Re: [PATCH v3 0/4] Bluetooth: Improve retrying of connection attempts

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

Hi Jonas,

On Wed, Jan 24, 2024 at 11:17 AM Jonas Dreßler <verdre@v0yd.nl> wrote:
>
> Hi Luiz,
>
> On 1/9/24 10:57 PM, Jonas Dreßler wrote:
> > Hi Luiz,
> >
> > On 1/9/24 18:53, Luiz Augusto von Dentz wrote:
> >> Hi Jonas,
> >>
> >> On Mon, Jan 8, 2024 at 5:46 PM Jonas Dreßler <verdre@v0yd.nl> wrote:
> >>>
> >>> Since commit 4c67bc74f016 ("[Bluetooth] Support concurrent connect
> >>> requests"), the kernel supports trying to connect again in case the
> >>> bluetooth card is busy and fails to connect.
> >>>
> >>> The logic that should handle this became a bit spotty over time, and also
> >>> cards these days appear to fail with more errors than just "Command
> >>> Disallowed".
> >>>
> >>> This series refactores the handling of concurrent connection requests
> >>> by serializing all "Create Connection" commands for ACL connections
> >>> similar to how we do it for LE connections.
> >>>
> >>> ---
> >>>
> >>> v1: https://lore.kernel.org/linux-bluetooth/20240102185933.64179-1-verdre@v0yd.nl/
> >>> v2: https://lore.kernel.org/linux-bluetooth/20240108183938.468426-1-verdre@v0yd.nl/
> >>> v3:
> >>>    - Move the new sync function to hci_sync.c as requested by review
> >>>    - Abort connection on failure using hci_abort_conn_sync() instead of
> >>>      hci_abort_conn()
> >>>    - Make the last commit message a bit more precise regarding the meaning
> >>>      of BT_CONNECT2 state
> >>>
> >>> Jonas Dreßler (4):
> >>>    Bluetooth: Remove superfluous call to hci_conn_check_pending()
> >>>    Bluetooth: hci_event: Use HCI error defines instead of magic values
> >>>    Bluetooth: hci_conn: Only do ACL connections sequentially
> >>>    Bluetooth: Remove pending ACL connection attempts
> >>>
> >>>   include/net/bluetooth/hci.h      |  3 ++
> >>>   include/net/bluetooth/hci_core.h |  1 -
> >>>   include/net/bluetooth/hci_sync.h |  3 ++
> >>>   net/bluetooth/hci_conn.c         | 83 +++-----------------------------
> >>>   net/bluetooth/hci_event.c        | 29 +++--------
> >>>   net/bluetooth/hci_sync.c         | 72 +++++++++++++++++++++++++++
> >>>   6 files changed, 93 insertions(+), 98 deletions(-)
> >>>
> >>> --
> >>> 2.43.0
> >>
> >> After rebasing and fixing a little bit here and there, see v4, looks
> >> like this changes is affecting the following mgmt-tester -s "Pair
> >> Device - Power off 1":
> >>
> >> Pair Device - Power off 1 - init
> >>    Read Version callback
> >>      Status: Success (0x00)
> >>      Version 1.22
> >>    Read Commands callback
> >>      Status: Success (0x00)
> >>    Read Index List callback
> >>      Status: Success (0x00)
> >>    Index Added callback
> >>      Index: 0x0000
> >>    Enable management Mesh interface
> >>    Enabling Mesh feature
> >>    Read Info callback
> >>      Status: Success (0x00)
> >>      Address: 00:AA:01:00:00:00
> >>      Version: 0x09
> >>      Manufacturer: 0x05f1
> >>      Supported settings: 0x0001bfff
> >>      Current settings: 0x00000080
> >>      Class: 0x000000
> >>      Name:
> >>      Short name:
> >>    Mesh feature is enabled
> >> Pair Device - Power off 1 - setup
> >>    Setup sending Set Bondable (0x0009)
> >>    Setup sending Set Powered (0x0005)
> >>    Initial settings completed
> >>    Test setup condition added, total 1
> >>    Client set connectable: Success (0x00)
> >>    Test setup condition complete, 0 left
> >> Pair Device - Power off 1 - setup complete
> >> Pair Device - Power off 1 - run
> >>    Sending Pair Device (0x0019)
> >> Bluetooth: hci0: command 0x0405 tx timeout
> >> Bluetooth: hci0: command 0x0408 tx timeout
> >>    Test condition added, total 1
> >> Pair Device - Power off 1 - test timed out
> >>    Pair Device (0x0019): Disconnected (0x0e)
> >> Pair Device - Power off 1 - test not run
> >> Pair Device - Power off 1 - teardown
> >> Pair Device - Power off 1 - teardown
> >>    Index Removed callback
> >>      Index: 0x0000
> >> Pair Device - Power off 1 - teardown complete
> >> Pair Device - Power off 1 - done
> >>
> >
> > Thanks for landing the first two commits!
> >
> > I think this is actually the same issue causing the test failure
> > as in the other issue I had:
> > https://lore.kernel.org/linux-bluetooth/7cee4e74-3a0c-4b7c-9984-696e646160f8@v0yd.nl/
> >
> > It seems that the emulator is unable to reply to HCI commands sent
> > from the hci_sync machinery, possibly because that is sending things
> > on a separate thread?
>
> Okay I did some further digging now: Turns out this actually not a problem
> with vhci and the emulator, but (in this test case) it's actually intended
> that there's the command times out, because force_power_off is TRUE for
> this test case, and the HCI device gets shut down right after sending the MGMT
> command.
>
> The test broke because the "Command Complete" MGMT event comes back with status
> "Disconnected" instead of "Not Powered": The reason for that is the
> hci_abort_conn_sync() that I added in the case where the "Create Connection" HCI
> times out. hci_abort_conn_sync() calls hci_conn_failed() with
> HCI_ERROR_LOCAL_HOST_TERM as expected, this in turn calls the hci_connect_cfm()
> callback (pairing_complete_cb), and there we we look up HCI_ERROR_LOCAL_HOST_TERM
> in mgmt_status_table, ending up with MGMT_STATUS_DISCONNECTED.
>
> When I remove the hci_abort_conn_sync() we get the "Not Powered" failure again,
> I'm not exactly sure why that happens (I assume there's some kind of generic mgmt
> failure return handler that checks hdev_is_powered() and then sets the error).
>
> So the question now is do we want to adjust the test (and possibly bluetoothd?)
> to expect "Disconnected" instead of "Not Powered", or should I get rid of the
> hci_abort_conn_sync() again? Fwiw, in hci_le_create_conn_sync() we also clean
> up like this on ETIMEDOUT (maybe the spec is just different there?), so
> consistency wise it seems better to adjust the test to expect "Disconnected".

Great that you find time to dig into this, and yes I think it is fine
to expect a different error if in the process we clean up using
hci_abort_conn_sync we just need to make sure nothing else is affected
by this change.

> Cheers,
> Jonas
>
> >
> > Cheers,
> > Jonas



-- 
Luiz Augusto von Dentz