Cluster Configuration

Contents

Cluster Configuration

A Bro Cluster is a set of systems jointly analyzing the traffic of a network link in a coordinated fashion. You can operate such a setup from a central manager system easily using BroControl because BroControl hides much of the complexity of the multi-machine installation.

This section gives examples of how to setup common cluster configurations using BroControl. For a full reference on BroControl, see the BroControl documentation.

Preparing to Setup a Cluster

In this document we refer to the user account used to set up the cluster as the “Bro user”. When setting up a cluster the Bro user must be set up on all hosts, and this user must have ssh access from the manager to all machines in the cluster, and it must work without being prompted for a password/passphrase (for example, using ssh public key authentication). Also, on the worker nodes this user must have access to the target network interface in promiscuous mode.

Additional storage must be available on all hosts under the same path, which we will call the cluster’s prefix path. We refer to this directory as <prefix>. If you build Bro from source, then <prefix> is the directory specified with the --prefix configure option, or /usr/local/bro by default. The Bro user must be able to either create this directory or, where it already exists, must have write permission inside this directory on all hosts.

When trying to decide how to configure the Bro nodes, keep in mind that there can be multiple Bro instances running on the same host. For example, it’s possible to run a proxy and the manager on the same host. However, it is recommended to run workers on a different machine than the manager because workers can consume a lot of CPU resources. The maximum recommended number of workers to run on a machine should be one or two less than the number of CPU cores available on that machine. Using a load-balancing method (such as PF_RING) along with CPU pinning can decrease the load on the worker machines. Also, in order to reduce the load on the manager process, it is recommended to have a logger in your configuration. If a logger is defined in your cluster configuration, then it will receive logs instead of the manager process.

Basic Cluster Configuration

With all prerequisites in place, perform the following steps to setup a Bro cluster (do this as the Bro user on the manager host only):

Edit the BroControl configuration file, <prefix>/etc/broctl.cfg, and change the value of any BroControl options to be more suitable for your environment. You will most likely want to change the value of the MailTo and LogRotationInterval options. A complete reference of all BroControl options can be found in the BroControl documentation.
Edit the BroControl node configuration file, <prefix>/etc/node.cfg to define where logger, manager, proxies, and workers are to run. For a cluster configuration, you must comment-out (or remove) the standalone node in that file, and either uncomment or add node entries for each node in your cluster (logger, manager, proxy, and workers). For example, if you wanted to run five Bro nodes (two workers, one proxy, a logger, and a manager) on a cluster consisting of three machines, your cluster configuration would look like this:
```
[logger]
type=logger
host=10.0.0.10

[manager]
type=manager
host=10.0.0.10

[proxy-1]
type=proxy
host=10.0.0.10

[worker-1]
type=worker
host=10.0.0.11
interface=eth0

[worker-2]
type=worker
host=10.0.0.12
interface=eth0
```
For a complete reference of all options that are allowed in the node.cfg file, see the BroControl documentation.
Edit the network configuration file <prefix>/etc/networks.cfg. This file lists all of the networks which the cluster should consider as local to the monitored environment.
Install Bro on all machines in the cluster using BroControl:
```
> broctl install
```
See the BroControl documentation for information on setting up a cron job on the manager host that can monitor the cluster.

PF_RING Cluster Configuration

PF_RING allows speeding up the packet capture process by installing a new type of socket in Linux systems. It supports 10Gbit hardware packet filtering using standard network adapters, and user-space DNA (Direct NIC Access) for fast packet capture/transmission.

Installing PF_RING

Download and install PF_RING for your system following the instructions here. The following commands will install the PF_RING libraries and kernel module (replace the version number 5.6.2 in this example with the version that you downloaded):
```
cd /usr/src
tar xvzf PF_RING-5.6.2.tar.gz
cd PF_RING-5.6.2/userland/lib
./configure --prefix=/opt/pfring
make install

cd ../libpcap
./configure --prefix=/opt/pfring
make install

cd ../tcpdump-4.1.1
./configure --prefix=/opt/pfring
make install

cd ../../kernel
make install

modprobe pf_ring enable_tx_capture=0 min_num_slots=32768
```
Refer to the documentation for your Linux distribution on how to load the pf_ring module at boot time. You will need to install the PF_RING library files and kernel module on all of the workers in your cluster.
Download the Bro source code.

Configure and install Bro using the following commands:

./configure --with-pcap=/opt/pfring
make
make install

Make sure Bro is correctly linked to the PF_RING libpcap libraries:

ldd /usr/local/bro/bin/bro | grep pcap
      libpcap.so.1 => /opt/pfring/lib/libpcap.so.1 (0x00007fa6d7d24000)

Configure BroControl to use PF_RING (explained below).
Run “broctl install” on the manager. This command will install Bro and required scripts to all machines in your cluster.

Using PF_RING

In order to use PF_RING, you need to specify the correct configuration options for your worker nodes in BroControl’s node configuration file. Edit the node.cfg file and specify lb_method=pf_ring for each of your worker nodes. Next, use the lb_procs node option to specify how many Bro processes you’d like that worker node to run, and optionally pin those processes to certain CPU cores with the pin_cpus option (CPU numbering starts at zero). The correct pin_cpus setting to use is dependent on your CPU architecture (Intel and AMD systems enumerate processors in different ways). Using the wrong pin_cpus setting can cause poor performance. Here is what a worker node entry should look like when using PF_RING and CPU pinning:

[worker-1]
type=worker
host=10.0.0.50
interface=eth0
lb_method=pf_ring
lb_procs=10
pin_cpus=2,3,4,5,6,7,8,9,10,11

Using PF_RING+DNA with symmetric RSS

You must have a PF_RING+DNA license in order to do this. You can sniff each packet only once.

Load the DNA NIC driver (i.e. ixgbe) on each worker host.
Run “ethtool -L dna0 combined 10” (this will establish 10 RSS queues on your NIC) on each worker host. You must make sure that you set the number of RSS queues to the same as the number you specify for the lb_procs option in the node.cfg file.

On the manager, configure your worker(s) in node.cfg:

[worker-1]
type=worker
host=10.0.0.50
interface=dna0
lb_method=pf_ring
lb_procs=10

Using PF_RING+DNA with pfdnacluster_master

You must have a PF_RING+DNA license and a libzero license in order to do this. You can load balance between multiple applications and sniff the same packets multiple times with different tools.

Load the DNA NIC driver (i.e. ixgbe) on each worker host.
Run “ethtool -L dna0 1” (this will establish 1 RSS queues on your NIC) on each worker host.
Run the pfdnacluster_master command on each worker host. For example:
```
pfdnacluster_master -c 21 -i dna0 -n 10
```
Make sure that your cluster ID (21 in this example) matches the interface name you specify in the node.cfg file. Also make sure that the number of processes you’re balancing across (10 in this example) matches the lb_procs option in the node.cfg file.
If you are load balancing to other processes, you can use the pfringfirstappinstance variable in broctl.cfg to set the first application instance that Bro should use. For example, if you are running pfdnacluster_master with “-n 10,4” you would set pfringfirstappinstance=4. Unfortunately that’s still a global setting in broctl.cfg at the moment but we may change that to something you can set in node.cfg eventually.