ARH_FIXED_LEN
mp->b_cont = allocb(AR_LL_HDR_SLACK + ARH_FIXED_LEN + (hlen * 4) +
cp += ARH_FIXED_LEN;
if (MBLKL(mp1) < ARH_FIXED_LEN + 2 * hlen + 2 * plen) {
arhp = (uchar_t *)arh + ARH_FIXED_LEN;
cp += ARH_FIXED_LEN;