Hello,
I am a Bluetooth Engineer at Google investigating an interoperability bug between an Android device and AirPods 4. When requesting an L2CAP connection (with PSM = AVDTP) to the AirPods during SDP service discovery, The AirPods L2CAP layer incorrectly responds with a "refused - no resources available" status followed by a Pending status and a Success status. This violates the specification, which says that the request has been fully rejected after the refused status and should not receive followup responses. I suspect the "no resources available" response is a bug. This prevents A2DP from working with the AirPods.
This bug does not exist with AirPods 2 firmware.
Here is a packet capture:
1602 1969-12-31 16:07:04.805261 0.062473 localhost () Apple_6b:db:09 (AirPods) L2CAP 17 Sent Connection Request (AVDTP, SCID: 0x22c6)
1603 1969-12-31 16:07:04.810953 0.005692 controller host HCI_EVT 8 Rcvd Number of Completed Packets
1604 1969-12-31 16:07:04.811078 0.000125 Apple_6b:db:09 (AirPods) localhost () SDP 27 Rcvd Service Search Attribute Request : Device Information: [Bluetooth Profile Descriptor List 0x0009]
1605 1969-12-31 16:07:04.821249 0.010171 localhost () Apple_6b:db:09 (AirPods) SDP 19 Sent Service Search Attribute Response
1606 1969-12-31 16:07:04.876396 0.055147 controller host HCI_EVT 8 Rcvd Number of Completed Packets
1607 1969-12-31 16:07:04.876464 0.000068 Apple_6b:db:09 (AirPods) localhost () L2CAP 21 Rcvd Connection Response - Refused - no resources available (SCID: 0x22c6)
1608 1969-12-31 16:07:04.942539 0.066075 Apple_6b:db:09 (AirPods) localhost () SDP 41 Rcvd Service Search Attribute Request : Unknown: [Bluetooth Profile Descriptor List 0x0009]
1609 1969-12-31 16:07:04.951052 0.008513 localhost () Apple_6b:db:09 (AirPods) SDP 19 Sent Service Search Attribute Response
1610 1969-12-31 16:07:05.010605 0.059553 controller host HCI_EVT 8 Rcvd Number of Completed Packets
1611 1969-12-31 16:07:05.080593 0.069988 Apple_6b:db:09 (AirPods) localhost () SDP 27 Rcvd Service Search Attribute Request : GATT: [Bluetooth Profile Descriptor List 0x0009]
1612 1969-12-31 16:07:05.087636 0.007043 localhost () Apple_6b:db:09 (AirPods) SDP 19 Sent Service Search Attribute Response
1613 1969-12-31 16:07:05.209417 0.121781 controller host HCI_EVT 8 Rcvd Number of Completed Packets
1614 1969-12-31 16:07:05.279491 0.070074 Apple_6b:db:09 (AirPods) localhost () L2CAP 21 Rcvd Connection Response - Pending (SCID: 0x22c6)
1615 1969-12-31 16:07:05.280731 0.001240 Apple_6b:db:09 (AirPods) localhost () L2CAP 21 Rcvd Connection Response - Success (SCID: 0x22c6, DCID: 0x0406)
Please file this bug with the AirPods Bluetooth team.
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