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Message-ID: <CA+FuTSeuUVPuf1paZgXQRr6W5YRJaPfWN57BsHtc2tG8qoS4iQ@mail.gmail.com>
Date: Mon, 15 Apr 2013 12:12:31 -0400
From: Willem de Bruijn <willemb@...gle.com>
To: Daniel Borkmann <dborkman@...hat.com>
Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] packet: move hw/sw timestamp extraction into a
small helper
On Mon, Apr 15, 2013 at 7:41 AM, Daniel Borkmann <dborkman@...hat.com> wrote:
> This patch introduces a small helper function, that is used by AF_PACKET.
> Based on the flags that are passed, it extracts the packet timestamp in
> the receive path. This is merely a refactoring to remove some duplicate
> code in tpacket_rcv(), make it more readable, and to enable others to use
> this function as well.
Good idea. I noticed that while browsing the code over the weekend, too.
One question I have is whether the code warrants adding a static
inline to skbuff.h. Regular socket paths do not use the test, as they
return all timestamps together.
> Cc: Willem de Bruijn <willemb@...gle.com>
> Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
> ---
> include/linux/skbuff.h | 20 ++++++++++++++++++++
> net/packet/af_packet.c | 38 ++++----------------------------------
> 2 files changed, 24 insertions(+), 34 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index e27d1c7..d0d436f 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -33,6 +33,7 @@
> #include <linux/dma-mapping.h>
> #include <linux/netdev_features.h>
> #include <net/flow_keys.h>
> +#include <linux/net_tstamp.h>
>
> /* Don't change this without changing skb_csum_unnecessary! */
> #define CHECKSUM_NONE 0
> @@ -739,6 +740,25 @@ static inline struct skb_shared_hwtstamps *skb_hwtstamps(struct sk_buff *skb)
> return &skb_shinfo(skb)->hwtstamps;
> }
>
> +static inline struct timespec skb_get_tstamp(struct sk_buff *skb,
> + unsigned int flags)
> +{
> + struct skb_shared_hwtstamps *ts = skb_hwtstamps(skb);
> +
> + if ((flags & SOF_TIMESTAMPING_SYS_HARDWARE) && ts->syststamp.tv64)
Also, packet sockets use the flags these SOF_... constants passed from
userspace directly, but regular socket paths convert this into socket
flags SOCK_..., so this code is more packet socket specific than it
seems. See __sock_recv_timestamp. I'd keep the function in
net/packet/af_packet.c solely for this reason, or add a comment.
> + return ktime_to_timespec(ts->syststamp);
> + else if ((flags & SOF_TIMESTAMPING_RAW_HARDWARE) && ts->hwtstamp.tv64)
> + return ktime_to_timespec(ts->hwtstamp);
> + else if (skb->tstamp.tv64)
> + return ktime_to_timespec(skb->tstamp);
> + else {
> + struct timespec tc;
> +
> + getnstimeofday(&tc);
> + return tc;
> + }
> +}
> +
> /**
> * skb_queue_empty - check if a queue is empty
> * @list: queue head
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index 77d71f8..2a2a62e 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -1681,9 +1681,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
> unsigned long status = TP_STATUS_USER;
> unsigned short macoff, netoff, hdrlen;
> struct sk_buff *copy_skb = NULL;
> - struct timeval tv;
> struct timespec ts;
> - struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
>
> if (skb->pkt_type == PACKET_LOOPBACK)
> goto drop;
> @@ -1767,24 +1765,16 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
>
> skb_copy_bits(skb, 0, h.raw + macoff, snaplen);
>
> + ts = skb_get_tstamp(skb, po->tp_tstamp);
> +
> switch (po->tp_version) {
> case TPACKET_V1:
> h.h1->tp_len = skb->len;
> h.h1->tp_snaplen = snaplen;
> h.h1->tp_mac = macoff;
> h.h1->tp_net = netoff;
> - if ((po->tp_tstamp & SOF_TIMESTAMPING_SYS_HARDWARE)
> - && shhwtstamps->syststamp.tv64)
> - tv = ktime_to_timeval(shhwtstamps->syststamp);
> - else if ((po->tp_tstamp & SOF_TIMESTAMPING_RAW_HARDWARE)
> - && shhwtstamps->hwtstamp.tv64)
> - tv = ktime_to_timeval(shhwtstamps->hwtstamp);
> - else if (skb->tstamp.tv64)
> - tv = ktime_to_timeval(skb->tstamp);
> - else
> - do_gettimeofday(&tv);
> - h.h1->tp_sec = tv.tv_sec;
> - h.h1->tp_usec = tv.tv_usec;
> + h.h1->tp_sec = ts.tv_sec;
> + h.h1->tp_usec = ts.tv_nsec / NSEC_PER_USEC;
> hdrlen = sizeof(*h.h1);
> break;
> case TPACKET_V2:
> @@ -1792,16 +1782,6 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
> h.h2->tp_snaplen = snaplen;
> h.h2->tp_mac = macoff;
> h.h2->tp_net = netoff;
> - if ((po->tp_tstamp & SOF_TIMESTAMPING_SYS_HARDWARE)
> - && shhwtstamps->syststamp.tv64)
> - ts = ktime_to_timespec(shhwtstamps->syststamp);
> - else if ((po->tp_tstamp & SOF_TIMESTAMPING_RAW_HARDWARE)
> - && shhwtstamps->hwtstamp.tv64)
> - ts = ktime_to_timespec(shhwtstamps->hwtstamp);
> - else if (skb->tstamp.tv64)
> - ts = ktime_to_timespec(skb->tstamp);
> - else
> - getnstimeofday(&ts);
> h.h2->tp_sec = ts.tv_sec;
> h.h2->tp_nsec = ts.tv_nsec;
> if (vlan_tx_tag_present(skb)) {
> @@ -1822,16 +1802,6 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
> h.h3->tp_snaplen = snaplen;
> h.h3->tp_mac = macoff;
> h.h3->tp_net = netoff;
> - if ((po->tp_tstamp & SOF_TIMESTAMPING_SYS_HARDWARE)
> - && shhwtstamps->syststamp.tv64)
> - ts = ktime_to_timespec(shhwtstamps->syststamp);
> - else if ((po->tp_tstamp & SOF_TIMESTAMPING_RAW_HARDWARE)
> - && shhwtstamps->hwtstamp.tv64)
> - ts = ktime_to_timespec(shhwtstamps->hwtstamp);
> - else if (skb->tstamp.tv64)
> - ts = ktime_to_timespec(skb->tstamp);
> - else
> - getnstimeofday(&ts);
> h.h3->tp_sec = ts.tv_sec;
> h.h3->tp_nsec = ts.tv_nsec;
> hdrlen = sizeof(*h.h3);
> --
> 1.7.11.7
>
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