Re: [PATCH 8/9] Bluetooth: Use a stream-oriented recvmsg with SOCK_STREAM L2CAP sockets.

[Marcel Holtmann <marcel@holtmann.org>]

Hi Mat,

> L2CAP ERTM sockets can be opened with the SOCK_STREAM socket type,
> which is a mandatory request for ERTM mode.
> 
> However, these sockets still have SOCK_SEQPACKET read semantics when
> bt_sock_recvmsg() is used to pull data from the receive queue.  If the
> application is only reading part of a frame, then the unread portion
> of the frame is discarded.  If the application requests more bytes
> than are in the current frame, only the current frame's data is
> returned.
> 
> This patch utilizes common code derived from RFCOMM's recvmsg()
> function to make L2CAP SOCK_STREAM reads behave like RFCOMM reads (and
> other SOCK_STREAM sockets in general).  The application may read one
> byte at a time from the input stream and not lose any data, and may
> also read across L2CAP frame boundaries.
> 
> Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
> ---
>  net/bluetooth/l2cap.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
> index 43e0eae..cd0e150 100644
> --- a/net/bluetooth/l2cap.c
> +++ b/net/bluetooth/l2cap.c
> @@ -1956,7 +1956,10 @@ static int l2cap_sock_recvmsg(struct kiocb *iocb, struct socket *sock, struct ms
>  
>  	release_sock(sk);
>  
> -	return bt_sock_recvmsg(iocb, sock, msg, len, flags);
> +	if (sock->type == SOCK_STREAM)
> +		return bt_sock_stream_recvmsg(iocb, sock, msg, len, flags);
> +	else
> +		return bt_sock_recvmsg(iocb, sock, msg, len, flags);
>  }
>  
>  static int l2cap_sock_setsockopt_old(struct socket *sock, int optname, char __user *optval, unsigned int optlen)

this is more a style issue, but I clearly prefer this:

	if (sock->type == SOCK_STREAM)
		return bt_sock_stream_recvmsg(iocb, sock, msg, len, flags);

	return bt_sock_recvmsg(iocb, sock, msg, len, flags);

Regards

Marcel