linux-kernel - Re: [PATCH v3] Bluetooth: iso: fix socket matching ambiguity between BIS and CIS

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Message-ID: <CABBYNZJu3izq6ZhNRKjMz-mW1CcP2VAE7Xs5oq=NupnVD7aayg@mail.gmail.com>
Date: Fri, 1 Aug 2025 11:57:41 -0400
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: yang.li@...ogic.com
Cc: Marcel Holtmann <marcel@...tmann.org>, Johan Hedberg <johan.hedberg@...il.com>, 
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] Bluetooth: iso: fix socket matching ambiguity between
 BIS and CIS

Hi Yang,

On Thu, Jul 31, 2025 at 4:00 AM Yang Li via B4 Relay
<devnull+yang.li.amlogic.com@...nel.org> wrote:
>
> From: Yang Li <yang.li@...ogic.com>
>
> When both BIS and CIS links exist, their sockets are in
> the BT_LISTEN state.

We probably need to introduce tests to iso-test that setup both then
to avoid reintroducing the problem.

> dump sock:
>   sk 000000001977ef51 state 6
>   src 10:a5:62:31:05:cf dst 00:00:00:00:00:00
>   sk 0000000031d28700 state 7
>   src 10:a5:62:31:05:cf dst00:00:00:00:00:00
>   sk 00000000613af00e state 4   # listen sock of bis
>   src 10:a5:62:31:05:cf dst 54:00:00:d4:99:30
>   sk 000000001710468c state 9
>   src 10:a5:62:31:05:cf dst 54:00:00:d4:99:30
>   sk 000000005d97dfde state 4   #listen sock of cis
>   src 10:a5:62:31:05:cf dst 00:00:00:00:00:00
>
> To locate the CIS socket correctly, check both the BT_LISTEN
> state and whether dst addr is BDADDR_ANY.
>
> Link: https://github.com/bluez/bluez/issues/1224
>
> Signed-off-by: Yang Li <yang.li@...ogic.com>
> ---
>  net/bluetooth/iso.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
> index eaffd25570e3..9a4dea03af8c 100644
> --- a/net/bluetooth/iso.c
> +++ b/net/bluetooth/iso.c
> @@ -1919,6 +1919,11 @@ static bool iso_match_pa_sync_flag(struct sock *sk, void *data)
>         return test_bit(BT_SK_PA_SYNC, &iso_pi(sk)->flags);
>  }
>
> +static bool iso_match_dst(struct sock *sk, void *data)
> +{
> +       return !bacmp(&iso_pi(sk)->dst, (bdaddr_t *)data);
> +}
> +
>  static void iso_conn_ready(struct iso_conn *conn)
>  {
>         struct sock *parent = NULL;
> @@ -1981,7 +1986,7 @@ static void iso_conn_ready(struct iso_conn *conn)
>
>                 if (!parent)
>                         parent = iso_get_sock(&hcon->src, BDADDR_ANY,
> -                                             BT_LISTEN, NULL, NULL);
> +                                             BT_LISTEN, iso_match_dst, BDADDR_ANY);
>
>                 if (!parent)
>                         return;
> @@ -2220,7 +2225,7 @@ int iso_connect_ind(struct hci_dev *hdev, bdaddr_t *bdaddr, __u8 *flags)
>                 }
>         } else {
>                 sk = iso_get_sock(&hdev->bdaddr, BDADDR_ANY,
> -                                 BT_LISTEN, NULL, NULL);
> +                                 BT_LISTEN, iso_match_dst, BDADDR_ANY);

Perhaps we should add helper function that wrap the iso_get_sock (e.g.
iso_get_sock_cis and iso_get_sock_bis) to make it clearer what is the
expected socket type, also if the hcon has been set perhaps that
should be matched as well with CIS_LINK/BIS_LINK, or perhaps we
introduce a socket type to differentiate since the use of the address
can make the logic a little confusing when the socket types are mixed
together.

Now looking at the source code perhaps we can have a separate list for
cis and bis sockets instead of global iso_sk_list (e.g. cis_sk_list
and bis_sk_list), that way we don't need a type and there is no risk
of confusing the sockets since they would never be in the same list.

>         }
>
>  done:
>
> ---
> base-commit: 9c533991fe15be60ad9f9a7629c25dbc5b09788d
> change-id: 20250731-bis_cis_coexist-717a442d5c42
>
> Best regards,
> --
> Yang Li <yang.li@...ogic.com>
>
>


-- 
Luiz Augusto von Dentz