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Date: Mon, 15 Apr 2013 19:02:03 +0200
From: Daniel Borkmann <dborkman@...hat.com>
To: Willem de Bruijn <willemb@...gle.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 04/15/2013 06:12 PM, Willem de Bruijn wrote:
> 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.
(See below.)
>> 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.
Hm, right. I do not really see a reason why we need to maintain this twice
(introduced by 614f60fa9 ``packet_mmap: expose hw packet timestamps to network
packet capture utilities'').
This could also have been implemented actually with normal SOCK_ flags, i.e.
since we use sock_tx_timestamp() which uses SOCK_ flags. I will respin and try
to address that.
>> + 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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