Update litep2p with WebRTC Transport Support

[timwu20]

Summary

• Updates litep2p from crates.io v0.13.0 to a git revision (27b110d1) that includes WebRTC transport support, and enables the new webrtc feature flag
• Adds WebRTC address parsing to the litep2p network backend so that /ip4/.../udp/.../webrtc listen addresses are recognized and routed to the WebRTC transport
• Extends known-address handling to recognize WebRTC and Certhash multiaddr protocols when appending /p2p/<peer_id> to addresses

Details

Dependency change (Cargo.toml)

The litep2p dependency is switched from a crates.io release to a pinned git commit from the chainsafe/litep2p repository, with the webrtc feature added alongside the existing rsa and websocket features. This also pulls in str0m (a WebRTC media/data library) as a new transitive dependency.

Listen address parsing (substrate/client/network/src/litep2p/mod.rs)

The previous implementation used an iterator-based filter_map + unzip pattern to split listen addresses into TCP and WebSocket buckets. This is refactored into an explicit for loop that classifies addresses into three categories:

Address pattern	Transport
/ip{4,6}/.../tcp/.../ws or /wss	WebSocket
/ip{4,6}/.../tcp/...	TCP
/ip{4,6}/.../udp/.../webrtc	WebRTC (new)

The WebRTC transport is conditionally configured — it is only added to the litep2p config when at least one WebRTC listen address is provided.

Known-address protocol matching

The address-matching logic in NetworkBackend::new is updated to also recognize Protocol::WebRTC and Protocol::Certhash(_) as valid terminal protocols before appending /p2p/<peer_id>, ensuring WebRTC addresses from the DHT or other discovery mechanisms are correctly handled.

Test plan

• Verify that existing TCP and WebSocket listen addresses continue to work as before
• Configure a node with a WebRTC listen address (e.g., /ip4/0.0.0.0/udp/30333/webrtc) and confirm it starts listening on WebRTC
• Confirm that WebRTC peer addresses discovered via DHT are properly formatted with the /p2p suffix
• Run cargo build -p polkadot --release to confirm successful compilation
• Run network-related tests: cargo test -p sc-network