mfc_add
if (mfc_add(&mfcctl2, &mfcctl2.mfcc_origin, &mfcctl2.mfcc_mcastgrp,
int mfc_add(struct mfcctl2 *, struct in_addr *, struct in_addr *,
mfc_add(NULL, &ip->ip_src, &ip->ip_dst, v->v_id,