How do I balance bandwidth over several virtual NICs?

[Julian Elischer]

On 9/22/14, 11:12 PM, Elof Ofel wrote:
> I have a single NIC, mon0, that constantly receive 800 Mbps of mirrored traffic.
> I want to split these 800 Mbps into smaller chunks and feed them to a couple of virtual interfaces.
> Each virtual interface can then have instance of 'snort' inspecting its traffic.
>
> Say approximately 200 Mbps per interface = four interfaces.
> That way, each of the four snort processes only get 200 Mbps of data to inspect instead of having *one* single snort process (single-threaded) trying to cope with 800 Mbps.
>
> (the problem I'm trying to solve is utilizing all cpu's. Currently one cpu runs snort at 100% while all the other cpu's idle.)
>
>
> The important thing though is that all packets in the connection need to be diverted to the same virtual NIC. You can't send the SYN to NIC0 and the SYN-ACK to NIC1, 'cause then neither snort-process-0 nor snort-process-1 see the other side of the connection.
> The loadbalancing must be based on a hash built from at least the mac-addresses+IP-addresses.
you can probably do this with ipfw and/or netgraph in about half a 
dozen different ways.

Firstly, are the packets COPIES, or are these packets "Live".?  (do we 
have to get the packets back?)
I'm going to assume they are not copies and htat we need ot copy them.

Secondly, do you want to run in inline mode so that snort can drop 
packets?
I'm going to assume no..

Here is one possibility:
firstly do a "check-state" in ipfw. This will effectively jump to 
another rule if the session has been seen before. (see below)
If the state fails, "skipto" based on a table, to send packets to one 
of N packet rules depending on some set of bits in the address(es).
On each set of rules we forward the packet to a different snort, with 
a 'keep-state' rule. This assures that all following packets will do 
the same thing (It's a little known fact that 'check state' is 
actually very close to a conditional skipto.. it effectively jumps to 
the rule that first matched that session.)


the set of rules can achieve the forwarding in a number of ways, but I 
suggest using the 'ngtee' rule to send a copy of the packet to 
netgraph. the netgraph node in question can send it to a virtual 
interface, from which snort is listenning using bpf.

At one stage there was a snort action to allow it to listen directly 
to divert packets, so you could use just a 'tee' rule.  However I 
THINK that may only work in inline mode.. but you may check.

You could also use the 'forward' rule to send different sessions to 
differnet virtual interfaces. from where you could look at them but 
you'd have to somehow gather them all together again after that (a 
bridge?).


>
>
> So, what I think I'm looking for is a way to configure a lagg0 interface in loadbalance mode, that take all the incoming traffic on mon0 and distribute it over four virtual member NICs. (these four NICs would then probably be configured to run in monitor mode.)
>
>
> Do FreeBSD support what I'm looking for? How do I do it? Where should I look?
>
> /Elof
>   		 	   		
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