if (likely(dst_ops->get_mss == NULL)) dst_ops->get_mss = xfrm_get_mss;
int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo){	int err = 0;	if (unlikely(afinfo == NULL))		return -EINVAL;	if (unlikely(afinfo->family >= NPROTO))		return -EAFNOSUPPORT;	write_lock(&xfrm_policy_afinfo_lock);	if (unlikely(xfrm_policy_afinfo[afinfo->family] != NULL))		err = -ENOBUFS;	else {		struct dst_ops *dst_ops = afinfo->dst_ops;		if (likely(dst_ops->kmem_cachep == NULL))			dst_ops->kmem_cachep = xfrm_dst_cache;		if (likely(dst_ops->check == NULL))			dst_ops->check = xfrm_dst_check;		if (likely(dst_ops->negative_advice == NULL))			dst_ops->negative_advice = xfrm_negative_advice;		if (likely(dst_ops->link_failure == NULL))			dst_ops->link_failure = xfrm_link_failure;		if (likely(dst_ops->get_mss == NULL))			dst_ops->get_mss = xfrm_get_mss;		if (likely(afinfo->garbage_collect == NULL))			afinfo->garbage_collect = __xfrm_garbage_collect;		xfrm_policy_afinfo[afinfo->family] = afinfo;	}	write_unlock(&xfrm_policy_afinfo_lock);	return err;}