19.2. Napatech

19.2.1. Contents

  • Introduction
  • Package Installation
  • Basic Configuration
  • Advanced Multithreaded Configuration

19.2.2. Introduction

Napatech packet capture accelerator cards can greatly improve the performance of your Suricata deployment using these hardware based features:

  • On board burst buffering (up to 12GB)
  • Zero-copy kernel bypass DMA
  • Non-blocking PCIe performance
  • Port merging
  • Load distribution to up 128 host buffers
  • Precise timestamping
  • Accurate time synchronization

The package uses a proprietary shell script to handle the installation process. In either case, gcc, make and the kernel header files are required to compile the kernel module and install the software.

19.2.3. Package Installation

Note that make, gcc, and the kernel headers are required for installation

Root privileges are also required

The latest driver and tools installation package can be downloaded from: https://www.napatech.com/downloads.

Note that you will be prompted to install the Napatech libpcap library. Answer “yes” if you would like to use the Napatech card to capture packets in Wireshark, tcpdump, or another pcap based application. Libpcap is not needed for Suricata as native Napatech API support is included

Red Hat Based Distros:

$ yum install kernel-devel-$(uname -r) gcc make
       $ ./package_install_3gd.sh

Debian Based Distros:

$ apt-get install linux-headers-$(uname .r) gcc make
       $ ./package_install_3gd.sh

To complete installation for all distros ntservice:

$ /opt/napatech3/bin/ntstart.sh -m

19.2.4. Suricata Installation

After downloading and extracting the Suricata tarball, you need to run configure to enable Napatech support and prepare for compilation:

$ ./configure --enable-napatech --with-napatech-includes=/opt/napatech3/include --with-napatech-libraries=/opt/napatech3/lib
$ make
$ make install-full

19.2.5. Suricata configuration

Now edit the suricata.yaml file to configure the system. There are three ways the system can be configured:

1. Auto-config without cpu-affinity: In this mode you specify the stream configuration in suricata.yaml file and allow the threads to roam freely. This is good for single processor systems where NUMA node configuration is not a performance concern.

2. Auto-config with cpu-affinity: In this mode you use the cpu-affinity of the worker threads to control the creation and configuration of streams. One stream and one worker thread will be created for each cpu identified in suricata.yaml. This is best in systems with multiple NUMA nodes (i.e. multi-processor systems) as the NUMA node of the host buffers is matched to the core on which the thread is running.

3. Manual-config (legacy): In this mode the underlying Napatech streams are configured by issuing NTPL commands prior to running Suricata. Suricata then connects to the existing streams on startup.

19.2.6. Example Configuration - Auto-config without cpu-affinity:

If cpu-affinity is not used it is necessary to explicitly define the streams in the Suricata configuration file. To use this option the following options should be set in the Suricata configuration file:

  1. Turn off cpu-affinity
  2. Enable the Napatech “auto-config” option
  3. Specify the streams that should be created on startup
  4. Specify the ports that will provide traffic to Suricata
  5. Specify the hashmode used to distribute traffic to the streams

Below are the options to set:

threading:
  set-cpu-affinity: no
    .
    .
    .
napatech:
    auto-config: yes
    streams: ["0-3"]
    ports: [all]
    hashmode: hash5tuplesorted

Now modify ntservice.ini. You also need make sure that you have allocated enough host buffers in ntservice.ini for the streams. It’s a good idea to also set the TimeSyncReferencePriority. To do this make the following changes to ntservice.ini:

HostBuffersRx = [4,16,-1] # [number of host buffers, Size(MB), NUMA node] TimeSyncReferencePriority = OSTime # Timestamp clock synchronized to the OS

Stop and restart ntservice after making changes to ntservice:

$ /opt/napatech3/bin/ntstop.sh
$ /opt/napatech3/bin/ntstart.sh

Now you are ready to start Suricata:

$ suricata -c /usr/local/etc/suricata/suricata.yaml --napatech --runmode workers

19.2.7. Example Configuration - Auto-config with cpu-affinity:

This option will create a single worker-thread and stream for each CPU defined in the worker-cpu-set. To use this option make the following changes to suricata.yaml:

  1. Turn on cpu-affinity
  2. Specify the worker-cpu-set
  3. Enable the Napatech “auto-config” option
  4. Specify the ports that will provide traffic to Suricata
  5. Specify the hashmode that will be used to control the distribution of traffic to the different streams/cpus.

When you are done it should look similar to this:

threading:
  set-cpu-affinity: yes
  cpu-affinity:
    management-cpu-set:
      cpu: [ 0 ]
    receive-cpu-set:
      cpu: [ 0 ]
    worker-cpu-set:
      cpu: [ all ]
      .
      .
      .
napatech:
  auto-config: yes
  ports: [all]
  hashmode: hash5tuplesorted

Prior to running Suricata in this mode you also need to configure a sufficient number of host buffers on each NUMA node. So, for example, if you have a two processor server with 32 total cores and you plan to use all of the cores you will need to allocate 16 host buffers on each NUMA node. It is also desirable to set the Napatech cards time source to the OS.

To do this make the following changes to ntservice.ini:

TimeSyncReferencePriority = OSTime  # Timestamp clock synchronized to the OS
HostBuffersRx = [16,16,0],[16,16,1] # [number of host buffers, Size(MB), NUMA node]

Stop and restart ntservice after making changes to ntservice:

$ /opt/napatech3/bin/ntstop.sh -m
$ /opt/napatech3/bin/ntstart.sh -m

Now you are ready to start Suricata:

$ suricata -c /usr/local/etc/suricata/suricata.yaml --napatech --runmode workers

19.2.8. Example Configuration - Manual Configuration

For Manual Configuration the Napatech streams are created by running NTPL commands prior to running Suricata.

Note that this option is provided primarily for legacy configurations as previously this was the only way to configure Napatech products. Newer capabilities such as flow-awareness and inline processing cannot be configured manually.

In this example we will setup the Napatech capture accelerator to merge all physical ports, and then distribute the merged traffic to four streams that Suricata will ingest.

The steps for this configuration are:
  1. Disable the Napatech auto-config option in suricata.yaml
  2. Specify the streams that Suricata is to use in suricata.yaml
  3. Create a file with NTPL commands to create the underlying Napatech streams.

First suricata.yaml should be configured similar to the following:

napatech:
  auto-config: no
  streams: ["0-3"]

Next you need to make sure you have enough host buffers defined in ntservice.ini. As it’s also a good idea to set up the TimeSync. Here are the lines to change:

TimeSyncReferencePriority = OSTime      # Timestamp clock synchronized to the OS
HostBuffersRx = [4,16,-1]               # [number of host buffers, Size(MB), NUMA node]

Stop and restart ntservice after making changes to ntservice:

$ /opt/napatech3/bin/ntstop.sh
$ /opt/napatech3/bin/ntstart.sh

Now that ntservice is running we need to execute a few NTPL (Napatech Programming Language) commands to complete the setup. Create a file will the following commands:

Delete=All                              # Delete any existing filters
Assign[streamid=(0..3)]= all    # Assign all physical ports to stream ID 0

Next execute those command using the ntpl tool:

$ /opt/napatech3/bin/ntpl -f <my_ntpl_file>

Now you are ready to start Suricata:

$ suricata -c /usr/local/etc/suricata/suricata.yaml --napatech --runmode workers

It is possible to specify much more elaborate configurations using this option. Simply by creating the appropriate NTPL file and attaching Suricata to the streams.

19.2.9. Bypassing Flows

On flow-aware Napatech products, traffic from individual flows can be automatically dropped or, in the case of inline configurations, forwarded by the hardware after an inspection of the initial packet(s) of the flow by Suricata. This will save CPU cycles since Suricata does not process packets for a flow that has already been adjudicated. This is enabled via the hardware-bypass option in the Napatech section of the configuration file.

When hardware bypass is used it is important that the ports accepting upstream and downstream traffic from the network are configured with information on which port the two sides of the connection will arrive. This is needed for the hardware to properly process traffic in both directions. This is indicated in the “ports” section as a hyphen separated list of port-pairs that will be receiving upstream and downstream traffic E.g.:

napatech:
  hardware-bypass: true
  ports[0-1,2-3]

Note that these “port-pairings” are also required for IDS configurations as the hardware needs to know on which port(s) two sides of the connection will arrive.

For configurations relying on optical taps the two sides of the pairing will typically be different ports. For SPAN port configurations where both upstream and downstream traffic are delivered to a single port both sides of the “port-pair” will reference the same port.

For example tap configurations have a form similar to this:

ports[0-1,2-3]

Whereas SPAN port configurations it would look similar to this:

ports[0-0,1-1,2-2,3-3]

Note that SPAN and tap configurations may be combined on the same adapter.

There are multiple ways that Suricata can be configured to bypass traffic. One way is to enable stream.bypass in the configuration file. E.g.:

stream:
  bypass: true

When enabled once Suricata has evaluated the first chunk of the stream (the size of which is also configurable) it will indicate that the rest of the packets in the flow can be bypassed. In IDS mode this means that the subsequent packets of the flow will be dropped and not delivered to Suricata. In inline operation the packets will be transmitted on the output port but not delivered to Suricata.

Another way is by specifying the “bypass” keyword in a rule. When a rule is triggered with this keyword then the “pass” or “drop” action will be applied to subsequent packets of the flow automatically without further analysis by Suricata. For example given the rule:

drop tcp any 443 <> any any (msg: "SURICATA Test rule"; bypass; sid:1000001; rev:2;)

Once Suricata initially evaluates the fist packet(s) and identifies the flow, all subsequent packets from the flow will be dropped by the hardware; thus saving CPU cycles for more important tasks.

The timeout value for how long to wait before evicting stale flows from the hardware flow table can be specified via the FlowTimeout attribute in ntservice.ini.

19.2.10. Inline Operation

Napatech flow-aware products can be configured for inline operation. This is specified in the configuration file. When enabled, ports are specified as port-pairs. With traffic received from one port it is transmitted out the the peer port after inspection by Suricata. E.g. the configuration:

napatech:
 inline: enabled
 ports[0-1, 2-3]

Will pair ports 0 and 1; and 2 and 3 as peers. Rules can be defined to pass traffic matching a given signature. For example, given the rule:

pass tcp any 443 <> any any (msg: "SURICATA Test rule";  bypass; sid:1000001; rev:2;)

Suricata will evaluate the initial packet(s) of the flow and program the flow into the hardware. Subsequent packets from the flow will be automatically be shunted from one port to it’s peer.

19.2.11. Counters

The following counters are available:

  • napa_total.pkts - The total of packets received by the card.
  • napa_total.byte - The total count of bytes received by the card.
  • napa_total.overflow_drop_pkts - The number of packets that were dropped because the host buffers were full. (I.e. the application is not able to process packets quickly enough.)
  • napa_total.overflow_drop_byte - The number of bytes that were dropped because the host buffers were full. (I.e. the application is not able to process packets quickly enough.)

On flow-aware products the following counters are also available:

  • napa_dispatch_host.pkts, napa_dispatch_host.byte:

    The total number of packets/bytes that were dispatched to a host buffer for processing by Suricata. (Note: this count includes packets that may be subsequently dropped if there is no room in the host buffer.)

  • napa_dispatch_drop.pkts, napa_dispatch_drop.byte:

    The total number of packets/bytes that were dropped at the hardware as a result of a Suricata “drop” bypass rule or other adjudication by Suricata that the flow packets should be dropped. These packets are not delivered to the application.

  • napa_dispatch_fwd.pkts, napa_dispatch_fwd.byte:

    When inline operation is configured this is the total number of packets/bytes that were forwarded as result of a Suricata “pass” bypass rule or as a result of stream or encryption bypass being enabled in the configuration file. These packets were not delivered to the application.

  • napa_bypass.active_flows:

    The number of flows actively programmed on the hardware to be forwarded or dropped.

  • napa_bypass.total_flows:

    The total count of flows programmed since the application started.

If enable-stream-stats is enabled in the configuration file then, for each stream that is being processed, the following counters will be output in stats.log:

  • napa<streamid>.pkts: The number of packets received by the stream.
  • napa<streamid>.bytes: The total bytes received by the stream.
  • napa<streamid>.drop_pkts: The number of packets dropped from this stream due to buffer overflow conditions.
  • napa<streamid>.drop_byte: The number of bytes dropped from this stream due to buffer overflow conditions.

This is useful for fine-grain debugging to determine if a specific CPU core or thread is falling behind resulting in dropped packets.

If hba is enabled the following counter will also be provided:

  • napa<streamid>.hba_drop: the number of packets dropped because the host buffer allowance high-water mark was reached.

In addition to counters host buffer utilization is tracked and logged. This is also useful for debugging. Log messages are output for both Host and On-Board buffers when reach 25, 50, 75 percent of utilization. Corresponding messages are output when utilization decreases.

Debugging:

For debugging configurations it is useful to see what traffic is flowing as well as what streams are created and receiving traffic. There are two tools in /opt/napatech3/bin that are useful for this:

  • monitoring: this tool will, among other things, show what traffic is arriving at the port interfaces.
  • profiling: this will show host-buffers, streams and traffic flow to the streams.

If Suricata terminates abnormally stream definitions, which are normally removed at shutdown, may remain in effect. If this happens they can be cleared by issuing the “delete=all” NTPL command as follows:

# /opt/napatech3/bin/ntpl -e "delete=all"

19.2.12. Napatech configuration options:

These are the Napatech options available in the Suricata configuration file:

napatech:
  # The Host Buffer Allowance for all streams
  # (-1 = OFF, 1 - 100 = percentage of the host buffer that can be held back)
  # This may be enabled when sharing streams with another application.
  # Otherwise, it should be turned off.
  #hba: -1

  # When use_all_streams is set to "yes" the initialization code will query
  # the Napatech service for all configured streams and listen on all of them.
  # When set to "no" the streams config array will be used.
  #
  # This option necessitates running the appropriate NTPL commands to create
  # the desired streams prior to running Suricata.
  #use-all-streams: no

  # The streams to listen on when auto-config is disabled or when threading
  # cpu-affinity is disabled. This can be either:
  #   an individual stream (e.g. streams: [0])
  # or
  #   a range of streams (e.g. streams: ["0-3"])
  #
  streams: ["0-3"]

  # Stream stats can be enabled to provide fine grain packet and byte counters
  # for each thread/stream that is configured.
  #
  enable-stream-stats: no

  # When auto-config is enabled the streams will be created and assigned
  # automatically to the NUMA node where the thread resides. If cpu-affinity
  # is enabled in the threading section, then the streams will be created
  # according to the number of worker threads specified in the worker cpu set.
  # Otherwise, the streams array is used to define the streams.
  #
  # This option cannot be used simultaneous with "use-all-streams".
  #
  auto-config: yes

  # Enable hardware level flow bypass.
  #
  hardware-bypass: yes

  # Enable inline operation. When enabled traffic arriving on a given port is
  # automatically forwarded out it's peer port after analysis by Suricata.
  # hardware-bypass must be enabled when this is enabled.
  #
  inline: no

  # Ports indicates which napatech ports are to be used in auto-config mode.
  # these are the port ID's of the ports that will be merged prior to the
  # traffic being distributed to the streams.
  #
  # When hardware-bypass is enabled the ports must be configured as a segment
  # specify the port(s) on which upstream and downstream traffic will arrive.
  # This information is necessary for the hardware to properly process flows.
  #
  # When using a tap configuration one of the ports will receive inbound traffic
  # for the network and the other will receive outbound traffic. The two ports on a
  # given segment must reside on the same network adapter.
  #
  # When using a SPAN-port configuration the upstream and downstream traffic
  # arrives on a single port. This is configured by setting the two sides of the
  # segment to reference the same port.  (e.g. 0-0 to configure a SPAN port on
  # port 0).
  #
  # port segments are specified in the form:
  #    ports: [0-1,2-3,4-5,6-6,7-7]
  #
  # For legacy systems when hardware-bypass is disabled this can be specified in any
  # of the following ways:
  #
  #   a list of individual ports (e.g. ports: [0,1,2,3])
  #
  #   a range of ports (e.g. ports: [0-3])
  #
  #   "all" to indicate that all ports are to be merged together
  #   (e.g. ports: [all])
  #
  # This parameter has no effect if auto-config is disabled.
  #
  ports: [0-1,2-3]

  # When auto-config is enabled the hashmode specifies the algorithm for
  # determining to which stream a given packet is to be delivered.
  # This can be any valid Napatech NTPL hashmode command.
  #
  # The most common hashmode commands are: hash2tuple, hash2tuplesorted,
  # hash5tuple, hash5tuplesorted and roundrobin.
  #
  # See Napatech NTPL documentation other hashmodes and details on their use.
  #
  # This parameter has no effect if auto-config is disabled.
  #
  hashmode: hash5tuplesorted

Note: hba is useful only when a stream is shared with another application. When hba is enabled packets will be dropped (i.e. not delivered to Suricata) when the host-buffer utilization reaches the high-water mark indicated by the hba value. This insures that, should Suricata get behind in its packet processing, the other application will still receive all of the packets. If this is enabled without another application sharing the stream it will result in sub-optimal packet buffering.

Make sure that there are enough host-buffers declared in ntservice.ini to accommodate the number of cores/streams being used.

19.2.13. Support

Contact a support engineer at: ntsupport@napatech.com

Napatech Documentation can be found at: https://docs.napatech.com (Click the search icon, with no search text, to see all documents in the portal.)