[Oisf-devel] Best userspace programming API for XDP features query to kernel?

Victor Julien lists at inliniac.net
Thu Apr 5 07:47:37 UTC 2018

On 04-04-18 14:28, Jesper Dangaard Brouer wrote:
> Hi Suricata people,
> When Eric Leblond (and I helped) integrated XDP in Suricata, we ran
> into the issue, that at Suricata load/start time, we cannot determine
> if the chosen XDP config options, like xdp-cpu-redirect[1], is valid on
> this HW (e.g require driver XDP_REDIRECT support and bpf cpumap).
> We would have liked a way to report that suricata.yaml config was
> invalid for this hardware/setup.  Now, it just loads, and packets gets
> silently dropped by XDP (well a WARN_ONCE and catchable via tracepoints).
> My question to suricata developers: (Q1) Do you already have code that
> query the kernel or drivers for features?
> At the IOvisor call (2 weeks ago), we discussed two options of exposing
> XDP features avail in a given driver.
> Option#1: Extend existing ethtool -k/-K "offload and other features"
> with some XDP features, that userspace can query. (Do you already query
> offloads, regarding Q1)

I think if it would use the ioctl ETHTOOL interface it'd be easiest for
us, as we already have code for this in place to check for offloading
settings. See [1].

> Option#2: Invent a new 'ip link set xdp' netlink msg with a query option.

Do you have an example of how this is queried?

> (Q2) Do Suricata devs have any preference (or other options/ideas) for
> the way the kernel expose this info to userspace?

Right now I think extending the ethtool logic is best for us.

[1] https://github.com/OISF/suricata/blob/master/src/util-ioctl.c#L326

Victor Julien
PGP: http://www.inliniac.net/victorjulien.asc

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