rename files dealing with low level conns to sys_conn

sys_conn_windows.go

@@ -0,0 +1,40 @@
+//go:build windows
+// +build windows
+
+package quic
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+func newConn(c OOBCapablePacketConn) (connection, error) {
+	return &basicConn{PacketConn: c}, nil
+}
+
+func inspectReadBuffer(c net.PacketConn) (int, error) {
+	conn, ok := c.(interface {
+		SyscallConn() (syscall.RawConn, error)
+	})
+	if !ok {
+		return 0, errors.New("doesn't have a SyscallConn")
+	}
+	rawConn, err := conn.SyscallConn()
+	if err != nil {
+		return 0, fmt.Errorf("couldn't get syscall.RawConn: %w", err)
+	}
+	var size int
+	var serr error
+	if err := rawConn.Control(func(fd uintptr) {
+		size, serr = windows.GetsockoptInt(windows.Handle(fd), windows.SOL_SOCKET, windows.SO_RCVBUF)
+	}); err != nil {
+		return 0, err
+	}
+	return size, serr
+}
+
+func (i *packetInfo) OOB() []byte { return nil }