Prerequisites

@@ -224,7 +225,6 @@ Howto run dpdk-testpmd with CNI plugin:

           capabilities:

              add:

                - CAP_NET_RAW

-               - CAP_BPF

Why the CAP_BPF is removed?

 

Good question. It's removed because in our case CAP_BPF is only needed when we want to load or unload the XDP program on the interface inside the Pod. In our case the CNI is loading the xdp program on the interface and then we are doing a handshake to get the xskmap file descriptor and so we don't need the CAP_BPF.

You will find a detailed listing of the permissions used at different stages when utilizing an XDP prog in this article https://next.redhat.com/2023/07/18/using-ebpf-in-unprivileged-pods/

I'm currently also working on enabling pinned map sharing with the af_xdp vdev eal arguments so we can integrate with bpfman for centralized BPF program lifecycle management [currently under test].

 

Correct me if I am wrong, Don’t we still need the CAP_BPF for bpf operations?

The only BPF operation in the Pod (when using the AF_XDP CNI) is interacting with the BPF maps via bpf_map_update_elem().

There's no BPF load/unload operations when you are using the AF_XDP DP and CNI (it does this for you) similar to what bpfman is doing in [1]. To interact with BPF maps you don't need CAP_BPF since the 5.19 Kernel please see [2], in addition to the previous links. In other words the only time you should need cap_bpf to access a map is if your kernel is <= 5.18. Which was the note I was referring to when I said I would update the documentation.

I've tested this patch in pod on Fedora 38 Kernel version: 6.5.12-200.fc38.x86_64 and there you don't need CAP_BPF.

Additionally Ubuntu 22.04 LTS is now shipping with a 6.2 Kernel [3], so you will not need it there either.

We don't want to give the pods more permissions than they need. CAP_BPF is in IMO an elevated permission.

If CAP_BPF is not need so do we need the CAP_NET_RAW also?

You need the CAP_NET_RAW to create the AF_XDP socket. 

[snip]

[1] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=c8644cd0efe7

[2] https://bpfd.dev/developer-guide/linux-capabilities/#removing-cap_bpf-from-bpfman-clients

[3] https://tuxcare.com/blog/ubuntu-22-04-3-is-here-with-linux-kernel-6-2/#:~:text=Initially%20released%20on%20April%2021,Ubuntu%2023.04%20(Lunar%20Lobster).