BFD: Fix superfluous reconfiguration of sessions

static void

bfd_reconfigure_iface(struct bfd_proto *p, struct bfd_iface *ifa, struct bfd_config *nc)

{

  struct bfd_iface_config *nic = bfd_find_iface_config(nc, ifa->iface);

  ifa->changed = !!memcmp(nic, ifa->cf, sizeof(struct bfd_iface_config));

  struct bfd_iface_config *new = bfd_find_iface_config(nc, ifa->iface);

  struct bfd_iface_config *old = ifa->cf;

  /* Check options that are handled in bfd_reconfigure_session() */

  ifa->changed =

    (new->min_rx_int != old->min_rx_int) ||

    (new->min_tx_int != old->min_tx_int) ||

    (new->idle_tx_int != old->idle_tx_int) ||

    (new->multiplier != old->multiplier) ||

    (new->passive != old->passive);

  /* This should be probably changed to not access ifa->cf from the BFD thread */

  birdloop_enter(p->loop);

  ifa->cf = nic;

  ifa->cf = new;

  birdloop_leave(p->loop);

}