config contains no listen addresses.

I will add the warnings and update the code to only call with_webrtc if webrtc_address is not empty!

[lexnv]

Nit: Should we specify that 0.0.0.0 isn't allowed and that the proper external IP address should be configured instead? Maybe we should double check for interface 0.0.0.0 in the provided list?