initial: ZeroTier-like P2P mesh VPN server with multi-tenant Web UI

internal/vl1/transport.go

@@ -0,0 +1,112 @@
+package vl1
+
+import (
+	"fmt"
+	"log/slog"
+	"net"
+	"sync"
+	"syscall"
+	"time"
+)
+
+type Transport struct {
+	conn   *net.UDPConn
+	port   int
+	mu     sync.RWMutex
+	closed bool
+	log    *slog.Logger
+}
+
+func NewTransport(port int, log *slog.Logger) (*Transport, error) {
+	addr := &net.UDPAddr{Port: port}
+	conn, err := net.ListenUDP("udp", addr)
+	if err != nil {
+		return nil, fmt.Errorf("bind UDP port %d: %w", port, err)
+	}
+	actualPort := conn.LocalAddr().(*net.UDPAddr).Port
+	log.Info("VL1 transport listening", "port", actualPort)
+	return &Transport{
+		conn: conn,
+		port: actualPort,
+		log:  log,
+	}, nil
+}
+
+func (t *Transport) Port() int {
+	return t.port
+}
+
+func (t *Transport) ReadFrom(buf []byte) (int, *net.UDPAddr, error) {
+	n, addr, err := t.conn.ReadFromUDP(buf)
+	return n, addr, err
+}
+
+func (t *Transport) SendTo(data []byte, addr *net.UDPAddr) error {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+	if t.closed {
+		return fmt.Errorf("transport closed")
+	}
+	_, err := t.conn.WriteToUDP(data, addr)
+	return err
+}
+
+func (t *Transport) SendPacket(pkt *Packet, addr *net.UDPAddr) error {
+	return t.SendTo(pkt.Encode(), addr)
+}
+
+func (t *Transport) Close() error {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	t.closed = true
+	return t.conn.Close()
+}
+
+func (t *Transport) SetSocketBuffers(rcvBuf, sndBuf int) error {
+	rawConn, err := t.conn.SyscallConn()
+	if err != nil {
+		return fmt.Errorf("get raw conn: %w", err)
+	}
+	var setErr error
+	err = rawConn.Control(func(fd uintptr) {
+		if rcvBuf > 0 {
+			if e := syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_RCVBUF, rcvBuf); e != nil {
+				setErr = fmt.Errorf("set SO_RCVBUF=%d: %w", rcvBuf, e)
+				return
+			}
+		}
+		if sndBuf > 0 {
+			if e := syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_SNDBUF, sndBuf); e != nil {
+				setErr = fmt.Errorf("set SO_SNDBUF=%d: %w", sndBuf, e)
+				return
+			}
+		}
+	})
+	if err != nil {
+		return err
+	}
+	return setErr
+}
+
+func (t *Transport) LocalAddr() net.Addr {
+	return t.conn.LocalAddr()
+}
+
+func (t *Transport) SetReadDeadline(deadline time.Time) error {
+	return t.conn.SetReadDeadline(deadline)
+}
+
+var packetBufPool = sync.Pool{
+	New: func() interface{} {
+		buf := make([]byte, MaxPacketSize)
+		return &buf
+	},
+}
+
+func GetPacketBuf() *[]byte {
+	return packetBufPool.Get().(*[]byte)
+}
+
+func PutPacketBuf(buf *[]byte) {
+	packetBufPool.Put(buf)
+}