linux-kernel - Re: [PATCH v2 4/4] Bluetooth: Remove pending ACL connection attempts

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Date: Mon, 8 Jan 2024 14:14:29 -0500
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: Jonas Dreßler <verdre@...d.nl>
Cc: Marcel Holtmann <marcel@...tmann.org>, Johan Hedberg <johan.hedberg@...il.com>, 
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH v2 4/4] Bluetooth: Remove pending ACL connection attempts

Hi Jonas,

On Mon, Jan 8, 2024 at 1:55 PM Jonas Dreßler <verdre@...d.nl> wrote:
>
> On 1/8/24 19:44, Jonas Dreßler wrote:
> > On 1/8/24 19:39, Jonas Dreßler wrote:
> >> With the last commit we moved to using the hci_sync queue for "Create
> >> Connection" requests, removing the need for retrying the paging after
> >> finished/failed "Create Connection" requests and after the end of
> >> inquiries.
> >>
> >> hci_conn_check_pending() was used to trigger this retry, we can remove it
> >> now.
> >>
> >> Note that we can also remove the special handling for COMMAND_DISALLOWED
> >> errors in the completion handler of "Create Connection", because "Create
> >> Connection" requests are now always serialized.
> >>
> >> This is somewhat reverting commit 4c67bc74f016 ("[Bluetooth] Support
> >> concurrent connect requests").
> >>
> >> With this, the BT_CONNECT2 state of ACL hci_conn objects should now be
> >> back to meaning only one thing: That we received a connection request
> >> from another device (see hci_conn_request_evt), but the actual connect
> >> should be deferred.
> >> ---
> >>   include/net/bluetooth/hci_core.h |  1 -
> >>   net/bluetooth/hci_conn.c         | 16 ----------------
> >>   net/bluetooth/hci_event.c        | 21 ++++-----------------
> >>   3 files changed, 4 insertions(+), 34 deletions(-)
> >>
> >> diff --git a/include/net/bluetooth/hci_core.h
> >> b/include/net/bluetooth/hci_core.h
> >> index 2c30834c1..d7483958d 100644
> >> --- a/include/net/bluetooth/hci_core.h
> >> +++ b/include/net/bluetooth/hci_core.h
> >> @@ -1330,7 +1330,6 @@ struct hci_conn *hci_conn_add(struct hci_dev
> >> *hdev, int type, bdaddr_t *dst,
> >>                     u8 role);
> >>   void hci_conn_del(struct hci_conn *conn);
> >>   void hci_conn_hash_flush(struct hci_dev *hdev);
> >> -void hci_conn_check_pending(struct hci_dev *hdev);
> >>   struct hci_chan *hci_chan_create(struct hci_conn *conn);
> >>   void hci_chan_del(struct hci_chan *chan);
> >> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> >> index 541d55301..22033057b 100644
> >> --- a/net/bluetooth/hci_conn.c
> >> +++ b/net/bluetooth/hci_conn.c
> >> @@ -2534,22 +2534,6 @@ void hci_conn_hash_flush(struct hci_dev *hdev)
> >>       }
> >>   }
> >> -/* Check pending connect attempts */
> >> -void hci_conn_check_pending(struct hci_dev *hdev)
> >> -{
> >> -    struct hci_conn *conn;
> >> -
> >> -    BT_DBG("hdev %s", hdev->name);
> >> -
> >> -    hci_dev_lock(hdev);
> >> -
> >> -    conn = hci_conn_hash_lookup_state(hdev, ACL_LINK, BT_CONNECT2);
> >> -    if (conn)
> >> -        hci_cmd_sync_queue(hdev, hci_acl_create_connection_sync,
> >> conn, NULL);
> >> -
> >> -    hci_dev_unlock(hdev);
> >> -}
> >> -
> >>   static u32 get_link_mode(struct hci_conn *conn)
> >>   {
> >>       u32 link_mode = 0;
> >> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> >> index e8b4a0126..91973d6d1 100644
> >> --- a/net/bluetooth/hci_event.c
> >> +++ b/net/bluetooth/hci_event.c
> >> @@ -117,8 +117,6 @@ static u8 hci_cc_inquiry_cancel(struct hci_dev
> >> *hdev, void *data,
> >>           hci_discovery_set_state(hdev, DISCOVERY_STOPPED);
> >>       hci_dev_unlock(hdev);
> >> -    hci_conn_check_pending(hdev);
> >> -
> >>       return rp->status;
> >>   }
> >> @@ -149,8 +147,6 @@ static u8 hci_cc_exit_periodic_inq(struct hci_dev
> >> *hdev, void *data,
> >>       hci_dev_clear_flag(hdev, HCI_PERIODIC_INQ);
> >> -    hci_conn_check_pending(hdev);
> >> -
> >>       return rp->status;
> >>   }
> >> @@ -2296,10 +2292,8 @@ static void hci_cs_inquiry(struct hci_dev
> >> *hdev, __u8 status)
> >>   {
> >>       bt_dev_dbg(hdev, "status 0x%2.2x", status);
> >> -    if (status) {
> >> -        hci_conn_check_pending(hdev);
> >> +    if (status)
> >>           return;
> >> -    }
> >>       set_bit(HCI_INQUIRY, &hdev->flags);
> >>   }
> >> @@ -2323,12 +2317,9 @@ static void hci_cs_create_conn(struct hci_dev
> >> *hdev, __u8 status)
> >>       if (status) {
> >>           if (conn && conn->state == BT_CONNECT) {
> >> -            if (status != HCI_ERROR_COMMAND_DISALLOWED ||
> >> conn->attempt > 2) {
> >> -                conn->state = BT_CLOSED;
> >> -                hci_connect_cfm(conn, status);
> >> -                hci_conn_del(conn);
> >> -            } else
> >> -                conn->state = BT_CONNECT2;
> >> +            conn->state = BT_CLOSED;
> >> +            hci_connect_cfm(conn, status);
> >> +            hci_conn_del(conn);
> >>           }
> >>       } else {
> >>           if (!conn) {
> >> @@ -3020,8 +3011,6 @@ static void hci_inquiry_complete_evt(struct
> >> hci_dev *hdev, void *data,
> >>       bt_dev_dbg(hdev, "status 0x%2.2x", ev->status);
> >> -    hci_conn_check_pending(hdev);
> >> -
> >>       if (!test_and_clear_bit(HCI_INQUIRY, &hdev->flags))
> >>           return;
> >> @@ -3247,8 +3236,6 @@ static void hci_conn_complete_evt(struct hci_dev
> >> *hdev, void *data,
> >>   unlock:
> >>       hci_dev_unlock(hdev);
> >> -
> >> -    hci_conn_check_pending(hdev);
> >>   }
> >>   static void hci_reject_conn(struct hci_dev *hdev, bdaddr_t *bdaddr)
> >
> > Please take a special look at this one: I'm not sure if I'm breaking the
> > functionality of deferred connecting using BT_CONNECT2 in
> > hci_conn_request_evt() here, as I don't see anywhere where we check for
> > this state and establish a connection later.
> >
> > It seems that this is how hci_conn_request_evt() was initially written
> > though, hci_conn_check_pending() only got introduced later and seems
> > unrelated.
>
> Ahh nevermind... The check for BT_CONNECT2 on "Conn Complete event" got
> introduced with 4c67bc74f01 ([Bluetooth] Support concurrent connect
> requests). And later the deferred connection setup on "Conn Request
> event" got introduced with 20714bfef8 ("Bluetooth: Implement deferred
> sco socket setup").
>
> I assume the latter commit was relying on the "Create Connection"
> request "Conn Complete event" that got introduced with the former commit
> then? That would imply that we use BT_CONNECT2 if there's already a
> "Create Connection" going on when the "Conn Request event" happens, and
> we must wait for that existing request to finish.. Is that how those
> deferred connections are supposed to work?

Well if you are not sure that works we better make sure we have tests
that cover this, for LE I know for sure it works because we have the
likes of iso-tester that do connect 2 peers simultaneously, but for
classic I don't recall having any test that does multiple connections.

> >
> > Thanks,
> > Jonas



-- 
Luiz Augusto von Dentz