L2TP_COPY_MBUF
if ((m = L2TP_COPY_MBUF(m, M_NOWAIT)) == NULL) {
if ((m = L2TP_COPY_MBUF(xwin[i], M_NOWAIT)) == NULL)
m = L2TP_COPY_MBUF(seq->xwin[0], M_NOWAIT);