22. Components » Flow Filter¶

The functionality of Flow Filter is described in depth in the Choosing a Method of DDoS Mitigation chapter. Unlike Packet Filter, which inspects every packet, Flow Filter obtains traffic data directly from Flow Sensor.

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

FLOW_FILTER_CONFIGURATION8.01_png

Flow Filter Configuration parameters:

● Filter Name – Assign a short, descriptive name to easily identify the Flow Filter

● Filter Color – By default, a random color is used in graphs. You can change it via the dropdown menu

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

● Device Group – Enter a description if you wish to organize components (e.g. by location, characteristics) or to permit fine-grained access for roles

● Filter Server – Choose a server that meets the minimum system requirements for running the Flow Filter

● Filtering Interface – Select on which interface to apply the filtering rules:

▪ None – Detects/reports filtering rules but does not apply them

▪ Inbound interface – Applies filtering on the inbound interface (defined below)

▪ Outbound interface – Applies filtering on the outbound interface (defined below)

● Inbound Interface – Enter the interface receiving incoming (ingress) traffic. This parameter can be omitted if Filtering Interface is the same as Outbound Interface. For bridged interfaces, prepend “physdev:” to the interface name

● Outbound Interface – Cleaned traffic is sent to the downstream router/switch via this interface, which should have a route to the default gateway. Omit if Filtering Interface is the same as Inbound Interface. For bridged interfaces, prepend “physdev:” to the interface name

● BGP Flowspec – Choose the policy to apply when sending BGP Flowspec announcements via a Response. The rate-limit policy applies only to bits/s anomalies; for pkts/s anomalies, any matched traffic is fully discarded

● Netfilter Firewall – Flow Filter utilizes the Netfilter framework in the Linux kernel for software-based packet filtering and rate limiting. Because Flow Filter avoids the connection tracking of stateful firewalls, it operates very quickly and remains highly flexible

▪ Disabled – Flow Filter detects/reports rules but does not invoke the Netfilter firewall

▪ Filtering rules drop matched traffic. Valid traffic is accepted – Flow Filter detects/reports/applies filtering rules via Netfilter. If a rule is not whitelisted, matched traffic is blocked; everything else passes

▪ Filtering rules drop matched traffic. Valid traffic is rate-limited – Flow Filter applies filtering rules, dropping non-whitelisted traffic and rate-limiting the rest. Netfilter only supports pkts/s thresholds, and some kernels fail above 10000 pkts/s

▪ Filtering rules rate-limit matched traffic. Valid traffic is accepted – Flow Filter rate-limits matched traffic to the threshold. Netfilter does not support bits/s thresholds; some kernels fail above 10000 pkts/s

▪ Apply the default Netfilter chain policy – For testing only. Flow Filter detects/reports rules, but all rules have the RETURN target

When using the Netfilter Firewall, the following options become available:

• Execution – Filtering rules can be applied automatically or manually (by clicking the Netfilter icon in Reports » Tools » Anomalies)

• Netfilter Table – The raw option typically offers better performance but needs both Inbound and Outbound interfaces to be set. It may not work on virtual interfaces. The filter option is usually slower

• Netfilter Chain – Use FORWARD if the server forwards traffic, or INPUT if it doesn’t

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

● Dataplane Firewall – Controls the built-in, DPDK-based firewall, which outperforms Netfilter but is less flexible and more complex to configure

• Execution – Filtering rules can be applied automatically or manually (by clicking the Dataplane icon in Reports » Tools » Anomalies)

● Hardware Offload – Choose a NIC hardware-filtering option if available. Because hardware filters don’t use CPU cycles, they can complement Netfilter or Dataplane Firewall for better performance

▪ Disabled – No hardware filters are applied

▪ Chelsio T5+ 10/40/100 Gigabit adapter with LE-TCAM filters – Uses the cxgbtool utility to apply up to 487 filtering rules for source/destination IPv4/IPv6 addresses, source/destination TCP/UDP ports, and IP protocols. The utility can be installed by the Chelsio Unified Wire driver. Drop counters are available for packets, not for bytes

▪ Mellanox ConnectX NIC with OFED driver – Uses the ethtool utility to apply up to 924 rules for source/destination IPv4/IPv6 addresses, source/destination TCP/UDP ports, and IP protocols. The utility must be installed by the OFED driver driver in /opt/mellanox/ethtool/sbin/. No drop counters available

▪ Intel x520+ 1/10/40 Gigabit adapter configured to block IPv4 sources – Programs the Intel chipset to drop IPv4 source IPs. Up to 4086 hardware filters; no drop counters

▪ Intel x520+ 1/10/40 Gigabit adapter configured to block IPv4 destinations – Programs the Intel chipset to drop IPv4 destination IPs. Up to 4086 hardware filters; no drop counters

When using Hardware Offload, the following option becomes available:

• Execution – Filtering rules can be applied automatically or manually (by clicking the NIC chipset icon in Reports » Tools » Anomalies)

● Whitelist – Contains a set of rules preventing critical traffic from being blocked. Refer to the Whitelist Template chapter for more information

● Comments – (Optional) Store internal notes about this Flow Filter. These notes are not displayed elsewhere

Enable the Flow Filter by clicking the on/off button next to its name in Configuration » Components. If a traffic anomaly triggers the Response action “Detect filtering rules and mitigate the attack with Wanguard Filter”, a Flow Filter instance is launched automatically. If there are no anomalies requiring a Filter instance, Reports » Devices » Overview displays “No active instance”.

Note

You can test any firewall supported by Flow Filter in Reports » Tools » Firewall by clicking [Add Firewall Rule].

22.1. Flow 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

✔ Go to Help » Software Updates to make sure that you are running the latest version of the software
✔ 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 82599 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 82599 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 Netfilter’s performance is too low, check if nf_conntrack is used and disable it, if possible. Packet Filter uses only stateless firewalls

✔ 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