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| | // SPDX-License-Identifier: EUPL-1.2+
// SPDX-FileCopyrightText: 2026 Demi Marie Obenour <demiobenour@gmail.com>
use std::fs::File;
use std::io::{Read as _, Seek as _, Write as _};
use std::os::unix::prelude::*;
use std::path::{Path, PathBuf};
use rustix::fs::{AtFlags, XattrFlags};
use rustix::path::Arg;
use rustix::{
fs::{Mode, OFlags, ResolveFlags},
io::Errno,
};
pub(crate) struct LeafCgroup {
path: PathBuf,
fd: OwnedFd,
}
pub enum Access {
Read,
Write,
}
impl LeafCgroup {
pub fn enable_delegation(&self) -> Result<(), Errno> {
rustix::fs::fsetxattr(self.fd.as_fd(), c"user.delegate", b"1", XattrFlags::empty())
}
pub fn open_subtree(&self, path: &std::path::Path, access: Access) -> Result<OwnedFd, Errno> {
rustix::fs::openat2(
self.fd.as_fd(),
path,
OFlags::NOATIME
| OFlags::CLOEXEC
| OFlags::NOFOLLOW
| match access {
Access::Write => OFlags::WRONLY,
Access::Read => OFlags::RDONLY,
},
Mode::empty(),
ResolveFlags::NO_SYMLINKS | ResolveFlags::BENEATH | ResolveFlags::NO_XDEV,
)
}
pub fn wait_for_empty(&self, kill: bool) -> std::io::Result<()> {
let kill_fd = if kill {
Some(self.open_subtree(std::path::Path::new("cgroup.kill"), Access::Write)?)
} else {
None
};
let wait_file = self.open_subtree(std::path::Path::new("cgroup.events"), Access::Read)?;
let poll_fd = wait_file.as_raw_fd();
let mut wait_fd = File::from(wait_file);
if let Some(kill_fd) = kill_fd {
assert_eq!(rustix::io::write(kill_fd.as_fd(), b"1")?, 1, "kernel bug");
}
let mut fds = libc::pollfd {
fd: poll_fd,
events: libc::POLLPRI | libc::POLLERR,
revents: 0,
};
let mut v = vec![];
loop {
v.clear();
// SAFETY: FFI call, valid arguments, fds contains 1 element
if unsafe { libc::poll(&raw mut fds, 1, -1) } != 1 {
panic!("poll failed");
}
wait_fd
.seek(std::io::SeekFrom::Start(0))
.expect("Seek on control group file should succeed");
wait_fd
.read_to_end(&mut v)
.expect("reading from control group should work");
if v.split(|&c| c == b'\n').any(|line| line == b"populated 0") {
break;
}
}
Ok(())
}
}
impl AsFd for LeafCgroup {
fn as_fd(&self) -> std::os::fd::BorrowedFd<'_> {
self.fd.as_fd()
}
}
impl LeafCgroup {
pub(crate) fn open_cgroup_at(&self, p: &Path) -> Result<Self, Errno> {
let fd = rustix::fs::openat2(
self.fd.as_fd(),
p,
OFlags::NOATIME
| OFlags::CLOEXEC
| OFlags::NOFOLLOW
| OFlags::RDONLY
| OFlags::DIRECTORY,
Mode::empty(),
ResolveFlags::NO_SYMLINKS | ResolveFlags::BENEATH | ResolveFlags::NO_XDEV,
)?;
Ok(Self {
fd,
path: self.path.join(p),
})
}
pub(crate) fn open_cgroup(fd: BorrowedFd, p: &Path) -> Result<Self, Errno> {
let fd = rustix::fs::openat2(
fd,
p,
OFlags::NOATIME
| OFlags::CLOEXEC
| OFlags::NOFOLLOW
| OFlags::RDONLY
| OFlags::DIRECTORY,
Mode::empty(),
ResolveFlags::NO_SYMLINKS,
)?;
Ok(Self {
fd,
path: p.to_owned(),
})
}
pub(crate) fn make_child(&self, p: &Path) -> Result<(), Errno> {
let r = rustix::fs::mkdirat(
self.fd.as_fd(),
p,
Mode::RUSR
| Mode::WUSR
| Mode::XUSR
| Mode::RGRP
| Mode::XGRP
| Mode::ROTH
| Mode::XOTH,
);
if r == Err(Errno::EXIST) { Ok(()) } else { r }
}
pub(crate) fn delete_child(&self, path: &Path) -> Result<(), Errno> {
remove_all(100, self.as_fd(), &path.as_cow_c_str().unwrap())
}
pub(crate) fn write_cgroup_value(&self, name: &str, value: &str) -> Result<(), String> {
let path = Path::new(name);
let fd = rustix::fs::openat2(
self.as_fd(),
path,
OFlags::NOATIME | OFlags::CLOEXEC | OFlags::NOFOLLOW | OFlags::WRONLY,
Mode::empty(),
ResolveFlags::NO_SYMLINKS | ResolveFlags::BENEATH | ResolveFlags::NO_XDEV,
)
.map_err(|e| format!("Cannot open {:?}: {}", path, e))?;
File::from(fd)
.write_all(value.as_bytes())
.map_err(|e| format!("Cannot write {:?} to {:?}: {}", value, path, e))
}
}
fn remove_recursively(fd: OwnedFd, remaining_depth: usize) -> Result<(), Errno> {
if remaining_depth < 1 {
panic!("control groups too deeply nested");
}
let mut d = rustix::fs::Dir::new(fd).expect("cannot start iterating");
while let Some(element) = d.next() {
let element = element.expect("Iterating through a cgroup directory failed?");
if element.file_type() != rustix::fs::FileType::Directory {
continue;
}
let remaining_depth = remaining_depth - 1;
let d: &rustix::fs::Dir = &d;
let dirfd = d.fd().unwrap();
let path = element.file_name();
remove_all(remaining_depth, dirfd, path)?;
}
Ok(())
}
fn remove_all(
remaining_depth: usize,
dirfd: BorrowedFd<'_>,
path: &std::ffi::CStr,
) -> Result<(), Errno> {
if path == c"." || path == c".." {
return Ok(());
}
if rustix::fs::unlinkat(dirfd, path, AtFlags::REMOVEDIR).is_ok() {
return Ok(());
}
let fd = rustix::fs::openat2(
dirfd,
path,
OFlags::NOATIME | OFlags::CLOEXEC | OFlags::NOFOLLOW | OFlags::RDONLY | OFlags::DIRECTORY,
Mode::empty(),
ResolveFlags::NO_SYMLINKS | ResolveFlags::BENEATH | ResolveFlags::NO_XDEV,
)?;
remove_recursively(fd, remaining_depth)?;
rustix::fs::unlinkat(dirfd, path, AtFlags::REMOVEDIR)?;
Ok(())
}
|