[PATCH v3 2/2] Bluetooth: hci_event: keep HCI_LE_ADV set if the host cancelled

[Valentin Kindschi <valentin.kindschi@fiveco.ch>]

le_conn_complete_evt() clears HCI_LE_ADV before looking at the event
status, on the premise stated in its comment that all controllers stop
advertising when a connection is created.

That premise fails for Unknown Connection Identifier (0x02), which is
what an HCI_LE_Connection_Complete carries after the host issued
LE Create Connection Cancel: no connection was created and the
controller never stopped advertising. Clearing the flag there makes the
host believe advertising is off while the controller has it on.

Other non-zero statuses must keep clearing it. Advertising Timeout
(0x3c) in particular means the controller gave up advertising on its
own, so the flag has to go; leaving it set would make the
"already advertising" shortcut in hci_schedule_adv_instance_sync() skip
the HCI commands and silently stop advertising altogether.

With legacy advertising the disagreement is self-sustaining. On the next
software rotation tick hci_enable_advertising_sync() runs:

  - hci_disable_advertising_sync() returns early without sending
    anything, because HCI_LE_ADV is clear;
  - LE Set Advertising Parameters is then sent while the controller is
    still advertising, and is correctly rejected with Command Disallowed
    (0x0c);
  - the function returns before LE Set Advertising Enable, so nothing
    re-sets HCI_LE_ADV.

hci_schedule_adv_instance_sync() re-arms adv_instance_expire every
HCI_DEFAULT_ADV_DURATION (2 s) and its "already advertising" shortcut
tests HCI_LE_ADV, which can no longer become true, so the command is
retried every 2 s indefinitely:

  Bluetooth: hci0: Opcode 0x2006 failed: -16

Captured on a BCM43455 (no LE Extended Advertising) after a central
connection attempt timed out and was cancelled:

  LE Set Advertising Parameters (0x2006)   Success
  LE Set Advertising Enable     (0x200a)   Success        HCI_LE_ADV set
  LE Create Connection Cancel   (0x200e)   Success
  LE Connection Complete                   Unknown Conn Id  <- flag cleared
  LE Set Advertising Parameters (0x2006)   Command Disallowed  [+2.033 s]
  LE Set Advertising Parameters (0x2006)   Command Disallowed  [+2.016 s]
  ...

Keep the flag only for the host-cancelled case.

Fixes: fbd96c151cdc ("Bluetooth: Fix clearing HCI_LE_ADV for LE connections")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5 btmon
Signed-off-by: Valentin Kindschi <valentin.kindschi@fiveco.ch>
---
Changes in v2:
- Rebased onto bluetooth-next; no functional change.
  v1's hci_event.c context lacked the hci_store_wake_reason() call
  present in mainline, so the hunk did not apply.

 net/bluetooth/hci_event.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -5720,10 +5720,12 @@ static void le_conn_complete_evt(struct hci_dev *hdev, u8 status,
 	hci_dev_lock(hdev);
 	hci_store_wake_reason(hdev, bdaddr, bdaddr_type);
 
-	/* All controllers implicitly stop advertising in the event of a
-	 * connection, so ensure that the state bit is cleared.
+	/* Advertising stops when a connection is created, and when the
+	 * controller gives up advertising on its own. It keeps advertising
+	 * when the host cancelled an outgoing connection.
 	 */
-	hci_dev_clear_flag(hdev, HCI_LE_ADV);
+	if (status != HCI_ERROR_UNKNOWN_CONN_ID)
+		hci_dev_clear_flag(hdev, HCI_LE_ADV);
 
 	/* Check for existing connection:
 	 *
--
2.34.1