Hi Maciej,
> > On Fri, Jun 28, 2019 at 03:35:52PM +0200, Jesper Dangaard Brouer wrote:
> > > On Fri, 28 Jun 2019 13:39:15 +0300
> > > Ilias Apalodimas <ilias.apalodi...@linaro.org> wrote:
> > >
> > > > +static int netsec_xdp_setup(struct netsec_priv *priv, struct bpf_prog
> > > > *prog,
> > > > + struct netlink_ext_ack *extack)
> > > > +{
> > > > + struct net_device *dev = priv->ndev;
> > > > + struct bpf_prog *old_prog;
> > > > +
> > > > + /* For now just support only the usual MTU sized frames */
> > > > + if (prog && dev->mtu > 1500) {
> > > > + NL_SET_ERR_MSG_MOD(extack, "Jumbo frames not supported
> > > > on XDP");
> > > > + return -EOPNOTSUPP;
> > > > + }
> > > > +
> > > > + if (netif_running(dev))
> > > > + netsec_netdev_stop(dev);
> > > > +
> > > > + /* Detach old prog, if any */
> > > > + old_prog = xchg(&priv->xdp_prog, prog);
> > > > + if (old_prog)
> > > > + bpf_prog_put(old_prog);
> > > > +
> > > > + if (netif_running(dev))
> > > > + netsec_netdev_open(dev);
> > >
> > > Shouldn't the if-statement be if (!netif_running(dev))
> > >
> > > > +
> > This is there to restart the device if it's up already (to rebuild the
> > rings).
> > This should be fine as-is
>
> I think that Jesper's concern was about that you could have already stopped
> the
> netdev earlier via netsec_netdev_stop (before the xchg)? So at this point
> __LINK_STATE_START might be not set.
>
> Maybe initially store what netif_running(dev) returns in stack variable and
> act on it, so your stop/open are symmetric?
I did not write the open/close originally but to my understanding,
netsec_netdev_stop() won't change that the .ndo_close will.
So this check is there to ensure a user won't bring the interface down during
loading/re-loading of the program. Keeping in the stack would break that,
wouldn't it?
Thanks
/Ilias
>
> >
> > > > + return 0;
> > > > +}
> >
> > Thanks
> > /Ilias
>
