netdev - Re: [PATCH v3 3/5] Bluetooth: ISO: add TX timestamping

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Message-ID: <CAL+tcoBZU8C76XTLoz9LEWR+e+x3ct_izbC0q-kKXkTxxqhoHg@mail.gmail.com>
Date: Mon, 10 Feb 2025 13:19:11 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Pauli Virtanen <pav@....fi>
Cc: linux-bluetooth@...r.kernel.org, 
	Luiz Augusto von Dentz <luiz.dentz@...il.com>, netdev@...r.kernel.org, davem@...emloft.net, 
	kuba@...nel.org, willemdebruijn.kernel@...il.com
Subject: Re: [PATCH v3 3/5] Bluetooth: ISO: add TX timestamping

On Sun, Feb 9, 2025 at 6:39 PM Pauli Virtanen <pav@....fi> wrote:
>
> Add BT_SCM_ERROR socket CMSG type.
>
> Support TX timestamping in ISO sockets.
>
> Support MSG_ERRQUEUE in ISO recvmsg.
>
> If a packet from sendmsg() is fragmented, only the first ACL fragment is
> timestamped.
>
> Signed-off-by: Pauli Virtanen <pav@....fi>
> ---
>  include/net/bluetooth/bluetooth.h |  1 +
>  net/bluetooth/iso.c               | 24 ++++++++++++++++++++----
>  2 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
> index 435250c72d56..bbefde319f95 100644
> --- a/include/net/bluetooth/bluetooth.h
> +++ b/include/net/bluetooth/bluetooth.h
> @@ -156,6 +156,7 @@ struct bt_voice {
>  #define BT_PKT_STATUS           16
>
>  #define BT_SCM_PKT_STATUS      0x03
> +#define BT_SCM_ERROR           0x04
>
>  #define BT_ISO_QOS             17
>
> diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
> index 44acddf58a0c..f497759a2af5 100644
> --- a/net/bluetooth/iso.c
> +++ b/net/bluetooth/iso.c
> @@ -518,7 +518,8 @@ static struct bt_iso_qos *iso_sock_get_qos(struct sock *sk)
>         return &iso_pi(sk)->qos;
>  }
>
> -static int iso_send_frame(struct sock *sk, struct sk_buff *skb)
> +static int iso_send_frame(struct sock *sk, struct sk_buff *skb,
> +                         const struct sockcm_cookie *sockc)
>  {
>         struct iso_conn *conn = iso_pi(sk)->conn;
>         struct bt_iso_qos *qos = iso_sock_get_qos(sk);
> @@ -538,10 +539,12 @@ static int iso_send_frame(struct sock *sk, struct sk_buff *skb)
>         hdr->slen = cpu_to_le16(hci_iso_data_len_pack(len,
>                                                       HCI_ISO_STATUS_VALID));
>
> -       if (sk->sk_state == BT_CONNECTED)
> +       if (sk->sk_state == BT_CONNECTED) {
> +               hci_setup_tx_timestamp(skb, 1, sockc);
>                 hci_send_iso(conn->hcon, skb);
> -       else
> +       } else {
>                 len = -ENOTCONN;
> +       }
>
>         return len;
>  }
> @@ -1348,6 +1351,7 @@ static int iso_sock_sendmsg(struct socket *sock, struct msghdr *msg,
>  {
>         struct sock *sk = sock->sk;
>         struct sk_buff *skb, **frag;
> +       struct sockcm_cookie sockc;
>         size_t mtu;
>         int err;
>
> @@ -1360,6 +1364,14 @@ static int iso_sock_sendmsg(struct socket *sock, struct msghdr *msg,
>         if (msg->msg_flags & MSG_OOB)
>                 return -EOPNOTSUPP;
>
> +       sockcm_init(&sockc, sk);

No need to initialize other irrelevant fields since Willem started to
clean up this kind of init phase in TCP[1].

[1]: https://lore.kernel.org/all/20250206193521.2285488-2-willemdebruijn.kernel@gmail.com/

> +
> +       if (msg->msg_controllen) {
> +               err = sock_cmsg_send(sk, msg, &sockc);
> +               if (err)
> +                       return err;
> +       }
> +

I'm not familiar with bluetooth, but I'm wondering if the above code
snippet is supposed to be protected by the socket lock as below since
I refer to TCP as an example? Is it possible that multiple threads
call this sendmsg at the same time?

>         lock_sock(sk);
>
>         if (sk->sk_state != BT_CONNECTED) {
> @@ -1405,7 +1417,7 @@ static int iso_sock_sendmsg(struct socket *sock, struct msghdr *msg,
>         lock_sock(sk);
>
>         if (sk->sk_state == BT_CONNECTED)
> -               err = iso_send_frame(sk, skb);
> +               err = iso_send_frame(sk, skb, &sockc);
>         else
>                 err = -ENOTCONN;
>
> @@ -1474,6 +1486,10 @@ static int iso_sock_recvmsg(struct socket *sock, struct msghdr *msg,
>
>         BT_DBG("sk %p", sk);
>
> +       if (unlikely(flags & MSG_ERRQUEUE))
> +               return sock_recv_errqueue(sk, msg, len, SOL_BLUETOOTH,
> +                                         BT_SCM_ERROR);
> +
>         if (test_and_clear_bit(BT_SK_DEFER_SETUP, &bt_sk(sk)->flags)) {
>                 sock_hold(sk);
>                 lock_sock(sk);
> --
> 2.48.1
>
>