From: John <linux.kernel@free.fr>
To: linux-net@vger.kernel.org
Cc: netdev@vger.kernel.org, linux.kernel@free.fr
Subject: CLOCK_MONOTONIC datagram timestamps by the kernel
Date: Wed, 28 Feb 2007 11:18:54 +0100 [thread overview]
Message-ID: <45E5570E.7050301@free.fr> (raw)
Hello,
I know it's possible to have Linux timestamp incoming datagrams as soon
as they are received, then for one to retrieve this timestamp later with
an ioctl command or a recvmsg call.
As far as I understand, one can either do
const int on = 1;
setsockopt(sock, SOL_SOCKET, SO_TIMESTAMP, &on, sizeof on);
then use recvmsg()
or not set the SO_TIMESTAMP socket option and just call
ioctl(sock, SIOCGSTAMP, &tv);
after each datagram has been received.
SIOCGSTAMP
Return a struct timeval with the receive timestamp of the last
packet passed to the user. This is useful for accurate round trip time
measurements. See setitimer(2) for a description of struct timeval.
As far as I understand, this timestamp is given by the CLOCK_REALTIME
clock. However, I would like to obtain a timestamp given by the
CLOCK_MONOTONIC clock.
Relevant parts of the code (I think):
net/core/dev.c
void net_enable_timestamp(void)
{
atomic_inc(&netstamp_needed);
}
void __net_timestamp(struct sk_buff *skb)
{
struct timeval tv;
do_gettimeofday(&tv);
skb_set_timestamp(skb, &tv);
}
static inline void net_timestamp(struct sk_buff *skb)
{
if (atomic_read(&netstamp_needed))
__net_timestamp(skb);
else {
skb->tstamp.off_sec = 0;
skb->tstamp.off_usec = 0;
}
}
do_gettimeofday() just calls __get_realtime_clock_ts()
Would it be possible to replace do_gettimeofday() by ktime_get_ts() with
the appropriate division by 1000 to convert the struct timespec back
into a struct timeval?
void __net_timestamp(struct sk_buff *skb)
{
struct timespec now;
struct timeval tv;
ktime_get_ts(&ts);
tv.tv_sec = now.tv_sec;
tv->tv_usec = now.tv_nsec/1000;
skb_set_timestamp(skb, &tv);
}
How many apps / drivers would this break?
Is there perhaps a different way to achieve this?
Regards.
next reply other threads:[~2007-02-28 10:18 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-28 10:18 John [this message]
2007-02-28 13:37 ` CLOCK_MONOTONIC datagram timestamps by the kernel John
2007-02-28 13:55 ` Eric Dumazet
2007-02-28 14:23 ` John
2007-02-28 14:55 ` Eric Dumazet
2007-02-28 16:07 ` John
2007-03-01 10:03 ` Evgeniy Polyakov
2007-03-01 11:30 ` Eric Dumazet
2007-03-01 15:54 ` Stephen Hemminger
2007-03-01 16:13 ` Eric Dumazet
2007-03-02 14:38 ` [PATCH] NET : convert network timestamps to ktime_t Eric Dumazet
2007-03-02 16:27 ` Stephen Hemminger
2007-03-02 21:02 ` Stephen Hemminger
2007-03-02 22:46 ` Eric Dumazet
2007-03-05 0:19 ` David Miller
2007-03-05 6:56 ` Eric Dumazet
2007-03-05 7:40 ` Eric Dumazet
2007-03-05 8:00 ` David Miller
2007-03-05 8:21 ` Eric Dumazet
2007-03-05 8:49 ` David Miller
2007-03-08 14:17 ` [PATCH] NET : Introduce SIOCGSTAMPNS ioctl to get timestamps with nanosec resolution Eric Dumazet
2007-03-08 16:28 ` Patrick McHardy
2007-03-08 16:42 ` Eric Dumazet
2007-03-08 16:45 ` Patrick McHardy
2007-03-09 4:39 ` David Miller
2007-03-09 18:39 ` [PATCH] NET : Adding SO_TIMESTAMPNS / SCM_TIMESTAMPNS support Eric Dumazet
2007-03-09 22:17 ` David Miller
2007-03-01 18:53 ` CLOCK_MONOTONIC datagram timestamps by the kernel Stephen Hemminger
2007-03-01 23:14 ` Eric Dumazet
2007-03-01 23:34 ` Stephen Hemminger
2007-03-02 0:56 ` Eric Dumazet
2007-03-02 9:26 ` John
2007-03-02 10:11 ` Eric Dumazet
2007-02-28 18:22 ` Stephen Hemminger
-- strict thread matches above, loose matches on Subject: below --
2007-02-25 21:29 John
2007-02-26 10:26 ` John
2007-02-26 12:20 ` Andi Kleen
2007-02-26 14:17 ` John
2007-02-28 11:23 ` John
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