[snip]
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).
