Re: Problem with frame time stamping
From: Eric Dumazet
Date: Tue Nov 13 2007 - 05:27:34 EST
Antoine Zen-Ruffinen a écrit :
What does it bring me to have a nanosecond precision if it is notI guess you misunderstood kernel source, because it is related to
arrival time, more exactly when it was processed by network stack.
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).
(Beware modern NICS can delay the rx interrupt by some us (ethtool -c
eth0), so that an interrupt can feed more than one packet to the OS)
Check net/core/dev.c function netif_rx()
So as soon your system as at least one socket 'asking for tsamps',
netstamp_needed is not null, and net_timestamp() will call __net_timestamp()
wich does :
skb->tstamp = ktime_get_real();
So you should not 'feed' tstamp.tv64 and let it being 0, so that
netif_rx() can do its job.
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