v2.1.0 — TCP API, dual-path WG handshake

What's New

TCP Socket API

• microlink_tcp_connect() / microlink_tcp_send() / microlink_tcp_recv() / microlink_tcp_close()
• TCP sockets route through the WireGuard tunnel by binding to the VPN IP internally
• Auto-triggers WG handshake and waits up to 30s for tunnel establishment
• Enables use cases like GPS trackers sending to Traccar over Tailscale

Dual-Path WireGuard Handshake

• Handshake initiation now sent via both DERP relay AND direct UDP simultaneously
• Wakes fully trimmed peers (idle >5 min) without waiting for DERP round-trip
• Reduces cold-start connection time significantly

Reliability Fixes

• Zombie peer fix: wireguardif_connect() no longer leaves active=true, preventing infinite 5-second handshake retries
• EarlyNoise slow-path: Handles proactive server frames arriving in separate TCP segments (common on cellular PPP)
• H2 END_STREAM early-break: do_register() scans for END_STREAM flag to break early instead of blocking 60s
• Enhanced WireGuard diagnostics: Detailed logging for handshake completion and periodic initiation

Example Updates

• cellular_connect example now supports UDP/TCP transport selection via menuconfig
• UDP remains the default transport