What is the biggest attack in GBPS you stopped

[Harvy66]

What is "KERN.IPC.NMBUF"? I can't find anything about it?

[Supermule]

Kernel buffers.

https://www.google.dk/search?q=KERN.IPC.NMBUF&ie=UTF-8

[Supermule]

It goes down so fast you dont see the utilization…

@Harvy66:

@Supermule:

8 cores

http://youtu.be/-xTtzLEQx08

Not as good as hoped but not running 100% CPU like all the others. It seems that the response on the WAN graph are related to the PING on WAN.

It seems that the 2 CORE setup is the one that performs best in beginning until around 35 seconds into the attack. Then crash. 4 and 8 cores keep the GUI online.

You may be at 100% cpu, but according to the dashboard, you're running at 311mhz even when at 100%.

[Supermule]

4mbps attack and 40% packetloss.

Netstat -L doesnt see any exhaustion of queues.

Anybody know how to change the backlog to 1024??

Just to see if it matters.

[Supermule]

Here is the output of vmstat -z

Anybody find something unusual in this?


[dennypage]

Guys, you need to be much more rigorous in collecting data. You are trying to diagnose a network packet processing problem. Using the web interface to execute shell commands will not produce a consistent and reliable result. Not only is the web interface heavy weight, it is lower priority than kernel packet processing. And most importantly, your diagnostic data collection is dependent upon the behavior of the system you are trying to diagnose.

Let's assume you don't want to build a custom kernel…

You need to shed as many variables as possible and get as close to real data as you can. Turn Snort off for crying out loud. And anything else optional that might interfere with metrics. If you want to use command line tools, execute them outside of network processing. This means using the console, not ssh. Create a shell script that collects information on a periodic basis. Elevate the priority of the script to ensure timely execution. And save the output for every run.

Here is a sample script:

#!/bin/sh
ps -axuwww
While true
do
    /bin/date
    /usr/bin/netstat -m
    sleep 2
done

Here is a sample execution:

/usr/bin/nice -n -19 myscript

[Supermule]

Done it at the console at no useful output was generated for people to see.

I stopped Snort running and here is the output from the DoS.

First 2 is idle and next 2 is under DoS.

[Supermule]

Done some more testing this morning.

2-3mbps is all it takes. Has downscaled the Mbufs and state max a little.

http://youtu.be/NPtDnM8ixXs

Dennypage. Thanks for the info. Want to help diagnose then contact me on PM.

[tim.mcmanus]

This link is probably important to note the differences between versions:  https://doc.pfsense.org/index.php/Does_pfSense_support_SMP_(multi-processor_and/or_core)_systems

2.1 was single-threaded and 2.2 is multi-threaded.  That's why you're seeing an impact/performance difference between the two; it's not hard to extrapolate how and why.

I think what you're trying to determine, and this is based on my review of the thread, is which part of pf is choking.  In order to determine this you need to debug each component in the chain from the NIC to the CPU and back out as well as the code.  I'm not entirely sure you know programmatically where and which networking event triggers the issue inside pf, only that a large volume of data of a specific type starts the event.

You've moved beyond evaluating pf from a networking perspective and more into evaluating the codebase.  This requires a different kind of data collection and troubleshooting.  It also take an excruciatingly long time to identify and resolve these kinds of issues.  It's a lot more than just tweaking a setting in some cases.

Best of luck in determining the root cause and solution to this issue.

[Supermule]

Thanks Tim.

You are 100% correct.

[kejianshi]

Silly question - Is it possible to set a max cpu % that may be used by the packet filter?  Keep some in reserve for other processes?

[Harvy66]

Someone needs to use DTrace and make a flame-graph of what methods are being called in the kernel.

[Supermule]

Shall we test again Harvy??

[Harvy66]

I don't know how to do flame graphs, I've only seen them in Netflix presentations talking about optimizing FreeBSD.

[Supermule]

Tested Fortigate Virtual Server and after enabling Flood Protection, it ran perfectly during all tests.

1CPU and 1GB RAM in a VmWare VM.

Had an email conversation with a guy named Dave Huffman and he was able to replicate the scenario but only using DoS and not DDoS. Not that important, but it seems pfSense is not able to handle legitimate traffic vs. offending IP's.

It chokes somewhere in the stack.

[Nullity]

Do you need help figuring out how to enable profiling or some other debugging software?

[Supermule]

Yes because I need to get to the bottom of this.

[tim.mcmanus]

I would start here.  http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug.html

You can do remote kernel debugging as an option.  It's not for the faint of heart.  Debugging never is.

[firewalluser]

@Supermule:

Yes because I need to get to the bottom of this.

Try a USB nic on the wan, see how the data is handled differently.

You'll find these useful as well.
https://software.intel.com/sites/default/files/profiling_debugging_freebsd_kernel_321772.pdf
https://2008.asiabsdcon.org/papers/P8B-paper.pdf

Mutexs can catch some people out, but they are just locks to ensure the code doesnt deadlock in a multicore environment.

IMO profiling is better than retrospectively debugging crash dumps as you can make the crash dumps misleading in some situations masking the real root cause of the problem. I've found bugs in programming languages that have existed for over 15 years, thats how difficult some of these bugs are to find, even though it took me less than a week to find, theres a lot of exposed software out there.

Main difficultly are multi cores when it comes to debugging, you could be looking at the code running on one core whilst a bug in code running on another core creates the problem which crashes the code running on the core you are looking at. You can mask some problems by running on a single core but you will still have the problem, just less often as these things are just inglorious clockwork turkmachines.

[Supermule]

Yes but doesnt crash as in crash….

It just goes to a standstill and is unresponsive. You dont see anything on the console and in the logs besides excessive traffic.

I dont see any queueing on the NIC's as well so its pretty odd.