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use std::fmt::Debug;
use std::os::unix::io::AsFd;
use std::os::unix::io::BorrowedFd;
use std::path::Path;
use std::path::PathBuf;
use std::ptr::NonNull;
use crate::query::LinkInfo;
use crate::util;
use crate::util::validate_bpf_ret;
use crate::AsRawLibbpf;
use crate::ErrorExt as _;
use crate::Program;
use crate::Result;
/// Represents an attached [`Program`].
///
/// This struct is used to model ownership. The underlying program will be detached
/// when this object is dropped if nothing else is holding a reference count.
#[derive(Debug)]
#[must_use = "not using this `Link` will detach the underlying program immediately"]
pub struct Link {
ptr: NonNull<libbpf_sys::bpf_link>,
}
impl Link {
/// Create a new [`Link`] from a [`libbpf_sys::bpf_link`].
///
/// # Safety
///
/// `ptr` must point to a correctly initialized [`libbpf_sys::bpf_link`].
pub(crate) unsafe fn new(ptr: NonNull<libbpf_sys::bpf_link>) -> Self {
Self { ptr }
}
/// Create link from BPF FS file.
pub fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
let path_c = util::path_to_cstring(path)?;
let path_ptr = path_c.as_ptr();
let ptr = unsafe { libbpf_sys::bpf_link__open(path_ptr) };
let ptr = validate_bpf_ret(ptr).context("failed to open link")?;
let slf = unsafe { Self::new(ptr) };
Ok(slf)
}
/// Takes ownership from pointer.
///
/// # Safety
///
/// It is not safe to manipulate `ptr` after this operation.
pub unsafe fn from_ptr(ptr: NonNull<libbpf_sys::bpf_link>) -> Self {
unsafe { Self::new(ptr) }
}
/// Replace the underlying prog with `prog`.
pub fn update_prog(&mut self, prog: &Program<'_>) -> Result<()> {
let ret =
unsafe { libbpf_sys::bpf_link__update_program(self.ptr.as_ptr(), prog.ptr.as_ptr()) };
util::parse_ret(ret)
}
/// Release "ownership" of underlying BPF resource (typically, a BPF program
/// attached to some BPF hook, e.g., tracepoint, kprobe, etc). Disconnected
/// links, when destructed through `bpf_link__destroy()` call won't attempt to
/// detach/unregistered that BPF resource. This is useful in situations where,
/// say, attached BPF program has to outlive userspace program that attached it
/// in the system. Depending on type of BPF program, though, there might be
/// additional steps (like pinning BPF program in BPF FS) necessary to ensure
/// exit of userspace program doesn't trigger automatic detachment and clean up
/// inside the kernel.
pub fn disconnect(&mut self) {
unsafe { libbpf_sys::bpf_link__disconnect(self.ptr.as_ptr()) }
}
/// [Pin](https://facebookmicrosites.github.io/bpf/blog/2018/08/31/object-lifetime.html#bpffs)
/// this link to bpffs.
pub fn pin<P: AsRef<Path>>(&mut self, path: P) -> Result<()> {
let path_c = util::path_to_cstring(path)?;
let path_ptr = path_c.as_ptr();
let ret = unsafe { libbpf_sys::bpf_link__pin(self.ptr.as_ptr(), path_ptr) };
util::parse_ret(ret)
}
/// [Unpin](https://facebookmicrosites.github.io/bpf/blog/2018/08/31/object-lifetime.html#bpffs)
/// from bpffs
pub fn unpin(&mut self) -> Result<()> {
let ret = unsafe { libbpf_sys::bpf_link__unpin(self.ptr.as_ptr()) };
util::parse_ret(ret)
}
/// Returns path to BPF FS file or `None` if not pinned.
pub fn pin_path(&self) -> Option<PathBuf> {
let path_ptr = unsafe { libbpf_sys::bpf_link__pin_path(self.ptr.as_ptr()) };
if path_ptr.is_null() {
return None;
}
let path = match util::c_ptr_to_string(path_ptr) {
Ok(p) => p,
Err(_) => return None,
};
Some(PathBuf::from(path.as_str()))
}
/// Detach the link.
pub fn detach(&self) -> Result<()> {
let ret = unsafe { libbpf_sys::bpf_link__detach(self.ptr.as_ptr()) };
util::parse_ret(ret)
}
/// Get information about this link.
pub fn info(&self) -> Result<LinkInfo> {
LinkInfo::from_fd(self.as_fd())
}
}
impl AsRawLibbpf for Link {
type LibbpfType = libbpf_sys::bpf_link;
/// Retrieve the underlying [`libbpf_sys::bpf_link`].
fn as_libbpf_object(&self) -> NonNull<Self::LibbpfType> {
self.ptr
}
}
// SAFETY: `bpf_link` objects can safely be sent to a different thread.
unsafe impl Send for Link {}
// SAFETY: `bpf_link` has no interior mutability.
unsafe impl Sync for Link {}
impl AsFd for Link {
#[inline]
fn as_fd(&self) -> BorrowedFd<'_> {
let fd = unsafe { libbpf_sys::bpf_link__fd(self.ptr.as_ptr()) };
// SAFETY: `bpf_link__fd` always returns a valid fd and the underlying
// libbpf object is not destroyed until the object is dropped,
// which means the fd remains valid as well.
unsafe { BorrowedFd::borrow_raw(fd) }
}
}
impl Drop for Link {
fn drop(&mut self) {
let _ = unsafe { libbpf_sys::bpf_link__destroy(self.ptr.as_ptr()) };
}
}