Hi Luiz,
> This use MSG_DONTROUTE to send a single message with highest possible
> priority without having to rely on socket options.
>
> This is useful for RFCOMM which relies on socket interface to send frames
> to L2CAP, but since some of this frames are actual commands that can
> timeout they should be sent as soon as possible.
>
> For userspace this also offer the convenience of not having to use
> setsockopt several times when only a single/some messages needs to be
> prioritize.
are you sure that we are not mis-using the MSG_DONTROUTE flag?
> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
> ---
> net/bluetooth/l2cap_sock.c | 9 ++++++++-
> 1 files changed, 8 insertions(+), 1 deletions(-)
>
> diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
> index c57027f..133c1f2 100644
> --- a/net/bluetooth/l2cap_sock.c
> +++ b/net/bluetooth/l2cap_sock.c
> @@ -699,6 +699,7 @@ static int l2cap_sock_sendmsg(struct kiocb *iocb, struct socket *sock, struct ms
> struct sock *sk = sock->sk;
> struct l2cap_chan *chan = l2cap_pi(sk)->chan;
> int err;
> + u32 priority;
>
> BT_DBG("sock %p, sk %p", sock, sk);
>
> @@ -711,12 +712,18 @@ static int l2cap_sock_sendmsg(struct kiocb *iocb, struct socket *sock, struct ms
>
> lock_sock(sk);
>
> + priority = sk->sk_priority;
> +
> + /* MSG_DONTROUTE send message at maximum possible priority */
> + if ((msg->msg_flags & MSG_DONTROUTE) && priority < HCI_PRIO_MAX - 1)
> + priority = HCI_PRIO_MAX - 1;
> +
you need to enforce the same privilege check that SO_PRIORITY does.
Otherwise every single application can just go and overwrite it.
> if (sk->sk_state != BT_CONNECTED) {
> release_sock(sk);
> return -ENOTCONN;
> }
>
> - err = l2cap_chan_send(chan, msg, len, sk->sk_priority);
> + err = l2cap_chan_send(chan, msg, len, priority);
>
> release_sock(sk);
> return err;
Regards
Marcel
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