Re: Problem with frame time stamping
From: Eric Dumazet
Date: Mon Nov 12 2007 - 12:11:59 EST
On Mon, 12 Nov 2007 16:42:34 +0100
"Antoine Zen-Ruffinen" <antoine.zen@xxxxxxxxx> wrote:
> Dear all,
> I'm writing a network analyzer software using Linux and I need a VERY
> precise frame time stamping. Therefor I am planing to add my own time
> stamping algorithm on a modified network driver. For test purpose I
> did so :
> skb->tstamp.tv64 = 0x00010002;
> On the user side, I ask for the timestamp that way :
> sock = socket(AF_PACKET, SOCK_RAW, type);
> //bind this socket with the interface using my modified driver.
> recvByteCount = recv(sock, buffer, 1514, 0);
> ioctl(sock, SIOCGSTAMP, &timeStamp);
> I was surprised to see that the var timeStamp was still holding a
> count of second since year 1970.
> Investigating a bit into the kernel code, I found that ioctl(sock,
> SIOCGSTAMP, ...) was giving just the current kernel time using
> Are my investigation wrong ?
> Is that a bug in kernel code ?
> Is there an other way to access skb.tstamp from user side ?
> Thank's to any one that can help me !
If your kernel is recent enough, you can already get nanosecond precision from skb tstamp, using SIOCGSTAMPNS ioctl or SO_TIMESTAMPNS / SCM_TIMESTAMPNS
(changes where done in March/April this year)
No need to modify a network driver :)
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