Re: [Snort-users] OS options to monitor traffic over a 1GiB and 10 GiB

[Livio Ricciulli <livio () metaflows com>]

I am all for sharing and collaborating. Use our work for whatever 
purpose you'd like. It would be great to make it into an howto.
In my experience, more transparency==better quality; so the more you can 
add the better for everyone. Luca is always very helpful..
Another issue I was exploring with not much success is hardware 
filtering with the 82599 (x520 is just a dual version of it).
I can translate a subset of bpf expressions to hw registers to install 
into the hardware instead the software bpf. Unfortunately I
run into a snag.. If anyone can add or subtract from the following I 
would appreciate it, since hw filtering would be very interesting for
10G Snort deployments.. Please tell me that I am wrong..

As far as I can tell the 82599 designers have made very powerful  
hardware exclusively designed
for endpoint (therefore simplex) filtering applications.
In plain English here is what the chip is capable of (using bpf language).

------------------------------------------------
128 5-tuple /32 rules capable of masking out any of the 5 fields.
These filters could only handle:
o 1/2 of a simplex class c.
For example to implement a bpf like (src net 192.168.1.128/25)
one could add (src host 192.168.1.128) or (src host 192.168.1.129) or 
..(src host 192.168.1.255)
o 1/4 of duplex class c.
For example to implement a bpf like (net 192.168.1.192/26)
one could add (src host 192.168.1.192) or (src host 192.168.1.193) or 
..(src host 192.168.1.255)
or (dst host 192.168.1.192) or (dst host 192.168.1.193) or ..(dst host 
192.168.1.255)
------------------------------------------------
8k perfect FDIR filters.
Unfortunately (&##*&@!!!) these filters have 1 single global 96-bit mask 
value for the source/destination addresses and ports.
So, you could only implement simplex things like:
o (src net 192.168.1.0/26 or src net 192.168.2.0/32 or src net 
10.1.0.0/24) #note that the masks can change because you could
enumerate 32-bit addresses up to 8k times with the same mask.
o (src portrange 0-8000) #in this case you would be masking both src and 
dst addresses.
o (vlan 19 or vlan 20 or vlan 21)
duplex address and port filters are impossible (afikt).
-----------------------------------------------

So, in short, you can have only very small and simple duplex expressions 
as 5-tuple filters or larger but only simplex FDIR expressions.

I think the best solution regarding the 82599 hw filtering is to do vlan 
ID filtering..
Would any of the other address filtering options (very small duplex or 
larger simplex) useful to you?
I am not sure if it is worth implementing them (even though I could do 
it with a few more days of work).
I guess if you wanted to do hw filtering using a inline 10Gbps box,
the simplex FDIR filtering could work by applying mirrored filters
on both interfaces. For example to implement an expression like
(net 192.168.1.0/24) eth1 would get src net 192.168.1.0/24 and eth2
would gets dst net 192.168.1.0/24.

I am not sure how many people would have a need for hw filtering
for an inline box based on a dual 82599..

I am trying to figure out if it is worth pursuing it further..
What do you think?



On 6/30/2012 12:21 AM, Robert Vineyard wrote:
> Livio,
>
> Hats off to you, it appears you've beat me to the punch :-)
>
> You've just done what I was about to do...
>
> For what it's worth, I'll be testing on a third-generation E5-1650 with
> VT-d technology (separate writeup coming soon on a similar, virtualized
> approach, leveraging IOV and related technologies).
>
> I've got an I350 waiting to install when the box arrives on Monday, and
> if all goes well, I'm going to see about acquiring an X520-based card too.
>
> It sounds like you've already done the heavy lifting on this. If you
> don't mind, I'd like to integrate your methods and lessons learned into
> my own HOWTO guides -- attributing all credit for that part of work to
> you, of course.
>
> Best regards,
> Robert Vineyard
>
>
> On 06/29/2012 02:23 PM, livio Ricciulli wrote:
> > You can also check out
> > https://www.metaflows.com/technology/10-gbps-pf_ring-2/
> >
> > It gives detailed instructions on how to build a reliable PF_RING-based
> > 10G box on CentOS using the Intel 82599 and compare the relative
> > performance of PF_RING in NAPI mode and DNA mode. DNA wins but note that
> > if you use DNA, you can only attach up 16 Snort processes using the
> > Intel 82599 and attach 1 application to the interface (for example
> > snort) but you could not (for example) run both Snort and Ntop at the
> > same time. NAPI lets you do that.
> >
> > The number of rules you run is extremely important in determining how
> > much bandwidth you can handle. With our traces we could process 4-6 Gigs
> > on a dual X5670 and 4000 to 7000 rules respectively.
> >
> > Livio.
> >
> > On 06/29/2012 07:41 AM, Robert Vineyard wrote:
> > > On 6/29/2012 9:23 AM, Joel Esler wrote:
> > > > Probably BSD. But I think it's less dependent on the OS, and is more dependent on hardware. When you are talking 
> > > > about 10 Gig, there's lots of factors that come into play.
> > > Some hardware options I'd recommend, in decreasing order of cost:
> > >
> > > http://www.pcapexpress.com/index.php/products
> > >
> > > http://www.endace.com/endace-dag-high-speed-packet-capture-cards.html
> > >
> > > http://www.silicom-usa.com/10_Gigabit_Ethernet_Networking_Server_Adapters
> > >
> > > http://www.myricom.com/products/network-adapters.html
> > >
> > > http://ark.intel.com/products/series/46825
> > >
> > >
> > > To monitor that much traffic reliably, you're going to have to employ a load-balancing technique. The best way I've 
> > > found to go about doing that is to use something that can perform a hash function on the 5-tuple of any given flow. 
> > > The 5-tuple is composed of the source and destination IP addresses, ports, and protocol. Hashing in this manner 
> > > ensures that traffic is distributed roughly evenly, and that bidirectional conversations are preserved and sent to 
> > > the same sensor engine.
> > >
> > > The more expensive products in my list above can do this in hardware, often using FPGA tricks and DMA buffering to 
> > > dramatically accelerate the process. When you're trying to monitor a fully-saturated link, every CPU cycle counts.
> > >
> > > The less expensive products (typically from Intel or Myricom) can do some of it in hardware, but they really shine 
> > > when you pair them with capture-optimized drivers like PF_RING DNA (http://www.ntop.org/products/pf_ring/dna/) or 
> > > Myricom Sniffer10G (http://www.myricom.com/support/downloads/sniffer.html).
> > >
> > > In any case you'll want a big server with lots of CPU cores and as much RAM as you can afford. If you'll be logging 
> > > payloads and/or expect heavy alert volumes, you'll also need fast disk, like SSD or a hardware RAID10 array. The 
> > > idea is to run multiple sensor engines (Snort, for example) and bind each one to one of the load-balanced virtual 
> > > network interfaces presented by the setup I just described. If your traffic is fairly predictable or you have 
> > > plenty of headroom on your sensor box, you can use CPU affinity to peg those engines to individual cores (there are 
> > > ways to do this for the firehose of interrupts coming from the NIC too) to avoid spurious context-switching and buy 
> > > yourself a few more precious CPU cycles. You'll want to run one sensor process per core.
> > >
> > > On the other hand, if your traffic is bursty and unpredictable, you may want to forgo the CPU affinity and let the 
> > > kernel scheduler do its job. For cases like that, I prefer to run two sensor processes per core (doubling the 
> > > number of required virtual interfaces on your packet-capture NIC). That way, the chunks are smaller and if one 
> > > needs to burst up to consume a full CPU core, the kernel scheduler will happily relocate the lesser-utilized 
> > > processes to other cores.
> > >
> > > Happy sniffing! :-)
> > >
> > > -- Robert Vineyard
> > >
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-- 
Livio Ricciulli
MetaFlows Inc.
(408) 835-5005


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