ccmp_get_header_len
M_PREPEND(m, ccmp_get_header_len(k), IEEE80211_M_NOWAIT);
ovbcopy(ivp + ccmp_get_header_len(k), ivp, hdrlen);
mtod(m, uint8_t *) + ccmp_get_header_len(k),
m_adj(m, ccmp_get_header_len(k));
data_len = m->m_pkthdr.len - (hdrlen + ccmp_get_header_len(key));
pos = mtod(m, uint8_t *) + hdrlen + ccmp_get_header_len(key);
space = m->m_len - (hdrlen + ccmp_get_header_len(key));
(hdrlen + ccmp_get_header_len(key) + ccmp_get_trailer_len(key));
pos = mtod(m, uint8_t *) + hdrlen + ccmp_get_header_len(key);
space = m->m_len - (hdrlen + ccmp_get_header_len(key));