pkg/datapath: require scrub attributes with netkit and endpoint routes#44960
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julianwiedmann merged 1 commit intocilium:mainfrom Mar 25, 2026
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Early versions of the netkit driver scrubbed skb metadata before BPF
programs are run, meaning identity metadata is not available in BPF.
This can cause network policy mis-classification if per-endpoint routes
are enabled.
A kernel patch landed in the driver [0] which adds new scrub attributes
to manage this, and a subsequent change was made in the Cilium datapath
connector [1] to make use of these new attributes. However, it's still
possible to run Cilium with netkit on a kernel that doesn't support
them, which is confusing [2] and may still result in strange behavior.
This commit introduces a runtime probe that will actively probe the
underlying host for netkit scrub attributes, if running with per-endpoint
routes. If the probe fails, we error out.
- With bpf.datapathMode={netkit,netkit-l2} this will error and the agent
will fail to start.
- with bpf.datapathMode=auto, this will log a warning and fall-back to
veth connector.
This commit also introduces additional test permutations to cover this.
[0] https://lore.kernel.org/bpf/20241004101335.117711-1-daniel@iogearbox.net
[1] cilium#35306
[2] cilium#40021
Signed-off-by: Alasdair McWilliam <alasdair.mcwilliam@isovalent.com>
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Early versions of the netkit driver scrubbed skb metadata before BPF programs are run, meaning identity metadata is not available in BPF. This can cause network policy mis-classification if per-endpoint routes are enabled.
A kernel patch landed in the driver [0] which adds new scrub attributes to manage this, and a subsequent change was made in the Cilium datapath connector [1] to make use of these new attributes. However, it's still possible to run Cilium with netkit on a kernel that doesn't support them, which is confusing [2] and may still result in strange behavior.
This commit introduces a runtime probe that will actively probe the underlying host for netkit scrub attributes, if running with per-endpoint routes. If the probe fails, we error out.
With
bpf.datapathMode={netkit,netkit-l2}this will error and the agent will fail to start.with
bpf.datapathMode=auto, this will log a warning and fall-back to veth connector.This commit also introduces additional test permutations to cover this.
[0] https://lore.kernel.org/bpf/20241004101335.117711-1-daniel@iogearbox.net
[1] #35306
[2] #40021