mfc_find
rt = mfc_find(ip->ip_src.s_addr, ip->ip_dst.s_addr);
mfc = mfc_find(req->bu_src.s_addr, req->bu_dst.s_addr);
mfc = mfc_find(req->bu_src.s_addr, req->bu_dst.s_addr);
rt = mfc_find(req->src.s_addr, req->grp.s_addr);
rt = mfc_find(mfccp->mfcc_origin.s_addr, mfccp->mfcc_mcastgrp.s_addr);