[Trilug-ontopic] ifconfig question.

Don Jerman djerman at pobox.com
Sun Feb 3 14:12:26 EST 2008


There you pass me. A quick grep or two shows that they're unsigned
longs from /proc, so they'll roll over every 4 gigabytes or 18
exabytes, depending on what %ul means to your architecture.  They
probably overflow independantly but I'm not able to delve into the
/proc sources so quickly, and it may be driver-dependent.

The best way to factor it out is to snapshot the statistics frequently
enough to get a rate and not have to worry about overflow.  Every 5
minutes would do for a start unless you're on a rather busy network.
If you'd like to roll your own snapshot from the /proc output, the
parsing for ifconfig is done in the lib/interface.c file in the
net-tools source tree - you could get the field order from there.

Besides, if this isn't where your problem is, then it probably doesn't
matter :).

On 1/29/08, Jason Watts <jsnonzzr at gmail.com> wrote:
> Don,
>
> Thanks for the answers.
>
> After chasing this down some more... it looks like the interface that I
> coppied that from isnt really were our problem is (though we are planning on
> changing the duplex stuff anyways.)
>
> When the counter overflows and resets, does just the one counter reset, or
> will it reset all of them, including the overrun counter?  (the box has
> acutally been up for 31 or so days.)
>
>
> On Jan 29, 2008 8:06 PM, Don Jerman <djerman at pobox.com> wrote:
> > The questions are quick...
> >
> > Looking at this I'd guess uptime has been a few hours, or else several
> > months, because the counters reset when they overflow or when you
> > restart the interface.
> >
> > Error rate is around 0.027%, so it might not be worth fixing.  Your call.
> >
> > Overruns are typically caused by the next packet arriving before the
> > interrupt service routine is done emptying the buffers.  That would
> > indicate a fast sender at the other end, many senders talking at once,
> > or a slow driver or malfunctioning card.  Check for duplex mismatch
> > too.  That's about all I can infer with this information (not that I
> > know all that much more about it).
> >
> >
> >
> >
> > On 1/29/08, Jason Watts <jsnonzzr at gmail.com> wrote:
> > > Guys, hopefully these are two quick questions.
> > >
> > > when I do an ifconfig -a on one of my boxes, I see a fairly large number
> of
> > > overruns.
> > >
> > > UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
> > >           RX packets:173319141 errors:0 dropped:0 overruns:46678 frame:0
> > >           TX packets:194764057 errors:0 dropped:0 overruns:1 carrier:0
> > >           collisions:0 txqueuelen:100
> > >           RX bytes:1809166178 (1725.3 Mb)  TX bytes:102562715 (97.8 Mb)
> > >           Interrupt:11 Base address:0xb800 Memory:ec0c3000-ec0c3038
> > >
> > > My 2 questions.
> > >
> > > 1)  How often do these numbers reset?
> > >
> > > 2)  to me, 47k seems like a large number, especially when all my other
> boxes
> > > are showing none, but what would be an acceptable number?  (I realize
> this
> > > is relative, but I'm asking for opinions as this is the first time I
> have
> > > ever researched this stuff and have little idea.)
> > >
> > > Thanks for any input and advice.
> > >
> > > jsn
> > >
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