On 10/7/2017 5:25 AM, Rainer Gerhards wrote:
2017-10-07 7:57 GMT+02:00 deoren
<rsyslog-users-lists.adiscon....@whyaskwhy.org>:
As I dig more into this, I'm beginning to think the only thing the Qualys
scan did was aggravate an existing problem and cause rsyslog to tip over
more quickly.
While I didn't observe the problem at the time, I recently made some
configuration changes to introduce a lookup table to map known IPs to known
hostnames (something I plan to programmatically build from a central db at
some point in the future). I opted to try this in an effort to stop using
$hostname directly (which gives odd results with invalid messages) for
dynamic directory/filenames.
A long story short, I found that systemd is now (without a Qualys scan
actively running) restarting rsyslog after it dies within a minute or so of
running. My guess is that when a remote client sees that the rsyslog
receiver is running again it retries delivery and when the receiver is
passed the message it performs the lookup. At that point the real cause for
the segfault is triggered and rsyslog goes down.
Looking at the output of the dmesg command I found many instances of
messages like this one:
[364581.440049] rs:main Q:Reg[82570]: segfault at 0 ip 00007faeb1fa55f4 sp
00007faeaac431d0 error 4 in libfastjson.so.4.1.0[7faeb1fa1000+a000]
I stopped rsyslog and then manually started it up like so:
rsyslogd -dn > rsyslog-debug.log 2>&1
This was printed to the console:
Segmentation fault (core dumped)
Here are the last 20 lines from the debug log file:
7587.842410212:main Q:Reg/w0 : ../action.c: action 'action 21': set
suspended state to 0
7587.842412422:main Q:Reg/w0 : rainerscript.c: STOP
7587.842418787:main Q:Reg/w0 : ruleset.c: processBATCH: next msg 44:
<167>2017-10-07T01:15:37.701Z vms2.example.com Rhttpproxy: verbose
rhttpproxy[79FC5B70] [Originator@6876 sub=Proxy Req 829
7587.842421471:main Q:Reg/w0 : rainerscript.c: CALL
[receiver-origin-hostname-lookup, queue:0]
7587.842427317:main Q:Reg/w0 : rainerscript.c: IF
7587.842433062:main Q:Reg/w0 : rainerscript.c: var 'fromhost-ip'
7587.842442260:main Q:Reg/w0 : rainerscript.c: ==
7587.842449663:main Q:Reg/w0 : rainerscript.c: string '127.0.0.1'
7587.842460890:main Q:Reg/w0 : rainerscript.c: eval expr 0x22147a0, type
'CMP_EQ'
7587.842463187:main Q:Reg/w0 : rainerscript.c: eval expr 0x22138e0, type
'V'
7587.842466060:main Q:Reg/w0 : rainerscript.c: rainerscript: (string) var
8: '192.168.5.142'
7587.842468406:main Q:Reg/w0 : rainerscript.c: eval expr 0x22138e0, return
datatype 'S':0
7587.842470812:main Q:Reg/w0 : rainerscript.c: eval expr 0x22147a0, return
datatype 'N':0
7587.842473056:main Q:Reg/w0 : ruleset.c: if condition result is 0
7587.842475315:main Q:Reg/w0 : rainerscript.c: IF
7587.842480945:main Q:Reg/w0 : rainerscript.c: var
'!origin!hostname'
7587.842490085:main Q:Reg/w0 : rainerscript.c: ==
7587.842497393:main Q:Reg/w0 : rainerscript.c: string ''
7587.842508499:main Q:Reg/w0 : rainerscript.c: eval expr 0x22148f0, type
'CMP_EQ'
7587.842511262:main Q:Reg/w0 : rainerscript.c: eval expr 0x22146f0, type
'V'
I checked my JSON lookup table file and found a duplicate key (but with
different values). This was unintentional and was a result of a mistake when
building out the file (copy, paste, modify, oops!).
I was hopeful that fixing that would resolve the issue, but no such luck.
Just in case it isn't readable above, here is the same output plus the
ruleset I'm using:
https://gist.github.com/deoren/7e8e799428d0d87c4e467fd4add51d09
Anything stand out as obviously wrong?
I've gone back over the Expressions, Control Structures and Variable
(Property) types docs and it doesn't appear that I'm attempting to
access/set the variables improperly, but I could be missing something.
The lookup table feature was added in 8.17.0 as an experimental
feature. There seems to be at least one hard-to-find bug inside it,
see here:
https://github.com/rsyslog/rsyslog/issues/1071
In the past days, I have looked at the issue as the original
contributor seems to have lost interest in it. It sounds like what you
experience is related to this problem. It would be great if you could
run rsyslog under valgrind and see if the problem persists and, if so,
what valgrind reports. You can use valgrind simply by installing the
distro-provided valgrind package and prefixing the command with
"valgrind", as such:
$ valgrind rsyslogd -dn > rsyslog-debug.log 2>&1
This would be very helpful. It might also be very, very useful if you
could add your findings to above-mentioned github issue tracker. I am
99.999% sure it is the same root cause.
Rainer
Thanks in advance for your help.
Sure, I can do that.
I ended up eventually getting my configuration to a "stable" point where
where rsyslog was no longer crashing, though I don't yet fully
understand why what I changed worked.
In my current "stable" configuration I have the same ruleset linked to
imudp (514/udp), imptcp (514/tcp) and imrelp (2514/tcp). This ruleset
essentially does the following (by calling other rulesets as needed):
#1) Runs mmjsonparse
#2) Sets $.tag equal to $syslogtag and $.msg equal to $msg, only if
$!tag and $!msg (respectively) were not set, otherwise the local
variables are set equal to the $! counterpart (e.g., $.msg equal to
$!msg, ...)
#3) Checks to see if '$!origin!hostname' is equal to "" and if so,
performs the lookup. If it is not empty, then $.hostname is set to that
value.
#4) A standard set of actions runs which records local copies of
forwarded messages and then forwards the received messages on to others
in the chain (test rsyslog instances and a Graylog instance).
This works fine now, even though the input on 514/udp and 514/tcp is
always a standard syslog message (no embedded CEE JSON).
Before setting the same ruleset on all three inputs, I had the 514/udp
and 514/tcp inputs use the ruleset which immediately applied step #3 and
step #4. Even with having steps #2 through #4 applied to those inputs
wasn't enough, I had to have step #1 run as well.
I didn't have debug logging turned on anymore at that point, but it
"appears" that there was an issue checking whether '$!origin!hostname'
was blank when mmjsonparse was not called against the incoming message
(which did not have a CEE payload included).
Perhaps this is in some way related to this issue?
https://github.com/rsyslog/rsyslog/issues/1283
I will try modifying my configuration to not even use the lookup table,
but instead just perform this check (which appears to trigger the segfault):
if ($!origin!hostname == "") then {
and then set a static value in place of the lookup table.
On a likely unrelated note, one of our rsyslog "client" nodes is now
unable to send messages to our main receiver (discussed above). I
checked the forward queue and it is filling up (both in-memory and
disk-assisted). I temporarily worked around the issue by forcing a
restart of the daemon on the client, but I did not check to see if the
messages were lost or eventually sent.
Later (as noted a moment ago), the queue is filling up again. I checked
netstat and lsof and there are no active connections to the receiver.
I toggled debug mode (debug on demand) and found messages like these:
9085.173631038:ForwardToReceiver1 queue[DA]:Reg/w0: omrelp.c:
relpTcpSend: sock 18, lenbuf 245, send returned 245 [errno 11]
9085.173634149:ForwardToReceiver1 queue[DA]:Reg/w0: omrelp.c: sendbuf
NOT added to unacked list
9085.173638247:ForwardToReceiver1 queue[DA]:Reg/w0: omrelp.c: resending
frame '16 syslog 273 <189>2017-09-27T07:01:53.077199-05:00 redmine1
redmine-prod @cee:{ "metadata": { "filename":
"\/opt\/redmine\/log\/production.log" }, "tag": "redmine-prod", "msg":
"REDMINE LOG CONTENT HERE" }
'
9085.173649270:ForwardToReceiver1 queue[DA]:Reg/w0: omrelp.c:
relpTcpSend: sock 18, lenbuf 288, send returned 288 [errno 11]
9085.173681929:ForwardToReceiver1 queue[DA]:Reg/w0: omrelp.c: sendbuf
NOT added to unacked list
9085.173686927:ForwardToReceiver1 queue[DA]:Reg/w0: omrelp.c: resending
frame '17 syslog 560 <189>2017-09-27T07:01:53.274558-05:00 redmine1
redmine-prod @cee:{ "metadata": { "filename":
"\/opt\/redmine\/log\/production.log" }, "tag": "redmine-prod", "msg":
"REDMINE LOG CONTENT HERE" }
'
9085.173693759:ForwardToReceiver1 queue[DA]:Reg/w0: omrelp.c:
relpTcpSend: sock 18, lenbuf 575, send returned -1 [errno 32]
9085.173697323:ForwardToReceiver1 queue[DA]:Reg/w0: omrelp.c: after
TryReestablish, sess state 4
We experienced this earlier in the week when the segfaults were first
triggered (but not immediately noticed thanks to systemd aggressively
restarting the primary receiver when it crashed, since the messages
appeared to eventually sync up).
I suspect that this is a separate issue, but figured it was worth
mentioning due to the context.
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