Crate libbpf_rs[−][src]

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libbpf-rs

libbpf-rs is a safe, idiomatic, and opinionated wrapper around libbpf.

libbpf-rs, together with libbpf-cargo (libbpf cargo plugin) allow you to write Compile-Once-Run-Everywhere (CO-RE) eBPF programs. Note this document uses “eBPF” and “BPF” interchangeably.

More information about CO-RE is available here.

High level workflow

Create new rust project (via cargo new or similar) at path $PROJ_PATH
Create directory $PROJ_PATH/src/bpf
Write CO-RE bpf code in $PROJ_PATH/src/bpf/${MYFILE}.bpf.c, where $MYFILE may be any valid filename. Note the .bpf.c extension is required.
Create a build script that builds and generates a skeleton module using libbpf_cargo::SkeletonBuilder
Write your userspace code by importing and using the generated module. Import the module by using the path attribute. Your userspace code goes in $PROJ_PATH/src/ as it would in a normal rust project.
Continue regular rust workflow (ie cargo build, cargo run, etc)

Alternate workflow

While using the skeleton is recommended, it is also possible to directly use libbpf-rs.

Follow steps 1-3 of “High level workflow”
Generate a BPF object file. Options include manually invoking clang, creating a build script to invoke clang, or using libbpf-cargo cargo plugins.
Write your userspace code in $PROJ_PATH/src/ as you would a normal rust project and point libbpf-rs at your BPF object file
Continue regular rust workflow (ie cargo build, cargo run, etc)

Design

libbpf-rs models various “phases”:

               from_*()        load()
                 |               |
                 v               v
   ObjectBuilder ->  OpenObject  -> Object
                         ^            ^
                         |            |
             <pre-load modifications> |
                                      |
                           <post-load interactions>

The entry point into libbpf-rs is ObjectBuilder. ObjectBuilder helps open the BPF object file. After the object file is opened, you are returned an OpenObject where you can perform all your pre-load operations. Pre-load means before any BPF maps are created or BPF programs are loaded and verified by the kernel. Finally, after the BPF object is loaded, you are returned an Object instance where you can read/write to BPF maps, attach BPF programs to hooks, etc.

You must keep the Object alive the entire duration you interact with anything inside the BPF object it represents. This is further documented in Object documentation.