Initial commit: waste-go skeleton

Ed25519/X25519/ChaCha20-Poly1305 crypto, peer handshake, mesh state,
IPC server, relay server, and NAT stub. Builds clean on Go 1.22+.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/nat/nat.go

@@ -0,0 +1,87 @@
+// Package nat handles relay registration and future hole-punching.
+package nat
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net"
+	"time"
+
+	"github.com/waste-go/internal/mesh"
+	"github.com/waste-go/internal/proto"
+)
+
+// Run connects to the relay server (if configured) and keeps the connection alive.
+// Pass an empty relayAddr to skip relay entirely (LAN-only mode).
+func Run(m *mesh.Mesh, relayAddr string) error {
+	if relayAddr == "" {
+		log.Println("nat: no relay configured, running in LAN-only mode")
+		select {} // block forever — task stays alive
+	}
+
+	for {
+		log.Printf("nat: connecting to relay at %s", relayAddr)
+		if err := connectRelay(relayAddr, m); err != nil {
+			log.Printf("nat: relay error: %v", err)
+		}
+		log.Printf("nat: reconnecting to relay in 10s...")
+		time.Sleep(10 * time.Second)
+	}
+}
+
+func connectRelay(addr string, m *mesh.Mesh) error {
+	conn, err := net.DialTimeout("tcp", addr, 10*time.Second)
+	if err != nil {
+		return fmt.Errorf("dial relay: %w", err)
+	}
+	defer conn.Close()
+
+	id := m.Identity
+	enc := json.NewEncoder(conn)
+	dec := json.NewDecoder(bufio.NewReader(conn))
+
+	// Register with the relay
+	reg := proto.RelayMessage{
+		Type:      proto.RelayRegister,
+		Peer:      ptr(id.PeerInfo()),
+		Signature: id.Sign([]byte(id.PeerID())),
+	}
+	if err := enc.Encode(reg); err != nil {
+		return fmt.Errorf("sending register: %w", err)
+	}
+	log.Printf("nat: registered with relay as %s", id.PeerID().Short())
+
+	// Ask for the current peer list (bootstrap)
+	if err := enc.Encode(proto.RelayMessage{Type: proto.RelayListPeers}); err != nil {
+		return fmt.Errorf("sending list_peers: %w", err)
+	}
+
+	// Read relay messages
+	for {
+		var msg proto.RelayMessage
+		if err := dec.Decode(&msg); err != nil {
+			return fmt.Errorf("reading relay message: %w", err)
+		}
+
+		switch msg.Type {
+		case proto.RelayPeerList:
+			log.Printf("nat: relay gave us %d peer hints", len(msg.Peers))
+			// TODO: attempt direct connections to each peer hint
+
+		case proto.RelayForwarded:
+			from := "unknown"
+			if msg.From != nil {
+				from = msg.From.Short()
+			}
+			log.Printf("nat: relayed envelope from %s — direct connection not yet implemented", from)
+			// TODO: decrypt and process as PeerMessage
+
+		case proto.RelayError:
+			log.Printf("nat: relay error: %s", msg.Message)
+		}
+	}
+}
+
+func ptr[T any](v T) *T { return &v }