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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Thu, 7 Jan 2021 17:29:22 -0800
Message-ID: <CABBYNZ+41BSkQEGbXsemCgWQhmaEjB3KOkLrFyOjv_=_zMQy_Q@mail.gmail.com>
Subject: Re: [PATCH] Bluetooth: L2CAP: Try harder to accept device not knowing options
To:     Bastien Nocera <hadess@hadess.net>
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>,
        Florian Dollinger <dollinger.florian@gmx.de>
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Hi,

On Tue, Dec 8, 2020 at 9:36 AM Bastien Nocera <hadess@hadess.net> wrote:
>
> The current implementation of L2CAP options negotiation will continue
> the negotiation when a device responds with L2CAP_CONF_UNACCEPT ("unaccepted
> options"), but not when the device replies with L2CAP_CONF_UNKNOWN ("unknown
> options").
>
> Trying to continue the negotiation without ERTM support will allow
> Bluetooth-capable XBox One controllers (notably models 1708 and 1797)
> to connect.
>
> btmon before patch:
> > ACL Data RX: Handle 256 flags 0x02 dlen 16                            #64 [hci0] 59.182702
>       L2CAP: Connection Response (0x03) ident 2 len 8
>         Destination CID: 64
>         Source CID: 64
>         Result: Connection successful (0x0000)
>         Status: No further information available (0x0000)
> < ACL Data TX: Handle 256 flags 0x00 dlen 23                            #65 [hci0] 59.182744
>       L2CAP: Configure Request (0x04) ident 3 len 15
>         Destination CID: 64
>         Flags: 0x0000
>         Option: Retransmission and Flow Control (0x04) [mandatory]
>           Mode: Basic (0x00)
>           TX window size: 0
>           Max transmit: 0
>           Retransmission timeout: 0
>           Monitor timeout: 0
>           Maximum PDU size: 0
> > ACL Data RX: Handle 256 flags 0x02 dlen 16                            #66 [hci0] 59.183948
>       L2CAP: Configure Request (0x04) ident 1 len 8
>         Destination CID: 64
>         Flags: 0x0000
>         Option: Maximum Transmission Unit (0x01) [mandatory]
>           MTU: 1480
> < ACL Data TX: Handle 256 flags 0x00 dlen 18                            #67 [hci0] 59.183994
>       L2CAP: Configure Response (0x05) ident 1 len 10
>         Source CID: 64
>         Flags: 0x0000
>         Result: Success (0x0000)
>         Option: Maximum Transmission Unit (0x01) [mandatory]
>           MTU: 1480
> > ACL Data RX: Handle 256 flags 0x02 dlen 15                            #69 [hci0] 59.187676
>       L2CAP: Configure Response (0x05) ident 3 len 7
>         Source CID: 64
>         Flags: 0x0000
>         Result: Failure - unknown options (0x0003)
>         04                                               .
> < ACL Data TX: Handle 256 flags 0x00 dlen 12                            #70 [hci0] 59.187722
>       L2CAP: Disconnection Request (0x06) ident 4 len 4
>         Destination CID: 64
>         Source CID: 64
> > ACL Data RX: Handle 256 flags 0x02 dlen 12                            #73 [hci0] 59.192714
>       L2CAP: Disconnection Response (0x07) ident 4 len 4
>         Destination CID: 64
>         Source CID: 64
>
> btmon after patch:
> > ACL Data RX: Handle 256 flags 0x02 dlen 16                          #248 [hci0] 103.502970
>       L2CAP: Connection Response (0x03) ident 5 len 8
>         Destination CID: 65
>         Source CID: 65
>         Result: Connection pending (0x0001)
>         Status: No further information available (0x0000)
> > ACL Data RX: Handle 256 flags 0x02 dlen 16                          #249 [hci0] 103.504184
>       L2CAP: Connection Response (0x03) ident 5 len 8
>         Destination CID: 65
>         Source CID: 65
>         Result: Connection successful (0x0000)
>         Status: No further information available (0x0000)
> < ACL Data TX: Handle 256 flags 0x00 dlen 23                          #250 [hci0] 103.504398
>       L2CAP: Configure Request (0x04) ident 6 len 15
>         Destination CID: 65
>         Flags: 0x0000
>         Option: Retransmission and Flow Control (0x04) [mandatory]
>           Mode: Basic (0x00)
>           TX window size: 0
>           Max transmit: 0
>           Retransmission timeout: 0
>           Monitor timeout: 0
>           Maximum PDU size: 0
> > ACL Data RX: Handle 256 flags 0x02 dlen 16                          #251 [hci0] 103.505472
>       L2CAP: Configure Request (0x04) ident 3 len 8
>         Destination CID: 65
>         Flags: 0x0000
>         Option: Maximum Transmission Unit (0x01) [mandatory]
>           MTU: 1480
> < ACL Data TX: Handle 256 flags 0x00 dlen 18                          #252 [hci0] 103.505689
>       L2CAP: Configure Response (0x05) ident 3 len 10
>         Source CID: 65
>         Flags: 0x0000
>         Result: Success (0x0000)
>         Option: Maximum Transmission Unit (0x01) [mandatory]
>           MTU: 1480
> > ACL Data RX: Handle 256 flags 0x02 dlen 15                          #254 [hci0] 103.509165
>       L2CAP: Configure Response (0x05) ident 6 len 7
>         Source CID: 65
>         Flags: 0x0000
>         Result: Failure - unknown options (0x0003)
>         04                                               .
> < ACL Data TX: Handle 256 flags 0x00 dlen 12                          #255 [hci0] 103.509426
>       L2CAP: Configure Request (0x04) ident 7 len 4
>         Destination CID: 65
>         Flags: 0x0000
> < ACL Data TX: Handle 256 flags 0x00 dlen 12                          #257 [hci0] 103.511870
>       L2CAP: Connection Request (0x02) ident 8 len 4
>         PSM: 1 (0x0001)
>         Source CID: 66
> > ACL Data RX: Handle 256 flags 0x02 dlen 14                          #259 [hci0] 103.514121
>       L2CAP: Configure Response (0x05) ident 7 len 6
>         Source CID: 65
>         Flags: 0x0000
>         Result: Success (0x0000)
>
> Signed-off-by: Florian Dollinger <dollinger.florian@gmx.de>
> Co-developed-by: Florian Dollinger <dollinger.florian@gmx.de>

Reviewed-by: Luiz Augusto Von Dentz <luiz.von.dentz@intel.com>

> ---
>  net/bluetooth/l2cap_core.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index 1ab27b90ddcb..3ab95ea2cd80 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -4513,6 +4513,7 @@ static inline int l2cap_config_rsp(struct l2cap_conn *conn,
>                 }
>                 goto done;
>
> +       case L2CAP_CONF_UNKNOWN:
>         case L2CAP_CONF_UNACCEPT:
>                 if (chan->num_conf_rsp <= L2CAP_CONF_MAX_CONF_RSP) {
>                         char req[64];
> --
> 2.29.2
>


-- 
Luiz Augusto von Dentz