plugins: Add new plugin to fix airpods pairing

Apple Airpods are discoverable and pairable in BREDR mode, but also advertise in unconnectable mode in LE with the same Public address, at the same time. As the pairing process uses the latest seen address, sometimes it uses the LE Public address to pair, which fails.

This commit adds a new adapter driver plugin which force the BREDR last seen time on LE Public address device found event related to an Apple device, allowing pairing process to always use the BREDR.

This commit is based on proposal
https://lore.kernel.org/all/[email protected]/

---
 Makefile.plugins  |   3 ++
 plugins/airpods.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 135 insertions(+)
 create mode 100644 plugins/airpods.c

Makefile.plugins +3 -0

index 4aa2c9c92..2ebd8aaf6 100644
@@ -11,6 +11,9 @@ builtin_sources += plugins/autopair.c
 builtin_modules += policy
 builtin_sources += plugins/policy.c
 
+builtin_modules += airpods
+builtin_sources += plugins/airpods.c
+
 if ADMIN
 builtin_modules += admin
 builtin_sources += plugins/admin.c

plugins/airpods.c new file +132 -1

new file mode 100644
index 000000000..5043f0cca
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *
+ *  BlueZ - Bluetooth protocol stack for Linux
+ *
+ *  Copyright (C) 2024 Frédéric Danis <[email protected]>
+ *
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <stdbool.h>
+
+#include <glib.h>
+
+#include "bluetooth/bluetooth.h"
+
+#include "lib/mgmt.h"
+#include "src/plugin.h"
+#include "src/adapter.h"
+#include "src/device.h"
+#include "src/eir.h"
+#include "src/log.h"
+#include "src/shared/mgmt.h"
+#include "src/shared/util.h"
+
+#define APPLE_INC_VENDOR_ID 0x004c
+
+static struct mgmt *mgmt;
+
+static bool eir_msd_is_apple_inc(GSList *msd_list)
+{
+       GSList *msd_l, *msd_next;
+
+       for (msd_l = msd_list; msd_l != NULL; msd_l = msd_next) {
+               const struct eir_msd *msd = msd_l->data;
+
+               msd_next = g_slist_next(msd_l);
+
+               if (msd->company == APPLE_INC_VENDOR_ID)
+                       return true;
+       }
+
+       return false;
+}
+
+static void airpods_device_found_callback(uint16_t index, uint16_t length,
+                                       const void *param, void *user_data)
+{
+       struct btd_device *dev;
+       const struct mgmt_ev_device_found *ev = param;
+       struct btd_adapter *adapter = user_data;
+       uint16_t eir_len;
+       uint32_t flags = le32_to_cpu(ev->flags);
+       struct eir_data eir_data;
+
+       dev = btd_adapter_find_device(adapter,  &ev->addr.bdaddr,
+                                       ev->addr.type);
+       if (!dev)
+               return;
+
+       if (length < sizeof(*ev)) {
+               warn("Too short device found event (%u bytes)", length);
+               return;
+       }
+
+       eir_len = btohs(ev->eir_len);
+       if (length != sizeof(*ev) + eir_len) {
+               warn("Device found event size mismatch (%u != %zu)",
+                                       length, sizeof(*ev) + eir_len);
+               return;
+       }
+
+       if (eir_len == 0)
+               return;
+
+       memset(&eir_data, 0, sizeof(eir_data));
+       eir_parse(&eir_data, ev->eir, eir_len);
+
+       if (eir_msd_is_apple_inc(eir_data.msd_list) &&
+                               (flags & MGMT_DEV_FOUND_NOT_CONNECTABLE) &&
+                               (ev->addr.type == BDADDR_LE_PUBLIC)) {
+               DBG("Force BREDR last seen");
+               device_set_bredr_support(dev);
+               device_update_last_seen(dev, BDADDR_BREDR, true);
+       }
+}
+
+static int airpods_probe(struct btd_adapter *adapter)
+{
+       if (!mgmt)
+               mgmt = mgmt_new_default();
+
+       if (!mgmt) {
+               fprintf(stderr, "Failed to open management socket\n");
+               return 0;
+       }
+
+       mgmt_register(mgmt, MGMT_EV_DEVICE_FOUND,
+                                       btd_adapter_get_index(adapter),
+                                       airpods_device_found_callback,
+                                       adapter, NULL);
+
+       return 0;
+}
+
+static void airpods_remove(struct btd_adapter *adapter)
+{
+       mgmt_unregister_index(mgmt, btd_adapter_get_index(adapter));
+}
+
+static struct btd_adapter_driver airpods_driver = {
+       .name   = "airpods",
+       .probe  = airpods_probe,
+       .remove = airpods_remove,
+};
+
+static int airpods_init(void)
+{
+       return btd_register_adapter_driver(&airpods_driver);
+}
+
+static void airpods_exit(void)
+{
+       btd_unregister_adapter_driver(&airpods_driver);
+}
+
+BLUETOOTH_PLUGIN_DEFINE(airpods, VERSION,
+               BLUETOOTH_PLUGIN_PRIORITY_LOW, airpods_init, airpods_exit)
--

2.34.1

Hi,

Quoted 5 lines · Frédéric Danis

Apple Airpods are discoverable and pairable in BREDR mode, but also advertise in unconnectable mode in LE with the same Public address, at the same time. As the pairing process uses the latest seen address, sometimes it uses the LE Public address to pair, which fails.

Quoted 4 lines

This commit adds a new adapter driver plugin which force the BREDR last seen time on LE Public address device found event related to an Apple device, allowing pairing process to always use the BREDR.

While I'm fine with having plugin for this specific case, I wonder if select_conn_bearer() shouldn't take
bearer's connectable state into account when selecting bearer for connection

Quoted 164 lines

This commit is based on proposal
https://lore.kernel.org/all/[email protected]/

---
  Makefile.plugins  |   3 ++
  plugins/airpods.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++
  2 files changed, 135 insertions(+)

create mode 100644 plugins/airpods.c

Makefile.plugins +3 -0

index 4aa2c9c92..2ebd8aaf6 100644
@@ -11,6 +11,9 @@ builtin_sources += plugins/autopair.c
  builtin_modules += policy
  builtin_sources += plugins/policy.c
 
+builtin_modules += airpods
+builtin_sources += plugins/airpods.c
+
  if ADMIN
  builtin_modules += admin
  builtin_sources += plugins/admin.c

plugins/airpods.c new file +132 -1

new file mode 100644
index 000000000..5043f0cca
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *
+ *  BlueZ - Bluetooth protocol stack for Linux
+ *
+ *  Copyright (C) 2024 Frédéric Danis <[email protected]>
+ *
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <stdbool.h>
+
+#include <glib.h>
+
+#include "bluetooth/bluetooth.h"
+
+#include "lib/mgmt.h"
+#include "src/plugin.h"
+#include "src/adapter.h"
+#include "src/device.h"
+#include "src/eir.h"
+#include "src/log.h"
+#include "src/shared/mgmt.h"
+#include "src/shared/util.h"
+
+#define APPLE_INC_VENDOR_ID 0x004c
+
+static struct mgmt *mgmt;
+
+static bool eir_msd_is_apple_inc(GSList *msd_list)
+{
+       GSList *msd_l, *msd_next;
+
+       for (msd_l = msd_list; msd_l != NULL; msd_l = msd_next) {
+               const struct eir_msd *msd = msd_l->data;
+
+               msd_next = g_slist_next(msd_l);
+
+               if (msd->company == APPLE_INC_VENDOR_ID)
+                       return true;
+       }
+
+       return false;
+}
+
+static void airpods_device_found_callback(uint16_t index, uint16_t length,
+                                       const void *param, void *user_data)
+{
+       struct btd_device *dev;
+       const struct mgmt_ev_device_found *ev = param;
+       struct btd_adapter *adapter = user_data;
+       uint16_t eir_len;
+       uint32_t flags = le32_to_cpu(ev->flags);
+       struct eir_data eir_data;
+
+       dev = btd_adapter_find_device(adapter,  &ev->addr.bdaddr,
+                                       ev->addr.type);
+       if (!dev)
+               return;
+
+       if (length < sizeof(*ev)) {
+               warn("Too short device found event (%u bytes)", length);
+               return;
+       }
+
+       eir_len = btohs(ev->eir_len);
+       if (length != sizeof(*ev) + eir_len) {
+               warn("Device found event size mismatch (%u != %zu)",
+                                       length, sizeof(*ev) + eir_len);
+               return;
+       }
+
+       if (eir_len == 0)
+               return;
+
+       memset(&eir_data, 0, sizeof(eir_data));
+       eir_parse(&eir_data, ev->eir, eir_len);
+
+       if (eir_msd_is_apple_inc(eir_data.msd_list) &&
+                               (flags & MGMT_DEV_FOUND_NOT_CONNECTABLE) &&
+                               (ev->addr.type == BDADDR_LE_PUBLIC)) {
+               DBG("Force BREDR last seen");
+               device_set_bredr_support(dev);
+               device_update_last_seen(dev, BDADDR_BREDR, true);
+       }
+}
+
+static int airpods_probe(struct btd_adapter *adapter)
+{
+       if (!mgmt)
+               mgmt = mgmt_new_default();
+
+       if (!mgmt) {
+               fprintf(stderr, "Failed to open management socket\n");
+               return 0;
+       }
+
+       mgmt_register(mgmt, MGMT_EV_DEVICE_FOUND,
+                                       btd_adapter_get_index(adapter),
+                                       airpods_device_found_callback,
+                                       adapter, NULL);
+
+       return 0;
+}
+
+static void airpods_remove(struct btd_adapter *adapter)
+{
+       mgmt_unregister_index(mgmt, btd_adapter_get_index(adapter));
+}
+
+static struct btd_adapter_driver airpods_driver = {
+       .name   = "airpods",
+       .probe  = airpods_probe,
+       .remove = airpods_remove,
+};
+
+static int airpods_init(void)
+{
+       return btd_register_adapter_driver(&airpods_driver);
+}
+
+static void airpods_exit(void)
+{
+       btd_unregister_adapter_driver(&airpods_driver);
+}
+
+BLUETOOTH_PLUGIN_DEFINE(airpods, VERSION,
+               BLUETOOTH_PLUGIN_PRIORITY_LOW, airpods_init, airpods_exit)
--

2.34.1