[Xymon] Debian 9 stretch clients - trends netstat graph bug?

Japheth Cleaver cleaver at terabithia.org
Mon Mar 18 18:30:22 CET 2019


This is not just a Debian thing -- it looks like it results from output 
changes in recent versions of netstat/net-tools (recent Fedora is 
affected too).

I think the easiest fix will be to move to PCRE parsing to catch the 
differing versions, which is how we're handling the BSDs and some of the 
esoteric unicies. (Although there's a legacy RHEL3 Linux OS type from 
back in the day, this is one of the things we'll want to catch centrally 
moving forward.)

Additionally, it's probably time to start adding 'ss' output into the 
client for future use.

Regards,
-jc

On 3/13/2019 7:53 AM, SebA wrote:
> Hi John,
>
> I can confirm that we have the same issue on Debian 9 clients on the 
> Network I/O (as labelled) graph.
>
> Kind regards,
>
> SebA
>
>
>
> On Tue, 12 Mar 2019 at 22:48, John Horne <john.horne at plymouth.ac.uk 
> <mailto:john.horne at plymouth.ac.uk>> wrote:
>
>     Hi,
>
>     We have three Debian 9 (stretch) servers running the xymon-client
>     package
>     (version 4.3.28-2). I noticed yesterday that the 'trends' column
>     for these
>     clients was showing a 'TCP/IP statistics' graph, but was only
>     showing values
>     for the 'In' graph. Both the 'Out' and 'Retrans' values were NaN.
>
>     If anyone else is running the Xymon client on a Debian 9 server,
>     or may be even
>     Debian 8, could they check their 'trends' graphs and see if the
>     same problem
>     exists for them. Thanks.
>
>     As far as I can tell this started when we upgraded the client
>     server O/S from
>     Debian 7 to 9 (a few months ago now!). It seems there were values
>     for all 3
>     graph lines when they ran Debian 7.
>
>     The RRD netstat file, which is used for the statistics graph,
>     shows a 'U' for
>     the 'Out' and 'Retrans' values. Looking at the actual code (in
>     xymond/rrd/do_netstat.c), it seems that the netstat output is
>     expected to be
>     the same for most Linux distributions and versions. It shows:
>
>     =========
>     /* This one matches all Linux systems */
>     static char *netstat_linux_markers[] = {
>             "packets received",
>             "packets sent",
>             "packet receive errors",
>             "active connections openings",
>             "passive connection openings",
>             "failed connection attempts",
>             "connection resets received",
>             "connections established",
>             "",
>             "",
>             "",
>             "",
>             "segments send out",    /* Yes, they really do write "send" */
>             "segments received",
>             "",
>             "segments retransmited",
>             NULL
>     };
>     =========
>
>     However, the netstat output collected by the clients shows,
>     looking at the TCP
>     section:
>
>     =========
>     Tcp:
>         3045575 active connection openings
>         251770 passive connection openings
>         9335 failed connection attempts
>         4520 connection resets received
>         37 connections established
>         1359715245 segments received
>         1330630207 segments sent out
>         119457 segments retransmitted
>         10 bad segments received
>         32339 resets sent
>         InCsumErrors: 2
>     =========
>
>
>     Some things seem to be wrong:
>
>     1) The code looks for 'active connections openings', but netstat
>     shows 'active
>     connection openings'. Singular on the 'connection' word.
>
>     2) The code looks for 'segments send out', but netstat shows
>     'segments sent
>     out'. So despite the comment in the code, the output uses 'sent'
>     rather than
>     'send'.
>
>     3) The code looks for 'segments retransmited', but the netstat
>     output shows
>     'segments retransmitted'. So there is a double 't' in
>     retransmitted (or 3 all
>     together).
>
>     4) The order of the 'segments' lines is different from the code,
>     but I'm not
>     sure if that is important. (Haven't looked at the code that much
>     in depth.)
>
>
>     I'm not sure if this is the cause of the TCP/IP stats graph not
>     showing values,
>     but it doesn't seem right.
>
>
>     Thanks,
>
>     John.
>
>     --
>     John Horne | Senior Operations Analyst | Technology and
>     Information Services
>     University of Plymouth | Drake Circus | Plymouth | Devon | PL4 8AA
>     | UK
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