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    Subject[PATCH v2] Bluetooth: Retry configure request if result is L2CAP_CONF_UNKNOWN
    Date
    Due to:

    * Current implementation of l2cap_config_rsp() dropping BT
    connection if sender of configuration response replied with unknown
    option failure (Result=0x0003/L2CAP_CONF_UNKNOWN)

    * Current implementation of l2cap_build_conf_req() adding
    L2CAP_CONF_RFC(0x04) option to initial configure request sent by
    the Linux host.

    devices that do no recongninze L2CAP_CONF_RFC, such as Xbox One S
    controllers, will get stuck in endless connect -> configure ->
    disconnect loop, never connect and be generaly unusable.

    To avoid this problem add code to do the following:

    1. Parse the body of response L2CAP_CONF_UNKNOWN and, in case of
    unsupported option being RFC, clear L2CAP_FEAT_ERTM and
    L2CAP_FEAT_STREAMING from connection's feature mask (in order to
    prevent RFC option from being added going forward)

    2. Retry configuration step the same way it's done for
    L2CAP_CONF_UNACCEPT

    Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
    Cc: Pierre-Loup A. Griffais <pgriffais@valvesoftware.com>
    Cc: Florian Dollinger <dollinger.florian@gmx.de>
    Cc: Marcel Holtmann <marcel@holtmann.org>
    Cc: Johan Hedberg <johan.hedberg@gmail.com>
    Cc: linux-bluetooth@vger.kernel.org
    Cc: linux-kernel@vger.kernel.org
    ---

    Changes since [v1]:

    - Patch simplified to simply clear L2CAP_FEAT_ERTM |
    L2CAP_FEAT_STREAMING from feat_mask when device flags RFC options
    as unknown

    [v1] lore.kernel.org/r/20190208025828.30901-1-andrew.smirnov@gmail.com

    net/bluetooth/l2cap_core.c | 59 ++++++++++++++++++++++++++++++++++++++
    1 file changed, 59 insertions(+)

    diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
    index b53acd6c9a3d..d5d682679128 100644
    --- a/net/bluetooth/l2cap_core.c
    +++ b/net/bluetooth/l2cap_core.c
    @@ -4185,6 +4185,50 @@ static inline int l2cap_config_req(struct l2cap_conn *conn,
    return err;
    }

    +static inline int l2cap_config_rsp_unknown(struct l2cap_conn *conn,
    + struct l2cap_chan *chan,
    + const u8 *data,
    + int len)
    +{
    + int o;
    + char req[64];
    +
    + if (!len || len > sizeof(req) - sizeof(struct l2cap_conf_req))
    + return -ECONNRESET;
    +
    + while (len--) {
    + const u8 option_type = *data++;
    +
    + BT_DBG("chan %p, unknown option type: %u", chan, option_type);
    +
    + /* "...Hints shall not be included in the Response and
    + * shall not be the sole cause for rejecting the
    + * Request.."
    + */
    + if (option_type & L2CAP_CONF_HINT)
    + return -ECONNRESET;
    +
    + switch (option_type) {
    + case L2CAP_CONF_RFC:
    + /* Clearing the following feature should
    + * prevent RFC option from being added next
    + * connection attempt
    + */
    + conn->feat_mask &= ~(L2CAP_FEAT_ERTM |
    + L2CAP_FEAT_STREAMING);
    + break;
    + default:
    + return -ECONNRESET;
    + }
    + }
    +
    + len = l2cap_build_conf_req(chan, req, sizeof(req));
    + l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ, len, req);
    + chan->num_conf_req++;
    +
    + return 0;
    +}
    +
    static inline int l2cap_config_rsp(struct l2cap_conn *conn,
    struct l2cap_cmd_hdr *cmd, u16 cmd_len,
    u8 *data)
    @@ -4240,6 +4284,21 @@ static inline int l2cap_config_rsp(struct l2cap_conn *conn,
    }
    goto done;

    + case L2CAP_CONF_UNKNOWN:
    + if (chan->num_conf_rsp <= L2CAP_CONF_MAX_CONF_RSP) {
    + if (l2cap_config_rsp_unknown(conn, chan, rsp->data,
    + len) < 0) {
    + l2cap_send_disconn_req(chan, ECONNRESET);
    + goto done;
    + }
    + break;
    + }
    + /* Once, chan->num_conf_rsp goes above
    + * L2CAP_CONF_MAX_CONF_RSP we want to go down all the
    + * way to default label (just like L2CAP_CONF_UNACCEPT
    + * below)
    + */
    + /* fall through */
    case L2CAP_CONF_UNACCEPT:
    if (chan->num_conf_rsp <= L2CAP_CONF_MAX_CONF_RSP) {
    char req[64];
    --
    2.21.0
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