2. Runtime Filtering

PF_RING 8.5 or later includes native support for runtime filtering, which is the ability to add filtering rules while the application is running.

Filtering rules are automatically converted into hardware rules and injected directly to the adapter, to be evaluated in hardware and add zero overhead. This requires an adapter supporting hardware filtering (e.g. NVIDIA/Mellanox ConnectX).

This allows you to run CPU bound applications (e.g. IDS/IPS) and receive (an process) only selected traffic, according to rules which are dinamically built and pushed to the capture engine. In order to achieve this the adapter is configured to discard all the traffic by default, and forward only packets matching hosts that require attention.

Filters are pushed to the capture engine by means of a Redis queue, and they can be added and removed by means of commands like “add host” or “remove host”.

2.1. Enabling Runtime Filtering

In order to enable Runtime Filtering in PF_RING, the PF_RING_RUNTIME_MANAGER environment variable should be set, using as value the name of the Redis queue used to push the filtering commands.

Example using pfcount:

PF_RING_RUNTIME_MANAGER="pfring.mlx5_0.filter.host.queue" pfcount -i mlx:mlx5_0 -0

2.2. Pushing Filters

Filters can be programmatically or manually pushed to the Redis queue using the “+<IP>” command to add a rule for a specific host, and the “-<IP>” command to remove a rule.

Example using redis-cli:

redis-cli RPUSH pfring.mlx5_0.filter.host.queue "+" "+" "+"
redis-cli RPUSH pfring.mlx5_0.filter.host.queue "-"

2.3. Redis Connection Settings

By default, when enabling Runtime Filtering, PF_RING connects to Redis on localhost port 6379. This can be controlled through the PF_RING_REDIS_SETTINGS environment variable. Supported formats are:



2.4. Debugging

In order to debug the Runtime Filtering component it is possible to enable logging of rules, with a message being printed to stderr every time a rule is added or removes. This can be enabled by setting the PF_RING_RUNTIME_MANAGER_DEBUG environment variable.


PF_RING_RUNTIME_MANAGER="pfring.mlx5_0.filter.host.queue" PF_RING_RUNTIME_MANAGER_DEBUG="1" pfcount -i mlx:mlx5_0