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>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>