[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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https://bugzilla.kernel.org/show_bug.cgi?id=203997

Ron Murray (rjmx@rjmx.net) changed:

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                 CC|                            |rjmx@rjmx.net

--- Comment #1 from Ron Murray (rjmx@rjmx.net) ---
Had same problem here with my Beats Wireless 810(?) headphones.
Reverting to kernel 5.1.14 fixed the problem.

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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--- Comment #3 from Daniel Ponte (amigan@gmail.com) ---
Seeing similar with Logitech H800 headphones. Sometimes it stays connected.
Curiously enough, HFP profile sometimes works (using tanuk's pulseaudio-hfp
patch), but A2DP absolutely will not activate. The headphones will even
register with pulseaudio as a bare device but A2DP remains unavailable.

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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Søren Holm (sgh@sgh.dk) changed:

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--- Comment #4 from Søren Holm (sgh@sgh.dk) ---
(In reply to Daniel Ponte from comment #3)
> Seeing similar with Logitech H800 headphones. Sometimes it stays connected.
> Curiously enough, HFP profile sometimes works (using tanuk's pulseaudio-hfp
> patch), but A2DP absolutely will not activate. The headphones will even
> register with pulseaudio as a bare device but A2DP remains unavailable.

I have the exact same problem also with H800 headset.

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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--- Comment #8 from Matias Karhumaa (matias.karhumaa@gmail.com) ---
Ah, I think recent regression fix [1] caused another bug:

--snip--
static bool l2cap_check_enc_key_size(struct hci_conn *hcon)
{
        /* The minimum encryption key size needs to be enforced by the
         * host stack before establishing any L2CAP connections. The
         * specification in theory allows a minimum of 1, but to align
         * BR/EDR and LE transports, a minimum of 7 is chosen.
         *
         * This check might also be called for unencrypted connections
         * that have no key size requirements. Ensure that the link is
         * actually encrypted before enforcing a key size.
         */
        return (!test_bit(HCI_CONN_ENCRYPT, &hcon->flags) ||
                hcon->enc_key_size > HCI_MIN_ENC_KEY_SIZE);
}
--snip--

If Encryption key size is 7, L2CAP connection will fail. I think it should be
something like this:

In l2cap_core.c

static bool l2cap_check_enc_key_size(struct hci_conn *hcon)
{
        /* The minimum encryption key size needs to be enforced by the
         * host stack before establishing any L2CAP connections. The
         * specification in theory allows a minimum of 1, but to align
         * BR/EDR and LE transports, a minimum of 7 is chosen.
         *
         * This check might also be called for unencrypted connections
         * that have no key size requirements. Ensure that the link is
         * actually encrypted before enforcing a key size.
         */
        return (!test_bit(HCI_CONN_ENCRYPT, &hcon->flags) ||
                hcon->enc_key_size >= HCI_MIN_ENC_KEY_SIZE);
}
--snip--

Could you test the fix?

[1]:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/net/bluetooth?id=693cd8ce3f882524a5d06f7800dd8492411877b3

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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--- Comment #10 from Eivind Eide (xenofil@gmail.com) ---
Compiled 5.1.15 kernel with this patch and it indeed fixes the problem of
pairing with KLIPSCH KMC 1. Thanks!

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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--- Comment #13 from Matias Karhumaa (matias.karhumaa@gmail.com) ---
Eivind and Martin, thanks for testing!

Søren, could it be that for some reason now headset is able to create
connection? In your previous btmon trace we can see that headset was trying to
connect HFP but failed because your SDP records did not have record for HFP AG.
Then your machine tried to connect but failed because of the bug introduced in
5.1.15.

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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--- Comment #15 from Søren Holm (sgh@sgh.dk) ---
(In reply to Jan Steffens from comment #14)
> If you're running 5.1.16-arch1, please note that the patch has been
> backported into this release.

I do - then that is why. Sorry for the noise.

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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Pavel (pavel@noa-labs.com) changed:

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--- Comment #16 from Pavel (pavel@noa-labs.com) ---
Hello,

I'm afraid you are not out of the woods yet. I tried 5.2 and still can't pair a
lot of BT LE products based on MXCHIP chipset, including my mouse. My fear is
that they do use a key size of 1 by default 8-[]

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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--- Comment #17 from Pavel (pavel@noa-labs.com) ---
Created attachment 284765
  --> https://bugzilla.kernel.org/attachment.cgi?id=284765&action=edit
Traffic capture of a broken pairing

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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--- Comment #19 from Pavel (pavel@noa-labs.com) ---
Matias, I'm afraid this also happening with all BT LE devices I have, including
ones not MXCHIP based like Microsoft mouses.

I'm very sure it is a BT related issues as when I switch to non-le 3.0 mode,
the mouse works fine. It started happening at some time during the 5.1 release
cycle.

I would better try to use a usb dongle for BT, trying to confirm if this is not
a modem (Qualcomm) issue.

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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--- Comment #20 from Pavel (pavel@noa-labs.com) ---
Created attachment 284773
  --> https://bugzilla.kernel.org/attachment.cgi?id=284773&action=edit
Capture of a mouse connection which leads to no mouse movement

I attached one more capture.

I see that connection lights up in the blueman UI, and then times out when I
stop pressing the mouse buttons after 30 seconds. All without a sign of mouse
movement.

Were there any changes to BTLE during 5.1, 5.2 release cycle?

I think this worth a separate bug report.

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[Bug 203997] [REGRESSION] Unable to connect BT audio device on 5.1.15

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--- Comment #21 from Pavel (pavel@noa-labs.com) ---
Matias, I ordered an Intel ax200 wifi+bluetooth card for testing. It should
arrive in a week or so.

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