Trait libbpf_rs::skel::OpenSkel

source ·

pub trait OpenSkel {
    type Output: Skel;

    // Required methods
    fn load(self) -> Result<Self::Output>;
    fn open_object(&self) -> &OpenObject;
    fn open_object_mut(&mut self) -> &mut OpenObject;
}

Expand description

A trait for opened skeleton.

In addition to the methods defined in this trait, skeletons that implement this trait will also have bespoke implementations of a few additional methods to facilitate access to global variables of the BPF program. These methods will be named bss(), data(), and rodata(). Each corresponds to the variables stored in the BPF ELF program section of the same name. However if your BPF program lacks one of these sections the corresponding rust method will not be generated.

The type of the value returned by each of these methods will be specific to your BPF program. A common convention is to define a single global variable in the BPF program with a struct type containing a field for each configuration parameter ^[source]. libbpf-rs auto-generates this pattern for you without you having to define such a struct type in your BPF program. It does this by examining each of the global variables in your BPF program’s .bss, .data, and .rodata sections and then creating Rust struct types. Since these struct types are specific to the layout of your BPF program, they are not documented in this crate. However you can see documentation for them by running cargo doc in your own project and looking at the imp module. You can also view their implementation by looking at the generated skeleton rust source file. The use of these methods can also be seen in the examples ‘capable’, ‘runqslower’, and ‘tproxy’.

If you ever doubt whether libbpf-rs has placed a particular variable in the correct struct type, you can see which section each global variable is stored in by examining the output of the following command (after a successful build):