Netmap is a high speed capture framework for Linux and FreeBSD. In Linux it is available as an external module, while in FreeBSD 11+ it is available by default.
19.5.1. Compiling Suricata¶
On FreeBSD 11 and up, NETMAP is included and enabled by default in the kernel.
To build Suricata with NETMAP, add
--enable-netmap to the configure line.
The location of the NETMAP includes (/usr/src/sys/net/) does not have to be
On Linux, NETMAP is not included by default. It can be pulled from github. Follow the instructions on installation included in the NETMAP repository.
When NETMAP is installed, add
--enable-netmap to the configure line.
If the includes are not added to a standard location, the location can
be specified when configuring Suricata.
./configure --enable-netmap --with-netmap-includes=/usr/local/include/netmap/
19.5.2. Starting Suricata¶
When opening an interface, netmap can take various special characters as options in the interface string.
the interface that netmap reads from will become unavailable for normal network operations. You can lock yourself out of your system.
Suricata can be started in 2 ways to use netmap:
suricata --netmap=<interface> suricata --netmap=igb0
In the above example Suricata will start reading from the igb0 network interface. The number of threads created depends on the number of RSS queues available on the NIC.
In the above example Suricata will take the
netmap block from the Suricata
configuration and open each of the interfaces listed.
netmap: - interface: igb0 threads: 2 - interface: igb1 threads: 4
For the above configuration, both
igb1 would be opened. With 2
igb0 and 4 capture threads for
This multi threaded setup only works correctly if the NIC has symmetric RSS hashing. If this is not the case, consider using the the ‘lb’ method below.
Suricata’s Netmap based IPS mode is based on the concept of creating a layer 2 software bridge between 2 interfaces. Suricata reads packets on one interface and transmits them on another.
Packets that are blocked by the IPS policy, are simply not transmitted.
netmap: - interface: igb0 copy-mode: ips copy-iface: igb1 - interface: igb1 copy-mode: ips copy-iface: igb0
19.5.3. Advanced setups¶
19.5.4. lb (load balance)¶
“lb” is a tool written by Seth Hall to allow for load balancing for single or multiple tools. One common use case is being able to run Suricata and Zeek together on the same traffic.
lb -i eth0 -p suricata:6 -p zeek:6
On FreeBSD 11, the named prefix doesn’t work.
netmap: - interface: suricata threads: 6
The interface name as passed to Suricata includes a ‘netmap:’ prefix. This tells Suricata that it’s going to read from netmap pipes instead of a real interface.
Then Zeek (formerly Bro) can be configured to load 6 instances. Both will get a copy of the same traffic. The number of netmap pipes does not have to be equal for both tools.
184.108.40.206. FreeBSD 11¶
On FreeBSD 11 the named pipe is not available.
lb -i eth0 -p 6
netmap: - interface: netmap:eth0 threads: 6
“lb” is bundled with netmap.
220.127.116.11. Single NIC¶
When an interface enters NETMAP mode, it is no longer available to the OS for other operations. This can be undesirable in certain cases, but there is a workaround.
By running Suricata in a special inline mode, the interface will show it’s traffic to the OS.
netmap: - interface: igb0 copy-mode: tap copy-iface: igb0^ - interface: igb0^ copy-mode: tap copy-iface: igb0
The copy-mode can be both ‘tap’ and ‘ips’, where the former never drops packets based on the policies in use, and the latter may drop packets.
Misconfiguration can lead to connectivity loss. Use with care.
This set up can also be used to mix NETMAP with firewall setups like pf or ipfw.
18.104.22.168. VALE switches¶
VALE is a virtual switch that can be used to create an all virtual network or a mix of virtual and real nics.
A simple all virtual setup:
vale-ctl -n vi0 vale-ctl -a vale0:vi0 vale-ctl -n vi1 vale-ctl -a vale0:vi1
We now have a virtual switch “vale0” with 2 ports “vi0” and “vi1”.
We can start Suricata to listen on one of the ports:
Then we can
19.5.5. Inline IDS¶
The inline IDS is almost the same as the IPS setup above, but it will not
netmap: - interface: igb0 copy-mode: tap copy-iface: igb1 - interface: igb1 copy-mode: tap copy-iface: igb0
The only difference with the IPS mode is that the
copy-mode setting is