Re: [PATCH 2/2] Bluetooth: Add BT_MODE socket option

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

Hi Marcel,

On Wed, Mar 18, 2020 at 4:19 AM Marcel Holtmann <marcel@holtmann.org> wrote:
>
> Hi Luiz,
>
> > This adds BT_MODE socket option which can be used to set L2CAP modes,
> > including modes only supported over LE which were not supported using
> > the L2CAP_OPTIONS.
> >
> > Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> > ---
> > include/net/bluetooth/bluetooth.h |  2 +
> > net/bluetooth/l2cap_sock.c        | 79 +++++++++++++++++++++++++------
> > 2 files changed, 66 insertions(+), 15 deletions(-)
> >
> > diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
> > index 1576353a2773..c361ec7b06aa 100644
> > --- a/include/net/bluetooth/bluetooth.h
> > +++ b/include/net/bluetooth/bluetooth.h
> > @@ -139,6 +139,8 @@ struct bt_voice {
> > #define BT_PHY_LE_CODED_TX    0x00002000
> > #define BT_PHY_LE_CODED_RX    0x00004000
> >
> > +#define BT_MODE                      15
> > +
>
> I would cleanly define the BT_MODE_xx constants here. They don’t need to match spec numbers from L2CAP actually. I would also leave the not used BR/EDR constants out of it and just add modes we do support.

Id leave the same values since it makes easier to fallback if BT_MODE
is not supported e.g. BT_IO_MODE would have to declare 2 different
namespaces for the new and the old sockopt.

> > __printf(1, 2)
> > void bt_info(const char *fmt, ...);
> > __printf(1, 2)
> > diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
> > index e43a90e05972..7a8a199c373d 100644
> > --- a/net/bluetooth/l2cap_sock.c
> > +++ b/net/bluetooth/l2cap_sock.c
> > @@ -619,6 +619,21 @@ static int l2cap_sock_getsockopt(struct socket *sock, int level, int optname,
> >                       err = -EFAULT;
> >               break;
> >
> > +     case BT_MODE:
> > +             if (!enable_ecred) {
> > +                     err = -ENOPROTOOPT;
> > +                     break;
> > +             }
> > +
> > +             if (chan->chan_type != L2CAP_CHAN_CONN_ORIENTED) {
> > +                     err = -EINVAL;
> > +                     break;
> > +             }
> > +
> > +             if (put_user(chan->mode, (u8 __user *) optval))
> > +                     err = -EFAULT;
> > +             break;
> > +
> >       default:
> >               err = -ENOPROTOOPT;
> >               break;
> > @@ -644,6 +659,29 @@ static bool l2cap_valid_mtu(struct l2cap_chan *chan, u16 mtu)
> >       return true;
> > }
> >
> > +static int l2cap_set_mode(struct l2cap_chan *chan, u8 mode)
> > +{
> > +     switch (chan->mode) {
> > +     case L2CAP_MODE_LE_FLOWCTL:
> > +     case L2CAP_MODE_EXT_FLOWCTL:
> > +             break;
> > +     case L2CAP_MODE_BASIC:
> > +             clear_bit(CONF_STATE2_DEVICE, &chan->conf_state);
> > +             break;
> > +     case L2CAP_MODE_ERTM:
> > +     case L2CAP_MODE_STREAMING:
> > +             if (!disable_ertm)
> > +                     break;
> > +             /* fall through */
> > +     default:
> > +             return -EINVAL;
> > +     }
> > +
> > +     chan->mode = mode;
> > +
> > +     return 0;
> > +}
> > +
> > static int l2cap_sock_setsockopt_old(struct socket *sock, int optname,
> >                                    char __user *optval, unsigned int optlen)
> > {
> > @@ -693,22 +731,9 @@ static int l2cap_sock_setsockopt_old(struct socket *sock, int optname,
> >                       break;
> >               }
> >
> > -             chan->mode = opts.mode;
> > -             switch (chan->mode) {
> > -             case L2CAP_MODE_LE_FLOWCTL:
> > -                     break;
> > -             case L2CAP_MODE_BASIC:
> > -                     clear_bit(CONF_STATE2_DEVICE, &chan->conf_state);
> > -                     break;
> > -             case L2CAP_MODE_ERTM:
> > -             case L2CAP_MODE_STREAMING:
> > -                     if (!disable_ertm)
> > -                             break;
> > -                     /* fall through */
> > -             default:
> > -                     err = -EINVAL;
> > +             err = l2cap_set_mode(chan, opts.mode);
> > +             if (err)
> >                       break;
> > -             }
> >
>
> I would not yet try to break this out into a separate helper. I think L2CAP_OPTIONS should maybe just stay as it is. And as noted above, we define our own list of constants.

That would complicate userspace code a little to much since that means
we would have 2 different namespace for BT_IO_MODE, as mentioned about
Id keep the same values for modes as in L2CAP_OPTIONS just adding new
definitions names, otherwise we will need a new option for bt_io to
avoid the namespaces to overlap but I rather not do that as BT_IO_MODE
already maps quite well to BT_MODE.

> >               BT_DBG("mode 0x%2.2x", chan->mode);
> >
> > @@ -963,6 +988,30 @@ static int l2cap_sock_setsockopt(struct socket *sock, int level, int optname,
> >
> >               break;
> >
> > +     case BT_MODE:
> > +             if (!enable_ecred) {
> > +                     err = -ENOPROTOOPT;
> > +                     break;
> > +             }
> > +
> > +             if (chan->chan_type != L2CAP_CHAN_CONN_ORIENTED) {
> > +                     err = -EINVAL;
> > +                     break;
> > +             }
>
> Especially here I would also check if the mode is valid on the choose transport. For me this would also mean we should require a bind() before allowing to set the mode. So we have at least some idea what transport is planned to be used.

I will make it check for BOUND state, though l2cap_set_mode does check
the mode already, or you are saying that if we do use a different
namespace we would have to convert, well I guess this further
reinforces my argument that making the values compatible makes things
a lot simpler.

> > +
> > +             if (get_user(opt, (u8 __user *) optval)) {
> > +                     err = -EFAULT;
> > +                     break;
> > +             }
> > +
> > +             err = l2cap_set_mode(chan, opt);
> > +             if (err)
> > +                     break;
> > +
> > +             BT_DBG("mode 0x%2.2x", chan->mode);
> > +
> > +             break;
> > +
> >       default:
> >               err = -ENOPROTOOPT;
> >               break;
>
> Regards
>
> Marcel
>


-- 
Luiz Augusto von Dentz