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From: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date: Thu, 28 Dec 2023 11:05:23 -0500
Message-ID: <CABBYNZLVZOJ6uAJdu876S5=jb1CeAX_ajn7jAUCurWdDOcKotQ@mail.gmail.com>
Subject: Re: [PATCH BlueZ 1/1] avdtp: fix incorrect transaction label in
 setconf phase
To: Xiao Yao <xiaokeqinhealth@126.com>
Cc: linux-bluetooth@vger.kernel.org, Xiao Yao <xiaoyao@rock-chips.com>
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Hi,

On Thu, Dec 28, 2023 at 9:07=E2=80=AFAM Xiao Yao <xiaokeqinhealth@126.com> =
wrote:
>
> From: Xiao Yao <xiaoyao@rock-chips.com>
>
> BLUETOOTH SPECIFICATION Page 61 of 140
> Audio/Video Distribution Transport Protocol Specification (V13)
> 8.4.6 Message integrity verification at receiver side
>
> - The receiver of an AVDTP signaling message shall not interpret corrupte=
d
> messages. Those messages are discarded and no signaling message is return=
ed
> to the sender if no error code is applicable. Possible corrupted messages
> are:
>
>   * Response messages where the transaction label cannot match a previous
>     command sent to the remote device
>
> Consider the following scenario:
> btmon log:
> ... ...
> AVDTP: Discover (0x01) Command (0x00) type 0x00 label 5 nosp 0
> AVDTP: Discover (0x01) Response Accept (0x02) type 0x00 label 5 nosp 0
> AVDTP: Get All Capabilities (0x0c) Command (0x00) type 0x00 label 6 nosp =
0
> AVDTP: Get All Capabilities (0x0c) Response Accept (0x02) type 0x00 label=
 6 nosp 0
> AVDTP: Get All Capabilities (0x0c) Command (0x00) type 0x00 label 7 nosp =
0
> AVDTP: Get All Capabilities (0x0c) Response Accept (0x02) type 0x00 label=
 7 nosp 0
>
> < AVDTP: Set Configuration (0x03) Command (0x00) type 0x00 label 8 nosp 0
> //Currently, a 'set configuration' message has been received from the
> //sender, which contains a transaction label valued at 8. This message
> //was then relayed to A2DP backend(PulseAudio/PipeWire) using the dbus
> //interface.
>     ---
>     set_configuration()(media.c)
>         msg =3D dbus_message_new_method_call(endpoint->sender, endpoint->=
path,
>                                                 MEDIA_ENDPOINT_INTERFACE,
>                                                 "SetConfiguration");
>         media_endpoint_async_call()
>         //dbus send
>         g_dbus_send_message_with_reply(btd_get_dbus_connection(),
>                                                 msg, &request->call,
>                                                 REQUEST_TIMEOUT(3 seconds=
))
>         dbus_pending_call_set_notify(request->call, endpoint_reply, reque=
st,NULL);
>         ...
>
> > AVDTP: Discover (0x01) Command (0x00) type 0x00 label 0 nosp 0
> //At this time, the A2DP reverse discovery issued an A2DP discover comman=
d.
> < AVDTP: Discover (0x01) Response Accept (0x02) type 0x00 label 0 nosp 0
> //After receiving the discover reply, the session->in.transaction is
> //changed to 0
>
> > AVDTP: Set Configuration (0x03) Response Accept (0x02) type 0x00 label =
0 nosp 0
> //The audio backend reply the dbus message
>     endpoint_reply (media.c)
>         setconf_cb (avdtp.c)
>             //Here avdtp_send sends an incorrect transaction value, causi=
ng
>             //the sender to discard the message. (The correct transaction
>             //value is 8)
>             avdtp_send(session, session->in.transaction, AVDTP_MSG_TYPE_A=
CCEPT,
>                                         AVDTP_SET_CONFIGURATION, NULL, 0)
>
> AVDTP: Delay Report (0x0d) Command (0x00) type 0x00 label 1 nosp 0
> AVDTP: Delay Report (0x0d) Response Accept (0x02) type 0x00 label 1 nosp =
0
> AVDTP: Get All Capabilities (0x0c) Command (0x00) type 0x00 label 2 nosp =
0
> AVDTP: Get All Capabilities (0x0c) Response Accept (0x02) type 0x00 label=
 2 nosp 0
> ... ...
>
> Therefore, a async_transaction that requires asynchronous return is
> recorded to prevent it from being incorrectly modified.
>
> Signed-off-by: Xiao Yao <xiaoyao@rock-chips.com>
> ---
>  profiles/audio/avdtp.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/profiles/audio/avdtp.c b/profiles/audio/avdtp.c
> index 10ef380d4..2171e7723 100644
> --- a/profiles/audio/avdtp.c
> +++ b/profiles/audio/avdtp.c
> @@ -286,6 +286,7 @@ struct in_buf {
>         gboolean active;
>         int no_of_packets;
>         uint8_t transaction;
> +       uint8_t async_transaction;

You can only have one transaction in each direction, so this doesn't
look right at all. What perhaps is the problem is that we are changing
the transaction ID also in case of responses in which case we need to
fix that.

>         uint8_t message_type;
>         uint8_t signal_id;
>         uint8_t buf[1024];
> @@ -1459,6 +1460,9 @@ static void setconf_cb(struct avdtp *session, struc=
t avdtp_stream *stream,
>         struct conf_rej rej;
>         struct avdtp_local_sep *sep;
>
> +       if (session->in.transaction !=3D session->in.async_transaction)
> +               session->in.transaction =3D session->in.async_transaction=
;
> +
>         if (err !=3D NULL) {
>                 rej.error =3D AVDTP_UNSUPPORTED_CONFIGURATION;
>                 rej.category =3D err->err.error_code;
> @@ -1569,6 +1573,7 @@ static gboolean avdtp_setconf_cmd(struct avdtp *ses=
sion, uint8_t transaction,
>                 session->version =3D 0x0103;
>
>         if (sep->ind && sep->ind->set_configuration) {
> +               session->in.async_transaction =3D transaction;
>                 if (!sep->ind->set_configuration(session, sep, stream,
>                                                         stream->caps,
>                                                         setconf_cb,
> --
> 2.34.1
>
>


--=20
Luiz Augusto von Dentz