From nobody Sat Sep 26 19:35:04 2026 Received: from remote.fiveco.ch (remote.fiveco.ch [46.14.118.250]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 540453D3327 for ; Mon, 31 Aug 2026 09:05:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=46.14.118.250 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788167122; cv=none; b=u2mN9L3uS25TZEER/Yz3wPJTyuljA7kt5Wh2aV4D6S3TwBrqld8V71JZCX+UvCQAauGQNBmp9lXcjf30xhvPINe25AIaOyIwJSKZeMQJRgvOBhUUBd+wRRA1J7V8EKABsJgnIk8XupPuahjtRVLoeNyKZMQZNIjZtiXiwReiwcg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788167122; c=relaxed/simple; bh=WDPVoqDu5sgqGFzGVVr3SKyG9fWrWvmMgllNy7RqRLg=; h=Content-Type:From:To:CC:Subject:Date:Message-ID:MIME-Version; b=updl9LE+MvOIBsXq/yQTlLpagHUiGuZnBkna/JNth765V8FJtftAZ5Tuiw2YTwItFPnt5Jup6IMf3Ta9Sd/dCxtONR7qcWJKT2/Ow53NWqyv9m8F+WyzOEQ9uKM1pMx3RM1SYAxIDqv1qOSKPSmd/fXG08qTJsEnPlReyHeElbY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=fiveco.ch; spf=pass smtp.mailfrom=fiveco.ch; dkim=pass (1024-bit key) header.d=fiveco.ch header.i=@fiveco.ch header.b=z96MjZpJ; arc=none smtp.client-ip=46.14.118.250 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=fiveco.ch Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=fiveco.ch Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=fiveco.ch header.i=@fiveco.ch header.b="z96MjZpJ" Received: from [192.168.16.44] (port=33631 helo=remote.fiveco.ch) by remote.fiveco.ch with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.96) (envelope-from ) id 1x0xul-000000002HK-15Yr; Mon, 31 Aug 2026 11:02:51 +0200 Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; d=fiveco.ch; s=fiveco; c=simple/simple; t=1788166971; h=from:subject:to:date:message-id; bh=WDPVoqDu5sgqGFzGVVr3SKyG9fWrWvmMgllNy7RqRLg=; b=z96MjZpJpKCrfR1WKnPAMt9AXz6nfUhSHWg8lfzjlFY2NachAy4RyDUML8usD31nYamIYEGYYOy mWxVfpO+tBFPagXqIHQpSuBmPRg/OvumWdPPBGuBZgx+xM+QvKz2HHc/ns8fHhg2HcjTq66oM8EwL jYmptrpR3bR+cHJokZI= Received: from fiveco-vm-vk1.fiveco.local (192.168.16.29) by FIVECO-MX01.fiveco.local (192.168.16.44) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.61; Mon, 31 Aug 2026 11:02:50 +0200 From: Valentin Kindschi To: CC: , , , , Valentin Kindschi , Subject: [PATCH v3] Bluetooth: hci_sync: pause advertising for the scan address update Date: Mon, 31 Aug 2026 11:02:32 +0200 Message-ID: <20260831090232.1726063-1-valentin.kindschi@fiveco.ch> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: FIVECO-MX01.fiveco.local (192.168.16.44) To FIVECO-MX01.fiveco.local (192.168.16.44) X-Sophos-OBS: success X-SASI-Version: Antispam-Engine: 6.0.0.1, AntispamData: 2026.8.31.82719 X-SASI-RCODE: 200 X-SASI-SpamProbability: 8% X-SASI-Hits: BODY_SIZE_6000_6999 0.000000, BODY_SIZE_7000_LESS 0.000000, CTE_8BIT 0.000000, DKIM_ALIGNS 0.000000, DKIM_SIGNATURE 0.000000, HTML_00_01 0.050000, HTML_00_10 0.050000, MULTIPLE_RCPTS 0.100000, NO_CTA_URI_FOUND 0.000000, NO_FUR_HEADER 0.000000, NO_URI_HTTPS 0.000000, OUTBOUND 0.000000, OUTBOUND_SOPHOS 0.000000, SENDER_NO_AUTH 0.000000, WEBMAIL_SOURCE 0.000000, WEBMAIL_XOIP 0.000000, WEBMAIL_X_IP_HDR 0.000000, __ANY_URI 0.000000, __BODY_NO_MAILTO 0.000000, __BULK_NEGATE 0.000000, __CC_NAME 0.000000, __CC_NAME_DIFF_FROM_ACC 0.000000, __CC_REAL_NAMES 0.000000, __CT 0.000000, __CTE 0.000000, __CT_TEXT_PLAIN 0.000000, __DKIM_ALIGNS_1 0.000000, __DKIM_ALIGNS_2 0.000000, __DQ_NEG_DOMAIN 0.000000, __DQ_NEG_HEUR 0.000000, __DQ_NEG_IP 0.000000, __FUR_RDNS_SOPHOS 0.000000, __HAS_CC_HDR 0.000000, __HAS_FROM 0.000000, __HAS_MSGID 0.000000, __HAS_XOIP 0.000000, __HAS_X_MAILER 0.000000, __MIME_TEXT_ONLY 0.000000, __MIME_TEXT_P 0.000000, __MIME_TEXT_P1 0.000000, __MIME_VERSION 0.000000, __MULTIPLE_RCPTS_CC_X2 0.000000, __NO_HTML_TAG_RAW 0.000000, __OUTBOUND_SOPHOS_FUR 0.000000, __OUTBOUND_SOPHOS_FUR_IP 0.000000, __OUTBOUND_SOPHOS_FUR_RDNS 0.000000, __PHISH_SPEAR_SUBJ_PREDICATE 0.000000, __RCVD_CTE 0.000000, __RCVD_EXIM_4_96_AES_128 0.000000, __RCVD_FROM_HOMEUSER 0.000000, __SANE_MSGID 0.000000, __SHIPPING_ACTION 0.000000, __SL_HEAVY 0.000000, __SUBJ_ALPHA_END 0.000000, __SUBJ_STARTS_S_BRACKETS 0.000000, __TO_MALFORMED_2 0.000000, __TO_NO_NAME 0.000000, __URI_MAILTO 0.000000, __URI_NO_WWW 0.000000, __URI_NS 0.000000 Content-Type: text/plain; charset="utf-8" hci_active_scan_sync() calls hci_update_random_address_sync() with require_privacy set on every active scan start, which generates a non-resolvable private address and programs it with LE Set Random Address. BLUETOOTH CORE SPECIFICATION Vol 4, Part E, 7.8.4 states the controller shall return Command Disallowed (0x0C) for LE Set Random Address while legacy advertising or scanning is enabled. Advertising is only stopped beforehand when LL privacy is in use. hci_pause_addr_resolution(), called just above, returns early when !use_ll_privacy(hdev), so its hci_pause_advertising_sync() never runs. On a device that advertises while active scanning - a peripheral that is also a central - every scan start therefore issues a command the host can already know will be rejected: Bluetooth: hci0: Opcode 0x2005 failed: -16 The address write is not retried either: hci_set_random_addr_sync() defers only when hdev->random_addr is already set, and it never becomes set because the write keeps failing, so HCI_RPA_EXPIRED is not used here. Observed on a BCM43455 with Privacy=3Doff, one advertising instance and continuous active discovery, at the scan restart period (~10 s): < LE Set Random Address Address: 02:16:91:90:F1:D4 (Non-Resolvable) > Command Complete LE Set Random Address, Command Disallowed < LE Set Random Address Address: 26:90:57:96:9A:3E (Non-Resolvable) > Command Complete LE Set Random Address, Command Disallowed < LE Set Random Address Address: 16:32:01:BC:B5:CE (Non-Resolvable) > Command Complete LE Set Random Address, Command Disallowed Pause advertising for the address update regardless of privacy, and resume it on every exit path. Previously the resume was guarded by use_ll_privacy() and only reached on the error path, which matched the pause being privacy-only. One caveat this widens: when HCI_ADVERTISING is set, hci_pause_advertising_sync() also clears HCI_DISCOVERABLE and zeroes discov_timeout, and hci_resume_advertising_sync() restores only HCI_ADVERTISING. That side effect previously happened only with LL privacy; it is now reachable on every active scan start, so a device made discoverable through mgmt while repeatedly running active discovery would lose discoverability. Restoring it belongs in the pause/resume pair rather than here, but it is worth flagging. With the patch, the same scan restart on the same hardware: < LE Set Advertising Enable Success < LE Set Random Address Success < LE Set Scan Parameters Success < LE Set Scan Enable Success < LE Set Advertising Parameters Success < LE Set Advertising Enable Success Over 35425 records / ~4 min of btmon with continuous active discovery and advertising enabled there were no Command Disallowed responses of any kind, against one per scan restart before. A central could still connect to the device, confirming advertising is restored after the pause. A second capture on the same device, 221 s with an out-of-range peer causing two cancelled outgoing connections, shows the same result under a different mix of traffic: 2 LE Set Random Address, both Success, and no Command Disallowed of any opcode. Tooling disclosure (Documentation/process/generated-content.rst): an AI coding assistant was used to investigate this and to draft the change; the patch text and code are its output, reviewed by me. Inputs were btmon captures and kernel logs from the affected device, with the request to identify what re-issues LE Set Random Address every ~10 s and to fix it. Three earlier explanations it proposed were discarded after being checked against the captures: bluetoothd restarting service discovery; RPA rotation (excluded, Privacy=3Doff); and the static-address branch of hci_update_random_address_sync() (excluded, both random_address and static_address read 00:00:00:00:00:00). The cause was only established after decoding the command payloads, which showed a freshly generated non-resolvable address per attempt. Testing is as described above, on the device, using btmon and a second device to confirm connectability. Fixes: abfeea476c68 ("Bluetooth: hci_sync: Convert MGMT_OP_START_DISCOVERY") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-5 btmon Signed-off-by: Valentin Kindschi --- Changes in v3: - Resend, no code change; v2 had no reply. Rechecked that it still applies to bluetooth-next. - Added the second capture described above, taken with the two patches from the "endless adv params retry" series applied, since in bluetooth-next, confirming the fix holds with cancelled outgoing connections in the mix. Changes in v2: - Rebased onto bluetooth-next: mainline renamed use_ll_privacy() to ll_privacy_capable(). No functional change. net/bluetooth/hci_sync.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c --- a/net/bluetooth/hci_sync.c +++ b/net/bluetooth/hci_sync.c @@ -6244,6 +6244,14 @@ static int hci_active_scan_sync(struct hci_dev *hdev= , uint16_t interval) if (err) goto failed; =20 + /* LE Set Random Address is disallowed while advertising is enabled, so + * pause it for the address update. hci_pause_addr_resolution() above + * only does this when LL privacy is in use. + */ + err =3D hci_pause_advertising_sync(hdev); + if (err) + goto failed; + /* All active scans will be done with either a resolvable private * address (when privacy feature has been enabled) or non-resolvable * private address. @@ -6272,13 +6280,18 @@ static int hci_active_scan_sync(struct hci_dev *hde= v, uint16_t interval) err =3D hci_start_scan_sync(hdev, LE_SCAN_ACTIVE, interval, hdev->le_scan_window_discovery, own_addr_type, filter_policy, filter_dup); - if (!err) + if (!err) { + /* Advertising was paused for the address update above. */ + hci_resume_advertising_sync(hdev); return err; + } =20 failed: - /* Resume advertising if it was paused */ - if (ll_privacy_capable(hdev)) - hci_resume_advertising_sync(hdev); + /* Resume advertising if it was paused. hci_resume_advertising_sync() + * is a no-op when hdev->advertising_paused is not set, so this covers + * both the privacy and the address-update pause. + */ + hci_resume_advertising_sync(hdev); =20 /* Resume passive scanning */ hci_update_passive_scan_sync(hdev); -- 2.34.1