21. Components » Packet Filter

The functionality of Packet Filter is described in depth in the Choosing a Method of DDoS Mitigation chapter.

To add a Packet Filter, click the [+] button found in the title bar of the Configuration » Components panel. To configure an existing Packet Filter, go to Configuration » Components and click its name.

Packet Filter Configuration parameters:

● Filter Name – A short name to help you identify the Packet Filter

● Filter Color – The color used in graphs for the Packet Filter. The default color is a random one. You can change it from the drop-down menu

● Filter Visibility – Toggles the listing inside the Reports » Devices panel

● Device Group – Optional parameter used to group components (e.g., by location or role). You can use it to restrict the access of Guest accounts

● Filter Server – Select a server that fulfills the minimum system requirements for running the Packet Filter. If this is not the Console server, follow the NFS configuration steps to make the raw packet data visible in the web interface

● Capture Engine – Select the preferred packet capturing engine:

• Embedded Libpcap – Select to use the built-in libpcap library. Libpcap requires no additional setup, but it cannot run on multiple threads, and it may be too slow for multi-gigabit sniffing

• System Libpcap – Select to use the libpcap library provided by the Linux distribution

• PF_RING – Select to use the PF_RING framework to speed up packet processing. PF_RING is much faster than Libpcap, but it requires the installation of additional kernel modules, and supports only a limited number of NICs. Click the button on the right for PF_RING-specific settings. PF_RING ZC is not supported by Packet Filter because it isolates the sniffed interface from the kernel, which will not be able to perform packet switching, routing or filtering

• DPDK – Select to use the DPDK framework, then click the button on the right of the Capture Engine field to configure DPDK-specific parameters as described in Appendix 1

• DPDK [Packet Sensor] – Select to use a DPDK-enabled Packet Sensor as a packet capturing engine. DPDK offers NIC access exclusively to a single process, so this option embeds the Packet Filter’s logic into a Packet Sensor in order to have both Wanguard components listening to the same interface

● Capture Engine Options – Click the button to set additional parameters for the selected Capture Engine. Packet Sampling (1/N) must be equal to the number of filtering servers activated when the Packet Filter is used in a clustered architecture where each filtering server receives traffic from a round-robin packet scheduler. The correct value in most cases is 1

● Sniffing Interface – The network interface(s) listened by the Packet Filter. Libpcap accepts only a single interface. PF_RING allows listening to multiple physical interfaces simultaneously when the interfaces are separated by semicolons (“;”). Listening to the Inbound Interface increases CPU usage because even the traffic that doesn’t get forwarded will be inspected. Listening to the Outbound Interface decreases CPU usage because only the forwarded traffic reaches that interface; in this case, Packet Filter may still be able to obtain traffic statistics about the dropped traffic from the NIC’s counters

● CPU Threads – Packet Filter can run multi-threaded on a given set of CPU cores. Each thread increases the RAM usage. With PF_RING, activating more than 6 CPU threads hurts performance. The number of threads used by each Filter instance is also dependent on the number of RSS queues

● Filtering Interface – Select where to apply the filtering rules:

• None – Packet Filter detects and reports filtering rule,s but it doesn’t apply them to a firewalled interface

• Inbound interface – Packet Filter applies the filtering rules on the inbound interface, which is defined below

• Outbound interface – Packet Filter applies the filtering rules on the outbound interface, which is defined below

● Traffic Diversion – Provides a selection of BGP Connectors that can be used for traffic diversion. If the server is deployed inline, or if you do not plan to deploy the server in a Side Filtering topology, leave this parameter set to Off

● Inbound Interface – Enter the interface that receives the incoming/ingress traffic. This parameter can be omitted if the Filtering Interface is the same as the Outbound Interface. Bridged interfaces should have the string “physdev:” prepended in front of the interface’s name

● Outbound Interface – The cleaned traffic is sent to the downstream router/switch via the outbound interface, which should hold the route to the default gateway. This parameter can be omitted if the Filtering Interface is the same as the Inbound Interface. Bridged interfaces should have the string “physdev:” prepended in front of the interface’s name

● BGP Flowspec – Select which policy to apply when the Response is configured to send BGP Flowspec announcements for filtering rules. The rate-limit policy works only for bits/s anomalies; anomalies detected for pkts/s will have the traffic matched by the filtering rule fully discarded

● Netfilter Firewall – Packet Filter can use the Netfilter framework included in the Linux kernel to do software-based packet filtering and packet rate limiting. Netfilter is very flexible, and because Packet Filter does not make any use of the connection tracking mechanism specific to stateful firewalls, it is also very fast.

• Disabled – Packet Filter detects and reports filtering rules, but the Netfilter firewall API is not used

• Filtering rules drop matched traffic. Valid traffic is accepted – Packet Filter detects, reports, and applies filtering rules using the Netfilter firewall. If the filtering rule is not whitelisted, the traffic matched by it is blocked. The remaining traffic is allowed to pass

• Filtering rules drop matched traffic. Valid traffic is rate-limited – Packet Filter detects, reports, and applies filtering rules, and rate-limits the remaining traffic. If the filtering rule is not whitelisted, the traffic matched by it is blocked. The traffic that exceeds the packets/second threshold value is not allowed to pass. Netfilter supports rate-limiting only for packets/s thresholds, not for bits/s thresholds. Also, some kernel versions will fail to rate-limit traffic above 10000 pkts/s and will block all traffic

• Filtering rules rate-limit matched traffic. Valid traffic is accepted – Packet Filter detects and reports filtering rules and rate-limits matched traffic to the threshold value. Netfilter supports rate-limiting only for packets/s thresholds, not for bits/s thresholds. Also, some kernel versions will fail to rate-limit traffic above 10000 pkts/s and will block all traffic

• Apply the default Netfilter chain policy – Packet Filter detects and reports filtering rules and applies them to the firewall using the default Netfilter chain policy. The Netfilter framework is still being used, but all rules have the RETURN target. This option is used exclusively for testing and debugging purposes

● Netfilter Firewall Options – Click the options button to configure the following additional parameters:

• Execution – Filtering rules can be applied automatically without end-user intervention or manually by an Operator or Administrator that clicks the Netfilter icons in Reports » Tools » Anomalies

• Netfilter Table – The raw option requires both Inbound and Outbound interfaces to be set, and it may not work for virtual interfaces. It provides a better packet filtering performance compared to the filter option

• Netfilter Chain – Set to FORWARD if the server forwards traffic, or INPUT if it does not

• Operating Layer – Set to OSI Layer 2 if the server is configured as a bridge, or OSI Layer 3 otherwise

● Dataplane Firewall – This parameter sets the filtering policy of the Dataplane Firewall, which is a built-in software-based firewall that uses DPDK. It is better performing than Netfilter but less flexible and harder to configure

● Hardware Offload – Select the appropriate option if you have a NIC that provides hardware filters. Since hardware filters do not consume CPU, use this feature to complement the Netfilter Firewall and Dataplane Firewall.

• Disabled – Hardware filters are not applied

• DPDK Flow API – Packet Filter uses the Flow API provided by the DPDK framework to offload the filtering of packets to the hardware

• Chelsio T5+ 10/40/100 Gigabit adapter with LE-TCAM filters – Packet Filter uses the cxgbtool utility to apply up to 487 filtering rules that may contain any combination of source/destination IPv4/IPv6 addresses, source/destination UDP/TCP port, and IP protocol. This utility is installed by the Chelsio Unified Wire driver. Drop traffic counters are available for packets, not for bytes

• Mellanox ConnectX NIC with OFED driver – Packet Filter uses the /opt/mellanox/ethtool/sbin/ethtool utility to apply up to 924 filtering rules that may contain any combination of source/destination IPv4/IPv6 addresses, source/destination UDP/TCP port, and IP protocol. The ethtool utility is installed in the specified path by the OFED driver from Mellanox. Drop traffic counters are not available

• Intel x520+ 1/10/40 Gigabit adapter configured to block IPv4 sources – Packet Filter programs the Intel chipset to drop IPv4 addresses from the filtering rules that contain source IPs. Up to 4086 hardware filters can be used. Drop traffic counters are not available

• Intel x520+ 1/10/40 Gigabit adapter configured to block IPv4 destinations – Packet Filter programs the Intel chipset to drop IPv4 addresses from the filtering rules that contain destination IPs. Up to 4086 hardware filters can be used. Drop traffic counters are not available

● Whitelist – See the dedicated Whitelist Template chapter

● Comments – Comments about the Packet Filter can be saved here. These observations are not visible elsewhere

Enable the Packet Filter by clicking the small play/stop button displayed next to its name in Configuration » Components. An instance of the Packet Filter will be launched when a traffic anomaly triggers the Response action “Detect filtering rules and mitigate the attack with Wanguard Filter”. When there is no traffic anomaly that requires its execution, Reports » Devices » Overview will show the “No active instance” message.

To test the firewall configuration, go to Reports » Tools » Firewall and click the [Add Firewall Rule] button.

21.1. Packet Filter Troubleshooting

✔ If the server is not switching packets although it should function as a network bridge, follow the steps required by your Linux distribution and make sure the following commands are executed during startup:

[root@localhost ~]# sysctl -w net.bridge.bridge-nf-call-ip6tables=1
[root@localhost ~]# sysctl -w net.bridge.bridge-nf-call-iptables=1
[root@localhost ~]# sysctl -w net.bridge.bridge-nf-filter-vlan-tagged=1

✔ If the server is not routing packets although it should function as a router, follow the steps required by your Linux distribution and make sure the following commands are executed during startup. To inject the packets back into the network, set a core router as default gateway, reachable through the Outbound Interface, either directly (recommended) or through a GRE or IP-in-IP tunnel.

[root@localhost ~]# sysctl -w net.ipv4.ip_forward=1
[root@localhost ~]# sysctl -w net.ipv4.conf.all.forwarding=1
[root@localhost ~]# sysctl -w net.ipv4.conf.default.rp_filter=0
[root@localhost ~]# sysctl -w net.ipv4.conf.all.rp_filter=0

✔ To view the traffic counters for each Netfilter or Chelsio filtering rule go to Reports » Tools » Firewall

✔ To see the filtering rules applied by the Netfilter firewall, execute on CLI as root:

[root@localhost ~]# iptables -L -n -v && iptables -L -n -v -t raw

To delete all chains:

[root@localhost ~]# for chain in `iptables -L -t raw | grep wanguard | awk '{ print $2 }'`; do iptables -X $chain; done

✔ To view the filtering rules applied on the Intel 80599 chipset:

[root@localhost ~]# ethtool --show-ntuple <filtering_interface>

or, for kernels >3.1:

[root@localhost ~]# ethtool --show-nfc <filtering_interface>

✔ To ensure that filtering rules can be applied on the Intel 80599 chipset, load the ixgbe driver with the parameter FdirPballoc=3. To prevent getting “Location out of range” errors from the ixgbe driver, load it with the right parameters in order to activate the maximum number of 8k filtering rules

✔ To view filtering rules applied on the Chelsio T4+ chipset:

[root@localhost ~]# cxgbtool <filtering_interface> filter show

✔ If the CPU usage of the Packet Filter instance is too high, install PF_RING (no ZC/DNA/LibZero needed), or use a network adapter that allows distributing Packet Filters over multiple CPU cores

✔ If the Netfilter’s performance is too low, check if nf_conntrack is used and disable it, if possible. Packet Filter uses only stateless firewalls

✔ For PF_RING installation issues, contact ntop.org. To increase the maximum number of PF_RING programs from 64 to 256, increase the MAX_NUM_RING_SOCKETS defined in kernel/linux/pf_ring.h and recompile the pf_ring kernel module

✔ The event log error “License key not compatible with the existing server” indicates that the server is unregistered and you need to send the string from Configuration » Servers » [Server] » Hardware Key to sales@andrisoft.com

✔ Go to Help » Software Updates to make sure that you are running the latest version of the software