[syslog-ng] Flag "no-multiline" not working on Syslog-ng

[Alan Sam]

Hello Community,

Thank you all for your help regarding this issue reported.

We finally concluded that Cisco devide is sending the log in two different
lines.

Now we have a new situation regarding the syslog-ng configuration file:

- A patch had to be created in order to concat the log.

- The logs that arrive to the server with syslog-ng come like this:
Mar 13 10:33:14 PE06PVAL01 1182434: Mar 13 10:33:13: %BGP-3-INVALID_MPLS:
Invalid MPLS label (1)
Mar 13 10:33:14 PE06PVAL01 1182435:          received in update for prefix
XXX:XXX:XX.X.XXX.0/24 from A.B.C.D
- The patch concats the log and generates a new line that is inserted into
the same cisco log file:
Mar 13 10:33:14 PE06PVAL01 1182434: Mar 13 10:33:13: %BGP-3-INVALID_MPLS:
Invalid MPLS label (1) received in update for prefix XXX:XXX:XX.X.XXX.0/24
from A.B.C.D

- This new line that has the whole log line is sent to another server (let
us call it Server X) with a syslog-ng tool running

- On server X, i get these two log lines:
Mar 13 10:33:14 PE06PVAL01 1182434: Mar 13 10:33:13: %BGP-3-INVALID_MPLS:
Invalid MPLS label (1)
Mar 13 10:33:14 PE06PVAL01 1182434: Mar 13 10:33:13: %BGP-3-INVALID_MPLS:
Invalid MPLS label (1) received in update for prefix XXX:XXX:XX.X.XXX.0/24
from A.B.C.D

The question is:
Is there a way to configure the syslog-ng in Server X so that:
- Discards the log line that contains "BGP-3-INVALID_MPLS: Invalid MPLS
label (1)"
- Accepts the log line that contains "BGP-3-INVALID_MPLS: Invalid MPLS
label (1) received in update for prefix"
- Accepts all other logs

The syslog-ng configuration file on Server X is the following:

> cat /etc/syslog-ng.conf
#@version: 3.0
# syslog-ng configuration file for the server.
#
# See syslog-ng(8) and syslog-ng.conf(8) for more information.
#

options { flush_lines (0);
          time_reopen (10);
          log_fifo_size (10000);
          long_hostnames (off);
          use_dns (yes);
          create_dirs (yes);
          keep_hostname (yes);
        };

# Client Source
source s_local { internal(); };
source s_syslog_udp { udp(port(514)); };

# Server Source
source s_juniper_tcp { tcp(port(1001) keep-alive(yes)); };
source s_cisco_tcp { tcp(port(1002) keep-alive(yes)); };

# Client Destination
destination d_local { file("/var/adm/syslog/syslog-ng.log"); };
destination d_juniper_tcp { file("/var/adm/syslog/juniper.log"); };
destination d_cisco_tcp { file("/var/adm/syslog/cisco.log"); };

# Server Destination
destination d_syslog { file("/var/adm/syslog/syslog.log"); };
destination d_mail { file("/var/adm/syslog/mail.log"); };

# Server Filter
filter f_mail   { facility(mail) and level(debug .. emerg); };
filter f_syslog   { level(info .. emerg) and not facility(mail) and not
program(syslog-ng); };
filter f_syslog-ng   { program(syslog-ng); };


# Client Log
log { source(s_local); destination(d_local); destination(d_syslog); };
log { source(s_syslog_udp); destination(d_syslog); };

# Server Log
log { source(s_local); filter(f_syslog-ng); destination(d_syslog); };
log { source(s_local); filter(f_mail); destination(d_mail); };
log { source(s_local); filter(f_syslog); destination(d_syslog); };
log { source(s_juniper_tcp); destination(d_juniper_tcp); };
log { source(s_cisco_tcp); destination(d_cisco_tcp); };


Thank you so much for your help.

Best regards,
Alan

On Fri, May 8, 2015 at 5:37 AM, PÁSZTOR György <
pasztor at linux.gyakg.u-szeged.hu> wrote:

> Hi,
>
> "Sandor Geller" <sandor.geller at ericsson.com> írta 2015-05-08 09:32-kor:
> > Wow, it was really 'low resolution'. Zooming in showed that there isn't
> > any kind of UDP packet fragmentation happening (not surprising, the
>
> That's what, why I asked a pcap file.
> It would required smaller attached file, and would gave us more info.
> I found a new theory, based on: 1 pic ~= 1 Mword
> 1 pcap ~= 1000 pic!
>
> > kernel would reassembele fragments transparently to syslog-ng) but the
> > sender device actually splits the logs into multiple packets so
> > syslog-ng does exactly what it should do. Yet another broken syslog
> > implementation on Cisco's side :(
>
> As basically all of their syslog implementation.
>
> > I'm not aware of how such logs could get concatenated without writing an
> > app which postprocesses the logs.
>
> That's another thing, I asked a pcap file. I gave up.
> Maybe there is a chance to do that with some patterndb magic, where we can
> "process" and "correlate", etc.
>
> Kind regards,
> Gyu
>
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