check_dup
extern struct interface *check_dup(naddr, naddr, naddr, int);
ifp = check_dup(ifs.int_addr,ifs.int_dstaddr,ifs.int_mask,
ifp = check_dup(gate,dst,netmask,state);
if (check_dup(e->filename)) {
if (check_dup(e->filename)) {