Re: packet re-ordering on SMP machines.

[Harald Welte <laforge@gnumonks.org>]

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On Tue, Aug 27, 2002 at 03:13:17PM +0200, Andi Kleen wrote:
> 
> On Tue, Aug 27, 2002 at 05:06:30PM +0400, A.N.Kuznetsov wrote:
> > Hello!
> > 
> > > Of course. The only problem is that the clock can be non mononotonous 
> > > sometimes and not be in sync with gettimeofday, but at least the kernel 
> > > users of packet timestamps do not care.
> > 
> > What kernel users? Where did you find them? :-)
> 
> Hmm, I thought TCP used it, but it seems to use jiffies directly.
> 
> Ok, no kernel users then. Not sure about sunrpc and out of tree stuff
> like SCTP.

The iptables ULOG target passes the skb receive timestamp to userspace, where
it is (depending on local ulogd configuration) written in logging/accounting
databases. (ULOG is in the kernel tree).  

The issue is that ULOG is batching multiple packets (or parts of packets) into
one netlink message sent to userspace.  If userspace would make a timestamp,
it would be very inaccurate.

There is at least one more iptables extension (out of the kernel tree) using
it - but I wouldn't consider this as important.

> -Andi

-- 
Live long and prosper
- Harald Welte / laforge@gnumonks.org               http://www.gnumonks.org/
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