xfrm_userpolicy_default
struct xfrm_userpolicy_default *up;
struct xfrm_userpolicy_default *up = nlmsg_data(nlh);
struct xfrm_userpolicy_default *r_up;
int len = NLMSG_ALIGN(sizeof(struct xfrm_userpolicy_default));
[XFRM_MSG_SETDEFAULT - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_default),
[XFRM_MSG_GETDEFAULT - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_default),