What does it bring me to have a nanosecond precision if it is not related to the actual arrival of frame time ? As it seem I can feel skb->tstamp with whatever I want, I always become something else using ioctl(). (I'm using kernel 2.6.23).
2007/11/12, Eric Dumazet <[EMAIL PROTECTED]>: > On Mon, 12 Nov 2007 16:42:34 +0100 > "Antoine Zen-Ruffinen" <[EMAIL PROTECTED]> 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; > > netif_rx(skb); > > > > 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 > > ktime_get_real(). > > > > 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) > > http://git2.kernel.org/?p=linux/kernel/git/davem/net-2.6.git;a=commit;h=b7aa0bf70c4afb9e38be25f5c0922498d0f8684c > > http://git2.kernel.org/?p=linux/kernel/git/davem/net-2.6.git;a=commit;h=ae40eb1ef30ab4120bd3c8b7e3da99ee53d27a23 > > http://git2.kernel.org/?p=linux/kernel/git/davem/net-2.6.git;a=commit;h=92f37fd2ee805aa77925c1e64fd56088b46094fc > > > No need to modify a network driver :) > > > - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
