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Message-ID: <aDn5VKgXkYg77Qk_@mini-arch>
Date: Fri, 30 May 2025 11:30:44 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: Pavel Begunkov <asml.silence@...il.com>
Cc: io-uring@...r.kernel.org, Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
Kuniyuki Iwashima <kuniyu@...zon.com>,
Paolo Abeni <pabeni@...hat.com>,
Willem de Bruijn <willemb@...gle.com>,
"David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH 1/5] net: timestamp: add helper returning skb's tx tstamp
On 05/30, Stanislav Fomichev wrote:
> On 05/30, Pavel Begunkov wrote:
> > Add a helper function skb_get_tx_timestamp() that returns a tx timestamp
> > associated with an skb from an queue queue.
> >
> > Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
> > ---
> > include/net/sock.h | 4 ++++
> > net/socket.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 53 insertions(+)
> >
> > diff --git a/include/net/sock.h b/include/net/sock.h
> > index 92e7c1aae3cc..b0493e82b6e3 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -2677,6 +2677,10 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
> > void __sock_recv_wifi_status(struct msghdr *msg, struct sock *sk,
> > struct sk_buff *skb);
> >
> > +bool skb_has_tx_timestamp(struct sk_buff *skb, struct sock *sk);
> > +bool skb_get_tx_timestamp(struct sk_buff *skb, struct sock *sk,
> > + struct timespec64 *ts);
> > +
> > static inline void
> > sock_recv_timestamp(struct msghdr *msg, struct sock *sk, struct sk_buff *skb)
> > {
> > diff --git a/net/socket.c b/net/socket.c
> > index 9a0e720f0859..d1dc8ab28e46 100644
> > --- a/net/socket.c
> > +++ b/net/socket.c
> > @@ -843,6 +843,55 @@ static void put_ts_pktinfo(struct msghdr *msg, struct sk_buff *skb,
> > sizeof(ts_pktinfo), &ts_pktinfo);
> > }
> >
> > +bool skb_has_tx_timestamp(struct sk_buff *skb, struct sock *sk)
> > +{
> > + u32 tsflags = READ_ONCE(sk->sk_tsflags);
> > + struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);
> > +
> > + if (serr->ee.ee_errno != ENOMSG ||
> > + serr->ee.ee_origin != SO_EE_ORIGIN_TIMESTAMPING)
> > + return false;
> > +
> > + /* software time stamp available and wanted */
> > + if ((tsflags & SOF_TIMESTAMPING_SOFTWARE) && skb->tstamp)
> > + return true;
> > + /* hardware time stamps available and wanted */
> > + return (tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
> > + skb_hwtstamps(skb)->hwtstamp;
> > +}
> > +
> > +bool skb_get_tx_timestamp(struct sk_buff *skb, struct sock *sk,
> > + struct timespec64 *ts)
> > +{
> > + u32 tsflags = READ_ONCE(sk->sk_tsflags);
> > + bool false_tstamp = false;
> > + ktime_t hwtstamp;
> > + int if_index = 0;
> > +
>
> [..]
>
> > + if (sock_flag(sk, SOCK_RCVTSTAMP) && skb->tstamp == 0) {
> > + __net_timestamp(skb);
> > + false_tstamp = true;
> > + }
>
> The place it was copy-pasted from (__sock_recv_timestamp) has a comment
> about a race between packet rx and enabling the timestamp. Does the same
> race happen here? Worth keeping the comment?
Or maybe you don't need this case at all? Since you're skipping the
tstamp == 0 cases anyway down below... Pass 'false' to skb_is_swtx_tstamp
instead?
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