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

John Horne john.horne at plymouth.ac.uk
Tue Mar 12 23:48:12 CET 2019


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",

However, the netstat output collected by the clients shows, looking at the 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

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

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.



John Horne | Senior Operations Analyst | Technology and Information Services
University of Plymouth | Drake Circus | Plymouth | Devon | PL4 8AA | UK

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