aspath_prepend
pdata = aspath_prepend(a->aspath, rde_local_as(), 0, &plen);
u_char *aspath_prepend(struct aspath *, uint32_t, int, uint16_t *);
np = aspath_prepend(state->aspath.aspath, prep_as,
np = aspath_prepend(state->aspath.aspath, prep_as,
np = aspath_prepend(state->aspath.aspath, prep_as, 1, &nl);