Sep 9 – 11, 2019
Europe/Lisbon timezone

Scaling container policy management with kernel features

Sep 11, 2019, 10:00 AM
Floriana/room-I (Corinthia Hotel Lisbon)


Corinthia Hotel Lisbon



Joe Stringer (


Cilium is an open source project which implements the Container Network
Interface (CNI) to provide networking and security functions in modern
application environments. The primary focus of the Cilium community recently
has been on scaling these functions to support thousands of nodes and hundreds
of thousands of containers. Such environments impose a high rate of churn as
containers and nodes appear and leave the cluster. For each change, the
networking plugin needs to handle the incoming events and ensure that policy is
in sync with network configuration state. This creates a strong incentive to
efficiently interpret and map down cluster events into the required Linux
networking configuration to minimize the window during which there are
discrepancies between the desired and realized state in the cluster---something
that is made possible through eBPF and other kernel features.

Cilium realizes these policy and container events through the use of many
aspects of the networking stack, from rules to routes, tc to socket hooks,
skb->mark to the skb->cb. Modelling the changes to datapath state involves a
non-trivial amount of work in the userspace daemon to structure the desired
state from external entities and allow incremental adjustments to be made,
keeping the amount of work required to handle an event proportional to its
impact on the kernel configuration. Some aspects of datapath configuration such
as the implementation of L7 policy have gone through multiple iterations, which
provides a window for us to explore the past, present and future of transparent

This talk will discuss the container policy model used by Cilium to apply
whitelist filtering of requests at layers 3, 4 and 7; memoization techniques
used to cache intermediate policy computation artifacts; and impacts on
dataplane design and kernel features when considering large container based
deployments with high rates of change in cluster state.

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Primary author

Joe Stringer (

Presentation materials

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