daemon: Fail agent startup on incompatible datapath mode#42482
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fristonio
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tklauser
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Cilium does not currently support migrating a live node with pods between `netkit` and `veth` datapath modes ([ref](https://docs.cilium.io/en/stable/operations/performance/tuning/#netkit-device-mode)). But there is currently no safety mechanisms to safeguard against it. This means that is it currently possible to accidentally switch datapath mode on a node and end up in an undefined and unexpected state. This PR aims to ensure this can not happen by adding a check in the endpoint restore logic to check the restored endpoint link type against the configured datapath mode and make the agent crash in case of incompatibility. Signed-off-by: Hadrien Patte <hadrien.patte@datadoghq.com>
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Cilium does not currently support migrating a live node with pods between
netkitandvethdatapath modes(ref). But there is currently no safety mechanisms to safeguard against it. This means that is it currently possible to accidentally switch datapath mode on a node and end up in an undefined and unexpected state.
This PR aims to ensure this can not happen by adding a check in the endpoint restore logic to check the restored endpoint link type against the configured datapath mode and make the agent crash in case of incompatibility.
The new errors look like this:
For context, we accidentally enabled netkit on nodes that had existing veth endpoints and it took us a while to understand that this was the issue as what we observed was a high volume of dropped ARP packets with reason
Unsupported L3 protocoland protocolunknown l4. This is because since netkit runs in L3 mode, netkit bpf programs are compiled without ARP support.