void *mtod_check(struct mbuf *m, size_t len)
{
    if (m->m_len >= len) {
        return m->m_data;
    }

    DEBUG_ERROR("mtod failed");

    return NULL;
}
void *mtod_check(struct mbuf *m, size_t len)
{
    if (m->m_len >= len) {
        return m->m_data;
    }

    DEBUG_ERROR("mtod failed");

    return NULL;
}