[systemd-devel] Filter/Parse NETLINK_KOBJECT_UEVENT Messages

[Ryan McClue]

Sorry, I should clarify. The code in sd-device related to BPF I don't understand. What is the 'input' in BPF?

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-------- Original Message --------
On 14 Sep. 2021, 5:24 pm, Lennart Poettering wrote:

> On Di, 14.09.21 01:08, Ryan McClue (re.mcclue at protonmail.com) wrote:
>
>> I understand this is slightly off-topic, but I'm completely new to
>> BPF. Analyzing libudev source and Internet I understand the general
>> idea. However, I don't understand how information/what information
>> is passed to the filter from the socket. For example, in my case the
>> socket payload, i.e. buf_str =
>> add@/devices/pci0000:00/0000:00:14.0/usb1/1-2/1-2.4/1-2.4:1.0/input/input38/event14
>
>> 1. How do I pass this string to the sock_filter/sock_fprog
>> structures?
>
> You don't. The bpf filtering, and in particular the bloom filter that
> is used for that is mostly internal to udev, and not something that is
> consider official API and should be reimplemented.
>
> Use sd-device/libudev, it implements all of this, and is the only official API
> to the bpf bloom filter stuff udev does there.
>
> Lennart
>
> --
> Lennart Poettering, Berlin
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