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Date: Tue, 23 Apr 2013 08:18:14 -0400
From: Willem de Bruijn <willemb@...gle.com>
To: Daniel Borkmann <dborkman@...hat.com>
Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
Paul Chavent <Paul.Chavent@...ra.fr>,
Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH net-next 4/5] packet: if hw/sw ts enabled in rx/tx ring,
report which ts we got
On Tue, Apr 23, 2013 at 6:39 AM, Daniel Borkmann <dborkman@...hat.com> wrote:
> Currently, there is no way to find out which timestamp is reported in
> tpacket{,2,3}_hdr's tp_sec, tp_{n,u}sec members. It can be one of
> SOF_TIMESTAMPING_SYS_HARDWARE, SOF_TIMESTAMPING_RAW_HARDWARE,
> SOF_TIMESTAMPING_SOFTWARE, or a fallback variant late call from the
> PF_PACKET code in software.
>
> Therefore, report in the tp_status member of the ring buffer which
> timestamp has been reported for RX and TX path. This should not break
> anything for the following reasons: i) in RX ring path, the user needs
> to test for tp_status & TP_STATUS_USER, and later for other flags as
> well such as TP_STATUS_VLAN_VALID et al, so adding other flags will
> do no harm; ii) in TX ring path, time stamps with PACKET_TIMESTAMP
> socketoption are not available resp. had no effect except that the
> application setting this is buggy. Next to TP_STATUS_AVAILABLE, the
> user also should check for other flags such as TP_STATUS_WRONG_FORMAT
> to reclaim frames to the application. Thus, in case TX ts are turned
> off (default case), nothing happens to the application logic, and in
> case we want to use this new feature, we now can also check which of
> the ts source is reported in the status field as provided in the docs.
>
> Reported-by: Richard Cochran <richardcochran@...il.com>
> Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
Acked-by: Willem de Bruijn <willemb@...gle.com>
> ---
> include/uapi/linux/if_packet.h | 5 +++++
> net/packet/af_packet.c | 36 +++++++++++++++++++++++-------------
> 2 files changed, 28 insertions(+), 13 deletions(-)
>
> diff --git a/include/uapi/linux/if_packet.h b/include/uapi/linux/if_packet.h
> index 4dfc234..b950c02 100644
> --- a/include/uapi/linux/if_packet.h
> +++ b/include/uapi/linux/if_packet.h
> @@ -100,6 +100,11 @@ struct tpacket_auxdata {
> #define TP_STATUS_SENDING (1 << 1)
> #define TP_STATUS_WRONG_FORMAT (1 << 2)
>
> +/* Rx and Tx ring - header status */
> +#define TP_STATUS_TS_SOFTWARE (1 << 29)
> +#define TP_STATUS_TS_SYS_HARDWARE (1 << 30)
> +#define TP_STATUS_TS_RAW_HARDWARE (1 << 31)
> +
> /* Rx ring - feature request bits */
> #define TP_FT_REQ_FILL_RXHASH 0x1
>
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index e7892a4..dd5cd49 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -339,34 +339,35 @@ static int __packet_get_status(struct packet_sock *po, void *frame)
> }
> }
>
> -static bool tpacket_get_timestamp(struct sk_buff *skb, struct timespec *ts,
> - unsigned int flags)
> +static __u32 tpacket_get_timestamp(struct sk_buff *skb, struct timespec *ts,
> + unsigned int flags)
> {
> struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
>
> if (shhwtstamps) {
> if ((flags & SOF_TIMESTAMPING_SYS_HARDWARE) &&
> ktime_to_timespec_cond(shhwtstamps->syststamp, ts))
> - return true;
> + return TP_STATUS_TS_SYS_HARDWARE;
> if ((flags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
> ktime_to_timespec_cond(shhwtstamps->hwtstamp, ts))
> - return true;
> + return TP_STATUS_TS_RAW_HARDWARE;
> }
>
> if (ktime_to_timespec_cond(skb->tstamp, ts))
> - return true;
> + return TP_STATUS_TS_SOFTWARE;
>
> - return false;
> + return 0;
> }
>
> -static void __packet_set_timestamp(struct packet_sock *po, void *frame,
> - struct sk_buff *skb)
> +static __u32 __packet_set_timestamp(struct packet_sock *po, void *frame,
> + struct sk_buff *skb)
> {
> union tpacket_uhdr h;
> struct timespec ts;
> + __u32 ts_status;
>
> - if (!tpacket_get_timestamp(skb, &ts, po->tp_tstamp))
> - return;
> + if (!(ts_status = tpacket_get_timestamp(skb, &ts, po->tp_tstamp)))
> + return 0;
>
> h.raw = frame;
> switch (po->tp_version) {
> @@ -387,6 +388,8 @@ static void __packet_set_timestamp(struct packet_sock *po, void *frame,
> /* one flush is safe, as both fields always lie on the same cacheline */
> flush_dcache_page(pgv_to_page(&h.h1->tp_sec));
> smp_wmb();
> +
> + return ts_status;
> }
>
> static void *packet_lookup_frame(struct packet_sock *po,
> @@ -1721,6 +1724,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
> unsigned short macoff, netoff, hdrlen;
> struct sk_buff *copy_skb = NULL;
> struct timespec ts;
> + __u32 ts_status;
>
> if (skb->pkt_type == PACKET_LOOPBACK)
> goto drop;
> @@ -1803,9 +1807,12 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
> spin_unlock(&sk->sk_receive_queue.lock);
>
> skb_copy_bits(skb, 0, h.raw + macoff, snaplen);
> - if (!tpacket_get_timestamp(skb, &ts, po->tp_tstamp))
> +
> + if (!(ts_status = tpacket_get_timestamp(skb, &ts, po->tp_tstamp)))
> getnstimeofday(&ts);
>
> + status |= ts_status;
> +
> switch (po->tp_version) {
> case TPACKET_V1:
> h.h1->tp_len = skb->len;
> @@ -1905,11 +1912,14 @@ static void tpacket_destruct_skb(struct sk_buff *skb)
> void *ph;
>
> if (likely(po->tx_ring.pg_vec)) {
> + __u32 ts;
> +
> ph = skb_shinfo(skb)->destructor_arg;
> BUG_ON(atomic_read(&po->tx_ring.pending) == 0);
> atomic_dec(&po->tx_ring.pending);
> - __packet_set_timestamp(po, ph, skb);
> - __packet_set_status(po, ph, TP_STATUS_AVAILABLE);
> +
> + ts = __packet_set_timestamp(po, ph, skb);
> + __packet_set_status(po, ph, TP_STATUS_AVAILABLE | ts);
> }
>
> sock_wfree(skb);
> --
> 1.7.11.7
>
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