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Message-ID: <985fa44991c27e773f2a4b4fafaf5879719eb6fb.camel@iki.fi>
Subject: Re: [PATCH v2 5/5] Bluetooth: add BT_NO_ERRQUEUE_POLL socket option
From: Pauli Virtanen <pav@iki.fi>
To: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: linux-bluetooth@vger.kernel.org
Date: Fri, 15 Mar 2024 12:49:31 +0200
In-Reply-To: <CABBYNZLWbwTGOuZeYvFou=+98_XNdYVu-hWiqrUFvZvuU50_yw@mail.gmail.com>
References: <cover.1710440392.git.pav@iki.fi>
	 <134027f3cbaeb7095d080c27cd4b1053d2eb560e.1710440392.git.pav@iki.fi>
	 <CABBYNZLWbwTGOuZeYvFou=+98_XNdYVu-hWiqrUFvZvuU50_yw@mail.gmail.com>
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Hi Luiz,

to, 2024-03-14 kello 23:18 -0400, Luiz Augusto von Dentz kirjoitti:
> Hi Pauli,
>=20
> On Thu, Mar 14, 2024 at 2:23=E2=80=AFPM Pauli Virtanen <pav@iki.fi> wrote=
:
> >=20
> > Add socket option to disable POLLERR on non-empty socket error queue.
> >=20
> > Applications can use this for sleeping socket error POLLERR waits, also
> > when using TX timestamping. This is useful when multiple layers of the
> > stack are using the same socket.
>=20
> So the idea here is that bluetoothd would set BT_NO_ERRQUEUE_POLL to
> not be awakened by timestamps? I wonder why this works on per
> fd/socket level while SO_TIMESTAMPING does apply to all sockets
> though, or perhaps that is not really related to SO_TIMESTAMPING but
> errqueue being the same to all cloned sockets? I'm a little hesitant
> to start introducing new socket options if the whole point was to
> avoid doing so with the use of SO_TIMESTAMPING.

It works the same as SO_TIMESTAMPING, setting BT_NO_ERRQUEUE_POLL
applies to all fds referring to the socket, so it is not per fd either.

The idea is that Pipewire sets BT_NO_ERRQUEUE_POLL before enabling
SO_TIMESTAMPING. Then nobody gets POLLERR on errqueue messages.

Instead, it reads MSG_ERRQUEUE always when sending the next packet,
instead of using POLLERR. This works fine in practice and is tested.


I'd appreciate if we can agree on the whole-stack plan.


***

For sockets vs. fds, see net/socket.c:sockfd_lookup

dup() of fd creates new int fd pointing to the same struct file &
struct socket, but not duplicate struct socket/sock, see fs/file.c:1412

Passing fds via unix socket like in DBus seems the same, see
include/net/scm.h:scm_recv_one_fd & fs/file.c:receive_fd

Indeed, you can also see this in debug logs, e.g.=C2=A0

[53573.676885] iso_sock_getname:1103: sock 0000000018c143a2, sk 000000002af=
f8d2b  (from BlueZ)
[53580.831753] iso_sock_getname:1103: sock 00000000419df212, sk 00000000526=
df659  (from BlueZ)
...
[53592.472038] iso_sock_sendmsg:1127: sock 0000000018c143a2, sk 000000002af=
f8d2b  (from PW)
[53592.472062] iso_sock_sendmsg:1127: sock 00000000419df212, sk 00000000526=
df659  (from PW)

setsockopt(), errqueue, RX queue etc. are struct socket level stuff.

>=20
>=20
> > Signed-off-by: Pauli Virtanen <pav@iki.fi>
> > ---
> >  include/net/bluetooth/bluetooth.h |  9 +++-
> >  net/bluetooth/af_bluetooth.c      | 72 ++++++++++++++++++++++++++++++-
> >  net/bluetooth/iso.c               |  8 ++--
> >  net/bluetooth/l2cap_sock.c        |  8 ++--
> >  net/bluetooth/sco.c               |  8 ++--
> >  5 files changed, 91 insertions(+), 14 deletions(-)
> >=20
> > diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/=
bluetooth.h
> > index 9280e72093ee..dcee5384d715 100644
> > --- a/include/net/bluetooth/bluetooth.h
> > +++ b/include/net/bluetooth/bluetooth.h
> > @@ -240,6 +240,8 @@ struct bt_codecs {
> >=20
> >  #define BT_ISO_BASE            20
> >=20
> > +#define BT_NO_ERRQUEUE_POLL    21
> > +
> >  __printf(1, 2)
> >  void bt_info(const char *fmt, ...);
> >  __printf(1, 2)
> > @@ -387,7 +389,8 @@ struct bt_sock {
> >  enum {
> >         BT_SK_DEFER_SETUP,
> >         BT_SK_SUSPEND,
> > -       BT_SK_PKT_STATUS
> > +       BT_SK_PKT_STATUS,
> > +       BT_SK_NO_ERRQUEUE_POLL
> >  };
> >=20
> >  struct bt_sock_list {
> > @@ -410,6 +413,10 @@ int  bt_sock_stream_recvmsg(struct socket *sock, s=
truct msghdr *msg,
> >                             size_t len, int flags);
> >  __poll_t bt_sock_poll(struct file *file, struct socket *sock, poll_tab=
le *wait);
> >  int  bt_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned lon=
g arg);
> > +int bt_sock_setsockopt(struct socket *sock, int level, int optname,
> > +                      sockptr_t optval, unsigned int optlen);
> > +int bt_sock_getsockopt(struct socket *sock, int level, int optname,
> > +                      char __user *optval, int __user *optlen);
> >  int  bt_sock_wait_state(struct sock *sk, int state, unsigned long time=
o);
> >  int  bt_sock_wait_ready(struct sock *sk, unsigned int msg_flags);
> >=20
> > diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.=
c
> > index 67604ccec2f4..997197aa7b48 100644
> > --- a/net/bluetooth/af_bluetooth.c
> > +++ b/net/bluetooth/af_bluetooth.c
> > @@ -500,6 +500,12 @@ static inline __poll_t bt_accept_poll(struct sock =
*parent)
> >         return 0;
> >  }
> >=20
> > +static bool bt_sock_error_queue_poll(struct sock *sk)
> > +{
> > +       return !test_bit(BT_SK_NO_ERRQUEUE_POLL, &bt_sk(sk)->flags) &&
> > +               !skb_queue_empty_lockless(&sk->sk_error_queue);
> > +}
> > +
> >  __poll_t bt_sock_poll(struct file *file, struct socket *sock,
> >                       poll_table *wait)
> >  {
> > @@ -511,7 +517,7 @@ __poll_t bt_sock_poll(struct file *file, struct soc=
ket *sock,
> >         if (sk->sk_state =3D=3D BT_LISTEN)
> >                 return bt_accept_poll(sk);
> >=20
> > -       if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue=
))
> > +       if (sk->sk_err || bt_sock_error_queue_poll(sk))
> >                 mask |=3D EPOLLERR |
> >                         (sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? EPOLLPR=
I : 0);
> >=20
> > @@ -582,6 +588,70 @@ int bt_sock_ioctl(struct socket *sock, unsigned in=
t cmd, unsigned long arg)
> >  }
> >  EXPORT_SYMBOL(bt_sock_ioctl);
> >=20
> > +int bt_sock_setsockopt(struct socket *sock, int level, int optname,
> > +                      sockptr_t optval, unsigned int optlen)
> > +{
> > +       struct sock *sk =3D sock->sk;
> > +       int err =3D 0;
> > +       u32 opt;
> > +
> > +       if (level !=3D SOL_BLUETOOTH)
> > +               return -ENOPROTOOPT;
> > +
> > +       lock_sock(sk);
> > +
> > +       switch (optname) {
> > +       case BT_NO_ERRQUEUE_POLL:
> > +               if (copy_from_sockptr(&opt, optval, sizeof(opt))) {
> > +                       err =3D -EFAULT;
> > +                       break;
> > +               }
> > +
> > +               if (opt)
> > +                       set_bit(BT_SK_NO_ERRQUEUE_POLL, &bt_sk(sk)->fla=
gs);
> > +               else
> > +                       clear_bit(BT_SK_NO_ERRQUEUE_POLL, &bt_sk(sk)->f=
lags);
> > +               break;
> > +
> > +       default:
> > +               err =3D -ENOPROTOOPT;
> > +               break;
> > +       }
> > +
> > +       release_sock(sk);
> > +       return err;
> > +}
> > +EXPORT_SYMBOL(bt_sock_setsockopt);
> > +
> > +int bt_sock_getsockopt(struct socket *sock, int level, int optname,
> > +                      char __user *optval, int __user *optlen)
> > +{
> > +       struct sock *sk =3D sock->sk;
> > +       int err =3D 0;
> > +       u32 opt;
> > +
> > +       if (level !=3D SOL_BLUETOOTH)
> > +               return -ENOPROTOOPT;
> > +
> > +       lock_sock(sk);
> > +
> > +       switch (optname) {
> > +       case BT_NO_ERRQUEUE_POLL:
> > +               opt =3D test_bit(BT_SK_NO_ERRQUEUE_POLL, &bt_sk(sk)->fl=
ags);
> > +               if (put_user(opt, (u32 __user *)optval))
> > +                       err =3D -EFAULT;
> > +               break;
> > +
> > +       default:
> > +               err =3D -ENOPROTOOPT;
> > +               break;
> > +       }
> > +
> > +       release_sock(sk);
> > +       return err;
> > +}
> > +EXPORT_SYMBOL(bt_sock_getsockopt);
> > +
> >  /* This function expects the sk lock to be held when called */
> >  int bt_sock_wait_state(struct sock *sk, int state, unsigned long timeo=
)
> >  {
> > diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
> > index a77ab9df7994..6f5af549a8cc 100644
> > --- a/net/bluetooth/iso.c
> > +++ b/net/bluetooth/iso.c
> > @@ -1596,8 +1596,8 @@ static int iso_sock_setsockopt(struct socket *soc=
k, int level, int optname,
> >                 break;
> >=20
> >         default:
> > -               err =3D -ENOPROTOOPT;
> > -               break;
> > +               release_sock(sk);
> > +               return bt_sock_setsockopt(sock, level, optname, optval,=
 optlen);
> >         }
> >=20
> >         release_sock(sk);
> > @@ -1667,8 +1667,8 @@ static int iso_sock_getsockopt(struct socket *soc=
k, int level, int optname,
> >                 break;
> >=20
> >         default:
> > -               err =3D -ENOPROTOOPT;
> > -               break;
> > +               release_sock(sk);
> > +               return bt_sock_getsockopt(sock, level, optname, optval,=
 optlen);
> >         }
> >=20
> >         release_sock(sk);
> > diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
> > index 9a9f933a748b..06277ce1fd6b 100644
> > --- a/net/bluetooth/l2cap_sock.c
> > +++ b/net/bluetooth/l2cap_sock.c
> > @@ -697,8 +697,8 @@ static int l2cap_sock_getsockopt(struct socket *soc=
k, int level, int optname,
> >                 break;
> >=20
> >         default:
> > -               err =3D -ENOPROTOOPT;
> > -               break;
> > +               release_sock(sk);
> > +               return bt_sock_getsockopt(sock, level, optname, optval,=
 optlen);
> >         }
> >=20
> >         release_sock(sk);
> > @@ -1102,8 +1102,8 @@ static int l2cap_sock_setsockopt(struct socket *s=
ock, int level, int optname,
> >                 break;
> >=20
> >         default:
> > -               err =3D -ENOPROTOOPT;
> > -               break;
> > +               release_sock(sk);
> > +               return bt_sock_setsockopt(sock, level, optname, optval,=
 optlen);
> >         }
> >=20
> >         release_sock(sk);
> > diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
> > index b3c2af7c7d67..b8b1b314aed4 100644
> > --- a/net/bluetooth/sco.c
> > +++ b/net/bluetooth/sco.c
> > @@ -968,8 +968,8 @@ static int sco_sock_setsockopt(struct socket *sock,=
 int level, int optname,
> >                 break;
> >=20
> >         default:
> > -               err =3D -ENOPROTOOPT;
> > -               break;
> > +               release_sock(sk);
> > +               return bt_sock_setsockopt(sock, level, optname, optval,=
 optlen);
> >         }
> >=20
> >         release_sock(sk);
> > @@ -1211,8 +1211,8 @@ static int sco_sock_getsockopt(struct socket *soc=
k, int level, int optname,
> >                 break;
> >=20
> >         default:
> > -               err =3D -ENOPROTOOPT;
> > -               break;
> > +               release_sock(sk);
> > +               return bt_sock_getsockopt(sock, level, optname, optval,=
 optlen);
> >         }
> >=20
> >         release_sock(sk);
> > --
> > 2.44.0
> >=20
> >=20
>=20
>=20